Epicardial and endocardial dispersion of ventricular repolarization. A study of monophasic action potential mapping in healthy pigs

OBJECTIVES: To investigate the total dispersion of ventricular repolarization of the epi- and endocardium. DESIGN: Monophasic action potentials (MAP) were recorded from 211+/-54 (151-353) left and right ventricular epi- and endocardial sites during atrial pacing in 10 pigs using the CARTO system. The activation time (AT), MAP duration (MAPd) and end of repolarization time (EOR) were measured. RESULTS: The total dispersion of AT, EOR and MAPd, defined as the maximal differences of these parameters over both the epi- and endocardium, were 57+/-10, 84+/-20, and 75+/-21 ms respectively and were significantly larger than the respective epi- and endocardial dispersions (p<0.05). The epicardial dispersion of AT, EOR and MAPd of both the right and left ventricles were significantly larger than that of each ventricle alone (p<0.02). Sternotomy did not affect these dispersion parameters. CONCLUSION: Detailed mapping of epicardial repolarization in vivo using the MAP mapping technique is feasible. Both the epi- and endocardium of the two ventricles contribute significantly to the total dispersion of repolarization.