The effect of tricyclic antidepressants on ventricular fibrillation and collateral blood supply following acute coronary occlusion.

In previous studies, we showed that dibenzepin HCl (D) and other tricyclic antidepressants (TCAD), given either before or during occlusion of the left anterior descending artery (LAD), decreased the incidence of ventricular fibrillation (VF) following occlusion and reperfusion. Moreover, once VF develops in treated animals, it changes into a transient type, reverting spontaneously to a sinus rhythm. In the treated cats, retrograde perfusion of the occluded coronary artery was observed, most likely as a result of increased collateral blood flow. This latter effect is the subject of the present study. The LAD was occluded at its origin in 43 cats, 28 of which were treated either with D or with 5-iminodibenzyl HCl; the remaining 15 were untreated controls. Two hours after the occlusion, methylene blue was injected into the left atrium to determine color demarcation between the perfused and unperfused myocardium, and the cat was then killed. After fixing for 2 or 3 days in 4% formaldehyde, the hearts were sectioned transversely. The results showed that in the 15 control cats, the blood-supplied (blue) area ranged between 16% and 56% of the left ventricular muscle (mean 39%), while in the 28 treated cats the blue area was between 44% and 83% (mean 66%). These results clearly indicate the beneficial effect of TCAD on the blood supply of the occluded area and can explain, in part, the ability of these drugs to prevent VF even if infused after the coronary occlusion, and their protective effect against VF following reperfusion. No other antiarrhythmic drugs have been shown to possess this latter action.(ABSTRACT TRUNCATED AT 250 WORDS)