Diurnal rhythms, the renin-angiotensin system and antihypertensive therapy

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.