White-Coat Effect Is Uncommon in Patients With Refractory Hypertension

Abstract

Refractory hypertension is a recently described phenotype of antihypertensive treatment failure defined as uncontrolled blood pressure (BP) despite the use of 5 or more different antihypertensive agents, including chlorthalidone and spironolactone. Recent studies indicate that refractory hypertension is uncommon, with a prevalence of approximately 5-10% of patients referred to a hypertension specialty clinic for uncontrolled hypertension. The prevalence of white coat effect i.e. uncontrolled automated office BP (AOBP) ≥135/85 mmHg and controlled out-of-office BP <135/85 mmHg by awake ambulatory BP monitor (ABPM) in hypertensive patients overall is approximately 30-40%. The prevalence of white coat effect among patients with refractory hypertension has not been previously reported. In this prospective evaluation, consecutive patients referred to University of Alabama at Birmingham (UAB) Hypertension Clinic for uncontrolled hypertension were enrolled. Refractory hypertension was defined as uncontrolled AOBP ≥135/85 mmHg with use of 5 or more antihypertensive agents, including chlorthalidone and spironolactone. AOBP measurements were based on 6 serial readings, done automatically with use of a BpTRU device unobserved in clinic. Out-of-office BP measurements were done by 24-hr ABPM. Thirty-four patients were diagnosed with refractory hypertension, of whom 31 had adequate ABPM readings. White coat effect was present in only two patients, or 6.5% of the 31 patients with refractory hypertension, suggesting that white coat effect is largely absent from patients with refractory hypertension. These findings suggest that white coat effect is not a common cause of apparent lack of BP control in patients failing maximal antihypertensive treatment.

Prevalence and Clinical Characteristics of Refractory Hypertension

“…Although its prevalence was considerably lower than that of RH,2 it is surprising that those patients were still receiving 5 or more drugs based only on clinic BP, without considering ABPM in earlier steps of management. A recent report10 has found that normal ABPM of RfH was present only in 2 out of 31 patients with RfH. Besides differences in sample size, discrepancies between studies are probably derived from patients’ origin, a highly specialized clinic in the report from Siddiqui and coworkers10 and a nationwide Registry in the current report.…”

“…A recent report10 has found that normal ABPM of RfH was present only in 2 out of 31 patients with RfH. Besides differences in sample size, discrepancies between studies are probably derived from patients’ origin, a highly specialized clinic in the report from Siddiqui and coworkers10 and a nationwide Registry in the current report. We can speculate that perhaps a previous normal ABPM has prevented an increase in antihypertensive treatment in patients attending a specialized hypertension clinic, thus selecting only those with a true resistance to 5 drugs.…”

“…We can speculate that perhaps a previous normal ABPM has prevented an increase in antihypertensive treatment in patients attending a specialized hypertension clinic, thus selecting only those with a true resistance to 5 drugs. In addition, the report from Siddiqui et al10 used automated office BP monitoring, which has been claimed to results in lower values than daytime BP obtained through ABPM 25. In contrast, our data derive from the implementation of ABPM in clinical settings where this tool was previously unavailable.…”

“…8,9 As in RH, 24-hour ambulatory blood pressure monitoring (ABPM) is of interest in RfH patients, considering that the magnitude of the white-coat effect could also be involved in RfH. A recent report 10 has suggested the white-coat effect was very uncommon in RfH patients, although results were based on a small group of patients attending a highly specialized hypertension clinic. This situation could be different when examining a broader spectrum of clinical care, which includes primary care centers.…”

Comparison of Automated Office Blood Pressure With Office and Out-Off-Office Measurement Techniques

“…Only attrition bias was relevant in 7 studies due to missing data (BP readings missing, patients lost at follow-up). 16 studies compared AOBP with traditional OBP taken by physicians 4,8,10,12,19,[21][22][23][24]27,28,30,[32][33][34]37 ; 16 studies compared AOBP with awake ABPM 4,8,10,18,19,20,22,[24][25][26]29,[33][34][35]37,38 ; AOBP was compared with HBPM in 7 studies 10,12,24,27,28,30,38 and with non-physician OBP in 10 studies 4,8,15,[18][19][20]31,[36][37][38] .…”