Baroreceptor reflexes and sudden cardiac death: experimental findings and background.

The identification of subjects at high risk for sudden cardiac death is a key factor for an adequate preventive strategy. Relevant animal models may provide both a better understanding of the pathophysiologic mechanism involved and suggestions for a more precise risk stratification. Vagal hyperactivity is generally beneficial in the setting of acute myocardial ischemia. In a conscious animal model for sudden cardiac death, electric vagal stimulation markedly reduces the incidence of ventricular fibrillation (VF) in a high risk subgroup, whereas muscarinic blockade increases malignant arrhythmias in low risk animals. Among 192 dogs, those that develop VF during an episode of acute myocardial ischemia one month after myocardial infarction, have a significantly lower baroreceptor reflex sensitivity, compared to the survivors (9.1 +/- 6.0 vs 17.7 +/- 6.5 msec/mmHg, p < 0.0001). Furthermore, the analysis of vagal reflexes may identify high risk animals also before myocardial infarction. Therefore, the experimental studies indicate that the analysis of baroreceptor reflexes may be a powerful tool in the stratification of risk for sudden cardiac death.