Chapter 19: II. Congenital Heart Disease

Chapter 19. II. Congenital Heart Disease

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Which of the following statements about ventricular septal defects (VSDs) is false?

A. The most common type of VSD is perimembranous.

B. Left-to-right shunting through a VSD causes a volume load on the right ventricle.

C. A patient with a large VSD may be asymptomatic at birth, but eventually develop congestive heart failure due to a drop in pulmonary vascular resistance.

D. In the presence of a perimembranous VSD, the bundle of His passes along the posterior and inferior rim of the defect, generally on the left ventricular side.

B. Left-to-right shunting through a VSD causes a volume load on the right ventricle. Ventricular septal defects are classified by their location in the ventricular septum. The most common type is perimembranous. Left-to-right shunting through a VSD causes a volume load on the left ventricle as blood returns from the lungs. The right ventricle does not experience a volume load, but is pressure loaded. Certainly, as PVR decreases after birth, congestive heart failure may develop in a previously asymptomatic patient with a large VSD as left-to-right shunting increases. Knowledge of the expected location of the conduction system is paramount in the surgical repair of a VSD. The AV node is an atrial structure that lies at the apex of an anatomic triangle (known as the triangle of Koch) formed by the coronary sinus, the tendon of Todaro, and the septal attachment of the tricuspid valve. The node then gives rise to the bundle of His, which penetrates the AV junction beneath the membranous septum. The bundle of His then bifurcates into right and left bundle branches, which pass along either side of the muscular ventricular septum. In the presence of a perimembranous VSD, the bundle of His passes along the posterior and inferior rim of the defect, generally on the left ventricular side. The bundle of His tends to run along the posterior and inferior margin of inlet VSDs as well. The conduction tissue is usually remote from outlet and trabecular VSDs.

Which of the following infants would benefit most from the initiation of PGE₁?

A. Neonate with prenatal diagnosis of aortic coarctation who develops acidosis, oliguria, and diminished pedal pulses 8 hours after birth.

B. Two-day-old neonate with prenatal diagnosis of complete atrioventricular canal with O₂ saturation of 80% and poor systemic perfusion.

C. Six-week-old infant presenting with irritability, poor feeding, and tachypnea who is diagnosed with ALCAPA and no PDA is seen on echocardiogram.

D. One-week-old infant with double aortic arch presenting with increasing respiratory distress.

A. Neonate with prenatal diagnosis of aortic coarctation who develops acidosis, oliguria, and diminished pedal pulses 8 hours after birth. In scenario A, the neonate described has inadequate systemic perfusion as demonstrated by oliguria and acidosis. With a prenatal diagnosis of aortic coarctation, one must be suspicious at 8 hours after birth that ductal closure has caused a critical narrowing of the aortic isthmus as it involutes. This patient will benefit by reopening the ductus arteriosus with PGE1. The patient described in option B is likely experiencing pulmonary overcirculation with congestive heart failure. Initiating PGE1 would be expected to exacerbate this problem. In option C, a 6-week-old child’s ductus would not be expected to reopen with prostaglandins. Also, the etiology of the heart failure symptoms described is due to myocardial ischemia and surgical correction of the coronary anomaly is required. PGE is not appropriate. In option D, the vascular ring described is likely causing a mechanical airway obstruction. Again, surgical intervention is required. PGE therapy has no role in this situation.

A newborn with d-transposition of the great arteries (d-TGA) remains severely cyanotic despite initiation of PGE₁ to maintain ductal patency. What is the recommended next step in management?

A. Initiate inhaled nitric oxide therapy

B. Diuresis with furosemide IV

C. Balloon atrial septostomy

D. Emergent arterial switch operation

C. Balloon atrial septostomy. d-transposition of the great arteries typically requires two or more levels of mixing in order to maintain adequate saturations. This may involve mixing at the atrial level (via an ASD), ventricular level (via a VSD), or at the level of the great arteries (via a PDA). In the situation described, the infant requires an additional level of mixing. This may be due to the absence of additional (intracardiac) shunts, or they may be too small if present. Emergent balloon atrial septostomy in the catheterization laboratory is indicated. The other options are not appropriate at this time.

What is the most common major coronary anomaly?

A. Left coronary from the pulmonary artery (ALCAPA)

B. Left anterior descending from the right coronary artery

C. Coronary AV fistula

D. Single coronary

C. Coronary AV fistula. Coronary AV fistula is the most common major coronary anomaly. The second most common is ALCAPA.

In which of the following diagnoses is a primary catheter-based approach most likely to be recommended over surgery?

A. Isolated aortic coarctation in a neonate

B. Isolated pulmonary stenosis in a neonate

C. PDA in a 1-kg premature infant with heart failure symptoms

D. Symptomatic perimembranous VSD in a 6-month-old infant

B. Isolated pulmonary stenosis in a neonate. Isolated aortic coarctation in a neonate is well managed with a primary extended end-to-end anastomosis and is almost always primarily approached surgically. Isolated pulmonary stenosis is typically primarily treated with balloon pulmonary valvuloplasty. This approach has been highly successful. The patient in option C is best managed with a trial of Indocin, followed by bedside surgical ligation if the ductus fails to close with medical management. Larger patients with PDAs requiring closure are frequently treated with catheter-based closure with excellent results. Perimembranous VSDs are best closed surgically. Device closure of VSDs in this location is associated with prohibitively high rates of complete heart block along with the risk of impairing the function of the aortic and/or tricuspid valve.

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Chapter 19: II. Congenital Heart Disease

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Chapter 19. II. Congenital Heart Disease

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