CHAPTER 5: Cardiology

AORTIC STENOSIS

A form of acyanotic congenital heart disease (CHD) in which obstruction of the left ventricular outflow tract leads to a systolic pressure gradient between the left ventricle (LV) and the aorta.

• Aortic valve stenosis: Most common form of aortic stenosis; frequently due to bicuspid aortic valve; identified in up to 2% of adults

• Subvalvular stenosis: Due to fibromuscular ring or shelf below the aortic valve; may be associated with malalignment ventricular septal defect (VSD) or aortic coarctation

• Supravalvular stenosis: Least common form of aortic stenosis; may be localized or diffuse; may be associated with Williams syndrome

EPIDEMIOLOGY

• 3–6% of congenital heart defects; male:female = 4:1

PATHOPHYSIOLOGY

• Critical aortic stenosis: High pressure gradients across the aortic valve may result in LV failure, low cardiac output, and pulmonary edema

• Pressure gradient may increase as cardiac output increases with growth during childhood

• Abnormal diastolic filling is due to LV hypertrophy

CLINICAL MANIFESTATIONS

• Often asymptomatic in infancy, but can present with irritability, paleness, tachycardia, tachypnea, retractions, and rales; symptoms depend on severity and location of obstruction

• Heart failure is most common in neonates with critical disease or in adults with untreated disease

• Ventricular arrhythmias and sudden death may occur

• Physical examination: Early systolic ejection click at the apex; harsh ejection systolic murmur at the base radiates to the neck; palpable left ventricular lift; precordial systolic thrill at base

DIAGNOSTICS

• Chest x-ray (CXR): May show cardiomegaly (evidence of LV hypertrophy) and pulmonary edema with critical obstruction

• ECG: LV hypertrophy or LV strain in severe disease

• Echocardiography: Defines anatomy and hemodynamic severity of the lesion

• Cardiac catheterization: Required to establish severity and measure pressure gradient across aortic valve, and for treatment of aortic stenosis

MANAGEMENT

Medical

• Prostaglandin E₁ (PGE₁) dilates the ductus arteriosus to augment systemic output in severely ill neonates with critical obstruction

• Inotropic support with dopamine or epinephrine may also be required to maintain adequate cardiac output both before and after the intervention

Surgical or Catheter-based Interventions

• Aortic valve stenosis: Percutaneous balloon aortic valvuloplasty is the preferred approach for aortic stenosis; surgical valvotomy; aortic valve replacement with pulmonary autograft or Ross procedure (preferred in infants and young children) prosthetic valve or aortic homograft

• Subaortic stenosis: Surgical removal of fibromuscular shelf or membrane, myomectomy may be required for muscular tunnel-like obstruction (Konno procedure)

• Supravalvular stenosis: Surgery to widen or repair stenotic segment

ATRIAL SEPTAL DEFECT

A form of acyanotic CHD characterized by openings in the atrial septum at one of the following four locations:

• Ostium secundum: Located at site of foramen ovale; accounts for 50–70% of all atrial septal defects (ASDs)

• Ostium primum: Located low in the septum; also called incomplete atrioventricular canal defect or endocardial cushion defect, and always associated with cleft in mitral valve

• Sinus venosus: Located high in the septum near the superior vena cava or located low in the septum near the inferior vena cava (least common); associated with anomalous pulmonary venous return

• Coronary sinus septal defect: A portion of the coronary sinus roof is missing, causing blood to shunt from the left atrium into the coronary sinus and then into the right atrium; least common type of ASD

EPIDEMIOLOGY

• 5–10% of CHD; male:female = 1:2; 1 in 1500 live births

PATHOPHYSIOLOGY

• Small defects may close spontaneously

• Magnitude of left-to-right shunt depends on size of the defect and pulmonary and systemic vascular resistance, and relative compliance of the ventricles

• Results in right atrial and right ventricular volume overload; if unrepaired pulmonary vascular disease can develop in adulthood

CLINICAL MANIFESTATIONS

• Often asymptomatic in childhood and cardiac evaluation is prompted by murmur; may not present until adulthood

• Occasionally presents in childhood with fatigue, dyspnea, respiratory infections, and congestive heart failure (CHF)

• CHF is more common if the ASD is associated with borderline left sided structures such as mitral valve abnormalities or mild coarctation

• Atrial dysrhythmias including fibrillation and supraventricular tachycardia are more common in adults

• Pulmonary hypertension is more common in adults

• Paradoxical emboli may occur

• Physical exam: S₁ is loud or normal; S₂ is widely split and fixed; prominent right ventricular cardiac impulse; midsystolic pulmonary ejection murmur; diastolic murmur at left lower sternal border (LLSB) may represent flow across the tricuspid valve if pulmonary to systemic flow ratio (Qp:Qs) is greater than 2:1

DIAGNOSTICS

• CXR: Right atrial enlargement, right ventricular hypertrophy (RVH), dilated pulmonary artery, and increased pulmonary vasculature

• ECG: Right axis deviation and RVH

• Echocardiography: Reveals location, size, and associated anomalies

• Cardiac catheterization: May be used to confirm presence of the defect and determine pulmonary to systemic flow ratio (Qp:Qs)

MANAGEMENT

Medical

• Heart failure symptoms may be managed with digoxin and diuretics (e.g., furosemide)

• Occasional arrhythmias may require medical management

• Secundum ASDs close spontaneously in about 40–50% of patients

Surgical or Catheter-based Interventions

• Usually recommended if pulmonary:systemic flow ratio (Qp:Qs) is greater than 2:1, patient is symptomatic, or ASD is moderate or large in size

• Uncomplicated ASDs are often closed between 2 and 4 years of age

• Defect is sutured or a patch is applied, often under cardiopulmonary bypass, though closure devices deployed by transvenous catheterization are increasingly used

COARCTATION OF THE AORTA

A form of acyanotic CHD in which there is narrowing of the aorta, most commonly just beyond the origin of the left subclavian artery.

• May occur in isolation or in association with other cardiac defects

EPIDEMIOLOGY

• 5–8% of congenital heart defects; male:female = 2:1

• Often associated with Turner syndrome

PATHOPHYSIOLOGY

• Degree of symptoms and timing of presentation depends on severity of coarctation

• Decreased blood flow to lower extremities and lower half of the body may occur, especially after closure of the ductus arteriosus

• LV outflow tract obstruction leads to LV hypertrophy and increased systolic pressures; eventually LV dysfunction may develop, causing low output cardiac failure and pulmonary edema

• Extensive collateral circulation may develop in older children and young adults who are not diagnosed early in life

CLINICAL MANIFESTATIONS

• Neonates: May present in the first 3 weeks of life (especially after closure of the ductus arteriosus) with tachypnea, poor feeding, diaphoresis, CHF, cardiogenic shock, and/or decreased femoral pulses

• Older children: Upper extremity hypertension and claudication

• On exam: Decreased or absent femoral pulses; systolic murmur at left sternal border between third and fourth intercostal space radiating to left infrascapular area; ejection click if bicuspid aortic valve is present

DIAGNOSTICS

• Four-extremity blood pressures (BPs): Differential in BP (>10 mm Hg) between right upper extremity and lower extremities

• CXR: Cardiomegaly and pulmonary edema is usually seen in neonates and infants, rib notching noted in children over 6 years of age

• ECG: LV hypertrophy and possible left atrial (LA) enlargement in older children; RV hypertrophy in neonates

• Echocardiography: Reveals segment of coarctation and associated anomalies

• Cardiac catheterization: May be performed to delineate affected segment and potentially for treatment in older children, adolescents, and adults

• MRI: May help define lesion and identify collateral vessels; used for serial follow-up

MANAGEMENT

Medical

• PGE₁ maintains patency of ductus to help provide distal perfusion in severely affected neonates. Inotropic support may be required for those presenting in extremis

• Rebound hypertension is common in the immediate postoperative period and may require antihypertensive medication, especially in older children

Surgical

• Timing depends on age of diagnosis, severity of disease, and related defects

• Surgery is usually preferred for neonates and infants. Techniques include end-to-end anastomosis, patch augmentation, and subclavian flap repair. Percutaneous balloon angioplasty or stent angioplasty for native coarctation is usually reserved for recurrent coarctation or primary therapy in older children, adolescents, or adults

ENDOCARDIAL CUSHION DEFECT

A form of acyanotic CHD in which there is malformation of the endocardial cushion resulting in defects in the interatrial and/or interventricular septum. Defects may be partial or incomplete (e.g., ostium primum atrial septal defect, common atrium, posterior ventricular septal defect) or complete (e.g., complete atrioventricular canal).

