To the Editor: Paramedical teams have found that 75 per cent of persons with out-of-hospital cardiac arrest have ventricular fibrillation, whereas the remainder have bradycardia or asystole.1 , 2 However, Winkle has pointed out that there are only eight reported cases of cardiac arrest during continuous ambulatory Holter recording.3 We wish to report another such case. A continuous ambulatory electrocardiographic recording was begun in a 71-year-old man as a screening examination for a research protocol. He had a history of hypertension, smoking, prior myocardial infarction, and ventricular ectopy. He was asymptomatic when the recording was initiated. On the same day, his standard. . .