Epicardial repolarization mapping in man

A simple method was developed for recording epicardial monophasicaction potentials intraoperatively in man. Potentials were recordedrapidly and reliably from multiple epicardial sites using ahand-held probe. The feasibility of repolarization mapping wasassessed in 30 patients. It was possible to record technicallyadequate signals from most left ventricular and posterior rightventricular sites (success rates 72% and 61%, respectively),but it was more difficult to achieve satisfactory recordingsover the free wall of the right ventricle (success rate 36%).The onset of cardiopulmonary bypass resulted in a transientrise in action potential duration of approximately 30–40ms in the first minutes of bypass. An approximate steady statewas achieved thereafter. Reproducibility of the method was assessedby mapping a small number of sites repeatedly. The 95% confidencelimits for an estimate of repolarization time, based on a singlepotential, were ±21 ms. With 4 probe applications ateach site, the confidence limits of the estimated site meanwere reduced to ±8 ms. Based on this approach, statisticallysignificant differences between sites were demonstrated in 9of 10 patients, confirming that the method is sensitive enoughto provide information on regional differences in repolarization. Intraoperative epicardial repolarization mapping has been shownto be a practical possibility. The technique holds promise asa means of assessing the role of dispersion of repolarizationin arrhythmogenesis in man.