Which CHD will lead to a left-to-right shunt, generally with cyanosis?
Correct Answer: Total anomalous pulmonary venous connection
Description: 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 propeies 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 the anomalous connection of the right inferior pulmonary vein to the right atrium. In the case of anomalous origin of the left coronary aery from the pulmonary aery, as pulmonary vascular resistance declines immediately after bih, perfusion of the left coronary aery 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 aery. In the absence of pulmonary hypeension, blood will flow from the aoa to the pulmonary aery throughout the cardiac cycle, resulting in a "continuous" 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. Ref - Harrison's principles of internal medicine 20e 1838 , pubmed.com
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