Effects of local epicardial cooling/warming on the complexity of the ventricular fibrillatory pattern

In ten Langendorff-perfused rabbit hearts localized cooling/warming were induced by a specific device in a ventricular epicardium area (modified zone, MZ) during ventricular fibrillation (VF). Epicardial electrical activity was mapped in MZ and another area of the same ventricle (NMZ), during basal temperature (37 ^oC), MZ-hypothermia (32 ^oC, 27 ^oC, 22 ^oC) and MZ-hyperthermia (42 ^oC). We analyzed: 1) the mean fibrillatory interval (VV) at each temperature step, and 2) the complexity of the activation maps (I, II and III classification, in increasing order) at basal temperature, hypothermia-22 ^oC and hyperthermia. In MZ, VF was decelerated by hypothermia (VV: 65 ± 16 vs 52 ± 10 ms, p<;0.05) and accelerated by hyperthermia (VV: 44 ± 7 vs 52 ± 7 ms, p<;0.05), in a reversible manner. VV changes with temperature in MZ fitted to a lineal model (r=-0.52, p<;0.0001). In NMZ, no significant differences were observed. Epicardial hypothermia induced a significant variation in the complexity of the VF activation maps in MZ respect NMZ, with type III increments and type II decrements (MZ-22 ^oC: I = 7%, II = 31%, III = 62%; NMZ-22 ^oC: I = 7%, II = 47%, III = 46%, p<;0.01). We conclude that local myocardial warming accelerates VF, and local myocardial cooling decelerates VF and increases the complexity of the VF activation pattern.