RELATIONSHIP OF NOCTURNAL BP AND DIPPING ACCORDING TO 24-HOUR URINARY SODIUM EXCRETION AND NOCTURNAL HEART RATE

Abstract

Objective: Blood pressure (BP) normally decreases during the night. Non-dipping is associated with increased cardiovascular risk. Altered autonomic and endocrine function is suspected to play a role. On the other hand, urinary sodium excretion is mainly controlled by pressure-natriuresis. However, relation between urinary sodium excretion and nocturnal dipping is complex and uncertain. Therefore, this study investigates the relation of 24hour urinary salt excretion and nocturnal dipping according to nighttime heart rate (HR).

Design and Method: From 2011 to 2012, data from 315 patients hospitalizing tertiary referral center in Korea were analyzed. These patients underwent ambulatory blood pressure monitoring (ABPM) and 24-hour urine collection.

Results: Mean nocturnal HR is 65.9 bpm. Mean 24-hour urine sodium excretion is 135.0 mEq/day. In the group with HR < the mean, nocturnal systolic and diastolic BP in patients excreting ≥ mean 24 hour urine sodium are 120.9/72.2 mmHg, significantly higher than 113.5/67.4 mmHg in patients excreting < mean 24 hour urine sodium. In the group with HR ≥ the mean, nocturnal dipping in patients excreting ≥ mean 24 hour urine sodium is 9.0%, significantly higher than 6.2% in patients excreting < mean 24 hour urine sodium.

Conclusions: According to nocturnal HR and 24-hour urine sodium excretion, nocturnal dipping, systolic BP and diastolic BP show different feature. We wish to draw attention to differences in the relationship of nocturnal BP to nocturnal HR and sodium excretion and to how pressure–natriuresis, autonomic function, and sodium sensitivity of blood pressure interact.