Modification of Ventricular Fibrillation Activation Patterns Induced by Local Stretching

Introduction: We hypothesize that local modifications in electrophysiological properties, when confined to zones of limited extent, induce few changes in the global activation process during ventricular fibrillation (VF). To test this hypothesis, we produced local electrophysiological modifications by stretching a circumscribed zone of the left ventricular wall in an experimental model of VF. Methods and Results: In 23 Langendorff-perfused rabbit hearts frequency, time–frequency and time-domain techniques were used to analyze the VF recordings obtained with two epicardial multiple electrodes before, during, and after local stretching produced with a left intraventricular device. Acute local stretching accelerated VF in the stretched zone reversibly and to a variable degree, depending on the magnitude of stretch and the time elapsed from its application. In the half time (5 minutes) of the analyzed period, a longitudinal lengthening of 12.1 ± 4.5% (vertical axis) and 11.8 ± 6.2% (horizontal axis) in the stretched zone produced an increase in the dominant frequency (DFr) (15.2 ± 1.9 versus 18.8 ± 2.5 Hz, P < 0.0001), a decrease in mean VV interval (63 ± 8 versus 53 ± 6 msec, P < 0.001), and an increase in the complexity of the activation maps—with more areas of conduction block and more breakthrough patterns (23% versus 37%, P < 0.01), without significant changes in the percentages of complete reentry patterns (9% versus 9%, ns). Simultaneously, in the nonstretched zone, no variations were observed in the DFr (15.2 ± 2.1 versus 15.3 ± 2.5 Hz, ns), mean VV intervals (66 ± 8 versus 65 ± 8 msec, ns), or types and percentages of maps with breakthrough (25% versus 20%, ns) or reentry patterns (12% versus 8%, ns). No significant correlation was observed between the DFr in the two zones (R = 0.24, P = 0.40). Conclusion: Local stretching increases the electrophysiological heterogeneity of myocardium and accelerates and increases the complexity of VF in the stretched area, without significantly modifying the occurrences of the types of VF activation patterns in the nonstretched zone.