Chapter 21. Congenital Heart Disease
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 will 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.
The correct answer is 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 prostaglandin E1 (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 oxygen saturation of 80% and poor systemic perfusion.
C. Six-week-old infant presenting with irritability, poor feeding, and tachypnea who is diagnosed with anomalous left coronary artery arising from the pulmonary artery (ALCAPA) and ...