[JM 5]BP measurements, while not always reliable, still yield valuable information

Blood pressure measurements, in spite of their potentially variable and unreliable nature, provide valuable information about cardiovascular disease and other complications of high blood pressure (BP), said an expert from Australia.

“It is often out of one reading that decisions are made, [which] are minor representations of what your blood pressure is, but paradoxically these decisions have led to major advances in the management of people and prevention of death,” said Professor Trefor Morgan, of the Department of Medicine and Physiology at the University of Melbourne.

Taking blood pressure measurements correctly and under controlled conditions can help guide treatment in individuals. But typically, blood pressure is taken in one or two random measurements, which often determine how a patient is treated, whether it is an acute or long-term issue.

It is clear in the elderly, Morgan said, that systolic blood pressure (SBP) should guide therapy. However, it is less clear in younger people because of variability in diastolic blood pressure (DBP). When a younger person has hypertension, DBP is elevated, which automatically elevates the SBP, but to a level that may still be below the cutoff for disease.

More measurements such as ambulatory BP and home BP can round out measurements in the clinic and reduce inaccuracy. A Japanese study of 1,360 adults in a rural community who underwent 24-hour BP monitoring and home BP measurements followed up for 10.6 years showed that these measures were useful for adding predictive cardiovascular disease (CVD) information. [J Hypertens 1997;15:357-364]

Tracking night and sleeping BP had predictive value for vascular complications including ischemic stroke, ischemic heart disease and other heart disease. Daytime BP, on the other hand, had superior predictive value for hemorrhagic stroke.

Still, people do not develop cardiovascular damage at the same rate, Morgan said.

“Some people will have very high blood pressure and never get complications. Others with relatively normal blood pressure might develop left ventricular heart disease.”

Certain conditions can cause changes in blood pressure, such as during pregnancy or in the presence of diabetes and metabolic syndrome, when complications can occur at lower levels of elevated blood pressure.

“With all the variations and problems associated with blood pressure, let alone the problems and inaccuracies in measurement, I am amazed that we have been so successful in altering the lives of the people that we treat,” Morgan said.