Subepicardial transmembrane potentials were recorded from intact pig hearts to observe the changes induced by acute ischemia. Ischemia shortened action potential duration, and decreased its amplitude, upstroke velocity, and resting potential. The cells were unresponsive after 12 to 15 minutes of coronary artery occlusion, yet near normal action potentials could be restored by flushing the occluded artery with saline as late as 40 minutes after occlusion. The unipolar extracellular electrogram reflected unresponsiveness by a monophasic potential. Local refractory periods initially shortened by up to 100 msec. Later, postrepolarization refractoriness occurred and refractory periods lengthened often in excess of basic cycle length, thus resulting in 2:1 responses. The onset of early ventricular arrhythmias often coincided with a period of alternation and 2:1 responses, especially when these got out of phase in different regions. Reperfusion frequently led to ventricular fibrillation, and was associated with marked inhomogeneity in cellular responses. Re-entry within ischemic myocardium was the most likely mechanism for arrhythmias.

Long-term complications of the right ventricular outflow tract were the main reason for reoperation. Mid-term survival and functional improvement after reoperation are excellent.

Most patients with VT late after repair of TOF have outflow tract aneurysms or pulmonary regurgitation, or both. These patients have a greater frequency of ventricular ectopic beats than arrhythmia-free patients after repair of TOF. A combined approach of correcting significant structural abnormalities (pulmonary valve replacement or right ventricular aneurysmectomy, or both) with intraoperative electrophysiologic-guided ablation may reduce the potential risk of deterioration in ventricular function and enable arrhythmia management to be optimized.

In adults with CHD, acute and long-term outcomes of RFCA for IART are similar to those reported for younger cohorts. Complex atrial surgery limits the success of RFCA, and older age is associated with a higher risk of IART recurrence.