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Atrial fibrillation in patients with Wolff-Parkinson-White (WPW) syndrome may lead to syncope, ventricular fibrillation, and sudden death. In a follow-up study of 241 patients with WPW syndrome in a relatively unselected population, 26 patients had documented atrial fibrillation (11%). These patients were followed up after 1-37 years (median 11 years; mean 15 years). During this period, 2 of 26 died suddenly. These 2 patients had the shortest RR interval during spontaneous atrial fibrillation (less than or equal to 220 msec), greater than or equal to 1 episodes of syncope, and a persistent delta wave in all available electrocardiograms. In comparison, sudden or tachycardia-related death was seen in 4 of the 241 patients. This difference is not statistically significant. Thus, atrial fibrillation of 26 patients with WPW syndrome was surprisingly well tolerated in our follow-up study with only 2 sudden deaths.

Plasma renin activity in the brachial artery and in the renal vein together with arterial noradrenaline Concentration were determined repeatedly during and after 10 min of dynamic exercise in eight cardiac patients. Arterial renin increased slightly during exercise and gradually returned to control level after exercise. Renal vein renin increased markedly during exercise and returned to the resting value immediately after exercise, similarly to the changes in plasma noradrenaline and heart rate. A close temporal relationship between the changes in the renal veno-arterial renin difference, plasma noradrenaline and heart rate strongly suggests that the sympathetic nervous system is a major determinant of renin release in man during exercise.