Search

Background: Aim of the study was to find out which myocardial repolarization parameters predict reperfusion ventricular tachycardia and fibrillation (VT/VF) and determine how these parameters express in ECG.Methods: Coronary occlusion and reperfusion (30/30min) was induced in 24 cats. Local activation and end of repolarization times (RT) were measured in 88 intramyocardial leads. Computer simulations of precordial electrograms were performed.Results: Reperfusion VT/VF developed in 10 animals. Arrhythmia-susceptible animals had longer RTs in perfused areas [183(177;202) vs 154(140;170) ms in susceptible and resistant animals, respectively, P<0.05]. In logistic regression analysis, VT/VFs were associated with prolonged RTs in the perfused area (OR 1.068; 95% CI 1.012-1.128; P=0.017). Simulations demonstrated that prolonged repolarization in the perfused/border zone caused precordial terminal T-wave inversion.Conclusions: The reperfusion VT/VFs were independently predicted by the longer RT in the perfused zone, which was reflected in the terminal negative phase of the electrocardiographic T-wave. [ABSTRACT FROM AUTHOR]

Background We simulated contributions of transmural, apicobasal, anteroposterior and interventricular action potential duration (APD) gradients to the body surface potential distribution (BSPD) with constant or varied magnitudes of the transmural and apicobasal gradients. Methods Simulations were done in the framework of the discrete computer model of the rabbit heart ventricles on the basis of realistic activation sequence and APDs. The APD gradients were set constant at 20 ms or varied in the range of ± 80 ms. Results The apicobasal, transmural and interventricular APD gradients of 20 ms produced similar BSPDs, whereas the BSPD inversion was caused by the inverted apicobasal or transmural 80 ms gradients. The transmural APD gradient produced transversal and mainly apicobasal T-wave vectors due to wall curvature and cancellation effects. The “normal” transversal and apicobasal repolarization gradients were decreased and increased by activation sequence, respectively. Conclusion The different APD gradients contributed consistently to the development of BSPD. [ABSTRACT FROM AUTHOR]

Abstract: Our study compared the contributions of activation sequence and local repolarization durations distribution in the organization of epicardial repolarization in animals with fast (rabbit) and slow (frog) myocardial activation under sinus rhythm. Activation times, repolarization times and activation–recovery intervals (ARI) were obtained from ventricular epicardial unipolar electrograms recorded in 13 Chinchilla rabbits (Oryctolagus cuniculus) and 10 frogs (Rana temporaria). In frogs, depolarization travels from the atrioventricular ring radially. ARIs increased progressively from the apex to the middle portion and finally to the base (502±75, 557±73, 606±79 ms, respectively; P <0.01). In rabbits, depolarization spread from two epicardial breakthroughs with the duration of epicardial activation being lower than that in frogs (17±3 vs. 44±18 ms; P <0.001). ARI durations were 120±37, 143±45, and 163±40 ms in the left ventricular apex, left, and right ventricular bases, respectively (P <0.05). In both species, repolarization sequence was directed from apex to base according to the ARI distribution with dispersion of repolarization being higher than that of activation (P <0.001). Thus, excitation spread sequence and velocity per se do not play a crucial role in the formation of ventricular epicardial repolarization pattern, but the chief factor governing repolarization sequences is the distribution of local repolarization durations. [Copyright &y& Elsevier]

Abstract: The study aimed at the simultaneous determination of the transmural and apicobasal differences in the repolarization timing and the comparison of the contributions of these two repolarization gradients to the development of the body surface T wave potentials in animals with the single heart ventricle (fishes and amphibians). Unipolar potentials were measured on the body surface, epicardium and in the intramural (subepicardial, Epi; midmyocardial; and subendocardial, Endo) ventricular layers of 9 pike and 8 frogs. Activation times, repolarization times and activation–recovery intervals were determined. A transmural gradient in repolarization durations in frogs (Endo>Epi, P<0.024) corresponds to the gradient in repolarization times. No significant transmural difference in repolarization duration is observed in pike that produces a repolarization sequence from Endo to Epi (Endo