Anatomy and physiology. In the most extreme cases of PA/IVS with RVDCC, the TV is extremely small (Z score -3 to -5) and the RV may be extremely diminutive (often walnut-like). There is at least one fistulous connection between the diminutive RV and the coronary circulation, most commonly the anterior descending and right coronary arteries. There may be focal stenoses (or rarely aortocoronary atresia) such that coronary perfusion is dependent upon RV filling and contractility. In these cases, even minor changes in RV preload (e.g. from diuresis, hypotension, dilation of the ASD, and prototypically the institution of CPB) or frank RV decompression (e.g. PV balloon valvuloplasty) can lead to coronary ischemia, manifest as ST-segment changes, increased troponin, heart block, ventricular ectopy, or even cardiac arrest. In these situations, ECMO or CPB rescue may be ineffective (particularly so in the case of bilateral coronary ostial atresia) since coronary perfusion is more or less derived not from the aorta but from the right ventricular cavity. In these patients, primary transplantation may be necessary. More commonly (and favorably), there are fistulous connections between the RV cavity and coronary arteries but the proximal coronaries are also patent and there is no coronary stenosis, such that coronary perfusion to certain regions may be dual supply, occurring both antegrade (from the aorta) and from the RV. In these cases, coronary perfusion is more stable, and coronary fistulae may regress over time.Management. The management strategy of these patients depends on the precise coronary anatomy, typically determined by coronary angiography. The degree of RV-dependence is determined based on the relative coronary blood flow from RV versus aorta, as well as the presence of focal stenoses or atresia of the coronary arteries, though the degree of RV-dependence is in some cases not definitive. When the circulation is judged to be ‘RV-dependent’, then RV decompression (by dilation of the PV) is contraindicated and the goal of the initial palliation is to provide a stable source of PBF without decompressing RV. In the modern era, this can take place through ductal stenting or BT shunt placement (without CPB). In most cases, patients are palliated down the single ventricle pathway (BDG followed by Fontan), although in some cases the coronary fistulae regress such that the RV can be effectively decompressed and recruited into the circulation. Such patients may be taken to a 1.5 ventricle circulation (SVC to BDG, IVC return to RV –> PA).
Post-intervention considerations. Following initial palliation (e.g. ductal stenting), attention must be paid to ensuring RV preload. Vasodilation (e.g. fevers, milrinone) or excessive diuresis may decrease RV filling and cause coronary insufficiency. Vigilant monitoring for coronary ischemia (12 lead EKG, telemetry for ventricular ectopy, troponin when concerned) permits the titration of RV preload to meet coronary demand. Venoconstrictors and volume administration (to augment preload), beta-blockade and mechanical ventilation (to decrease myocardial work) may be useful when coronary insufficiency is present.