• Complete atrioventricular canal: One large atrioventricular valve, and both ASD and VSD

EPIDEMIOLOGY

• 4–5% of CHD; 0.19 in 1000 live births

• 30% of children with complete endocardial cushion defects have Down syndrome; 20–25% of children with Down syndrome have endocardial cushion defects

PATHOPHYSIOLOGY

• Varying degrees of left-to-right shunt result in CHF and recurrent pneumonia. The hemodynamic effect of the lesion depends on the specific location of the defect, the degree of shunting, and valvular incompetence

CLINICAL MANIFESTATIONS

• Usually present within the first few weeks of life with failure to thrive, tachypnea, tachycardia, respiratory infections, and/or heart failure

• Untreated defects may lead to Eisenmenger syndrome (irreversible pulmonary arterial hypertension resulting from long-standing excessive pulmonary blood flow)

• Physical exam findings depend on the extent of the lesion and may include hyperdynamic precordium with palpable thrill at LLSB; accentuated pulmonic component of S₂; variable systolic murmur may be inaudible or grade 3–4/6 and holosystolic; signs of heart failure

DIAGNOSTICS

Findings depend on the extent of the lesion and may include:

• CXR: Cardiomegaly, pulmonary vascular congestion, prominent main pulmonary artery

• ECG: Left or superior deviation of QRS axis (−40 to −150 degrees), ventricular hypertrophy (right and/or left)

• Echocardiography: Helps define size of the defects, size of the ventricles, and anatomy of the valve

• Cardiac catheterization: May be used to evaluate pulmonary hypertension and to look for additional VSDs

MANAGEMENT

Medical

• Anti-congestive medications: Digoxin, diuretics, ACE inhibitors

Surgical

• Definitive surgical treatment is usually recommended before 6 months of age, particularly in infants with Down syndrome

• Palliative pulmonary artery banding is usually reserved for cases in which more definitive surgical options are challenging (e.g., prematurity)

HYPOPLASTIC LEFT HEART SYNDROME

A form of cyanotic CHD characterized by underdevelopment of the LV and ascending aorta. The mitral and aortic valves are atretic or critically stenosed. Systemic circulation is dependent on a patent ductus arteriosus (PDA).

EPIDEMIOLOGY

• 1% of CHD, more common in males

• Most common cause of cardiac death in the first month of life

• Chromosomal abnormalities in up to 25% of patients

PATHOPHYSIOLOGY

• Blood returning from the lungs passes through a patent foramen ovale or an ASD into the right atrium (RA) and RV

• If a VSD is present and the aortic valve is not completely stenotic, a small amount of blood may enter the aorta directly. Otherwise, there is complete mixing of systemic and pulmonary blood, which enters the pulmonary artery and passes through a PDA into the systemic circulation, including retrograde flow in the ascending aorta

• As the PDA closes, systemic output decreases and metabolic acidosis ensues

CLINICAL MANIFESTATIONS

• Most present within 48–72 hours of life as the ductus arteriosus closes

• Cyanosis, dyspnea, poor feeding, heart failure, hepatomegaly, poor perfusion, decreased peripheral pulses, shock

• A minority with a restrictive ASD or intact atrial septum present immediately after birth with profound cyanosis, respiratory failure, and circulatory collapse

• On exam: Right parasternal lift; single, loud S₂; soft, nonspecific systolic ejection murmur

DIAGNOSTICS

• Prenatal ultrasound: Allows for antenatal diagnosis, counseling, and time to consider treatment options; increasingly predominant method for diagnosis in current era

• CXR: Cardiomegaly, pulmonary venous congestion, pulmonary edema

• ECG: RV hypertrophy

• Echocardiography: Defines anatomy

• Cardiac catheterization: Rarely needed in the current era except for diagnosis and treatment of restrictive ASD

MANAGEMENT

Medical

• Without intervention, hypoplastic left heart syndrome (HLHS) is fatal within the first month of life

• PGE₁ maintains ductal patency and systemic perfusion

• Ratio of pulmonary vascular resistance (PVR) to systemic vascular resistance (SVR) is actively managed to assure adequate oxygenation and systemic output. Generally, oxygen saturation (SaO₂) greater than 70% is adequate and SaO₂ greater than 90% is undesirable because it indicates pulmonary overcirculation. Supplemental oxygen is usually NOT required

Surgical

• Norwood Procedure: First stage in a three-staged surgical palliation of HLHS. While survival has improved, there is still a substantial risk of death during childhood

• Hybrid: Consisting of bilateral pulmonary artery bands and stenting of the PDA is the preferred neonatal palliation in some centers

• Orthotopic Heart Transplantation: Will be needed in many HLHS patients, though rare as a primary therapy; requires lifelong immunomodulatory therapy; shortage of available donors

TETRALOGY OF FALLOT

A form of cyanotic CHD resulting from a malaligned infundibular/subpulmonary septum and characterized by (1) overriding aorta; (2) right ventricular outflow tract obstruction; (3) malalignment VSD; and (4) RV hypertrophy.

EPIDEMIOLOGY

• 5–7% of CHD; incidence: 1 in 2700

• 15% of patients with TOF have DiGeorge syndrome; 50% of patients with DiGeorge syndrome have TOF

PATHOPHYSIOLOGY

• Pulmonary valve annulus has variable size and helps determine degree of RV outflow tract obstruction

• Severity of symptoms determined by degree of RV outflow tract obstruction (related to subvalvular pulmonary stenosis) and right-to-left shunt; degree of shunt depends on PVR, SVR, and presence or absence of a PDA

• VSD is usually large and unrestrictive

• Mild cases may have imperceptible cyanosis (“pink tet”)

CLINICAL MANIFESTATIONS

• Paroxysmal Hypercyanotic Attacks (“Tet spells”)

  • ✓ Characterized by the sudden onset of increased cyanosis, dyspnea, and change in mental status (often with irritability)

  • ✓ Due to sudden increased ratio of pulmonary to SVR resulting in increased right-to-left shunting across the VSD and reduction in pulmonary blood flow

  • ✓ May lead to severe hypoxemia, metabolic acidosis, and death

  • ✓ Onset generally between 2 and 9 months of age

• If untreated, cyanosis is observed in most patients by 1 year of age; dyspnea with exertion; clubbing and tendency to assume a “knee-to-chest” or squatting position are seen in older children

• On exam: RV impulse harsh systolic ejection murmur at left sternal border; single second heart sound

DIAGNOSTICS

• CXR: “Boot-shaped” heart, clear lung fields, possible right aortic arch

• ECG: Right axis deviation, RV hypertrophy, dominant R-wave or RSR’ pattern in precordial leads

• Echocardiography: Defines anatomy

• Cardiac catheterization: May rarely be required to delineate coronary artery anatomy

MANAGEMENT

“Tet” Spells

• Remove restrictive clothing, calm patient, and place the baby in parent’s lap in knee-to-chest position

• Oxygen

• Morphine

• Phenylephrine or IV beta-blocker rarely required

Medical

• In neonates, avoid stressors such as cold, and monitor blood glucose levels

• If RV outflow tract obstruction is severe, infants may be dependent on a PDA and require PGE₁

• Oral propranolol may decrease frequency and severity of “Tet” spells

Surgical

• Palliative surgery: Systemic-to-pulmonary artery shunt (e.g., modified Blalock–Taussig shunt) can augment pulmonary blood flow in severely affected infants

• Total surgical correction: Often done during infancy

TOTAL ANOMALOUS PULMONARY VENOUS RETURN

A form of cyanotic CHD in which the pulmonary veins drain anomalously into systemic veins. There are four types of total anomalous pulmonary venous return (TAPVR):

1. Supracardiac: Pulmonary veins course superiorly to a “vertical vein,” which drains into the innominate vein. Blood then flows to the superior vena cava and the RA

2. Infracardiac: Pulmonary veins course inferiorly through a descending vein, which drains into the portal system. Blood then flows to the hepatic veins, inferior vena cava, and RA. Pulmonary venous obstruction may occur at multiple levels in the descending vein

3. Cardiac: Pulmonary veins insert directly into the coronary sinus and RA

4. Mixed: Combination of other types

EPIDEMIOLOGY

• 1–2% of congenital heart defects; male > female

• Most common supracardiac > infracardiac > cardiac > mixed

PATHOPHYSIOLOGY

• Because pulmonary venous return enters systemic venous circulation, mixing through an ASD or a patent foramen ovale must occur for survival

