Monitoring Blood Pressure – What is the Best Measure?


English: Blood pressure measurement.

Blood pressure measurement. (Photo credit: Wikipedia)

Blood pressure is a vital sign. Traditional methods of measuring blood pressure can be inaccurate and misleading. Repeated office measurements are an unscientific approach to assessing and monitoring blood pressure control.

Uncontrolled hypertension causes most strokes and heart-attacks. If hypertension goals were achieved, strokes would reduce by 50% and heartattacks by 15 to 20%.

Three blood pressure measurement procedures are used:

  • Clinical conventional office measurements in the doctor’s surgery.
  • Self-blood pressure measurement or home measurement.
  • Ambulatory blood pressure measurement.

Office measurements can be very inaccurate for detecting hypertension if not performed with accuracy and reproducibility. So why do doctors still rely on the office method to monitor this vital heart risk parameter?

Up to three major aspects of blood pressure contribute to heart disease risk including average blood pressure, diurnal variation, and short-term variability.

Problems with Office Measurements

Taking repeated measurements of blood pressure can highlight a potential problem of high blood pressure in some patients. It does not diagnose hypertension unless we repeat the higher than normal blood pressure measurements.

The silent killer reputation of hypertension is reinforced by the misleading reliance on single or once repeated measurements in the office setting. Measurements taken in the office setting leads to some patients being misclassified as being hypertensive based. In contrast, some at-risk patients who would benefit from management strategies are missed.

Taking accurate, repeated measurements is the only way to ensure adequate control is being achieved in the hypertensive patient. The various approaches to control can only be deemed a success if blood pressure is accurately determined. So if measurements are inaccurate during the intervention, then effectiveness can never be determined.

Three major contributors to inaccuracy of office measurements are: poor measurement technique or equipment, white coat hypertension and blood pressure variability.

An incorrect diagnosis is made in 30-40% of cases. For example, in 20-25% of diagnosed hypertensives, blood pressure is only raised in the presence of a health professional – white coat hypertension. Similarly, high blood pressure may appear normal in the office setting, masked hypertension, in up to 10-15% of the general population, and thus may be missed.

There are no markers of white coat hypertension. It is usually suspected if office measurements are extremely variable or if the blood pressure measurement is extremely high in someone with no other risk factors for cardiovascular disease. It can result in unnecessary antihypertensive treatment.

Masked hypertension if missed underestimates the individual’s risk of cardiovascular events and may mean at risk patients are not being identified and treated appropriately.

Even if readings are taken by a trained professional, they may not being adhering to recommended guidelines with respect to proper procedure. For example, the use of incorrect cuff sizes, the reliance on one or two measurements only perhaps for expediency, or the neglecting to ensure that the patient is at rest at measurement.

The traditional sphygmanometer device can produce accurate results. There are some reports that automated devices or devices that rely on aneroid or oscillometric measurement may in some cases not be as accurate.

Self Measurements

Self-measurement of blood pressure in the home using commercially available devices, including wrist devices, has risen in popularity among the general population. It is a misconception that this is superior to office measurements and avoids the white coat effect confounder. Wrist devices and inaccurate technique can produce errors in readings.

Ambulatory Blood Pressure

Twenty-four-hour ambulatory monitoring gives a better prediction of risk than office measurements and is useful for diagnosing white-coat hypertension.

Ambulatory blood pressure measurements are currently recommended for people with borderline hypertension, suspected autonomic dysfunction, episodic hypertension, drug resistance and to assess drug compliance.

Night-Time Dippers

Ambulatory blood pressure measurement is superior at predicting outcomes in hypertensive patients because it also measures night-time blood pressure, which is the greater predictor of all in terms of risk. The dipping pattern is particularly important and non-dippers are at greater risk than those who have a dip in blood pressure.

Normally, blood pressure tends to taper off towards the end of the day. So blood pressure is higher during the day and falls to a pressure nadir in the early morning and rises again in the morning.

In an estimated 10% of those with high blood pressure there is no nocturnal dipping of between 10-20% in blood pressure. These are thought to be at greatest risk of subsequent cardiovascular events and it is for these patients that ambulatory blood pressure will be of greatest benefit.

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