Effect of beta-adrenergic blocker therapy on the circadian rhythm of heart rate variability in patients with chronic stable angina pectoris.

The circadian rhythm of heart rate variability is present in normal subjects and in patients with angina, with the greatest variation in the normal population and a smaller but significant variation in the anginal group. With beta-adrenergic blockade, significant improvement occurs in all daytime time domain parameters, nocturnal percentage of RR intervals with >50-ms variation, and square root of mean-squared differences of successive RR intervals, daytime total power, and high-frequency band, representing significant improvement in parasympathetic function.