What is white coat hypertension?

The 2017 American College of Cardiology and American Heart Association hypertension guidelines¹ define white coat hypertension (WCH) as systolic blood pressure greater than 130 mm Hg but less than 160 mm Hg or diastolic blood pressure greater than 80 mm Hg but less than 100 mm Hg that occurs when blood pressure is measured in an office, clinical, or healthcare setting, but is not high in a home, nonhealthcare, or ambulatory blood pressure monitoring (ABPM) setting. The estimated prevalence of WCH in the general population is between 15% and 30%.^2,3 It is common in elderly people and pregnant women.

The guidelines¹ further recommend screening adults who have untreated blood pressure in this range for WCH by using either daytime ABPM or home blood pressure monitoring (HBPM). Diagnosis of WCH can be made if blood pressure measured correctly by ABPM or HBPM is consistently below 130/80 mm Hg after three months of measurement and lifestyle modification. If diagnosed with WCH, annual monitoring is warranted with ABPM or HBPM to watch for transition to sustained hypertension. Identifying WCH can prevent patient anxiety and unnecessary medication and healthcare costs.^4-6 However, lifestyle modification is recommended to prevent transition to sustained hypertension and possible cardiac organ damage.¹ Nonpharmacological therapy includes healthy diet, weight loss, sodium reduction, exercise, enhanced intake of dietary potassium, smoking cessation, and moderating alcohol consumption.

Cause of WCH

WCH is thought to be caused by stress or anxiety felt by some people in a clinical setting. Stress response is a term used to describe the numerous changes that take place in the body when a person is faced with a stressful situation.⁷ Perceived stress may be caused by emotional, environmental, or physical threats, but the body’s protective response is predictable. Changes occur in the central nervous system and certain target organs when the stress hormones cortisol and adrenaline are released. The changes appear to serve the purpose of increasing a person’s arousal to focus attention on the perceived threat. Specifically, the heart rate and blood pressure (BP) increase to bring oxygen and nutrition to the heart, brain, and skeletal muscles to coordinate a “fight or flight” response. So, BP does rise in response to acute stress.

This BP rise is temporary.^7,8 When the stressful situation is over, the BP returns to the pre-stress level. This adaptation to stress might have been helpful for the survival of the species in earlier times, but scientists are now studying the effect of the stress response in modern times, when a fight or flight response may no longer be as healthy an adaptation. The links between chronic stressors present in today’s world and elevated BP are still not completely understood.

Cardiovascular Risk of WCH

Once thought to be a benign condition, some recent studies suggest that people with WCH have a higher risk of cardiovascular disease than normotensive people.

A 2015 meta-analysis⁹ of 25 studies that included 7,382 untreated adult patients (3,184 hypertensive, 2,493 normotensive, and 1,705 WCH patients) looked at cardiac organ damage. The authors found that left ventricular mass index was higher in WCH than in normotensive patients (standardized difference in mean [SDM] 0.50, p<0.01). Patients with WCH compared to normotensives also had a lower ratio of early to late peak of mitral inflow (SDM -0.27, p<0.01) and the left atrium diameter was larger (SDM 0.29, p<0.05). The analysis found hypertensive patients showed even greater deficits than WCH patients.

Another study¹⁰ analyzed data from five population studies (from Greece, Finland, Montevideo, and two from Japan) to determine cardiovascular risk in patients with WCH, masked hypertension, and sustained hypertension compared to normotensive patients. Cardiovascular events included cardiovascular-related death, myocardial infarction, heart failure, stroke, pacemaker implantation, and coronary revascularization procedures. Analysis determined that the cardiovascular risk was higher for patients with white coat hypertension (adjusted hazard ratio [HR] 1.42, 95% confidence interval [CI] [1.06 – 1.91], p=0.02) compared to normotensive patients.

Another systematic review and meta-analysis of 14 cohort studies examined patients with WCH (n=4,806) to normotensive patients (n=13,538) and patients with sustained hypertension (n=10,756) who had at least eight years of follow-up. Patients with WCH had significantly higher number of cardiovascular events than normotensives (odds ratio [OR] 1.73, 95% CI [1.27 – 2.36], p=0.006). Death due to cardiovascular disease occurred in 4% of WCH patients as opposed to 1.2% of normotensive patients. Stroke was reported in 2.7% of WCH patients as opposed to 3.4% of normotensive patients.

Tientcheu et al. performed a study¹¹ of 3,027 patients, of which 50% were African American, to determine the risk of cardiovascular events and target organ damage due to hypertension in people with WCH (n=123), masked hypertension (n=582), and sustained hypertension (n=518) compared with normotensives (n=1,804) over a median of 9.4 year follow-up. They did find that WCH was related to markers of target organ damage, as measured as increased aortic stiffness and kidney damage. The risk for cardiovascular events barely reached statistical significance in the full WCH group (adjusted HR 2.02, 95% CI [1.01 – 4.03]) compared to significantly higher risks in the sustained and masked hypertension groups. However, a subgroup analysis found that African Americans with WCH had significantly higher risk of cardiovascular events similar compared to non-black patients with WCH.

^References

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