The importance of 24-hour ambulatory blood pressure monitoring in patients at risk of cardiovascular events.

The accuracy of clinic blood pressure (BP) measurements is limited due to the presence of 24-hour BP variability and white-coat or masked hypertension. In contrast, 24-hour ambulatory BP monitoring (ABPM) has evolved into an accurate and reproducible tool for the assessment and management of hypertension. Various out-of-office measurements can be obtained using ABPM data, including morning, daytime, night-time and average 24-hour BP. Thus, in clinical practice, ABPM can be used to identify masked hypertension or excessive BP reduction. Furthermore, ABPM data can identify early-morning hypertension and excessive BP variability, both of which correlate with target-organ damage and cardiovascular outcomes. In large outcomes trials, ABPM sub-studies are increasingly performed to help further understand patient outcomes. However, it is evident that control of BP over the full 24-hour period, particularly during the risky early morning period, is not being achieved in general practice. In clinical trials of antihypertensive efficacy, a useful calculation is the smoothness index. This measure assesses the degree of 24-hour BP reduction, as well as its distribution pattern, throughout the 24-hour period. Importantly, the index correlates with hypertension-associated target organ damage, unlike the commonly used trough to peak ratio. Smooth BP control according to this index is achieved with long-acting drugs, such as telmisartan or amlodipine, which provide smooth 24-hour BP control, even during the early morning period. In summary, the use of ABPM is expanding, both in clinical practice and in trials, as it provides a closer correlation to prognosis than clinic BP measures. When choosing an antihypertensive agent for patients with hypertension, it is important to consider reducing BP variability by using longer acting antihypertensives, which may help to prevent cardiovascular morbidity and mortality.