INHERITED VENTRICULAR ARRHYTHMIAS AND SUDDEN-DEATH IN GERMAN-SHEPHERDDOGS

Objectives. This report describes a unique group of German shepherd do gs with inherited ventricular arrhythmias and sudden death. Before dea th, these dogs have no evidence of cardiovascular failure. Background. There are few spontaneous animal models of sudden death that permit i ntensive investigation. Methods. To determine the temporal evolution o f ventricular arrhythmias and to characterize the syndrome of sudden c ardiac death in these dogs, 24-h ambulatory electrocardiographic (ECG) monitoring, echocardiograms, electrophysiologic testing and breeding studies were conducted. Results. The 24-h ambulatory ECGs from dogs th at died showed frequent ventricular arrhythmias with rapid polymorphic ventricular tachycardia (rates >480 beats/min). Affected dogs had a w indow of vulnerability for arrhythmias, with the highest incidence and severity of arrhythmias between 20 to 30 and 40 to 50 weeks of age. A ffected dogs that died did not have prolongation of the QT interval ov er a spectrum of heart rates compared with unaffected dogs. The clinic al arrhythmia was not induced in dogs during programmed electrical sti mulation. Severely affected dogs monitored >5 years did not develop an y evidence of heart failure or cardiomyopathy, and no histopathologic abnormalities existed. Seventeen dogs died suddenly (age 4 to 30 month s) and were either 1) found dead at first observation in the morning ( n = 8), 2). observed to die during sleep (n = 4), 3) observed to die w hile resting after exercise (n = 3), or 4) observed to die during exer cise (n = 2). All sudden deaths occurred between the end of September and April, with most (n = 11) during January and February. Conclusions . The cause of the inherited severe ventricular arrhythmias and sudden death in these young German shepherd dogs is still undetermined. A pu rely arrhythmic disorder is supported by the lack of cardiac pathology . Moreover, the window of vulnerability to ventricular arrhythmias and the age and circumstances of death invite speculation about the role of the autonomic nervous system.