[Value of the isoprenaline test in arrhythmogenic heart diseases]

The sympathetic nervous system seems to play a major role in the genesis of ventricular arrhythmias. The authors studied this adrenergic factor prospectively by exercise stress testing and intravenous isoprenaline in 107 patients referred for evaluation of arrhythmias or symptoms thought to be due to arrhythmias: 30 patients had morphologically normal hearts (15 ventricular extrasystoles, 15 bursts of ventricular tachycardia); 55 patients had dilated cardiomyopathy and 22 had probable or proven arrhythmogenic right ventricular dysplasia. Exercise testing was carried out with 30 watt increments every 3 minutes. Ventricular tachycardia was induced in 6 patients with apparently normal hearts (17%), 13 patients with dilated cardiomyopathy (31%) and 7 patients with arrhythmogenic right ventricular dysplasia (40%). Isoprenaline was infused for 3 minutes at a dose of 8-12 g/min: ventricular tachycardia was induced in 7 patients with apparently normal hearts (24%) and 23 patients with dilated cardiomyopathy. In some patients presenting with syncope, an arrhythmogenic response to isoprenaline was the only abnormality detected by the study protocol. An arrhythmia was induced by isoprenaline in 17 of the 18 patients with confirmed right ventricular dysplasia (94%), 12 of whom had sustained mono or polymorphic ventricular tachycardia. Two of these patients did not have significant right ventricular wall motion abnormalities. Four asymptomatic subjects related to patients with right ventricular dysplasia underwent the isoprenaline test; bursts of ventricular tachycardia were recorded in 3 of them. Polymorphic ventricular tachycardia was specifically associated with cardiac disease. The maximum heart rate attained by exercise testing (148 +/- 19/min) was higher than that attained with isoprenaline (148 +/- 22/min).(ABSTRACT TRUNCATED AT 250 WORDS)