Dispersion of the monophasic action potential duration in patients with polymorphic ventricular tachycardia

The mechanism of polymorphic ventricular tachycardia (PMVT) remains unclear . To investigate the electrophysiologic mechanism of PMVT, monophasic actio n potentials (MAPs) were recorded with a contact electrode technique from r ight ventricular sites during sinus rhythm and right ventricular pacing. MA Ps were obtained from 6 patients with PMVT (PMVT group) and 11 patients wit hout PMVT (control group). The duration from the onset of the upstroke to 9 0% repolarization of the MAP (MAPD90) during right ventricular pacing at bo th pacing cycle lengths of 600 and 400 ms was significantly longer in the P MVT group than in the control group (332 +/- 60 ms vs 279 +/- 33 ms [P < .0 05] and 276 +/- 32 ms vs 229 +/- 23 ms [P < .0001], respectively). Dispersi on of the MAPD90 in sinus rhythm was significantly larger in the PMVT group than in the control group (52.5 +/- 34.6 ms vs 26.1 +/- 12.0 ms [P < .005] ), and dispersion of the MAPD90 during right ventricular pacing at both pac ing cycle lengths of 600 and 400 ms was also significantly larger in the PM VT group than in the control group (86.0 +/- 44.2 ms vs 37.4 +/- 28.6 ms [P < .005], and 48.8 +/- 19.3 ms vs 27.1 +/- 7.1 ms [P < .05], respectively). Dispersion of repolarization time (activation time plus MAPD90) at a pacin g cycle length of 600 ms was longer in the PMVT group than in the control g roup (104.3 +/- 38.9 ms vs 49.4 +/- 31.2 ms [P < .05]). These results sugge st that the patients with PMVT have a greater regional dispersion of ventri cular repolarization time and that the heterogeneity of ventricular repolar ization may play an important role in the genesis of PMVT.