Posts: 3,675,934
Threads: 734,342
Joined:
Sep 2021
Reputation:
5
Which of the following congenital cardiac disorders
will lead to a left-to-right shunt, generally with cyanosis?
A. Anomalous origin of the left coronary artery from
the pulmonary trunk
B. Patent ductus arteriosus without pulmonary hypertension
C. Total anomalous pulmonary venous connection
D. Ventricular septal defect
E. Sinus venosus atrial septal defect
Posts: 3,675,934
Threads: 734,342
Joined:
Sep 2021
Reputation:
5
The answer is C. Left-to-right shunts occur in all
types of atrial and ventricular septal defects but generally do not result in cyanosis,
whereas large right-to-left shunts frequently do. The magnitude of the shunt depends on
the size of the defect, the diastolic properties of both ventricles, and the relative impedance
of the pulmonary and systemic circulations. Defects of the sinus venosus type occur
high in the atrial septum near the entry of the superior vena cava or lower near the orifice
of the inferior vena cava and may be associated with anomalous connection of the
right inferior pulmonary vein to the right atrium. In the case of anomalous origin of the
left coronary artery from the pulmonary artery, as pulmonary vascular resistance declines
immediately after birth, perfusion of the left coronary artery from the pulmonary
trunk ceases and the direction of flow in the anomalous vessel reverses. Twenty percent
of patients with this defect can survive to adulthood because of myocardial blood supply
flowing totally through the right coronary artery. In the absence of pulmonary hypertension
blood will flow from the aorta to the pulmonary artery throughout the cardiac cycle,
resulting in a œcontinuous murmur at the left sternal border. In total anomalous
pulmonary venous connection all the venous blood returns to the right atrium; therefore,
an interatrial communication is required and right-to-left shunts with cyanosis are
common.
