Role of autonomics in the initiation of electromechanical dissociation

The onset of electromechanical dissociation during acute cardiac tamponade in mongrel dogs is significantly prolonged by either surgical or pharmacologic sympathectomy. Bilateral vagotomy does not have any apparent effect on the initiation of electromechanical dissociation. Pretreatment with isoproterenol just prior to tamponade does not significantly increase heart rate or the double product. Cardiopulmonary sympathetic efferent stimulation significantly decreases the time to the onset of electromechanical dissociation by increasing the heart rate and double product. The early onset of electromechanical dissociation appears to be related to cardiac work and oxygen consumption.