Novel Description of the 24-Hour Circadian Rhythms of Brachial Versus Central Aortic Blood Pressure and the Impact of Blood Pressure Treatment in a Randomized Controlled Clinical Trial

Abstract

Abstract-Elevated brachial blood pressure (BP) is associated with increased cardiovascular risk and predicts morbidity and mortality in humans. Recently, 24-hour ambulatory BP monitoring and assessment of central aortic BP have been introduced to improve BP phenotyping. The Ambulatory Central Aortic Pressure (AmCAP) study combines these approaches and describes, for the first time, the diurnal patterns of simultaneously measured 24-hour ambulatory brachial and central pressures in a prespecified substudy embedded within a clinical trial of BP lowering in patients with hypertension. Twenty-four-hour ambulatory brachial and central pressure measurements were acquired using a tonometer mounted into the articulating strap of a wristwatch-like device (BPro) in 171 participants with hypertension recruited into the ASSERTIVE (AliSkiren Study of profound antihypERtensive efficacy in hyperTensIVE patients) trial. Participants were randomly assigned to BP lowering with either aliskiren 300 mg QD or telmisartan 80 mg QD for 12 weeks. Ambulatory brachial and central BP was measured in all participants both at baseline and at study end. Brachial and central BP both demonstrated typical diurnal patterns with lower pressures at night. However, night time was associated with smaller reductions in central relative to brachial pressure and decreased pulse pressure amplification (P<0.0001 for both). These effects were not modulated after BP lowering and were maintained after adjustment for day and night-time BP and heart rate (P=0.02

Effects of treatment withdrawal on brachial and central aortic pressure after direct renin inhibition or angiotensin receptor blockade

“…These data imply sustained inhibition of the RAAS with aliskiren withdrawal, while RAAS activity was gradually restored upon telmisartan withdrawal, and is consistent with other findings using these treatment types. 7,13 Persistence in the BP lowering and aldosterone lowering effects of aliskiren over the 7-day withdrawal period is consistent with tissue localisation studies with this drug. Animal studies indicate persistent accumulation of aliskiren in the kidney.…”

Ambulatory Central Blood Pressure

“…The study by Williams et al 7 has further merits that deserve to be emphasized. For example, the number of patients from whom the data were collected was remarkably high, considering the technical difficulty of the study and its large multicentric nature.…”

“…[4][5][6] Studies on central blood pressure have almost invariably made measurements only in resting conditions, resting brachial blood pressure measurements serving for comparison. The study by Williams et al 7 published in this issue of Hypertension makes an important step forward by providing, via a new tonometric-based technology, central blood pressure values throughout the 24 hours and by comparing for the first time the circadian central blood pressure profile with the simultaneously measured peripheral blood pressure. The results confirm that systolic and pulse pressures are lower centrally than at brachial artery level.…”

“…The above limitations do not detract from the importance of the study performed by Williams et al 7 It is an easy prediction that the availability of ambulatory central blood pressure measurements will open a new field of investigation (as it happened when ambulatory peripheral blood pressure measurements became available) and that, in this context, a large number of topics will enjoy a renewed or expanded interest. Just to mention a few, the special prognostic importance attributed to brachial night-time blood pressure in the general population, as well as in patients with hypertension and diabetes mellitus, [8][9][10] will have a chance to be reassessed via measurement of its central counterpart, with perhaps a revisitation of a popular classification of individuals into dippers and nondippers.…”

Antihypertensive treatment decreases arterial stiffness at night but not during the day. Results from the Hypertension in the Very Elderly Trial

“…The inverse relationship between heart rate and arterial compliance has also been reported in the AMCap Study. [33] Cremer et al [32] have suggested that QKD may be employed, with mean brachial systolic BP, heart rate and height, to measure central systolic BP, as a reduction in central BP is associated with better outcome. [33] It is possible that the combination of indapamide and perindopril produces benefits from either lowering Ao-PWV or central pressure or both.…”