CHAPTER 5: Cardiology

CONGENITAL HEART DISEASE

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:...