Discussion

Pulmonary atresia with intact ventricular septum is rare congenital heart disease with an estimated prevalence of 4.5/100.000 births.^{Reference Freedom, Yoo, Dyamenahalli, Freedom, Yoo, Mikailian and Williams1} The presence of coronary anomalies and the degree of right ventricular hypoplasia affect therapeutic management and prognosis.

The coronary anomalies are described in up to 75% of the patients, and more frequently in the presence of marked right ventricular hypoplasia (unipartite right ventricle).^{Reference Freedom, Yoo, Dyamenahalli, Freedom, Yoo, Mikailian and Williams1–Reference Calder, Peebles and Occleshaw3} They include: 1) myocardial sinusoids, connecting coronary capillaries to the right ventricular inter-trabeculated spaces; 2) ventriculo-arterial communications or fistulas, connecting coronary main trunks to inter-trabeculated spaces and sometimes associated with stenosis or interruptions of the coronaries; 3) the anomalous origin of the left or right coronary artery. Histologically, one-third of the patients has normal coronary artery walls; one-third shows thickening of the media and intima; the last third has very thickened walls with the destruction of the wall architecture resulting in stenosis or obstructions.^{Reference Calder and Sage2,Reference Calder, Peebles and Occleshaw3} Significant fistulas and/or coronary stenosis or atresia may result in a right ventricle-dependant coronary circulation, contra-indicating right ventricular decompression. Indeed, the sudden drop of right-ventricle pressure may reduce coronary blood flow and cause ischaemia.

When the right ventricle is tripartite with adequate tricuspid valve z-score, decompression of the right ventricle is considered after birth, usually by percutaneous radiofrequency perforation, in order to achieve a bi-ventricular circulation. Although coronary anomalies are less frequently associated with a well-developed right ventricle, imaging of the coronary perfusion remains highly recommended. Myocardial ischaemia may occur during initial management, as a result of misappraisal of those coronary anomalies.^{Reference Popoiu, Eicken, Genz, Schreiber and Hess6}

In the presence of a small, unipartite right ventricular cavity, right ventricle decompression is not an option and the child is oriented towards uni-ventricular palliation. Right ventriculography and aortic root opacification, are recommended in all such patients before initial surgery, to document the frequently associated coronary anomalies.^{Reference Calder and Sage2} Our clinical case reminds us that ischaemic events may happen during remote follow-up, even late after uneventful surgical completion.^{Reference Calder and Sage2,Reference Calder, Peebles and Occleshaw3} The natural history of the coronary lesions remains poorly described and understood, but it is possible that late ischaemic events relate either to the persistence of macroscopic fistulas, to evolving main coronary artery stenosis, or to distal anomalies of microvasculature, as suggested in our patient by the important collateral network.

In everyday practice, it remains difficult to investigate evolving coronary lesions and the risk of myocardial ischaemia in those children. No clear recommendations exist for follow-up and long-term treatment. The high incidence of coronary anomalies must encourage us to systematically perform selective coronarography and/or perfusion MRI before the Fontan operation, which was not performed in our patient. Events such as the appearance of tricuspid valve regurgitation, or right ventricular cavity thrombosis must be looked for as they may induce ischaemia in the right ventricle-dependant coronary circulation.^{Reference Freedom, Yoo, Dyamenahalli, Freedom, Yoo, Mikailian and Williams1}

Regular exercise testing and imaging, including MRI with perfusion myocardial sequences and stress cardiac MRI, must be considered in order to detect ventricular ischaemia, dysfunction, and arrhythmias. Anti-aggregant therapy, beta-blockade, and strenuous exercise avoidance seem reasonable in the presence of coronary lesions with ischaemic events but no scientific data exist to support this. Cardiac transplantation or implantable cardioverter-defibrillator (ICD) may be considered in case of respectively terminal heart failure or arrhythmic ventricular events.^{Reference Calder, Peebles and Occleshaw3}