Reversal of fenestration flow during ventricular systole in Fontan patients in junctional or ventricular paced rhythm

Sinus node dysfunction is relatively common in patients with Fontan palliation for single ventricle congenital heart disease, and such patients often are in junctional rhythm or may have pacemaker systems for bradycardia. Because the physiologic determinants of left atrial pressure play a major role in determining pulmonary blood flow and therefore cardiac output in Fontan patients, the loss of atrioventricular (AV) synchrony in junctional rhythm or demand ventricular pacing in these patients might be expected to influence cardiac output. We report two cases of Fontan patients with the absence of AV synchrony that resulted in reversal of flow through the Fontan fenestration during ventricular systole. In both cases, restoration of AV synchrony by atrial pacing resulted in the elimination of retrograde fenestration flow, increased cardiac output, and improved clinical status.