Continuous electrocardiographic (ECG) records were made over 24 hours in 130 ambulant outpatients complaining of syncope, dizzy turns, or palpitation. In all these patients resting ECGs had failed to show significant dysrhythmias. Exercise testing was performed on 64 patients and also failed to reveal any dysrhythmias. Analysis of the tape recordings, however, showed appreciable dysrhythmias in 74% of the group. In most cases the dysrhythmias were complex mixtures of rapid supraventricular and ventricular rhythms. bouts of ventricular tachycardia were seen in seven patients, all of whom were women. Episodic complete heart block was seen in only two patients, but prolonged ventricular gaps (greater than 1-5 s), not associated with ectopic beats, were found in 26. No episodes of ventricular fibrillation were recorded. We conclude that many patients with vague symptoms suggestive of transient cerebral ischaemia or irregular heart action have significant and often dangerous dysrhythmias which can be diagnosed only by long-term recording of the ECG under fully ambulant conditions.

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