• Right atrial, ventricular, and pulmonary artery dilation are common due to volume overload

• If pulmonary venous obstruction exists (common with infracardiac TAPVR), pulmonary congestion and pulmonary hypertension develop. In this case, neonates will be profoundly cyanotic and show signs of respiratory distress immediately after birth

• If there is no pulmonary venous obstruction and the ASD is not restrictive, then oxygen saturations above 90% are common. These patients are still at risk for right heart failure

CLINICAL MANIFESTATIONS

• If pulmonary venous obstruction exists, patients present at 24–48 hours of life with cyanosis, tachypnea, and tachycardia

• If pulmonary venous obstruction does not exist, patients present with mild cyanosis, failure to thrive, dyspnea, and/or CHF

• With pulmonary venous obstruction: Single, loud S₂; gallop; faint or no murmur

• Without pulmonary venous obstruction: Increased right ventricular impulse; S₂ widely split and fixed; 2/6–3/6 systolic ejection murmur at left upper sternal border; middiastolic rumble at LLSB

DIAGNOSTICS

• CXR: If pulmonary venous obstruction exists, pulmonary edema is seen. If pulmonary venous obstruction does not exist, cardiomegaly is seen

• ECG: RV hypertrophy

• Echocardiography: Large RV, compressed LV, ASD, or patent foramen ovale

• MRI: May be used to confirm diagnosis and help define anatomy

• Cardiac catheterization and angiography: Helps define anatomy, ratio of pulmonary to systemic flow, and degree of pulmonary hypertension

MANAGEMENT

• Supplemental oxygen

• PGE₁ may decrease venous obstruction in infracardiac TAPVR by maintaining patency of the ductus venosus. However, PGE₁ carries a risk of worsening pulmonary congestion by increasing left to right shunt through a PDA

• In obstructive type of TAPVR, emergent surgery will relieve pulmonary venous obstruction. In the absence of obstruction, surgery is generally recommended in infancy

• Goal of surgery is to redirect/connect pulmonary venous return to the LA

TRANSPOSITION OF THE GREAT ARTERIES

A form of cyanotic CHD whereby the aorta arises from the morphological RV and the pulmonary artery arises from the morphological LV.

• The most common form is dextra-transposition of the great arteries (d-TGA) in which the aorta is anterior and to the right of the pulmonary artery

• Associated abnormalities include VSD, pulmonary stenosis, and coarctation of the aorta

EPIDEMIOLOGY

• 5% of CHD; male:female = 3:1

PATHOPHYSIOLOGY

• TGA results in two parallel circuits such that deoxygenated blood is carried by the aorta to the body, while oxygenated blood is carried by the pulmonary artery to the lungs

• To sustain life, mixing must occur through an associated PDA, VSD, or ASD, with the best mixing occurring at the level of the ASD

• If untreated, TGA is usually fatal in the neonatal period

CLINICAL MANIFESTATIONS

• Cyanosis immediately after birth is typical in TGA with intact ventricular septum

• On exam: Often, no murmur is appreciated; murmur of VSD may be noted; single, loud S₂

DIAGNOSTICS

• Hyperoxia Test: 100% oxygen is administered via oxyhood for 10 minutes. If PaO₂ increases above 100 mm Hg, parenchymal lung disease is suspected, whereas a PaO₂ less than 50 indicates cyanotic heart disease

• CXR: Mild cardiomegaly, “egg-on-a-string” appearance of cardiac silhouette, pulmonary vascular congestion

• ECG: Right axis deviation, RV hypertrophy

• Echocardiography: Confirms anatomy and associated defects; helps estimate degree of mixing

• Cardiac catheterization: Angiogram may be used to define coronary anatomy; may be accompanied by balloon atrial septostomy as initial palliative procedure for adequate mixing

MANAGEMENT

Medical

• PGE₁: Maintains patency of the ductus arteriosus in order to augment mixing

• Oxygen

Surgical

• Balloon Atrial Septostomy (Rashkind Procedure): Increases interatrial mixing and indicated in the presence of cyanosis and a restrictive ASD

• Arterial Switch Operation (ASO): Restores LV as the systemic pump

• Atrial Switch Operation (Mustard or Senning technique): Risk of late RV failure and arrhythmias and rarely used in the current era

TRICUSPID ATRESIA

A form of cyanotic CHD in which there is no outlet from the RA to the RV and the RV is hypoplastic. The entire systemic blood flow enters the LA via a patent foramen ovale or an ASD.

EPIDEMIOLOGY

• 1% of congenital heart defects

PATHOPHYSIOLOGY

A VSD is usually present. The pathophysiology in tricuspid atresia depends on whether the great arteries are normally related or transposed, and whether there is any obstruction to pulmonary or systemic blood flow.

CLINICAL MANIFESTATIONS

• In the presence of pulmonary atresia or severe pulmonary stenosis, presentation is within 24–48 hours

• Most patients present by 2 months of age with cyanosis and tachypnea

• Occasionally, patients with TGA develop pulmonary overcirculation and present with CHF

• Rarely, older patients present with cyanosis, dyspnea on exertion, polycythemia, and easy fatigability

• On exam: May have holosystolic murmur at left sternal border or ejection systolic murmur at left upper sternal border; single S₂; increased LV impulse

DIAGNOSTICS

• CXR: May see pulmonary undercirculation or overcirculation

• ECG: Left axis deviation, RA enlargement, LV hypertrophy

• Echocardiography: Usually sufficient to delineate anatomic features

MANAGEMENT

Medical

• PGE₁ in severely cyanotic infants (e.g., pulmonary atresia or severe pulmonic stenosis and subpulmonic stenosis) maintains patency of ductus arteriosus and promotes pulmonary blood flow

• Treatment of CHF may be necessary in patients with high pulmonary flow

Surgical

• If pulmonary blood flow is diminished, initial palliative procedures may include balloon atrial septostomy, Blalock–Taussig shunt, or surgical septectomy

• If pulmonary blood flow is increased, pulmonary arterial banding may be beneficial

• Ultimate goal is staged palliation to Fontan completion

TRUNCUS ARTERIOSUS

A form of cyanotic CHD in which a single arterial trunk arising from the heart supplies the coronary, pulmonary, and systemic, circulations.

• One semilunar valve with two to seven septal leaflets, which may be stenotic or regurgitant

• Large VSD

EPIDEMIOLOGY

• 1–3% of congenital heart defects

• May be associated with 22q11 microdeletion/DiGeorge syndrome

PATHOPHYSIOLOGY

• Because blood leaves the heart through a single trunk, complete mixing occurs and cyanosis may be minimal

• Degree of arterial SaO₂ depends on the ratio of SVR to PVR

• As PVR decreases postnatally, pulmonary blood flow increases and heart failure often develops

• Associated anomalies may include truncal stenosis, truncal insufficiency, and interrupted aortic arch

CLINICAL MANIFESTATIONS

• Usually present with mild cyanosis, and tachypnea in the first month of life

• Neonates with truncus and interrupted aortic arch present within the first 24–48 hours when the ductus arteriosus constricts

• Features of 22q11 microdeletion/DiGeorge syndrome

• On physical exam: Bounding pulses; systolic ejection click; single S₂; harsh systolic murmur; diastolic decrescendo murmur if truncal insufficiency

DIAGNOSTICS

• CXR: Cardiomegaly, boot-shaped heart, pulmonary congestion, possible right aortic arch

• ECG: LV hypertrophy, RV hypertrophy

• Echocardiography: Usually sufficient to delineate anatomy

MANAGEMENT

• Prostaglandin for truncus with interrupted aortic arch

• Surgery is recommended in the neonatal period

Surgical

• Patch closure of the VSD, placement of a conduit from the RV to the pulmonary arteries after separating them from the truncus

• In the past, surgical banding of pulmonary arteries was used to limit pulmonary overcirculation; this strategy is no longer used due to the high incidence of pulmonary hypertension

VENTRICULAR SEPTAL DEFECT

A form of acyanotic CHD characterized by an opening in the ventricular septum in one of four locations:

1. Perimembranous or conoventricular: Defect involving the membranous septum beneath the aortic valve; 70% of VSDs

2. Muscular (trabecular): Defect within the muscular septum between the LV and RV; often involves multiple, small defects which may be difficult to repair surgically; 5–20% of VSDs

3. Outlet (supracristal, subpulmonary, malalignment, conoseptal hypoplasia, subarterial): Defect beneath the pulmonic valve which communicates with the RV outflow tract; 5–7% of VSDs

