White Coat Hypertension: Relevance to Clinical and Emergency Medical Services Personnel

Abstract

Context

White-coat hypertension (WCHT) is a relatively unexplored cause of elevated blood pressure readings in the clinic and in prehospital emergency medical services (EMS) settings.

Objective

The purpose is to summarize WCHT in the clinical office setting and speculate on its relevance in the prehospital setting. This review emphasizes the etiology, diagnosis, prognosis, and application of WCHT in both the clinical and prehospital settings.

Data sources

A systematic literature review was undertaken with the Medline PubMed database, UpToDate, and Web of Science. The following search queries were used: “prehospital WCHT,” “prehospital white coat hypertension,” “EMS WCHT,” “emergency medical services white coat hypertension,” “ambulatory WCHT,” “ambulatory white coat hypertension,” “labile HTN,” “labile hypertension,” “variable HTN,” and “variable hypertension” limited to 1980-July 2006. Only human studies published in English were included.

Study selection

The reviews yielded 233 articles initially, which were narrowed down to those mentioned herein by direct relevance to either the observed WCHT effect in the clinic or the prehospital setting.

Data synthesis

WCHT has not been applied or explored in the prehospital setting as of yet, and thus all data were shown to be related to clinical WCHT. It was found that WCHT may not be simply a benign entity but rather part of a continuum in the development of true essential hypertension. It was found that WCHT patients, when followed, had higher morbidity than non-WCHT patients but less morbidity than established essential hypertensive patients.

Conclusions

WCHT may be a significant step toward the evolution into full-blown hypertension. For many populations, routine access to a healthcare provider is not possible, and thus their only interaction with healthcare providers may be in the prehospital EMS setting. On the basis of findings of true organic morbidity in WCHT, it comes to reason that contact with patients in the setting should be thorough – including urging follow-up for those whose blood pressure is found to be elevated in the presence of healthcare professionals.

Introduction

White-coat hypertension (WCHT) refers to elevation in blood pressure (BP) due to anxiety associated with visits to the physician's office. WCHT may be an early indicator of true hypertension, and although documented in clinical offices, WCHT has not been studied in the prehospital or EMS setting. Because contact with EMS may be the only interaction that some patients have with a medical provider, this is a potential screening point for hypertension. The purpose of this review is to summarize WCHT in the office setting, and from that, speculate on its relevance to prehospital care.

Background

BP is classified into 4 stages: normal, prehypertension, stage I hypertension, and stage II hypertension. Normal BP values are below 120 mm Hg systolic and 80 mm Hg diastolic. A systolic pressure of 120–139 mm Hg or a diastolic pressure of 80–89 mm Hg is considered prehypertensive. A BP reading between 140–159 mm Hg systolic and 90–99 mm Hg diastolic is considered stage I elevated hypertension. Stage II hypertension is defined as BP values greater than 160 mm Hg systolic and greater than 100 mm Hg diastolic. Table 1 summarizes the BP classifications as described by the American Heart Association.[1]

Table 1.

Blood Pressure Classification System

Systolic (mm Hg)	Category	Diastolic (mm Hg)
< 120	Normal	< 80
120-139	Prehypertension	80-89
140-159	Stage I hypertension	90-99
≥ 160	Stage II hypertension	> 100

American Heart Association recommendation guideline for blood pressure

WCHT is an ill-defined phenomenon. The most accepted definition is a high BP in the physician's office with normal BP at rest or while ambulatory. WCHT is presumably due to the patient being anxious in the physician's office, which leads to an increase in their BP through a systemic sympathetic response system. WCHT can be tested in 1 of 2 ways – either as the difference between the daily average ambulatory BP and physician office BP or the BP change from directly before the visit to during the visit. The Progetto Ipertensione Umbria Monitoraggio Ambulatoriale (PIUMA) study believes that the first method is most accurate in measuring WCHT because the former method does not clearly identify WCHT from other forms of hypertension. Thus, the average BP will not give an accurate account of the change in BP between the outside environment and the physician's office. The latter method is a more reliable way to measure WCHT according to Angeli and colleagues,[2] because it gives a much more accurate account of the change in BP between the 2 settings by monitoring it over a set period of time. Using the second method mentioned above, Mancia and colleagues[3] described from their research that the WCHT on average is 27/14 mm Hg. They further stated that the BP is at its highest during the first physician encounter and lasts approximately 10 minutes. These values give a general understanding for what to expect in patients with WCHT.[2]

Methods

A systematic literature review was undertaken with the Medline PubMed database, UpToDate, and Web of Science. The following search queries were used: “prehospital WCHT,” “prehospital white coat hypertension,” “EMS WCHT,” “emergency medical services white coat hypertension,” “ambulatory WCHT,” “ambulatory white coat hypertension,” “labile HTN,” “labile hypertension,” “variable HTN,” and “variable hypertension.” The search years were limited to 1980-July 2006. Only human studies published in English were included. This yielded 233 articles initially, which were narrowed down to those mentioned herein by direct relevance to either the observed WCHT effect in the clinic or the prehospital setting.

