Sinus bradycardia in obstructive jaundice--correlation with total serum bile acid concentrations.

Obstructive jaundice is often listed among the causes of sinus bradycardia. The latter is usually attributed to the effect of bile salts on the sino-atrial node. The purpose of this study was to determine the frequency of sinus bradycardia (heart rate less than 50/min) in 50 patients with severe or moderate cholestasis, and to relate sinus rate and intracardiac conduction to total serum conjugated bile acid concentrations. The latter were measured using a solid-phase 125I radio-immunoassay. The mean sinus rate (+/- SD) in the patients was 74.1 +/- 11.6/min (range 47-100/min). One patient had a sinus rate of less than 50/min and 2 had rates of 50-60/min. The mean total serum conjugated bile acid concentration was 251.1 +/- 198.8 mumol/l (range 13-1000 mumol/l). There was no correlation in individual patients between total serum bile acid concentration and sinus rate (r = +0.097), P-R interval (r = +0.210) or corrected Q-T interval (r = -0.085). We conclude that sinus bradycardia is not a feature of obstructive jaundice and that high serum bile acid concentrations do not exert a slowing effect on the sino-atrial node.