Effect of underlying heart disease on the frequency content of ventricularfibrillation in the dog heart

Although prior studies have examined the frequency content of local electro gram characteristics during fibrillation, little is know about the effects of underlying heart disease on these parameters. This study was designed to compare the frequency content of local electrograms during VF in canine mo dels of acute ischemia, subacute infarction, and chronic myocardial infarct ion (MI) to those in control animals to test the hypothesis that underlying heart disease can alter the basic characteristics of VF. VF was induced us ing burst pacing in three groups of mongrel dogs. Five dogs were evaluated 8 weeks after LAD occlusion MI, five were evaluated 5 days after experiment al MI, and 5 had VF induced before (control) and immediately after LAD occl usion (ischemia). During SIF, unipolar electrograms were recorded from 122 sites on the anterior LV and electrograms were evaluated 15 and 30 seconds after VF initiation in each group. Electrograms were analyzed by fast Fouri er transform. No significant time dependent changes in VF characteristics w ere noted. The peak frequency was highest in control animals and 8-week MI, intermediate in 5-day MI, and lowest in acute ischemia (P < 0.01 for pairw ise comparisons). In contrast, the fractional of energy within a bandwidth of 25% peak amplitude Mas highest in acute ischemia, (P < 0.001) and simila r in the other three groups. Infarction decreased total energy by approxima tely 50%. In conclusion, the pressure of ischemia or infarction alters the frequency content of VF in a complex fashion. In addition to decreasing the peak frequency the shape of the power spectral curve is altered in models of structural heart disease. These results suggest that the electrophysiolo gical changes produced by infarction or ischemia alter the structural organ ization of ventricular fibrillation.