It is important to distinguish white-coat hypertension from real hypertension and consider whether it should be treated. By Michael Lim

YOU visit your doctor’s clinic and you are told that the blood pressure is elevated. Does it really mean that you have high blood pressure (hypertension)? A 76-page document forms the European Society of Cardiology and the European Society of Hypertension (ESH/ESC) 2013 guidelines for hypertension – a telling sign that not all the experts can agree on many of the issues pertaining to hypertension.

While the latest guidelines state that “it is recommended that the diagnosis of hypertension be based on at least two blood pressure measurements per visit on at least two occasions”, it recognises the limitations of basing the diagnosis of hypertension on the current definition and supports the use of home blood pressure monitoring in hypertension management.

In the latest guidelines, the criterion for the diagnosis of hypertension based on a blood pressure reading of 140/90mm Hg or more has remained largely unchanged.

White-coat phenomenon

Diagnosing a person as having hypertension is not as simple as it seems. For a long time, physicians have noticed that there are patients who have a higher blood pressure reading whenever they visit a doctor but the blood pressure reading is lower outside the clinic or hospital environment. This observed blood pressure pattern is termed the “white-coat phenomenon” in reference to the white coats commonly worn by doctors. Elevation of the blood pressure without reaching hypertension thresholds is described as the white-coat effect and is present in almost everyone who visits a clinic.

This is thought to be due to the activation of the nervous system by the brain. However, through multiple visits, the blood pressure can gradually decrease as a result of the person being conditioned to the environment.

The presence of the white-coat effect can also occur in those with proven hypertension and may create a false impression that the patient’s hypertension is resistant to medication; this may result in excessive medication being dispensed and the patient complaining of dizzy spells at home.

White-coat hypertension

The latest European guidelines define white-coat hypertension as clinic systolic (upper reading) and diastolic (lower reading) blood pressure readings of 140/90mm Hg and a 24-hour blood pressure of less than 130/80mm Hg; the US guidelines define white-coat hypertension as a clinic blood pressure of 140/90mm Hg and an average daytime ambulatory blood pressure reading of less than 135/85mm Hg.

The 24-hour blood pressure reading is obtained by putting the patient on an ambulatory blood pressure monitor, usually on the arm, and recording blood pressure readings at regular intervals over a 24-hour period.

Patients who are considered to have white-coat hypertension do not have evidence of damage of blood pressure on the body’s organs and do not require medication.

Data from papers published by the European Society of Hypertension in the Journal of Hypertension in 2013 and British Hypertension Society in British Medical Journal in 2000 shows that about 15 per cent to 30 per cent of patients who have elevated clinic blood pressure readings have white-coat hypertension and this is more frequently present in women than men.

Distinguishing white-coat hypertension from real hypertension is important as it avoids unnecessary medication, unnecessary costs and unnecessary premium payments for insurance.

In the elderly, the administration of medication to those with white-coat hypertension can have the unintended effects of dizzy spells and falls with serious consequences. In those with white-coat hypertension, it has been noted that the clinic blood pressure can decrease by up to 15 mm Hg for the systolic blood pressure in subsequent clinic visits and probably represents conditioning of the patient to the clinic environment.

In some patients, it may require up to six clinic visits for the blood pressure to become stable.

Is white-coat hypertension of any consequence?

There is evidence that patients with white-coat hypertension are more likely to develop long-term sustained high blood pressure. In one study, slightly more than one-third of patients with white-coat hypertension progressed to sustained high blood pressure over a mean period of 2 1/2 years and this progression was associated with evidence of thickening of the heart muscle resulting from high blood pressure.

Those who are more likely to continue having sustained high blood pressure are those who are older with blood pressure near hypertensive limits, and those with underlying medical conditions that predispose them to high blood pressure (such as sleep-related breathing problems, diabetes and impaired kidney function).

Should white-coat hypertension be treated?

The question of whether patients with white-coat hypertension should be treated remains very controversial primarily because there is data from the 2012 International Database on Ambulatory Blood Pressure in Relation to Cardiovascular Outcomes (IDACO) study to show that in men and in patients with diabetes mellitus, the presence of white-coat hypertension is associated with increased risk of heart disease.

While there is no consensus as to when patients with white-coat hypertension should be treated, generally, those with high-risk factors for heart disease and those with evidence of damage to the body from the effects of elevated high blood pressure should be considered for treatment.

Evidence of damage to the body can be detected by using ultrasound to measure the degree of narrowing of the neck (carotid artery), thickening of heart muscle (due to strain on the heart), detection of albumin in the urine (due to kidney damage) and increased stiffness of the arteries.

A simple indicator of significant stiffness of the arterial system is that the difference between the systolic and the diastolic blood pressure readings (pulse pressure) is more than 60mm Hg. In most healthy people, the pulse pressure is usually not more than 40mm Hg.

Some advice

If you have an elevated blood pressure reading (more than 140/90mm Hg) at your doctor’s clinic, you should consider repeated measurements both at home and at your doctor’s clinic before starting on medication.

If however you already show evidence of organ damage from sustained high blood pressure, you should commence medication. If you have persistent white-coat hypertension, you should consider lifestyle changes such as salt reduction and stress reduction as there is evidence that it can potentially be detrimental.

If there is considerable variability of your blood pressure and/or presence of a pulse pressure of more than 60mm Hg, you should discuss treatment with your physician as there is data to show that blood pressure variability and severe arterial stiffness are associated with adverse consequences.

If you are on medication for hypertension and you get frequent dizzy spells, especially when you get up from a lying or sitting position, it may be possible that you may have white-coat hypertension. The most important point to remember is this: ensure you do not have white-coat hypertension before you commence any treatment for elevated blood pressure.