[Atrial fibrillation in patients after aortocoronary bypass. Correlation with electrophysiologic properties evaluated intraoperatively].

An electrophysiologic study (EPS) has been performed before and after cardioplegia in 50 patients (pts) who underwent a coronary by-pass graft intervention (CBPG) in order to investigate the possible mechanism explaining the frequent episodes of paroxysmal atrial fibrillation (PAF) complicating the early follow-up and the possible role of the type of caval cannulation. Twenty-five pts underwent a separate caval cannulation and twenty-five only cannulation of the inferior vena cava. EPS has been performed before (34 degrees C) and after cardioplegia (37 degrees C). PAF complicated the 15 days early follow-up of 32% of the pts; 24% of the pts operated with 1 cannula and 40% of the operated with 2 cannulae respectively (N.S.). The pts with AF had an high percentage of splitting of the atrial signals during atrial premature stimulation (77% vs 5%, p less than 0.002) and a significant dispersion of the conduction times between high and low right atrium (36 +/- 21 vs vs 11 +/- 14 msec, p less than 0.002). In conclusion PAF has an high incidence in the early follow-up of CABG operation and occurs independently of the type of caval cannulation. The presence of a major dispersion of intra right atrial conduction together with an high incidence of fractionizing potentials already before cardioplegia in the pts with AF suggests that the atria with intrinsic conduction delays can be per se predisposed to develop atrial tachyarrhythmias during the early follow-up.