Evaluation of arrhythmogenicity of surgically induced endocardial versus ischemic myocardial damage

Ventricular tachyarrhythmias are common sequelae of ischemic myocardial damage. To assess the susceptibility to sustained ventricular tachycardia in a canine model in which endocardial excision was performed, 30 adult mongrel dogs were divided into three groups and studied in an open-chest condition, anesthetized under pentobarbital anesthesia, 7 to 14 days after undergoing one of three alternative procedures: (Group A) sham-operated controls, 10 dogs; (Group B) left ventricular endocardial excision, 10 dogs; and (Group C) myocardial infarction produced by a 2-hour occlusion and subsequent reperfusion of the left anterior descending coronary artery, 10 dogs. Using programmed ventricular pacing with two extrastimuli via plunge electrodes at 10 normal sites in the distribution of the left anterior descending coronary artery in each dog, sustained ventricular tachycardia was induced in 0/10 Group A dogs at 0/100 sites and in 0/10 Group B dogs at 0/100 sites; in contrast, in Group C, 7/10 (70%, p less than 0.01) dogs had inducible sustained ventricular tachycardia and at 39/70 (56%, p less than 0.001) sites. Thus, 7 to 14 days following endocardial excision, dogs are no more susceptible to the initiation of sustained ventricular tachycardia than are sham-operated control animals. This is in contrast to dogs with chronic heterogeneous infarctions (Group C) due to coronary occlusion and reperfusion, which are highly susceptible to ventricular tachycardia initiation.