Relative and Combined Prognostic Importance of On-Treatment Mean and Visit-to-Visit Blood Pressure Variability in ONTARGET and TRANSCEND Patients
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In 28 790 patients recruited for the ONTARGET (Ongoing Treatment Alone and in Combination With Ramipril Global End Point Trials) and TRANSCEND (Telmisartan Randomized Assessment Study in ACE Intolerant Subjects With Cardiovascular Disease) trials, we investigated the prognostic value for cardiovascular events (primary outcome) of (1)on-treatment visit-to-visit systolic blood pressure (SBP) variability versus mean SBP and (2) the 2 measures together. SBP variability was measured by the coefficient of variation (CV) of mean SBP to which it was unrelated. Confounders such as variable time and number of visits from which to calculate SBP-CV were avoided by using the same number of visits at identical times in all patients. The covariate-adjusted risk of the primary outcome (Cox models) increased as SBP-CV or mean on-treatment quintile SBP increased, but only for mean on-treatment SBP, the relationship achieved statistical significance: global test for trend, P=0.12 versus P<0.0001. SBP-CV showed a relationship with fatal events, but it was unrelated to the risk of myocardial infarction and stroke, which were predicted by on-treatment mean SBP. Prediction of the primary outcome improved by the combined use of both measures: global test for trend, P<0.0001; hazard ratio for combined fifth versus first quintile, 1.42 (1.20-1.68) compared with 1.13 (1.01-1.27) for SBP-CV and 1.24 (1.11-1.40) for mean SBP. Thus, in the present study, on-treatment mean SBP provided an overall better prediction of cardiovascular risk than visit-to-visit SBP-CV. Prediction improved by their combined use, which may thus offer a more precise estimate of the protective effect of treatment. CLINICAL TRIAL REGISTRATION: URL: http//www.clinicaltrial.gov. Unique identifier: NCT153.101.
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