Circulation and Congenital Heart Disease

Dramatic cardiac changes occur in the perinatal period. In this section, we explain fetal and neonatal circulation, describe commonly encountered congenital heart diseases in the neonatal period, and depict immediate stabilization of neonates with cardiac issues. Please refer to Structural Heart Disease in the Pediatric Cardiology rotation guide for further discussion of pediatric cardiac defects.

Fetal and Neonatal Circulation

Oxygenation during fetal life occurs through the placenta. Therefore, fetal circulation provides blood flow to the brain and body, largely bypassing the lungs. Once the infant is born, the blood must travel to the lungs for oxygenation. The transition requires several fetal shunts to close relatively quickly after delivery. The clamping of the umbilical cord along with the neonate crying and decreasing pulmonary vascular resistance all assist in closing these shunts.

The fetal shunts include the foramen ovale, ductus venosus, and ductus arteriosus. The foramen ovale functionally closes during the first day of life as right and left atrial pressure equalize. The ductus arteriosus closes with increased oxygen exposure and declining concentrations of prostaglandin. Typically, in a full-term infant, the ductus arteriosus has functionally closed by 96 hours with anatomical closure occurring later as tissue proliferates. Closure of the ductus arteriosus is variable in premature infants.

Ultimately, the foramen ovale becomes the fossa ovalis, the ductus venosus becomes the ligamentum teres, and the ductus arteriosus becomes the ligamentum arteriosum.

Images of fetal and neonatal circulation can be found here.

Patent Ductus Arteriosus

In full-term infants, the ductus arteriosus functionally closes typically by 96 hours with increased oxygen exposure and decreased prostaglandin exposure. Preterm infants often have delayed closure of the ductus arteriosus or patency of the ductus arteriosus (PDA), which can cause hemodynamic instability and require medical or surgical closure. Despite extensive research and debate, no consensus exists about whether the ductus should or should not be closed in an asymptomatic infant.

A PDA presents as a loud, continuous, machinery-type murmur with increased oxygen requirement and work of breathing due to pulmonary over-circulation. A PDA can be associated with widened pulse pressure with low diastolic blood pressure and bounding pulses. Reduced effective perfusion can lead to reduced urine output and intolerance to feeds because of reduced mesenteric blood flow caused by “ductal steal.” A PDA is a risk factor for pulmonary hemorrhage. Treatment: The treatment of symptomatic PDA can be medical or surgical. Medical treatment involves the administration of indomethacin, ibuprofen, or acetaminophen. Both indomethacin and ibuprofen block prostaglandin synthesis and its action on the PDA, thereby promoting closure of the ductus. During administration of these medications, urine output, creatinine levels, and platelet counts should be monitored carefully. Once treatment is completed, a follow-up echocardiogram can determine the status of the ductus. Ibuprofen and indomethacin can reduce blood flow to the mesentery. Acetaminophen is another option for medical closure, but its mechanism of action is unclear, and it often requires longer duration of treatment. In contrast with ibuprofen and indomethacin, acetaminophen typically does not require withholding of feeds but does require monitoring of liver function. If medical management has been attempted and failed and the patient remains symptomatic, surgical treatment is usually indicated and involves a left thoracotomy in which the PDA is approached and clipped. A recent alternative to surgical closure is percutaneous transcatheter ductal closure. Device closure is becoming more common as compared to surgical PDA ligation.

Congenital Cyanotic Cardiac Lesions

Cyanotic cardiac lesions are named for the relative hypoxia induced in the neonate due to abnormal shunting of deoxygenated blood to the body and mixing of the deoxygenated and oxygenated blood at differing levels in the heart. We review the five main types of cyanotic heart lesions. A sixth type — hypoplastic left heart syndrome — is a complex disorder that is beyond the scope of this guide.

Abbreviations: ASD, atrial septal defect; VSD, ventricular septal defect; CHF, congestive heart failure; PDA, patent ductus arteriosus; AV, atrioventricular

Congenital Acyanotic Cardiac Lesions

Acyanotic cardiac lesions do not have the same type of mixing of deoxygenated and oxygenated blood as seen in cyanotic heart lesions. However, in some circumstances (e.g., atrioventricular canal), enough mixing may occur that cyanosis develops. These lesions do not require as urgent repair as some cyanotic heart lesions.

Acyanotic Cardiac Lesions

Abbreviations: ASD, atrial septal defect; VSD, ventricular septal defect; CHF, congestive heart failure; PDA, patent ductus arteriosus; AV, atrioventricular

Critical Congenital Heart Disease (CCHD) Screening

In 2011, the AAP published recommendations for universal CCHD screening to identify infants in the first 24 to 48 hours of life at risk for seven main CCHD targets (hypoplastic left heart syndrome, pulmonary atresia, tetralogy of Fallot, total anomalous pulmonary venous return, transposition of the great arteries, tricuspid atresia, and truncus arteriosus) prior to hospital discharge. The goal of screening is early identification of infants who might otherwise present critically with lesions that require surgical intervention at a young age. A positive screen is not diagnostic but rather indicates the need for further evaluation including an electrocardiogram (ECG) and echocardiogram.

A pulse-oximetry probe is placed on the infant in a preductal (right hand) and post-ductal position (either foot) to determine if a differential of ≥4% exists between the two or if there is a saturation of <95% in either location, indicating need for further testing. Screens should be performed when infants are awake and alert and at >24 hours of life. See algorithm below.

(Source: Critical CHD Screening Methods. Division of Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention 2018.)