4. Inlet or canal type: Located posteriorly and inferiorly to perimembranous VSDs; 5–8% of VSDs; often associated with endocardial cushion defects

EPIDEMIOLOGY

• Two to six per 1000 live births; 25% of CHD

• Most common form of CHD

PATHOPHYSIOLOGY

• Small defects (restrictive) are not usually hemodynamically significant

• Large defects (unrestrictive) allow significant left-to-right shunting as the PVR declines, causing pulmonary overcirculation, and heart failure

• Large, unrepaired defects can lead to pulmonary vascular obstructive disease and Eisenmenger’s syndrome

• Complications include pulmonary vascular obstructive disease, RV outflow tract obstruction, aortic regurgitation, and endocarditis

CLINICAL MANIFESTATIONS

• May be asymptomatic and present with a murmur

• Symptomatic VSDs often present at 4–6 weeks of age as PVR decreases and may present with dyspnea, poor growth, feeding difficulties, sweating, fatigue

• VSDs are often silent in the newborn period while PVR is similar to SVR

• Physical exam findings vary depending on size and location of the VSD as well as the degree of PVR and may include loud, harsh, blowing holosystolic murmur at LLSB; palpable thrill at LLSB with parasternal lift and apical thrust; S₃ and a middiastolic rumble may be present. Small defects may be associated with loud murmurs

DIAGNOSTICS

• CXR: May be normal or may reveal cardiomegaly and increased pulmonary vasculature

• ECG: May be normal or may reveal evidence of LV hypertrophy, LA hypertrophy, and biventricular hypertrophy

• Echocardiography: Reveals the size and location of the VSD

• Cardiac catheterization: Rarely indicated in the current era

MANAGEMENT

Medical

• Small VSDs are often well tolerated

• Approximately 70% of VSDs close spontaneously. Small, muscular defects are most likely to close spontaneously

• If signs of heart failure, consider diuretics, ACE inhibitors, or digoxin

Surgical

• Indications for surgery include uncontrolled heart failure, development of aortic regurgitation, RV outflow tract obstruction

• Surgical closure with a Dacron or Gortex patch

• Pulmonary arterial palliative banding is usually reserved for complicated cases and premature infants

SURGERIES FOR CONGENITAL HEART DISEASE

ARTERIAL SWITCH OPERATION (OF JATENE)

• Indication: Transposition of the great arteries (TGA)

• Definition: The coronary arteries are reimplanted into the pulmonary artery (neoaorta). The pulmonary artery and aorta are transected above the sinus of Valsalva, the pulmonary artery is usually brought in front of the neo-aorta (Lecompte maneuver), and reattached

BLALOCK–TAUSSIG SHUNT

• Indication: Tetralogy of Fallot, tricuspid atresia, pulmonary atresia

• Definition: Direct anastomosis of the subclavian artery to the ipsilateral pulmonary artery, thereby creating a systemic to pulmonary shunt

BLALOCK–TAUSSIG SHUNT, MODIFIED

• Indication: Tetralogy of Fallot, tricuspid atresia, pulmonary atresia

• Definition: A Gortex graft connects the subclavian artery to the ipsilateral pulmonary artery, thereby creating a systemic to pulmonary shunt

NORWOOD PROCEDURE OR STAGE I

• Indication: Usually first stage for single ventricle heart disease (e.g., HLHS and variants)

• Reconstruction of the hypoplastic ascending aorta and the aortic arch using the main pulmonary artery and homograft patch, placement of a Blalock–Taussig shunt or shunt from RV to the pulmonary artery (Sano modification), and removal of the atrial septum

BIDIRECTIONAL GLENN SHUNT OR HEMI-FONTAN (4–6 MONTHS)

• Indication: Usually second stage for single ventricle heart disease (e.g., tricuspid atresia, HLHS)

• Definition: Direct connection of the superior vena cava to undivided right pulmonary artery, allowing blood flow to both lungs

FONTAN PROCEDURE (2–4 YEARS)

• Indication: Usually third stage for single ventricle heart disease

• Definition: Connection of the inferior vena cava to the right pulmonary artery. Modifications include lateral tunnel and extracardiac conduit with or without fenestration

MUSTARD AND SENNING PROCEDURE

• Indication: Transposition of the great arteries (TGA)

• Definition: Use of native atrial or prosthetic baffles to divert pulmonary venous blood to the RV and systemic venous blood to the LV

PULMONARY ARTERY BANDING

• Indication: Single ventricle heart disease with increased pulmonary blood flow, complicated VSD

• Definition: Constriction of the pulmonary artery to reduce pulmonary blood flow

ROSS PROCEDURE

• Indication: Aortic stenosis, aortic regurgitation, or mixed aortic valve disease

• Definition: Replacement of diseased aortic valve and root with patient’s own pulmonary valve and root (autograft). A homograft is placed into the position of the pulmonary valve, and the coronary arteries are reimplanted into the autograft

HEART FAILURE

Heart failure occurs when oxygen delivery by the heart is impaired secondary to an inability of the heart to fill or eject blood.

ETIOLOGY

• Congenital cardiac causes of heart failure (symptoms generally arise from excessive blood flow to the lungs in left to right shunting lesions): Atrioventricular septal defect, coarctation of the aorta, critical aortic or pulmonary stenosis, PDA, TGA, tricuspid atresia, HLHS, truncus arteriosus, VSD, and TAPVR

• Acquired cardiac causes of heart failure: Arrhythmias, Kawasaki disease, viral myocarditis, rheumatic heart disease, metabolic disorder, muscular dystrophy, chemotherapy (e.g., doxorubicin), idiopathic dilated cardiomyopathy, hypertrophic cardiomyopathy, restrictive cardiomyopathy (RCM)

• Noncardiac causes of heart failure: Acute hypertension, anemia, hyper- and hypothyroidism, obstructive sleep apnea

CLINICAL MANIFESTATIONS

• Infants: Failure to thrive, increased work of breathing, feeding difficulties, excessive perspiration

• Children and adolescents: Shortness of breath, reduced exercise tolerance, peripheral edema, cough, orthopnea

• On exam: Hepatomegaly, rales, tachypnea, tachycardia, gallop rhythm

DIAGNOSTICS

• CXR: Helps assess degree of cardiomegaly and pulmonary edema

• ECG: May demonstrate increased voltages, abnormal ST segments, T-wave inversions, Q-waves, and/or rhythm disturbances. The ECG is rarely normal in advanced cardiomyopathy or heart failure

• Echocardiography: Helps define congenital heart defects, ventricular size, ventricular function, shortening fraction, ejection fraction, and evidence of diastolic dysfunction

MANAGEMENT

• General measures: Treatment of precipitating factors such as fluid overload, fever, anemia, infection, hypertension, and arrhythmias

• Diuretics:

  • ✓ Loop diuretics (e.g., furosemide) are considered first-line therapy for heart failure. Electrolyte abnormalities (e.g., hypokalemia, hypochloremia) are common

  • ✓ Thiazide diuretics (e.g., chlorothiazide, hydrochlorothiazide) work at the distal tubule and are often used to complement loop diuretics

  • ✓ Spironolactone is potassium sparing and is often used in combination with loop or thiazide diuretics

• Digoxin increases cardiac contractility; toxicities include bradycardia, heart block, and ventricular arrhythmias

• Afterload Reducing Agents:

  • ✓ Reduction in afterload results in increased stroke volume and improved cardiac output

  • ✓ ACE Inhibitors (e.g., captopril, enalapril): Reduce PVR by blocking the conversion of angiotensin I to angiotensin II. ACE inhibitors are also thought to have a positive effect on myocardial remodeling

  • ✓ Intravenous afterload reducing agents such as milrinone, nitroprusside, and hydralazine are usually reserved for intensive care unit (ICU) patients with decompensated heart failure and low cardiac output

• Intravenous Inotropic Agents: Dopamine, dobutamine, and milrinone are generally reserved for ICU patients with decompensated HF and evidence of life-threatening low cardiac output

Cardiomyopathies are broadly defined as diseases of the heart muscle.

The common cardiomyopathies encountered in childhood are dilated cardiomyopathy, hypertrophic cardiomyopathy, left ventricular noncompaction (LVNC), and RCM.

