Discussion

Incidence of anomalous left coronary artery connection to pulmonary artery is 1 in 300,000 of live births or 0.5% of all congenital heart diseases.^{Reference Heifetz, Robinowitz and Muller2} Rarely, this condition can be associated with ventricular septal defect, patent ductus arteriosus, coarctation aorta, truncus arteriosus, or tetralogy of fallot.^{Reference Vlodaver, Neufeld and Edwards3} Very few single-stage successful surgically treated cases of this association have been reported.^{Reference Bitar, Kveselis and Smith4–Reference Morell, Feccia and Cullen8} Unlike previous reported cases, which were from neonate to 8 years, our patient is 9 years of age, the oldest reported case till now.

Only 10% cases of anomalous left coronary artery connection to pulmonary artery survive infancy because of modest left coronary perfusion either antegrade or by intercoronary collaterals through circle of Vieussens from right coronary artery. When tetralogy is associated with this anomalous left coronary artery connection, clinical presentation depends on adequacy of left coronary and lung perfusion. The supply demand mismatch of right ventricle in tetralogy due to severe hypertrophy causing subendocardial ischemia is aggravated by coronary steal here. Not only left ventricle is compromised, onset of right ventricle dysfunction and failure is aggravated. When associated with tetralogy of fallot, clinical presentation depends on intercoronary collaterals, severity of pulmonary stenosis, and coronary artery dominance.^{Reference Kurup, Daniel and Kumar9} The intercoronary collaterals develop gradually from the right coronary system to provide a decent left coronary perfusion retrogradely and contribute a good amount to lung perfusion by drainage through the anomalous left coronary ostium into the pulmonary trunk. In our case, the rich intercoronary collaterals from the dominant right coronary artery allowed adequate left coronary perfusion along with underloaded left ventricle to maintain good left ventricular function and delayed the clinical presentation. Even though pulmonary stenosis was severe, significant intercoronary collaterals and few aortopulmonary collaterals provided near adequate pulmonary perfusion to delay the clinical manifestation. Pre- or intraoperative pulmonary arterial oxygen saturation measurement could give an idea of left-to-right shunt fraction even though it was not measured in this case. If the right coronary artery is dominant, it helps to maintain adequate left coronary and pulmonary artery perfusion, thereby delaying the clinical presentation. The right coronary artery, which is commonly hypertrophied in tetralogy of fallot, is exaggerated here because of increased distal runoff to both left coronary and pulmonary artery through collaterals to maintain adequate perfusion.

Misdiagnosis of anomalous connection of left coronary artery from pulmonary artery with the coronary to pulmonary artery fistula by transthoracic echocardiogram is possible. Poor lateral resolution of left coronary sinus to visualise left coronary origin, difficult visualisation of pulmonary origin, retrograde flow in left coronary artery, and intraseptal collaterals leads to a possible misdiagnosis of coronary artery to pulmonary artery fistula. Computerised tomographic angiogram is of immense use in such complex case, by providing excellent resolution of images, post-processing ability, and three-dimensional reconstruction for clear delineation of anatomy. Undoubtedly, two coronary system establishment is the treatment of choice, as left ventricle has to cope with the increase in work post-intracardiac repair of tetralogy of fallot. As the left coronary artery anatomy was suitable, direct translocation to ascending aorta was done. As it was possible to relieve the right ventricular outflow tract obstruction and also to reconstruct it without the division of the giant collateral, it was preserved in this case. But, one should not compromise on the completeness of repair of right ventricular outflow tract obstruction to preserve an intercoronary collateral. The incidence of late coronary stenosis following button technique varies from 5 to 8%, so by not dividing the collateral, there exists a theoretical advantage of maintaining the collateral circulation.^{Reference Agnoletti, Bajolle and Bonnet10}

To conclude, the association of anomalous left coronary artery from pulmonary artery with tetralogy of fallot is very rare, so high index of suspicion is needed for accurate preoperative diagnosis and proper plan to execute successful single-stage.