BACKGROUND: The coexistence of cardiac hypertrophy (H) and ischemia (I) can create a particularly arrhythmogenic substrate. Most studies investigate the effects of global I on H. However, global I is not a good surrogate model of the clinical situation. OBJECTIVE: The purpose of this study was to investigate the electrophysiological effects of regional I superimposed on H using optical mapping of membrane voltage. METHODS: We investigated the guinea pig model of left ventricular H (LVH) induced by suprarenal banding of abdominal aorta. Twelve hearts with or without LVH were mounted in a Langendorff preparation, and regional I was induced by 20 minutes of ligation of the left anterior descending artery. RESULTS: Left ventricle epicardial action potential duration (APD) was significantly prolonged in the LVH group compared with controls. I significantly shortened APD in the I risk zone in both groups, but the percentages of APD shortening (28% vs. 40%) and the magnitudes of shortening (57 +/- 18 vs. 105 +/- 32 ms) were greater in the LVH group. The greater dispersion of repolarization (DR) across the border of the I zone resulted in arcs of functional conduction block and circulating wave fronts. Tachycardia-dependent APD alternans developed more often in the LVH group, and the area of alternans versus the area of the I zone was significantly larger. Ventricular tachyarrhythmias (VTs) developed in all 12 hearts with LVH including six non-self-terminating VTs, compared with four control hearts with self-terminating VT. CONCLUSION: Regional I superimposed on LVH resulted in greater DR at the border between the I and non-I zones as well as in a greater tendency to develop APD alternans. Both arrhythmogenic mechanisms correlated with an increased incidence of VT.
BACKGROUND: The coexistence of cardiac hypertrophy (H) and ischemia (I) can create a particularly arrhythmogenic substrate. Most studies investigate the effects of global I on H. However, global I is not a good surrogate model of the clinical situation. OBJECTIVE: The purpose of this study was to investigate the electrophysiological effects of regional I superimposed on H using optical mapping of membrane voltage. METHODS: We investigated the guinea pig model of left ventricular H (LVH) induced by suprarenal banding of abdominal aorta. Twelve hearts with or without LVH were mounted in a Langendorff preparation, and regional I was induced by 20 minutes of ligation of the left anterior descending artery. RESULTS: Left ventricle epicardial action potential duration (APD) was significantly prolonged in the LVH group compared with controls. I significantly shortened APD in the I risk zone in both groups, but the percentages of APD shortening (28% vs. 40%) and the magnitudes of shortening (57 +/- 18 vs. 105 +/- 32 ms) were greater in the LVH group. The greater dispersion of repolarization (DR) across the border of the I zone resulted in arcs of functional conduction block and circulating wave fronts. Tachycardia-dependent APD alternans developed more often in the LVH group, and the area of alternans versus the area of the I zone was significantly larger. Ventricular tachyarrhythmias (VTs) developed in all 12 hearts with LVH including six non-self-terminating VTs, compared with four control hearts with self-terminating VT. CONCLUSION: Regional I superimposed on LVH resulted in greater DR at the border between the I and non-I zones as well as in a greater tendency to develop APD alternans. Both arrhythmogenic mechanisms correlated with an increased incidence of VT.
Authors: Katherine A Sheehan; Grace M Arteaga; Aaron C Hinken; Fernando A Dias; Cibele Ribeiro; David F Wieczorek; R John Solaro; Beata M Wolska Journal: J Mol Cell Cardiol Date: 2010-11-01 Impact factor: 5.000
Authors: Robert E Park; Laszlo Saghy; Erica S Zado; Cory M Tschabrunn; Francis E Marchlinski Journal: J Interv Card Electrophysiol Date: 2011-12-15 Impact factor: 1.900