DILATED CARDIOMYOPATHY

EPIDEMIOLOGY

• The most common cardiomyopathy of childhood, characterized by an enlarged (dilated) ventricle with depressed ventricular function. The incidence is 0.6–0.7 per 100,000 children

ETIOLOGY

• Multiple etiologies including cytoskeletal protein abnormalities, metabolic diseases, myocarditis, endocrinopathies, though most cases are idiopathic

CLINICAL MANIFESTATIONS

• Often leads to heart failure and need for heart transplantation. Transplant-free survival only about 50% at 5 years in pediatric dilated cardiomyopathy patients

MANAGEMENT

• Medical treatment often includes inhibition of the renin-angiotensin-aldosterone system (e.g., ACE-inhibitors, angiotensin receptor blockers, and aldosterone antagonists), beta-adrenergic receptor blockade, diuretics, and digoxin

• Device therapy may include implantable cardioverter-defibrillators with or without the ability to perform cardiac resynchronization therapy (CRT), and ventricular assist devices (VADs)

HYPERTROPHIC CARDIOMYOPATHY

EPIDEMIOLOGY

• The second most common cardiomyopathy diagnosed in childhood, characterized by a thickened (hypertrophied) non-dilated LV, with the observed hypertrophy not occurring secondary to another disease (e.g., aortic valve stenosis)

ETIOLOGY

• Most cases caused by a mutation of genes encoding for sarcomeric proteins. However, other etiologies including glycogen storage diseases, Noonan’s syndrome, and mitochondrial diseases can also lead to the hypertrophic cardiomyopathy phenotype

CLINICAL MANIFESTATIONS

• LV outflow tract obstruction can occur from subaortic hypertrophy and systolic anterior motion of the mitral valve

• The most common disease leading to sudden death with athletics in the United States

• Symptoms can include chest pain, palpitations, arrhythmias, and heart failure. However, many patients are asymptomatic

OTHER CARDIOMYOPATHIES

EPIDEMIOLOGY

• Left ventricular noncompaction

  • ✓ Increasingly recognized cardiomyopathy characterized by prominent trabeculations in the LV giving a characteristic “spongy” appearance to the myocardium

  • ✓ True incidence and prevalence of LV noncompaction is unknown and may be associated with other disorders such as Barth’s syndrome, chromosomal abnormalities, and mitochondrial disorders

• Restrictive cardiomyopathy

  • ✓ Least common cardiomyopathy encountered in childhood with an estimated incidence of 0.03–0.04 per 100,000 children

CLINICAL MANIFESTATIONS

• Left ventricular noncompaction

  • ✓ Wide variability in disease ranging from coexisting with complex CHD, associated with a dilated or hypertrophied ventricle, to normal LV size and function

  • ✓ Prognosis is variable but arrhythmias, dilation, hypertrophy, and dysfunction portend a worse prognosis

• Restrictive cardiomyopathy

  • ✓ Characterized by a severe abnormality in the diastolic functioning of the myocardium. The systolic function is usually preserved

  • ✓ Poor prognosis with most children not surviving 2–3 years after the diagnosis. There is a high risk of sudden death, pulmonary hypertension, and thromboembolism

MANAGEMENT

• Restrictive cardiomyopathy

  • ✓ No known effective medical therapies; heart transplantation is often recommended in newly diagnosed patients

Myocarditis is inflammation of the myocardium with myocellular necrosis.

EPIDEMIOLOGY

• Typically sporadic, but occasionally epidemic

• Infants usually have more acute and fulminant course

• Has been implicated in sudden infant death syndrome

ETIOLOGY

• Viral is most common (e.g., parvovirus, coxsackievirus, adenovirus)

• Other infectious agents: Bacterial, fungal, parasitic, Borrelia burgdorferi

• Trypanosoma cruzi (Chagas disease) and Clostridium diphtheriae are common outside the United States

• Collagen vascular disease

• Immune mediated: Kawasaki disease, rheumatic fever

• Toxin induced (e.g., cocaine)

• Giant cell myocarditis: Rare, but often severe and fatal

PATHOPHYSIOLOGY

• Involves damage to the myocardium from the initial infection, as well as the subsequent immune response

• May result in dilated cardiomyopathy

CLINICAL MANIFESTATIONS

• Often preceded by a flu-like illness

• May present with new onset CHF or arrhythmias

• Dyspnea, exercise intolerance, fevers

• May be acute and fulminant or chronic

• On exam: Fever, tachycardia, tachypnea, gallop, signs of CHF, murmur of mitral insufficiency

DIAGNOSTICS

• CXR: Cardiomegaly +/− pulmonary edema

• ECG: Tachycardia, low QRS voltages, ST/T-wave changes, arrhythmias

• Echocardiography: Enlarged chambers, impaired LV function, mitral regurgitation

• Laboratory studies: ESR, CRP, cardiac enzymes, serum viral titers

• Endomyocardial biopsy: Gold standard for diagnosis. Viral polymerase chain reaction (PCR) on biopsy sample is more sensitive than serum PCR

• MRI: Increasingly utilized for the diagnosis. Can demonstrate myocardial inflammation and quantitative function

MANAGEMENT

Medical

• Heart Failure: Afterload reduction and diuretics. Inotropic agents should be used with caution as the damaged myocardium is more sensitive to arrhythmias and reserved for patients with poor perfusion

• Immunosuppression may be appropriate depending on etiology: IVIG (2 g/kg) and occasionally corticosteroids

• Outcome: Approximately one-third of patients recover, one-third have residual dysfunction, and one-third develop chronic heart failure requiring transplant

Surgical

• Transplant may be necessary

• LVAD (left ventricular assist device) and ECMO (extracorporeal membrane oxygenation) may be used as a bridge to recovery or transplant

Pericarditis is defined as inflammation of the pericardium.

EPIDEMIOLOGY

• Infectious type is more common in younger children

• Incidence slightly higher in males

ETIOLOGY

• Viral: Echovirus and coxsackie B most common

• Bacterial, including Mycoplasma tuberculosis

• Collagen vascular: Rheumatoid arthritis, systemic lupus erythematosus

• Uremia

• Neoplastic or radiation induced

• Drug induced (e.g., procainamide, hydralazine)

• Post-pericardiotomy syndrome: Seen in about 10% of children 1–4 weeks after cardiac surgery

PATHOPHYSIOLOGY

• Deposits of infectious material or an inflammatory infiltrate results in an immune response and leads to changes in pericardial membrane function

• A pericardial effusion may result if altered hydrostatic and/or oncotic pressure leads to fluid accumulation

• Tamponade: An increase in intrapericardial pressure results in restriction of ventricular filling and a decrease in cardiac output

• Constrictive pericarditis is the late result of earlier pericarditis and is characterized by a thick, fibrotic, calcified pericardium

• Post-pericardiotomy syndrome: A nonspecific hypersensitivity reaction after manipulation of the pericardial space

CLINICAL MANIFESTATIONS

• Fever, dyspnea

• Chest pain often radiates to the back or left shoulder, is worse with lying down, and is alleviated by leaning forward

• On exam: Fever, tachypnea, tachycardia, friction rub, muffled heart sounds (if an effusion is present)

• With tamponade, may have signs of CHF, pulsus paradoxus (exaggerated decrease in systolic BP by greater than 10 mm Hg with inspiration), or Kussmaul’s sign (paradoxical rise in jugular venous pressure during inspiration)

DIAGNOSTICS

• CXR: Cardiomegaly with “water bottle” appearance if effusion present

• ECG: Tachycardia, diffuse ST elevation, T-wave inversion; may see electrical alternans if effusion present (variation of QRS axis with each beat due to movement of the heart within the pericardial fluid)

• Echocardiogram: With effusion, will see fluid in the pericardial space. In tamponade: RV collapse in early diastole, atrial collapse in end-diastole and early systole

MANAGEMENT

• Viral: Usually self-limited. Treatment includes rest, analgesia, anti-inflammatory medications

• Bacterial: Open drainage and aggressive antibiotic therapy

• Collagen vascular: Steroids and salicylates often used

• Post-pericardiotomy: Rest, nonsteroidal anti-inflammatory agents

• Constrictive pericarditis: Pericardial stripping

• Pericardiocentesis: Indications include hemodynamic compromise, bacterial pericarditis, and as a diagnostic aid; send pericardial fluid for cell count, culture, and cytology; complications can include arrhythmias and hemopericardium

Infection/inflammation of the cardiac endothelium with associated immunologic response.

EPIDEMIOLOGY

• Incidence is increasing due to IV drug use, survivors of cardiac surgery, patients taking immunosuppressants, and chronic IV catheters

• More common with CHD associated with a steep pressure gradient: PDA, restrictive VSD, left-sided valvular disease, systemic-pulmonary communications

ETIOLOGY

• Common organisms: Streptococcus viridans group (about 50%); Staphylococcus aureus (about 30%)

• Other organisms: For example, fungal, HACEK group (Haemophilus spp., Actinobacillus actino-mycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella spp.)

