The ventricular fibrillation (VF) spectral analysis, allows the knowledge of the dominant frequency (DF) of VF. It is related with ventricular refractoriness and myocardial damage. We determined in an isolated working heart model, the DF of VF modifications to evaluate the electrophysiological heterogeneity changes and myocardial damage by acute ischemia. Eight NZW rabbits were anaesthetized (ketamine, 10 mg/kg i.v.), killed and the hearts placed in a Langendorff system. A latex balloon connected to a catheter was positioned into the left ventricle to produce a load (end diastolic pressure, 4 mmHg). A pacing electrode and a 256-leading recording electrodes plaque, were positioned on the left ventricle to obtain multiple VF recordings. VF was induced by pacing (increasing frequencies) five minutes before coronary occlusion. Mean DF of VF and its standard deviation was calculated in multiple points in each experiment, to analyze the variation coefficient (VC), as index of myocardial heterogeneity. Minimum DF was also calculated. Data processing was performed with Matlab software. To compare basal values vs. 5 and vs. 10 min. post-occlusion, paired Student's t test was used. p<0.05 was considered significant.

Minimum DF decreased 5 min after occlusion (9.7±3.4Hz) vs. basal(13.05±2.4Hz), but did not change after 10 min of CO (10.4±3.1Hz). VC increased 5 min and 10 min after oclussion (19.5±10.5 and 19.6±8.3%, respectively) vs. basal value (12.05±7.2%). Minimum DF decrease seems to be in accordance with myocardial damage. We conclude that in our isolated working heart model, acute coronary occlusion increases the heterogeneity of the VF frequency.