I read with interest the two articles on pulmonary atresia and intact ventricular septum by Laks H, et al (Ann.Thorac.Surg. 1995;59:342-347) and Waldman JD, et al (Ann.Thorac. Surg.1995;59:933-941) concerning management of important right ventricle to coronary artery connections.
In this complex congenital anomaly, choice of operation is determined by right ventricular volume, size of the tricuspid annulus (TA) and presence of coronary artery abnormalities. After initial palliation in neonates by a systemic to pulmonary shunt, the choice of the next procedure is controversial. Presently, if it is felt that a significant amount of left ventricular myocardium will be placed at risk by decompressing the right ventricle (RV), all treatment protocols lead to a Fontan type univentricular repair.
It has not yet been possible to identify a group of patients in the neonatal period who have RV and TA that are too small to ever provide all the necessary pulmonary blood flow. In the Boston Children's Hospital experience (1), even when RV volumes were below 8 ml/sq.m. and tricuspid annulus size was less than 9 mm., a two ventricle repair was ultimately possible. Data from de Leval and coworkers (2) show survival after a two ventricle repair when TV diameters were larger than 3 standard deviations below normal (Z value greater than -3). However, the Congenital Heart Surgeons Society (CHSS) multicenter study has shown that so far no patient with TA diameter more than 4 standard deviations below normal has progressed to a two ventricle correction (1).
In very small right ventricles with hypoplastic tricuspid valves, TA diameter does not increase as the patient grows unless the RV is decompressed.
Decompression of the small RV unfortunately is contraindicated by the presence of a right ventricle dependent coronary circulation. If there is no native coronary artery narrowing, blood flows into the RV in diastole (`coronary steal') causing ischemia. If the proximal coronary artery is stenotic, on the other hand, antegrade perfusion from the RV will be reduced by lowering RV pressures. In the Boston Children's Hospital analysis (1), RV decompression is tolerated as long as not more than one major coronary artery is stenosed. However, the procedure is associated with increased LV dysfunction, and myocardial preservation is important for survival in these patients, especially in Fontan candidates.
Two approaches were discussed for this situation :
Both procedures seem somewhat nihilistic in that they condemn the RV to non-development, eventuating in a Fontan type repair only. In addition, the disadvantages of leaving behind a small but hypertrophied RV include arrhythmogenicity and interference with normal LV contractility (3).
In another rare congenital defect, anomalous origin of the left coronary artery from the pulmonary artery, a somewhat similar situation obtains. Initially the LV is perfused with deoxygenated blood from the pulmonary artery. Once intercoronary collaterals are formed, diversion of blood into the low resistance pulmonary circuit may result in LV ischemia. The resultant LV myocardial dysfunction has been reversed by grafting the internal thoracic artery (ITA) to the anomalous LCA in infancy (4).
Conceptually, I think it might be possible to anastomose ITAs to the abnormal coronary arteries in PA with IVS too. Grafts can be connected distal to the site of obstruction if any. The RV to coronary connections can then be dealt with just as any other coronary to RV fistula. The options include surgical (ligation, tangential arterriorhaphy or closure from within RV) or transcatheter closure.
At one stroke this approach would then obviate all limitations imposed by the abnormal coronary circulation and allow further decision regarding surgical management to be made based on the status of the RV and TA, and their predicted growth potentials.
If the RV enlarges sufficiently, a two ventricle repair can be performed. If not, a one and half ventricle repair (bidirectional cavopulmonary shunt with RV to PA connection) may be feasible and give better long term outcomes than a Fontan operation. If all else fails, the performance of a Fontan type procedure would not be precluded, and in fact may be more successfully performed because the LV is no longer ischemic.
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