• Common associations: CHD: S. aureus; dental procedures: S. viridans group; bowel/GU surgery: group D Strep; IV drug use: Pseudomonas spp., Serratia spp.; cardiac surgery: Candida spp.

PATHOPHYSIOLOGY

• Turbulent blood flow damages the endothelium

• Damaged site serves as nidus for adherence of bacteria

• Platelets and fibrin form a vegetation that may embolize

• Immune response produces systemic symptoms

CLINICAL MANIFESTATIONS

• Fevers, chills, night sweats, dyspnea, arthralgias, central nervous system manifestations, chest/abdominal pain

• On exam: Tachycardia; new or changing murmur; splenomegaly; manifestations of heart failure; Roth spots (pale retinal lesions surrounded by hemorrhage); Janeway lesions (flat, painless, on palms and soles); Osler nodes (painful nodes on pads of fingers and toes)

DIAGNOSTICS

• Blood cultures drawn from two separate sites

• Elevated erythrocyte sedimentation rate and C-reactive protein

• Leukocytosis, anemia, hypogammaglobulinemia

• Hematuria may result from immune complex glomerulonephritis with hypocomplementemia and positive rheumatoid factor (10–70%)

• Echocardiography: Can detect vegetations greater than 2–3 mm; may detect valvular dysfunction; transesophageal echocardiography is more sensitive

Modified Duke Criteria

• Major criteria: Positive blood culture (typical microorganism from two different blood cultures; enterococcus without primary focus; positive serology for Q fever) or echocardiographic evidence

• Minor criteria: Predisposing condition, temperature greater than 38.0°C, vascular or immunologic phenomena on physical exam, laboratory studies suggestive of infection

• Definite endocarditis: Pathologic diagnosis, 2 major, 1 major and 3 minor, or 5 minor

• Possible endocarditis: 1 major and 1 minor or 3 minor

• Rejected: Alternate diagnosis accounts for symptoms, resolution of manifestations with ≤4 days of antibiotic therapy, or no pathologic evidence at surgery

MANAGEMENT

Empiric therapies based on American Heart Association guidelines (therapy may be tailored based on susceptibilities):

• S. viridans group: Penicillin G for 4–6 weeks

• S. aureus: Nafcillin for 6–8 weeks

• HACEK group: Third generation cephalosporin for 4 weeks

• Culture-negative: Ceftriaxone and gentamycin (add nafcillin or vancomycin if high level of suspicion for staphylococcal endocarditis) for 4–6 weeks

• Fungal: Amphotericin B; surgery often indicated

• Indications for surgery: Intracardiac abscess, severe valvular regurgitation, recurrent embolic disease, heart failure, infected prosthetic material

• Outcome: Most relapses occur in 1–8 weeks after therapy; mortality is 20–25% with antibiotics; serious morbidity (e.g., heart failure, systemic, or pulmonary emboli) in 50–60% of patients

ENDOCARDITIS PROPHYLAXIS

Adapted from Prevention of Infective Endocarditis : Guidelines from the American Heart Association: A Guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation. 2007;116(15):1736–1754.

Infective endocarditis prophylaxis for dental procedures is reasonable only for patients with underlying cardiac conditions associated with the highest risk of adverse outcome from infective endocarditis from dental procedures. The administration of prophylactic antibiotics solely to prevent endocarditis is no longer recommended for patients who undergo GU or GI tract procedures, including diagnostic esophagogastroduodenoscopy or colonoscopy.

High-Risk Patients

• Prosthetic cardiac valve or prosthetic material used for cardiac valve repair

• Previous infectious endocarditis

• Cardiac transplantation recipients with cardiac valvular disease

• Congenital heart disease only in the following categories:

  • ✓ Unrepaired cyanotic CHD, including palliative shunts and conduits

  • ✓ Completely repaired congenital heart defect with prosthetic material or device, whether placed by surgery or by catheter intervention, during the first 6 months after the procedure

  • ✓ Repaired CHD with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device (which inhibit endothelialization)

PROPHYLAXIS RECOMMENDATIONS

Dental and Oral Procedures

• Regimen: Single dose 30–60 minutes before procedure

• Oral: Amoxicillin 50 mg/kg (children) or 2 g (adult)

• Cephalexin, clindamycin, or azithromycin are acceptable alternatives for penicillin allergic patients

PRECORDIAL LEAD PLACEMENT

V1: 4th intercostal space (ICS) ICS, right sternal border (RSB)

V2: 4th ICS, LSB

V3: Equidistant between V2 and V4

V4: 5th ICS, left MCL

V5: Horizontal to V4, left AAL

V6: Horizontal to V4, left MAL

V3R, V4R, V5R, V6R: Mirror image to V3, V4, V5, and V6 on the right side of the chest.

Note: ICS, intercostal space; RSB, right sternal border; LSB, left sternal border; MCL, midclavicular line; AAL, anterior axillary line; MAL, midaxillary line; MCL, midclavicular line

RATE

• On a standard ECG, paper moves at 25 mm/sec

• Each small square is 1 mm (0.04 seconds) and each large square is 5 mm (0.2 seconds) (Figure 5-1)

• Heart rate can be estimated by counting the number of large boxes between QRS intervals where 1 box = 300 bpm, 2 boxes = 150 bpm, 3 boxes = 100 bpm, 4 boxes = 75 bpm, 5 boxes = 60 bpm, and 6 boxes = 50 bpm

RHYTHM

• The cardiac rhythm may be determined by examining the rhythm strip that appears at the bottom of a standard 12-lead ECG

AXIS

• The QRS axis represents the net direction of electrical activity during ventricular systole (Figure 5-2 and Table 5-1)

P-WAVE

• Represents sinus node depolarization (Figure 5-1)

• Best seen in leads II and V₁

• In children, P-wave is normally less than 2.5 mm tall and 0.10 seconds in duration

• Tall P-waves may represent right atrial enlargement whereas wide P-waves may represent LA enlargement

PR INTERVAL

• From beginning of P-wave to beginning of QRS complex

• Refer to Table 5-2 for PR Interval Norms

QRS COMPLEX

• Represents ventricular depolarization (see Table 5-2)

QT INTERVAL

• Measured from beginning of QRS complex to end of T-wave

• QT interval varies with heart rate and is corrected by Bazett’s formula as follows:

• QT_c greater than 0.44 seconds may be abnormal (see “Long QT syndrome”)

ST SEGMENT

• Segment between the end of the QRS complex and beginning of the T-wave

• Displacement by more than 1–2 mm from the isoelectric line may represent myocardial injury, pericarditis, or a repolarization abnormality

T-WAVE

• Represents ventricular repolarization

• Normally upright in leads I and II and inverted in aVR

• Abnormalities may represent ischemia or electrolyte abnormalities

LEFT VENTRICULAR HYPERTROPHY, ECG SIGNS

• Left axis deviation (Table 5-3)

• R-wave in I, II, III, aVL, V5, or V6 greater than upper limit of normal

• S-wave in V1 or V2 greater than upper limit of normal

• Signs of volume overload: Q-wave in V5 and V6 5 mm or greater and tall, symmetric T-waves

• Signs of strain: Inverted T-waves in leads I or aVF, V5–V6

RIGHT VENTRICULAR HYPERTROPHY, ECG SIGNS

• Right axis deviation

• R-wave in V1, V2, or aVR greater than upper limit of normal

• S-wave in I or V6 greater than upper limit of normal

• Q-wave in V1

• Signs of strain: T axis outside normal range (0 to −90 degrees), inverted in V1

ATRIAL FIBRILLATION

An ectopic atrial foci leads to an extremely fast atrial rate (350–600bpm). The ventricular response is usually fast (greater than 100 bpm) and “irregularly irregular.” The fast, disorganized ventricular response may lead to decreased cardiac output. Atrial fibrillation is much more common in adults than in children.

ETIOLOGY

• Structural heart disease, dilated atria, myocarditis, digitalis toxicity, cardiac surgery

MANAGEMENT

• For sustained atrial fibrillation (>48 hours), consider anticoagulation with warfarin or heparin and echocardiogram to look for thrombus

• Digoxin with or without beta-blockers may control the ventricular rate

• Termination of atrial fibrillation may be achieved through direct current cardioversion (especially in unstable patients) or with antiarrhythmic medications (e.g., amiodarone)

ATRIAL FLUTTER

An intra-atrial reentrant circuit leads to a rapid atrial rate around 300bpm with a characteristic sawtooth pattern on ECG. Because the ventricles cannot respond at 300bpm, there is often 2:1, 3:1, or 4:1 block.

