NORMAL CARDIAC ANATOMY (SEE FIGURE 34-1)
PATENT DUCTUS ARTERIOSUS (PDA) (SEE FIGURE 34-2)
Patent ductus arteriosus.
Occurrence: The ductus arteriosus is a normal part of fetal circulation. It is a vessel that connects the aorta to the pulmonary artery. Closure of the ductus usually occurs within the first 12 to 24 hours of life as a result of the increase in arterial oxygen tension and decrease in pulmonary vascular resistance. When the ductus closes, it becomes fibrous, forming the ligamentum arteriosus.
In neonates with ductal-dependent cyanotic heart lesions, prostaglandin will be administered to maintain the patent ductus arteriosus (PDA) until palliation or corrective surgery can be accomplished. In utero, the placenta was a major source of prostaglandin. In neonates with cyanotic lesions or premature infants with lung immaturity or disease, the ductus may remain patent due to the lack of a rise or delayed rise in arterial oxygen tension or due to scarring of the duct from rubella during fetal life.
Preoperative symptoms: If the ductus remains patent after birth, blood will flow from the aorta to the pulmonary artery due to decreased pulmonary vascular resistance. This left-to-right shunting will cause pulmonary overcirculation. Patients may present with congestive heart failure due to pulmonary overcirculation and left heart enlargement. Pulses will be noted to be bounding in older infants and demonstrate a widened pulse pressure as a result of a decrease in diastolic blood pressure and ventricular hypertrophy. Patients may present with tachypnea, poor feeding, and diaphoresis. Symptoms are directly proportional to the hemodynamics of the PDA.
Operative repair: If the PDA remains open and detected in the first two weeks of life, treatment options may include a prostaglandin synthetase inhibitor. After the first two weeks it may be surgically corrected by ligation or division and oversewing. It may also be closed with coil occlusion in the cardiac catheterization lab if the PDA is of the right size and configuration.
Postoperative considerations: Complications of coil occlusions in small patients include increased risk of embolization and pulmonary artery occlusion with the device, so surgical closure is preferred. Postoperative complications for surgical repair include chylous effusion and recurrent laryngeal nerve damage.
ATRIAL SEPTAL DEFECTS (SEE FIGURE 34-3)
Occurrence: An atrial septal defect (ASD) is an abnormal opening in the atrial septum. In the fourth to sixth week of gestation the common atrium is divided into two chambers. The ...