Twenty-Four-Hour Central Ambulatory Blood Pressure: Relationship With Measures of Cardiovascular Subclinical Organ Damage in Healthy Individuals.

BACKGROUND: In most, but not all, observational studies, ambulatory central systolic blood pressure (cSBP) is more closely related to left ventricular mass index than ambulatory brachial SBP. However, the association with other markers of subclinical organ damage is poorly understood. We investigated the association between ambulatory brachial SBP or cSBP and measures of subclinical organ damage, together with the influence of waveform calibration method, in a large community-based population of untreated individuals. METHODS: In all, 1311 participants (mean age, 45±18 years; 589 women) had simultaneous measurements of ambulatory brachial and central pressure over 24 hours. Of these, left ventricular mass index was assessed in 675 individuals, carotid intima-media thickness in 610 individuals and carotid-femoral (aortic) pulse-wave velocity in 1091 individuals. RESULTS: Left ventricular mass index was most strongly associated with cSBP, calibrated using mean and diastolic blood pressure, with a β coefficient of 0.237 (95% CI, 0.225-0.453; P<0.001). The adjusted (partial) correlation coefficient for this association was also significantly higher versus both brachial SBP and cSBP derived from calibration using SBP and diastolic blood pressure (P<0.001 for both). The same was true for carotid intima-media thickness (β coefficient=0.141 [95% CI, 0.777-2.502]; P<0.001), although the adjusted correlation coefficients did not differ significantly between ambulatory blood pressure indices. In contrast, aortic pulse-wave velocity shared a similar association with both brachial and central ambulatory pressure, with no obvious effect of waveform calibration method. CONCLUSIONS: Ambulatory cSBP may provide valuable additional information concerning cardiovascular risk, although the method of waveform calibration exerts a marked impact.