Results

Measuring BP

Watson and colleagues[4] found that in patients who are diagnosed as being hypertensive on their first visit to a physician, their measured BP drops by a mean of 15 mm Hg systolic and 7 mm Hg diastolic by their third visit. This drop in BP is not restricted to the first few visits, and some patients do not reach a stable value until their sixth visit.[4]

Pickering and colleagues[5] studied patients who had been diagnosed as hypertensive by a clinical diastolic BP between 90 and 104 mm Hg. When having their BP measured at home, work, or by ambulatory BP monitoring, 20% to 25% of these patients were found to be in the normal range of BP.

A study conducted at Columbia University Medical Center, New York, NY, monitored the ambulatory- and physician-measured BPs in 226 normotensive and hypertensive patients. After multivariate regression, they concluded that both expectancy and anxiety had independent effects on increasing diastolic WCHT.[6]

A study by Mancia and colleagues[3] has shown that BP can be reduced by 47% or more if measured by a nurse instead of a physician.

WCHT and Health Outcome

It should be clearly mentioned that patients with WCHT are not necessarily healthy. A study by Julius and colleagues[7] had 700 untreated patients with a mean age of 31 years measure their BP first at home and then have their BP measured in the clinic. They were then categorized as being either normotensive, WCHT with an elevated BP in the clinic but normal when measured at home, or sustained hypertensive with an elevated office and home BP. The study found that patients who were in the WCHT category had similar BP results as those who have sustained hypertension, that is, they were found to have had higher BPs when screened at various times, were found to have higher systemic vascular resistance, were more likely to be obese or overweight, and tended to have higher plasma triglyceride and insulin levels relative to the normotensive category.[7]

In the HARVEST trial, 95 age- and sex-matched controls underwent echocardiography to measure left ventricular mass index. Left ventricular mass index was noted at 82, 89, and 94 g/m² for the normotensive, WCHTs, and the sustained hypertensive patients, respectively.[8] Left ventricular mass index is a well-known predictor of heart failure and is commonly found elevated in hypertensive patients.[9]

Karter and colleagues[10] performed biochemical, echocardiographic, and funduscopic examinations on 50 normotensive, 90 WCHT, and 101 hypertensive patients. WCHT patients were found to have higher body mass index, higher left ventricular mass index, higher rates of hypertensive retinopathy, higher urinary albumin excretion, and higher total cholesterol than normotensive patients but less than true hypertensive patients.[10]

In a review of hypertension, Genest[11] noted that in the early and labile phase of hypertension, increased tonicity and responsiveness of the arterioles to angiotensin II and norepinephrine may lead to long-term structural changes in the vessel, an increased media and media/lumen ratio, and a state of established hypertension.

Bidlingmeyer and colleagues[12] found in a study of 81 patients that individuals who have WCHT may progress to sustained hypertension. These patients had a clinical mean BP of 154/97 mm Hg while having a normal mean ambulatory BP of 125/77 mm Hg, and after a 5- to 6-year follow-up, 60 were found to have a mean ambulatory BP above 140/90 mm Hg.[12]

Discussion

Is WCHT a true phenomenon? A challenge in understanding WCHT is the ambiguity in terminology. WCHT describes a general phenomenon and has been interchanged with the terms labile hypertension (LHT) and prehypertension. In our search, we found only 2 articles on labile hypertension, both of which only described what it was. LHT is a term used to describe changing levels of elevated BP. Stress is a known trigger of LHT and has come to be referred to as “borderline” or “prehypertension” by many. LHT is a term seldom used today for its inability to specify a pathogenic cause of the observed hypertension. Presumably, LHT is worrisome because it can progress to full-time hypertension if not properly controlled. WCHT and LHT may indeed be 2 terms for the same phenomenon, part of the same hypertension continuum. It is important to note that as of now, WCHT and LHT are not recognized forms of hypertension and thus are not categorized as diagnoses. Regrettably, there are no studies of WCHT in the prehospital setting. WCHT as a phenomenon seen in physicians' offices is most likely also seen in the prehospital setting.

When diagnosing hypertension, it is important to take multiple readings before an active diagnosis is determined. The findings by Watson and colleagues[4] demonstrated that when measuring BP, it should be performed at least 3 times over a period of time to truly diagnose hypertension as recommended by the American Heart Association. This is an important finding because BP measurements tend not to be followed up by the paramedics. It may thus be beneficial for the patient if paramedics urge patients to seek follow-up monitoring of their BP by their physician.

