Author response

We read the comments of Prof S. S. Kothari regarding the article, “Dilemma in the management of disconnected pulmonary arteries with double arterial ducts”.[1] The contention was unifocalisation of an isolated pulmonary artery with low pulmonary vascular resistance to the other hypertensive pulmonary artery would always result in a favorable outcome as the mean resistance in the pulmonary circuit after the surgery would always be lower than the resistance in the lung with hypertensive vasculature. In the article quoted where an ascending aortic origin of right pulmonary artery with a stenotic lumen protected the right lung vasculature, the left lung was hypertensive.[2] Surgical repair was uneventful with modest reduction of vascular resistance from 31 Wood units to 20 wood units, though the pulmonary artery pressures remained very high.

We agree that the mean resistance following the surgery would always be less than the preoperative vascular resistance in the hypertensive lung. However in cases of very severely elevated (but unrecognized) vascular resistance in the affected lung, a postoperative redistribution of majority of the pulmonary blood flow to the protected lung might result in significant unilateral hyperperfusion lung injury. Management of this pulmonary hyperperfusion in the lung with low vascular resistance would be difficult in acute postoperative setting as drugs such as endothelin receptor antagonist or phosphodiesterase-5 inhibitor might lead to mismatch of ventilation and perfusion with nonspecific fall in the vascular resistance on the same side that was already affected with hyperperfusion injury.

In addition, it is recognized that the larger right lung contributes to marginally more alveolar segments than the anatomically smaller left lung in most patients with levocardia. If the anatomically larger right lung is protected compared to a hypertensive left lung, the postoperative outcome would be more favorable as the larger vascular bed of a right lung would accommodate the selectively redistributed lung flows. Whenever certain cyanotic malformations were associated with absence of left pulmonary artery, a single lung intracardiac repair perfusing the right lung was both feasible and uneventful as the larger right lung accommodated the entire systemic venous return. However in our patient, the larger right lung was hypertensive leaving the smaller left lung to accept the postoperative pulmonary flows. This was yet another reason, why we resorted to invasive hemodynamic assessment.