Predicting cardiovascular risk using conventional vs ambulatory blood pressure in older patients with systolic hypertension

Context The clinical use of ambulatory blood pressure (BP) monitoring requi res further validation in prospective outcome studies. Objective To compare the prognostic significance of conventional and ambula tory BP measurement in older patients with isolated systolic hypertension. Design Substudy to the double-blind placebo-controlled Systolic Hypertensio n in Europe (Syst-Eur) Trial, started in October 1988 with follow up to Feb ruary 1999. The conventional BP at randomization was the mean of 6 readings (2 measurements in the sitting position at 3 visits 1 month apart). The ba seline ambulatory BP was recorded with a noninvasive intermittent technique . Setting Family practices and outpatient clinics at primary and secondary re ferral hospitals, Participants A total of 808 older (aged greater than or equal to 60 years) patients whose untreated BP level on conventional measurement at baseline w as 160 to 219 mm Hg systolic and less than 95 mm Hg diastolic. Interventions For the overall study, patients were randomized to nitrendipi ne (n = 415; 10-40 mg/d) with the possible addition of enalapril (5-20 mg/d ) and/or hydrochlorothiazide (12.5-25.0 mg/d) or to matching placebos (n = 393), Main Outcome Measures Total and cardiovascular mortality, all cardiovascula r end points, fatal and nonfatal stroke, and fatal and nonfatal cardiac end points. Results After adjusting for sex, age, previous cardiovascular complications , smoking, and residence in western Europe, a 10-mm Hg higher conventional systolic BP at randomization was not associated with a worse prognosis, whe reas in the placebo group, a 10-mm Hg higher 24-hour BP was associated with an increased relative hazard rate (HR) of most outcome measures leg, HR, 1 .23 [95% confidence interval {CI}, 1.00-1.50] for total mortality and 1.34 [95% CI, 1.03-1.75] for cardiovascular mortality). In the placebo group, th e nighttime systolic BP (12 AM-6 AM) more accurately predicted end points t han the daytime lever. Cardiovascular risk increased with a higher night-to -day ratio of systolic BP independent of the 24-hour BP (10% increase in ni ght-to-day ratio; HR for all cardiovascular end points, 1.41; 95% CI, 1.03- 1.94). At randomization, the cardiovascular risk conferred by a conventiona l systolic BP of 160 mm Hg was similar to that associated with a 24-hour da ytime or nighttime systolic BP of 142 mm Hg (95% CI, 128-156 mm Hg), 145 mm Hg (95% CI, 126-164 mm Hg) or 132 mm Hg (95% CI, 120-145 mm Hg), respectiv ely. In the active treatment group, systolic BP at randomization did not si gnificantly predict cardiovascular risk, regardless of the technique of BP measurement. Conclusions In untreated older patients with isolated systolic hypertension , ambulatory systolic BP was a significant predictor of cardiovascular risk over and above conventional BP.