Author + information
- †Department of Medicine, Hospital of Assisi, Assisi, Italy
- ‡Cardiology and Cardiovascular Pathophysiology, Hospital “S.M. della Misericordia”, Perugia, Italy
- §Department of Medicine, University of Perugia, Perugia, Italy
- ↵∗Reprint requests and correspondence:
Dr. Paolo Verdecchia, Department of Medicine, Hospital of Assisi, Via Valentin Müller, 1, Assisi 06081, Italy.
Masked hypertension (MH) reflects the false impression that because patients’ blood pressure (BP) is <140/90 mm Hg in the office, their BP is either normal (if they are untreated) or well controlled (if they are treated), although their average BP levels are abnormally elevated out of the office, using either home BP or 24-h ambulatory BP monitoring (1–4).
In this issue of the Journal, Tientcheu et al. (5) present an analysis of the DHS (Dallas Heart Study), a population study designed to investigate ethnic differences in cardiovascular health at the community level (6). About 54% of subjects enrolled in this study were African Americans (6). In this analysis, the investigators compared subjects with office normotension, white-coat hypertension (WCH), MH, and sustained hypertension on some indexes of organ damage and cardiovascular outcome. Groups were defined on the basis of BP measured in the office and at home, not with 24-h ambulatory BP monitoring. Evaluation criteria included some markers of arterial stiffness and proteinuria and, more notably, the risk for major cardiovascular events over a 9-year follow-up period (5).
Over the past 20 years, several studies have shown measurements of BP outside the office to be superior to measurements of BP in the office in predicting target organ damage and the risk for major cardiovascular events (7,8). The novelty of the present study stems from the surprising paucity of data on the prognostic impact of clinical phenotypes of out-of-office BP, particularly of MH and WCH, in African Americans. However, it is well known that African Americans are at increased risk for hypertensive organ damage and cardiovascular complications (9).
The issue of MH (i.e., elevated BP outside the office in patients with normal BP in the office) continues to be challenging and intriguing. Some comprehensive reviews (1–3,10) have shown that the prevalence of MH varies between 8% and 50%, probably depending on differences across studies in several important factors, including baseline office BP, antihypertensive treatment, age, prevalence of smoking, and other demographic features (2,3,10). For both MH and WCH, the definition is more properly applied to untreated patients (3,8). The apparent impression of controlled (in MH) or uncontrolled (in WCH) office BP in treated patients may be explained not only by a different alerting reaction to the office visit but also by a differential drop in office versus out-of-office BP, possibly related to the timing of drug administration, the duration of the antihypertensive effect, and other reasons (8).
In the present study, Tientcheu et al. (5) found a 17.8% prevalence of MH and a 3.3% prevalence of WCH in the total sample (13.6% and 2.2%, respectively, in the untreated sample). In untreated patients, aortic pulsed wave velocity and the ratio of urinary albumin to creatinine were significantly higher in the WCH and MH groups, and differences remained significant after multivariate adjustment for some potential confounders. Conversely, some of the differences between the groups did not achieve significance in treated patients. The risk for cardiovascular events (a composite pool of 194 hard and less hard events, including unstable angina, transient ischemic attack, revascularization, myocardial infarction, stroke, hospitalization for atrial fibrillation and heart failure, and cardiovascular death) was assessed over a median 9-year follow-up period. After adjustment for several potential confounders, the risk for events was significantly higher in the MH and sustained hypertension groups compared with the normotensive group, whereas it barely approached significance (adjusted hazard ratio: 2.02; 95% confidence interval: 1.01 to 4.03) in the WCH group.
Interestingly, a subgroup analysis showed almost the same risk for events in the normotensive group and in the WCH group among nonblacks, whereas a significantly higher risk for events was found in the WCH group compared with the normotensive group in blacks. The p test for interaction was not statistically significant, but the analysis was probably underpowered to test the significance of such an interaction. These findings support the hypothesis that the prognostic impact of WCH differs in blacks versus nonblacks, an intriguing hypothesis that merits testing in future studies.
Some limitations of the present study must be acknowledged when interpreting its results. First, the definition of groups is on the basis of home BP, not 24-h ambulatory BP. An obvious advantage of 24-h ambulatory BP over home BP is the ability of 24-h ambulatory BP to capture not only nocturnal MH but also transient or persistent BP elevations out of the home setting, possibly triggered by physical and emotional stress. In a study from Spain, 31% of 4,608 treated hypertensive patients with office BP <140/90 mm Hg showed MH due to isolated increases of nighttime BP in 27.3% (first session) and 28.7% (second session) of patients (11). While waiting for outcome-based studies on the prognostic impact of MH using different time windows, 24-h ambulatory BP monitoring should be theoretically preferred to home BP recording in those subjects in whom MH is suspected (10).
A second limitation of the study by Tientcheu et al. (5) is inherent in the schedule of home and office BP measurements in the DHS. The first data collection, which included home BP measurement, occurred during a single in-home visit carried out by health care professionals. This is not exactly the same situation as several home BP readings by a patient in the privacy of his or her home over different days and times of day. According to an international consensus document on home BP monitoring, home BP should be monitored for 7 days, with at least 2 morning and 2 evening measurements. For clinical decision making, we should consider the average of all values, except for the first day, which should be discarded (12). Some stress-induced overestimation of home BP might have occurred in this study. However, the prevalence of MH was unlikely to be inflated, as it was comparable with that observed in the Jackson Heart Study, a study conducted in African Americans that used 24-h ambulatory BP monitoring (13).
A final limitation relates to the temporal separation between the visits. Some weeks after the first data collection, there was a second in-home visit that included a blood drawing for biochemical analyses. After several weeks, a third clinical visit was carried out in the hospital, during which traditional office BP was measured. It is unknown whether drug treatment changed between the first and the third visits, and this is, perhaps, the more serious potential limitation of the present study. However, one might expect that treatment did not change in most patients, because community-based screening programs show negligible changes in drug treatment due solely to the effect of screening visits (14–16).
The present study has several strengths. Most notably, for the first time, the evidence that MH is associated with an excess risk for organ damage and major cardiovascular events is extended to a multiethnic population with a high prevalence of African Americans, thus extending the current database on the adverse prognostic impact of MH. A meta-analysis from our group showed a 2-fold higher risk for cardiovascular events in patients with MH than in fully normotensive subjects, regardless of the use of home BP or 24-h ambulatory BP (16).
From a practical standpoint, we have no evidence from controlled trials that patients with MH should be treated, or treated more aggressively to further lower their BP outside the office. The European Society of Cardiology and European Society of Hypertension guidelines suggest that life-style measures and antihypertensive drug treatment “should be considered” in patients with MH because “this type of hypertension has been consistently found to have a cardiovascular risk very close to that of in- and out-of-office hypertension” (17). The guidelines made the same recommendation for untreated and treated patients with MH, and this is a Class IIA, Level of Evidence: C recommendation (17). Randomized intervention studies should be undertaken to compare different BP targets outside the office, regardless of BP measured in the office, in multiethnic populations of patients with MH.
↵∗ Editorials published in the Journal of the American College of Cardiology reflect the views of the authors and do not necessarily represent the views of JACC or the American College of Cardiology.
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
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