Key result
Local stretching of the left ventricular wall in rabbit hearts significantly increased the dominant frequency of ventricular fibrillation (18.8 vs 15.2 Hz, P<0.0001) and decreased mean VV intervals.
Why the study?
Does local stretching modify ventricular fibrillation activation patterns in an experimental rabbit heart model?
Does local stretching modify ventricular fibrillation activation patterns in an experimental rabbit heart model?
Local stretching increases electrophysiological heterogeneity and accelerates ventricular fibrillation in the stretched area without affecting nonstretched zones in an experimental rabbit model.
Answers are grounded in this paper and cite their sources.
Local stretch minimally alters global VF activation in rabbit hearts; leaves open whether focal interventions can modulate clinical VF.
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.
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Chorro et al. (2005) studied Ventricular fibrillation (n=23). Local stretching vs. Before stretching / nonstretched zone was evaluated on Dominant frequency (DFr) in the stretched zone (p=<0.0001). Local stretching of the left ventricular wall in rabbit hearts significantly increased the dominant frequency of ventricular fibrillation (18.8 vs 15.2 Hz, P<0.0001) and decreased mean VV intervals.
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