ETIOLOGY

• Structural heart disease, myocarditis, digitalis toxicity, cardiac surgery, dilated atria with mitral insufficiency

MANAGEMENT

• To prevent thromboembolism, consider anticoagulation with warfarin or heparin before cardioversion

• Vagal maneuvers or adenosine may produce a temporary slowing of the heart rate, but do not terminate the rhythm

• Procainamide or amiodarone may terminate the rhythm

• Digoxin slows the ventricular rate by increasing the AV block

• Direct current cardioversion often restores normal sinus rhythm

ATRIOVENTRICULAR BLOCK

AV block (“heart block”) occurs when conduction through the atrioventricular node is impaired.

FIRST-DEGREE AV BLOCK

• Definition: Indicates that the PR interval is above the upper limit of normal for age

• Etiology: Rheumatic fever, cardiomyopathy, ASD, Ebstein’s anomaly, infectious diseases, ischemic heart disease, hyperkalemia, digitalis toxicity, other medications

• Management: Generally asymptomatic and does not require treatment

SECOND-DEGREE AV BLOCK, MOBITZ TYPE I (WENCKEBACH)

• Definition: Progressive lengthening of PR interval with eventual dropped beat

• Etiology: Myocarditis, cardiomyopathy, myocardial infarction, congenital heart defect, cardiac surgery, digitalis toxicity, other medications

• Management: Usually does not progress and does not require treatment

SECOND-DEGREE AV BLOCK, MOBITZ TYPE II

• Definition: Normal PR intervals are followed by episodes of heart block (i.e., P-wave is not conducted to the ventricles)

• Etiology: Myocarditis, cardiomyopathy, myocardial infarction, congenital heart defect, cardiac surgery, digitalis toxicity, other medications

• Management: May progress to complete heart block; may require pacemaker

THIRD-DEGREE AV BLOCK

• Definition: Complete dissociation of atrial and ventricular activity (i.e., no relationship between P-wave and QRS complex)

• Etiology: Isolated anomaly, maternal SLE, Sjögren syndrome, congenital heart defect, cardiac surgery, myocarditis, endocarditis, Lyme carditis, acute rheumatic fever, cardiomyopathy, myocardial infarction, certain drug overdoses

• Management: Patients are often unstable and may require transcutaneous pacing, atropine, or isoproterenol. A transvenous or permanent pacemaker is often required

LONG QT SYNDROME

A cardiac repolarization abnormality characterized by prolongation of the QT interval, which can result in torsades de pointes and sudden cardiac death.

• Corrected QT interval is calculated by Bazett’s formula (see above)

ETIOLOGY

Hereditary Causes of Long QT Syndrome

• Jervell–Lange-Nielsen Syndrome: Autosomal recessive, congenital deafness

• Romano–Ward Syndrome: Autosomal dominant transmission, normal hearing

• Sporadic mutations in potassium and sodium channels

Acquired Causes of a Prolonged QT Interval

• Electrolyte Abnormalities: Hypokalemia, hypomagnesemia, hypocalcemia

• Drugs: Antiarrhythmics, tricyclic antidepressants, erythromycin, antihistamines, phenothiazine, cocaine, organophosphates

• Other: Stroke, subarachnoid hemorrhage, myocardial ischemia, liquid protein diets

PATHOPHYSIOLOGY

• Lengthening of ventricular repolarization leads to R on T phenomena and precipitation of torsades de pointes

• Congenital long QT syndrome may result from a variety of mutations that affect transmembrane ion channels responsible for cardiac repolarization

CLINICAL MANIFESTATIONS

• Often presents with unexplained syncope or sudden cardiac death brought on by exercise or fright

• May present with presyncope, seizures, dizziness, and palpitations

DIAGNOSTICS

• Family History: Long QT syndrome or unexplained sudden cardiac death

• ECG: Increased QT_c, torsades de pointes, T-wave alternans, notched T-waves, low resting heart rate

• Corrected QT interval: QT_c greater than 440 msec is suspicious and QT_c greater than 460 msec is concerning

• Exercise Stress Test: Prolongation of QT_c seen with exercise

• 24 Holter Monitor: May demonstrate arrhythmia

MANAGEMENT

Short Term

• Immediate cardioversion of torsades de pointes

• Magnesium bolus and infusion

• Maintain high normal level of potassium

• Temporary cardiac pacing

• Withdrawal of offending drugs

• Correction of electrolyte abnormalities

• Isoproterenol in cases of acquired long QT

Long Term

• Beta-blockers

• Left thoracic sympathectomy

• Permanent pacemaker and cardioverter-defibrillator

• May have to avoid sports and stressful activities

PREMATURE ATRIAL CONTRACTION (PAC)

An atrial beat arising from an ectopic stimulus in the left or right atrium, which occurs before the next normal sinus beat is due.

• The P-wave has a different shape than the normal sinus P-wave

• If the PAC is conducted, the QRS complex is generally the same as the QRS complex of preceding beats

• Occasionally, the PAC is conducted aberrantly through the ventricles causing a wide QRS complex

• If the PAC reaches the AV node while it is still refractory, the PAC may not be conducted to the ventricles

ETIOLOGY

• PACs are very common in normal people and do not necessarily indicate the presence of disease

• Other causes: Emotional stress, hyperthyroidism, caffeine, structural heart disease, medications (epinephrine, theophylline)

MANAGEMENT

• Medical management generally not required if PACs are an isolated finding

PREMATURE VENTRICULAR CONTRACTION

A premature ventricular contraction (PVC) is a ventricular beat arising from an ectopic ventricular stimulus, which occurs before the next normal sinus beat is due.

• Wide QRS complex (greater than 0.08 seconds in infants, greater than 0.12 seconds in children)

• Two PVCs in a row are called a “couplet” or a “pair”

• Three PVCs in a row define ventricular tachycardia

• PVCs may be uniform indicating they arise from a single focus

• Multiform PVCs may arise from different foci or from the same focus and often signify underlying heart disease

• R on T Phenomenon: When PVCs occur during the T-wave of the preceding beat, they may precipitate ventricular tachycardia or ventricular fibrillation

ETIOLOGY

• PVCs often occur in normal hearts

• Other causes: Anxiety, caffeine, hypoxemia, sympathomimetics, myocardial infarction, electrolyte abnormalities, and structural heart disease

MANAGEMENT

• PVCs are often benign and usually do not require treatment

• Correction of underlying abnormalities (e.g., electrolyte abnormalities) may reduce the frequency of PVCs

• Medications such as beta-blockers or antiarrhythmics are occasionally considered

SUPRAVENTRICULAR TACHYCARDIA (SVT)

A reentrant supraventricular rhythm may occur when there are two conducting pathways, unidirectional block in one pathway, and slow conduction in the other pathway. SVT may also be due to an automatic atrial rhythm. The two most common forms of reentrant SVT are:

• Atrioventricular nodal reentry tachycardia: The AV node consists of a slow, posterior pathway and a fast, anterior pathway. Onset may be triggered by a premature atrial impulse, which reaches the AV node when the fast pathway is still refractory. The premature impulse conducts anterogradely through the slow pathway and then retrogradely through the fast pathway. Atrioventricular nodal reentry tachycardia is more common in teens and young adults

• Atrioventricular reentry tachycardia: An accessory pathway exists outside of the AV node. Anterograde conduction typically occurs via the AV node and retrograde conduction via the accessory pathway (orthodromic). This results in a normal QRS complex. Anterograde conduction occasionally occurs via the accessory pathway and retrograde conduction via the AV node (antidromic). This results in a wide QRS complex, which may be difficult to differentiate from ventricular tachycardia. Atrioventricular reentry tachycardia is common in Wolff–Parkinson–White (WPW) syndrome and is more common in infants and toddlers

CLINICAL MANIFESTATIONS

• Rapid, regular heart rate, usually 150–250 bpm

• Palpitations, syncope, near-syncope, lightheadedness, shortness of breath

DIAGNOSTICS

• Laboratory studies: Consider electrolytes

• CXR: May show infection, cardiomyopathy, pulmonary edema

• Echocardiogram: If structural heart defect suspected

• ECG during SVT: Heart rate 150–250 bpm, P-wave may be within or after QRS, typically narrow QRS, occasionally wide QRS

• ECG after termination of the SVT: May show a delta wave (upsloping QRS complex) in WPW syndrome

• Adenosine: May terminate the arrhythmia

MANAGEMENT

Short Term

• If unstable, direct current cardioversion: (0.5 J/kg increased in steps to 2 J/kg)

• Vagal maneuvers: Ice to face, Valsalva, carotid sinus massage

• Adenosine by rapid IV push (initial dose 0.1 mg/kg [max 6 mg], increase by 0.05 mg/kg if unsuccessful to maximum of 0.35 mg/kg or 12 mg)

• Calcium channel blockers (avoid in infants less than 1 year old), class IC agents, digoxin (controversial), and amiodarone may also be effective

Long Term

• Antiarrhythmic drug therapy: Propranolol, verapamil, amiodarone, procainamide, quinidine, flecainide, digoxin

• Radiofrequency catheter ablation is often successful in ablating the accessory pathway

• No treatment is sometimes an acceptable alternative

• Digoxin and calcium channel blockers are contraindicated in WPW syndrome

SYNCOPE

Syncope is transient loss of consciousness and postural tone due to inadequate cerebral perfusion.

