Up to 37% of resistant office hypertension is actually white-coat hypertension, according to an analysis of ambulatory blood pressure monitoring data from more than 8,000 patients published online March 28 in Hypertension.
Meanwhile, the remaining 63% who are truly resistant have a starkly worse clinical profile than do their white-coat counterparts, including significantly higher likelihoods of smoking, and having diabetes, left ventricular hypertrophy, microalbuminuria, and cardiovascular disease.
Dr. Alejandro de la Sierra of the University of Barcelona, and colleagues, looked at 2009 data from the Spanish Ambulatory Blood Pressure Monitoring Registry (ABPM), which included 68,045 patients with good quality office BP data, ambulatory BP data, and information about prescribed antihypertensives, including at least one diuretic.
Ambulatory BP measurements were acquired using an automated, noninvasive oscillometric device placed by a physician, and which registered BP at 20-minute intervals over a 24-hour period.
"Valid registries had to fulfill a series of pre-established criteria, including greater than or equal to 80% of systolic BP (SBP) and diastolic BP (DBP) successful recordings during the daytime and nighttime periods, 24-hour duration, and at least one BP measurement per hour," wrote the authors.
Patients returned the following day to their doctors for removal of the device.
Overall, 12% of participants in the registry (8,295 patients; 51% male, mean age 64 years) met Dr. de la Sierra’s criteria for resistant hypertension: office BP greater than or equal to 140 mmHg systolic and/or 90 mm Hg diastolic while being treated with three or more antihypertensive agents at "appropriate" doses.
ABPM patients were classified in two groups: 5,182 patients (62.5%) had ambulatory 24-hour BP values greater than or equal to 130 and/or 80 mm Hg and were diagnosed as true RH, and 3,113 patients (37.5%) showed 24-hour BP values below this limit and were considered as having white-coat RH, wrote the authors (Hypertension 2011 March 28 [doi: 10.1161/HYPERTENSIONAHA.110.168948]).
White-coat RH patients were slightly but significantly older (65 versus 64 years), and more likely to be female (54%).
Truly resistant patients, however, were more likely to be smokers (15% versus 10%), to be diabetic (35% versus 28%), and to have cardiovascular disease (19% versus 16%), compared with the white-coat RH patients.
Moreover, 19% of the true RH patients had left ventricular hypertrophy, as seen on electrocardiogram, versus 14% of white-coat patients.
They also had higher creatinine levels than did their white-coat counterparts (75 versus 72 micromol/L), higher urinary albumin excretion (11 versus 7 mg/g), and a higher percentage of patients with a urinary albumin excretion greater than 30 mg/g (30% versus 20%).
Circadian BP patterns also showed slight differences between groups, with a higher proportion of risers – who have an increase in BP during nighttime – among the true RH cohort, based on either systolic (22% versus 18%) or diastolic (12% versus 10%) measurements.
Body mass index and total cholesterol did not vary significantly between groups.
According to the authors, the study represents the first time that the prevalence of resistant hypertension was assessed in such a large cohort of patients.
However, the researchers pointed to one major weakness of the study: the inability to confirm that patients prescribed antihypertensive drugs were adherent to their medication regimen, "thus possibly overestimating the true prevalence of RH."
And despite the findings of significant differences in clinical characteristics between groups, "their discriminating value in clinical practice is probably low," cautioned the authors.
The authors disclosed that the Spanish ABPM Registry was initiated and is maintained by Lacer Laboratories, which makes valsartan. The authors also disclosed having attended meetings funded by Lacer.