For patients in the EMS setting, they are often already at a heightened state of anxiety, and under stress, patients will often present with bouts of increased BP. Then to have their BP measured by paramedics in uniform in a flashy, loud, and attention-drawing ambulance or fire truck may even further raise their BP by potentiating their stress response. Thus, it is crucial to understand that the BP measured very likely will not accurately represent the patient's true status – hence necessitating again the idea of urging patient follow-up to monitor BP.

The studies by Julius and colleagues,[7] Karter and colleagues,[10] Genest,[11] Bidlingmeyer and colleagues,[12] and the HARVEST trial strengthen the association of health status and WCHT by concluding that WCHT patients were an intermediate both in the physical findings and predictive factors of morbidity outcome between hypertensive and normotensive patients. The above 5 studies appear to suggest that WCHT is part of the evolution of normotensive patients into clinical hypertension.

If WCHT is a form of prehypertension, then identifying WCHT accurately is even more important because the above studies have demonstrated an observable pathologic change in these patients, hence necessitating the early and accurate identification of this phenomenon. The concern about WCHT being a precursor to clinical hypertension is with worry because studies have demonstrated that morbidity and mortality are substantially higher among the WCHT population compared with normotensives. This solidifies the fact that WCHT is indeed part of the hypertension continuum. Thus, it should be accurately addressed and identified in all phases of healthcare, including but not limited to prehospital EMS care.

Limitations

No objective definition of WCHT or LHT exists to date, and the phenomena are not true diagnoses. Although the WCHT phenomenon is described in the clinical setting, there is no literature on its prevalence or incidence in the EMS setting.

Conclusion

WCHT is a phenomenon that is difficult to identify because the terminology is confusing and not objective. Despite the confusing terminology, WCHT appears to be a real phenomenon and to have clinical significance. The literature supports that WCHT is a real phenomenon associated with morbidity and is very likely part of the hypertension continuum. Thus, it is important to identify patients with possible WCHT in the prehospital setting and to counsel them to seek further medical care and follow-up to allow early identification of true hypertension and its sequelae.

Given the literature reviewed, we suggest that all elevated BP readings in patients without a history of hypertension should be repeated in 5–10 minutes. Patients whose BP returns to normal should be told that they may be prehypertensive and should seek follow-up with a healthcare provider. By urging a systematic approach of identifying anomalous BP readings, the EMS system may be able to accurately identify and assist the patient in preemptively treating their state of elevated BP, thus delaying the transition to full clinical hypertension.

Table 2.

Review of Articles

Study	Number of Patients	Main Findings	Conclusion
Watson et al[4]	32	Increasing the number of visits reduced the chance of error	Before establishing a diagnosis of HTN, at least 6 visits with elevated BP should be recorded
Pickering et al[5]	292	21% of patients with untreated borderline HTN were found to have normal ambulatory daytime BP	In some patients, the pressor response can lead to significant misclassification of HTN
Jhalani et al[6]	226	Only expectancy had an independent effect on the systolic BP; both anxiety and expectancy had independent effects on the diastolic BP	Anxiety and blood pressure expectancy may elevate clinic BP
Mancia et al[3]	46	BP was repeatedly measured elevated in 4 instances over 2 days when measured by a physician; nurses measured 46.7% less rise in BP	BP readings can be lowered when measured by a nonphysician staff due to the WCHT effect
Julius et al[7]	737	7.1% of the group had WCHT and 5.1% had sustained HTN; WCHT patients had elevated lipids, triglycerides, insulin, and other outcomes higher than normotensives but less than sustained hypertensives.	WCHT patients are not equivalent to normotensives and have physiologic findings in-between the normotensive group and the hypertensive group, part of the HTN continuum
Palatini et al[8]	942	Left ventricular wall thickness was found to be between the sustained hypotensives and normotensives	WCHTs have a smaller degree of hypertensive complications than sustained hypotensives but are at greater risk than normotensives
Karter et al[10]	241	Hypertensive retinopathy, urinary albumin excretion, and cholesterol were elevated, and compliance and distensibility of the heart were decreased for WCHT compared with normotensives	WCHT patients represent an intermediate group between normotensives and sustained hypotensives in which target organ damage and cardiovascular risk are concerned
Bidlingmeyer et al[12]	81	After 5–6 years of follow-up, 74% had a mean 12-hour daytime ambulatory BP greater than 140/90 mm Hg	Patients with isolated elevated clinic BP should not be considered truly normotensive individuals

HTN = hypertension; BP = blood pressure; WCHT = white-coat hypertension