Blockade of frontocortical-brain stem pathway prevents ventricular fibrillation of ischemic heart.

The hypothesis tested was that functional blockade of a pathway known to travel from the frontal cortex through the posterior hypothalamus to the brain stem might prevent the occurrence of ventricular fibrillation (VF) in the ischemic heart of conscious stressed pigs. The hypothesis was based on previous findings that 1) psychological stress is a necessary factor for the initiation of VF in the ischemic heart of conscious pigs, 2) the frontal cortex and its related thalamic gating mechanism, uniquely show neuroelectric responses to stressful stimuli, and 3) direct electric stimulation of either the frontal cortex, posterior hypothalamus, or fields of Forel will produce ventricular arrhythmias and myocardial necrosis. In the present study it was found that cryogenic blockade of the forebrain, posterior hypothalamus, or fields of Forel prevents or delays VF after left anterior descending coronary artery occlusion in conscious stressed pigs (P less than 0.01). Blockade of control structures adjacent to these loci in another group of pigs had no effect on VF latency. Neither heart rate nor electroencephalographic changes could explain the differences between the groups. The results show that blockade of the frontocortical-brain stem pathway prevents the lethal consequences of myocardial ischemia in stressed animals.