Doubt cast on worth of BP load

By Eleanor McDermid, Senior medwireNews Reporter

Blood pressure (BP) load may not be a useful clinical measure, say researchers.

Yan Li (The Shanghai Institute of Hypertension, China) and team found that BP load – the proportion of time for which BP is elevated – was not associated with target-organ damage independently of actual BP level in 869 patients who underwent 24-hour ambulatory BP monitoring.

“The clinical implication of our findings is that we should focus on the control of BP level in the management of hypertension,” they write in the Journal of Hypertension.

Editorialists Gianfranco Parati (University of Milano-Bicocca, Italy) and colleagues agree that BP load is unlikely to add prognostic value, because it would be high in patients with frequent but very mild BP elevations.

“Given that cardiovascular risk increases proportionally to BP elevation, a proper assessment of BP burden on circulation should consider also the magnitude and not only the rate of BP elevations, which makes BP load an imperfect index of BP-related cardiovascular risk because of its inability to quantify the degree of BP rise above threshold,” they say.

However, they caution against dismissing the usefulness of BP load, despite the present findings.

Li et al measured patients’ brachial-ankle pulse wave velocity (baPWV) and carotid-femoral pulse wave velocity, left ventricular mass index, and estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio to quantify target-organ damage. But this was done at a similar time to BP measurements, providing cross-sectional associations rather than determining the long-term cumulative effect of BP load.

All measures of target-organ damage with the exception of eGFR significantly increased as BP load increased, and this remained so after adjusting for multiple confounders but disappeared after further adjustment for 24-hour systolic BP levels.

For example, average adjusted baPWV was 13.8 m/s in patients in the first tertile of BP load (exceeded normal BP for <23% of recording time), rising to 14.6 m/s and 15.6 m/s in people in the second (23–54%) and third (>54%) tertiles, respectively. After accounting for 24-hour systolic BP, these values were 14.8, 14.7, and 14.5 m/s, respectively.

Parati et al point out that, despite the average BP level of the cohort being within normal limits, two-thirds of the patients actually had sustained mild hypertension, leaving a relatively small proportion of the cohort in which the relative impact of BP level and BP load could be determined.

They say that the researchers’ conclusion that physicians should focus on BP level needs to be further tested in longitudinal studies of patients with normal or high-normal BP.

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