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Dispersion of repolarization in patients with ventricular tachycardia
Selected Abstracts From the 21st Annual Meeting of the International Society of Electrocardiology
Dispersion of Repolarization in Patients With Ventricular Tachycardia* S. Yuan, B. Wohlfart, S. B. Olsson, C. B-Lundqvist,* Departments of Cardiology, University Hospitals of Lund and *Uppsala, Sweden The role of increased dispersion of repolarization in the genesis of torsade de pointes and ventricular fibrillation has been well recognized, but not yet in the genesis of monomorphic ventricular tachycardia (VT). Monophasic action potentials (MAPs) were recorded simultaneously from the right ventricular apex (RVA) and outflow tract (RVOT) during sinus rhythm, RV pacing, and single programmed extrastimulation (ES) in 24 patients with VT. The activation time (AT), MAP duration (MAPd), and repolarization time (RT = AT + MAPd) were measured and their dispersions, defined as the differences in these parameters between RVA and RVOT, were calculated. During sinus rhythm and RV pacing, the dispersions of AT, MAPd, and RT were significantly larger in the 17 patients with inducible VT than in those without. During ES, the dispersions were further augmented in the extra beats in the seven patients with inducible sustained VT, the maximal dispersion of RT being 85 _+ 22 ms (mean 60% increase). Both the dispersion of AT and that of MAPd contributed to the dispersion of RT. In two patients with sustained VT induced during MAP recording, a marked increase in dispersion ofRT ( 140 and 190 ms, respectively) was observed immediately before the initiation of the VT (see figure above). A link between the dispersions and the inducibility of monomorphic VT was found, which suggests that *This is an abstract of "'Dispersion of Repolarization in Patients With Ventricular Tachycardia'" from European Heart Journal to be published in 1995.
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the increased dispersion of repolarization plays an important role in the genesis of monomorphic VT.
Transient Decrease of the R Wave During the Hyperacute Phase of Myocardial Ischemia Reflects Stretch of the Left Ventricular Wall Accompanied by Early Contractile Failure T. Saito, T. Abe, K. Takahashi, Y. Kimura, T. Fujiwara, H. Miura, A. Nakagomi, M. Miura, Second Department of Internal Medicine, Akita University, Akita, Japan To determine the mechanism of transient R wave decreases during hyperacute myocardial ischemia, epicardial electrocardiographic changes during 2minute occlusion of the left anterior descending coronary artery in canine hearts (n = 25) were monitored with simultaneous measurements of regional wall motion by sonomicrometry, extracellular K + (KC) by the valinomycin K + electrode, and myocardial tissue pH by a field effect transistor sensor. In a separate study using isovolumetrically beating isolated perfused rabbit hearts (n = 14), the effects of 4 minutes of global ischemia and incremental left ventricular (LV) volume expansion by inflation of an intraventricular latex balloon on epicardial bipolar potential (EP) were evaluated. R wave amplitude showed the transient decrease (84.3% of the control value, P < .01) in the first 45 seconds followed by the progressive increase in the late phase. The biphasic change similar to the R wave was also observed in activation time (AT) measured from the upstroke of the R wave. They had a close correlation in both phases (r -- .92 and .85, respectively). The first decrease in the R wave was accompanied by stretch and thinning of the LV wall in-
Dispersion of Repolarization in Patients With Ventricular Tachycardia* S. Yuan, B. Wohlfart, S. B. Olsson, C. B-Lundqvist,* Departments of Cardiology, University Hospitals of Lund and *Uppsala, Sweden The role of increased dispersion of repolarization in the genesis of torsade de pointes and ventricular fibrillation has been well recognized, but not yet in the genesis of monomorphic ventricular tachycardia (VT). Monophasic action potentials (MAPs) were recorded simultaneously from the right ventricular apex (RVA) and outflow tract (RVOT) during sinus rhythm, RV pacing, and single programmed extrastimulation (ES) in 24 patients with VT. The activation time (AT), MAP duration (MAPd), and repolarization time (RT = AT + MAPd) were measured and their dispersions, defined as the differences in these parameters between RVA and RVOT, were calculated. During sinus rhythm and RV pacing, the dispersions of AT, MAPd, and RT were significantly larger in the 17 patients with inducible VT than in those without. During ES, the dispersions were further augmented in the extra beats in the seven patients with inducible sustained VT, the maximal dispersion of RT being 85 _+ 22 ms (mean 60% increase). Both the dispersion of AT and that of MAPd contributed to the dispersion of RT. In two patients with sustained VT induced during MAP recording, a marked increase in dispersion ofRT ( 140 and 190 ms, respectively) was observed immediately before the initiation of the VT (see figure above). A link between the dispersions and the inducibility of monomorphic VT was found, which suggests that *This is an abstract of "'Dispersion of Repolarization in Patients With Ventricular Tachycardia'" from European Heart Journal to be published in 1995.
79
the increased dispersion of repolarization plays an important role in the genesis of monomorphic VT.
Transient Decrease of the R Wave During the Hyperacute Phase of Myocardial Ischemia Reflects Stretch of the Left Ventricular Wall Accompanied by Early Contractile Failure T. Saito, T. Abe, K. Takahashi, Y. Kimura, T. Fujiwara, H. Miura, A. Nakagomi, M. Miura, Second Department of Internal Medicine, Akita University, Akita, Japan To determine the mechanism of transient R wave decreases during hyperacute myocardial ischemia, epicardial electrocardiographic changes during 2minute occlusion of the left anterior descending coronary artery in canine hearts (n = 25) were monitored with simultaneous measurements of regional wall motion by sonomicrometry, extracellular K + (KC) by the valinomycin K + electrode, and myocardial tissue pH by a field effect transistor sensor. In a separate study using isovolumetrically beating isolated perfused rabbit hearts (n = 14), the effects of 4 minutes of global ischemia and incremental left ventricular (LV) volume expansion by inflation of an intraventricular latex balloon on epicardial bipolar potential (EP) were evaluated. R wave amplitude showed the transient decrease (84.3% of the control value, P < .01) in the first 45 seconds followed by the progressive increase in the late phase. The biphasic change similar to the R wave was also observed in activation time (AT) measured from the upstroke of the R wave. They had a close correlation in both phases (r -- .92 and .85, respectively). The first decrease in the R wave was accompanied by stretch and thinning of the LV wall in-