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On 24-hour ambulatory ECG, 17 patients with mitral valve prolapse displayed more frequent and serious arrhythmias than a control group of 17. Neither resting ECG, treadmill ECG, nor other external recordings were capable of predicting which of the patients were prone to development of arrhythmias.

Digitalis still remains a source of astonishment to electrophysiologists as well as clinicians. The presently known effects on the neurovegetative system and the action potential are described, and some clinical problems which may lead to ineffective digitalization or digitalis intoxication are stressed. Clinical and ECG manifestations and some therapeutic aspects are pointed out.

17 medicine undergraduates sitting their final examinations underwent continous ECG recording during a period of 3 h. Their usual heart rate was 71 +/- 9 per minute, accelerating to 149 +/- 13, most often at the moment of entering the examination room. This reaction was usual in all candidates despite their knowledge that the failure rate at the exams is always very low; all of this group likewise passed. Two subjects exhibited marked alterations in the terminal phase compatible with myocardial ischemia. In 6 cases severe sinus rhythm variations evidenced an unstable balance of the vagal and adrenergic stimulations. No other arrhythmias, augmentation in the number of premature beats or atrio-ventricular blockade were observed. Analysis of the results shows that the heart response to psychic aggression differs from that to physical effort.