Global Repolarization Sequence of the Ventricular Endocardium: Monophasic Action Potential Mapping in Swine and Humans

The aim of this study was to evaluate the global sequence of repolarization over the ventricular endocardium. Disturbances in myocardial repolarization are associated with the genesis of arrhythmias. However, little is known about the global sequence of repolarization. Monophasic action potentials (MAPs) were recordedfrom 61 +/- 18 LV and/or RV sites in ten healthy pigs and from 43 +/- 15 LV or RV sites in eight patients using the CARTO system. Local activation time (AT), end-of-repolarization (EOR) time, and MAP duration were calculated and three-dimensional global maps of AT, EOR, and MAP duration constructed. LV maps were obtained from all ten pigs and RV maps from three pigs. Five RV maps and five LV maps were obtained from the eight patients. (1) EOR sequence was recognizable in 12 of 13 pig maps and in all the patient maps. (2) EOR followed the sequence of activation in 12 of 13 pig maps and 8 of 10 patient maps. (3) The longest MAPs were recorded in or near the earliest activation area, and the shortest ones in or near the latest activation area in all the pig maps and in nine often and eight often patient maps, respectively. (4) In all maps, MAP duration and AT were negatively correlated, and EOR and AT positively correlated. In conclusion, repolarization gradients exist over the pig and the human ventricular endocardium. The activation sequence is a determinant for the repolarization sequence. The magnitude of the progressive MAP shortening with progressively later activation, relative to local AT, is a critical factor governing the direction and pattern of the EOR.