EPIDEMIOLOGY

• 15% of children and adolescents between ages 8 and 18 experience syncope

• Unusual under age 6 except in the setting of seizure disorders, breath-holding, and cardiac abnormalities

ETIOLOGY

• Neurocardiogenic syncope (vasodepressor, vasovagal):

  • ✓ Most common type of syncope; may be provoked by increased vagal tone during micturition, defecation, cough, or hair brushing; may be provoked by peripheral vasodilation during “fight or flight” response, warm temperature, anxiety, or blood drawing

  • ✓ Decreased cardiac filling leads to increased cardiac contractility and activation of stretch receptors. A reflex increase in vagal tone further compromises cardiac output, resulting in syncope

• Cardiac syncope:

  • ✓ Dysrhythmias may include SVT, ventricular tachycardia (VT), heart block, WPW, long QT syndrome

  • ✓ Outflow tract obstruction: Hypertrophic obstructive cardiomyopathy (HOCM), pulmonary hypertension

  • ✓ Inflow obstruction: Restrictive cardiomyopathy, effusion

  • ✓ May be accompanied by brief seizure (Stokes–Adams syndrome)

• Neuropsychiatric syncope: Seizures, migraines, hypoglycemia, “hysterical” syncope, hyperventilation (e.g., panic attack)

CLINICAL MANIFESTATIONS

• Symptoms of “presyncope” may include diaphoresis, lightheadedness, palpitations, and tunnel vision

• Cardiac symptoms may include palpitations, shortness of breath, chest pain, and color changes

• Family history may be notable for sudden death, arrhythmias, CHD, seizures, metabolic disorders, and psychiatric history

• Significant physical exam findings are uncommon in children

• Vital signs may demonstrate orthostasis

• Systolic ejection murmur that increases with Valsalva or standing is concerning for HOCM

• Loud second heart sound may indicate pulmonary hypertension

DIAGNOSTICS

• ECG recommended regardless of cardiac symptoms

• If concern for seizure activity or trauma: Neurology referral, EEG, head CT

• If concern for cardiac disease: ECG, CXR, echocardiogram, exercise stress test, Holter monitor

• Tilt table testing may help diagnose neurocardiogenic syncope

MANAGEMENT

Acute Management

• Keep patient supine until fully recovered

• For an arrhythmia, consider pharmacologic treatment, defibrillation, or cardioversion as per Pediatric Advanced Life Support protocols

Cardiac Syncope

• Congenital heart disease present: Treat underlying cause

• Arrhythmia present: May need internal defibrillator, medication, radiofrequency ablation in catheterization laboratory (e.g., WPW syndrome)

• Exercise stress test and electrophysiologic testing in catheterization laboratory may aid in diagnosis

Neurocardiogenic Syncope

• Volume expansion: Encourage fluid and salt intake

• Mineralocorticoids (e.g., Florinef) increase circulating volume and help maintain cerebral perfusion pressure. Efficacy is approximately 60–80%

• Beta-blockers modify the abnormal feedback loop and prevent increased vagal output

VENTRICULAR FIBRILLATION

An uncoordinated, chaotic ventricular rhythm with QRS complexes of varying size and shape. Ventricular fibrillation is a pulseless rhythm without effective cardiac output and is terminal unless an effective ventricular beat is restored.

ETIOLOGY

• Hyperkalemia, severe hypoxia, surgery, myocarditis, myocardial infarction

• Drugs and toxins: Digitalis, quinidine, catecholamines, anesthetics

MANAGEMENT

• CPR, airway, oxygen, IV or IO access

• Defibrillate up to three times (2 J/kg, 4 J/kg, 4 J/kg) and then with 4 J/kg 30–60 seconds after each medication

• Epinephrine (first dose: 0.1 mL/kg of 1:10,000 IV/IO or 0.1 mL/kg of 1:1000 via ETT; subsequent doses 0.1 mL/kg of 1:1000 IV/IO/ETT)

• Amiodarone (5 mg/kg IV/IO)

• Lidocaine (1 mg/kg IV/IO)

VENTRICULAR TACHYCARDIA

Ventricular tachycardia (VT) is defined as at least three premature ventricular beats in a row at a rate above 120bpm (varies by age) characterized by wide QRS complexes.

• Sustained VT lasts longer than 30 seconds

ETIOLOGY

• Cardiomyopathy, myocarditis, cardiac surgery, electrolyte abnormalities, drugs and toxins, long QT syndrome, anomalous left coronary artery

MANAGEMENT

Ventricular Tachycardia with Pulses

• Early cardiology consultation is recommended

• The following medications may be considered: amiodarone (5 mg/kg IV over 20–60 minutes), procainamide (15 mg/kg over 30–60 minutes), or lidocaine (1 mg/kg over 2–4 minutes)

• If signs of shock are present, immediate synchronized cardioversion is indicated (0.5–1 J/kg initially, up to 2 J/kg)

• Magnesium (25 mg/kg over 10–20 minutes) is indicated if torsades de pointes is suspected

Pulseless Ventricular Tachycardia

• CPR, airway, oxygen, IV or IO access

• Defibrillate up to three times (2 J/kg, 4 J/kg, 4 J/kg) and then with 4 J/kg 30–60 seconds after each medication

• Epinephrine (first dose: 0.1 mL/kg of 1:10,000 IV/IO or 0.1 mL/kg of 1:1000 via ETT; subsequent doses 0.1 mL/kg of 1:1000 IV/IO/ETT)

• Amiodarone (5 mg/kg IV/IO)

• Lidocaine (1 mg/kg IV/IO)

• Magnesium (25 mg/kg over 10–20 minutes) is indicated if torsades de pointes is suspected

WOLFF–PARKINSON–WHITE SYNDROME (WPW)

A form of ventricular pre-excitation in which an accessory pathway bypasses the AV node leading to a variety of supraventricular tachyarrhythmias.

EPIDEMIOLOGY

• Affects 0.1–3% of general population

• Occasionally inherited in an autosomal dominant pattern

• May be associated with Ebstein anomaly or corrected transposition

PATHOPHYSIOLOGY

• Atrial impulses bypass the AV node through the accessory pathway causing pre-excitation

• Paroxysmal SVT in WPW usually results from antegrade conduction through the AV node and retrograde conduction through the accessory pathway (orthodromic)

• Paroxysmal SVT may result from antegrade conduction through the accessory pathway and retrograde conduction through the AV node (antidromic). In this case, the QRS complex is wide and the rhythm may be difficult to distinguish from VT

• Patients are also at risk for atrial fibrillation, atrial flutter, and ventricular fibrillation (rare)

CLINICAL MANIFESTATIONS

• Palpitations, dizziness, syncope, chest discomfort, shortness of breath

DIAGNOSIS

• Family History: WPW, SVT, sudden cardiac death, unexplained early death (e.g., car accidents, drownings)

• ECG: Shortening of the PR interval, widening of the QRS complex, slurred upstroke of the QRS complex (delta wave)

MANAGEMENT

• Vagal maneuvers such as ice to face, Valsalva, carotid sinus massage (hemodynamically stable patients)

• Adenosine: Initial drug of choice (initial dose: 0.1 mg/kg IV; maximum 6 mg)

• Other potential agents: Calcium channel antagonists, beta-blockers, digoxin, procainamide; however, caution should be used with digoxin and calcium channel blockers, which may increase the ventricular rate during atrial fibrillation and can lead to ventricular fibrillation

• Radiofrequency catheter ablation is the treatment of choice in symptomatic and high-risk patients