Diurnal Rhythms, the Renin-Angiotensin System and Antihypertensive Therapy

Michael Schachter


Br J Cardiol. 2004;11(4) 

In This Article

Abstract and Introduction

The circadian rhythms of the cardiovascular system are related to the risk of events such as myocardial infarction and stroke. The so-called 'morning surge' in heart rate and blood pressure at around the time of waking is a particularly hazardous period. The sympathetic nervous system and the renin-angiotensin system are thought to be the main regulators of these rhythms and a potential target of antihypertensive medication is the blunting of the morning surge through action on these systems. This article reviews some of the mechanisms involved and recent therapeutic approaches to this problem.

Circadian rhythms are so obvious that we rarely think about them. We also tend to assume that their mechanism and implications are now more or less fully understood. We would be mistaken. One area where we should certainly take a greater interest as clinicians is the rhythms governing variations in heart rate and, even more importantly, blood pressure. This is relevant from both pathophysiological and therapeutic perspectives. Firstly, the daily rhythms in blood pressure have a major influence on the timing of cardiovascular events, including myocardial infarction, stroke and sudden death. Secondly, arising from this, it must be of importance to control blood pressure to minimise the effect of these fluctuations, especially of rapid rises in individuals with hypertension.