Influence of parasympathetic pathways on early post--infarction arrhythmias.

The close relation between heart rhythm disorders that follow acute myocardial infarction (MI) and autonomic nervous system activity has come into focus recently. In order to evaluate the influence of the parasympathetic outflow on the incidence and characteristics of the early arrhythmias that follow myocardial infarction, the authors developed an experimental model of MI in rabbits by acute occlusion of the left ventricular artery. They have found that after the acute experimental MI an early stage of rhythm disorders is developed in 60% of the animals. In a second group of animals submitted to vagotomy prior to coronary occlusion none of rabbits exhibited arrhythmias. A third experimental series was performed in animals pretreated with atropine before and during the coronary occlusion; in this group the incidence of arrhythmias was the same as in control animals. The haemodynamic data obtained from the animals pretreated with atropine were similar to those obtained in control animals. The influence of vagal afferent and efferent pathways and their role in the genesis of the early arrhythmias is discussed.