Nine cases of major ventricular
arrhythmia (
tachycardia (VT), fibrillation (VF), torsades de pointe) are reported in patients with sequellae of
myocardial infarction but without residual angina or
cardiac failure. --Six of these disturbances of excitability occurred after a
bradycardia due to sino atrial block (SAB) which favoured the breakthrough of abnormal automatic foci. This form of the
bradycardia-
tachycardia syndrome was demonstrated by endocavitary electrophysiological exploration.. These were the only cases of major ventricular
arrhythmia observed in a series of 88 SABs. Reputedly benign, they illustrate the potential gravity of a conduction defect in patients with sequellae of
myocardial infarction. --Three other cases of abnormal ventricular excitability complicating the administration of 1 mg/kg of
Ajmaline to test for paroxysmal block after
myocardial infarction. These were the only cases of VT observed in a series of 800
Ajmaline tests. The three patients have had no further episodes of VT after 1 year's follow-up. On the other hand, in 43
Ajmaline tests without VT in patients with
myocardial infarction, 6 cases of VT and 1 lethal VF were later observed. This demonstrates the lack of significance of episodes of VT during
Ajmaline tests, the depressant action of the
drug on intracardiac conduction favouring the initiation of reentry. In conclusion, a history of
myocardial infarction exposes the patient to the risk of major ventricular arrhythmias in SAB, the detection of which should indicate pacemaker
therapy from the first symptoms. The use of an intravenous antiarrhythmic agent should be avoided as it may aggravate arrhythmias. However, the
arrhythmia is of no prognostic significance.