Evaluation of blood pressure control in treated hypertensive patients. When and how clinic blood pressure should be measured?

Abstract

Clinic blood pressure (BP) values are still the “gold standard” for diagnosing hypertension and evaluating treatment efficacy. Different studies have estimated a BP control between 25 and 35% in developed countries. Recent results indicate that almost 90% of the patients are evaluated at the clinic under the effect of morning dose of antihypertensive treatment [Am J Hypertens. 2004;17(5):36]. We have evaluated the influence of how BP is measured at the clinic in the proper evaluation of BP control. We studied 144 patients with grade 1–2 essential hypertension (84 men), 53.3±13.2 years of age. All patients were on the same regimen of antihypertensive treatment with morning dosing for at least 3 months. BP was measured by ambulatory monitoring (ABPM) at 20-min intervals from 07:00 to 23:00 hours and at 30-min intervals at night for 48 consecutive hours. Clinic BP values (6 per study visit) were obtained between 09:00 and 11:00 hours with a validated automatic oscillometric device just before and after the 2 days of ABPM, once with the patients under the effect of antihypertensive medication taken that same morning, and the other time with the patients untreated for at least 24 hours, in a random order. The average of 6 clinic BP values obtained for each patient in the absence of treatment was significantly higher than the average of BP values obtained under the effect of morning dosing of antihypertensive drugs (mean difference of 13.8 and 5.6 mm Hg for systolic and diastolic BP, P<0.001). All patients showed a systolic BP reduction when evaluated under the effect of medication. The percentage of controlled patients (clinic BP <140/90 mm Hg for systolic/diastolic BP) was 71% for subjects evaluated under the effect of treatment. This percentage was significantly reduced to just 27% when the same patients were measured without the morning dose of treatment. Clinic BP measurement should always be performed in the absence of same-day treatment. Differences between clinic and daytime ABPM measurements below the reported 15 mm Hg in systolic BP for untreated subjects could indicate that patients were indeed evaluated under the effect of treatment, invalidating conclusions on BP control and drug efficacy.