White-coat hypertension

In his recent CMAJ editorial on white-coat hypertension,1 David Spence reviews the question of 24-hour ambulatory monitoring of blood pressure, which often demonstrates a lower blood pressure reading than that done in a medical centre. I agree with this phenomenon.

The patients I refer to a cardiologist for ambulatory monitoring are those whose blood pressure is uncontrolled by combinations of antihypertensive drugs. The cardiologist often measures a normal ambulatory reading, leaving me looking like a fool.

When these patients return to me, do I proceed to ignore the readings over 150/100 mm Hg in my office because their ambulatory numbers were normal? No, I treat on the basis of the higher readings I see in my office. If I am charged with overtreatment, Spence will back me up, as he correctly states that our current success in preventing heart attacks and strokes comes from treating on the basis of office blood pressure readings.

There are now blood pressure testing machines in many drugstores, and many patients also take their own readings at home with equipment we recommend. In virtually every case, the systolic numbers are at least 20 mm Hg lower than what I find at the office.

I advise patients that the office readings, taken in a more stressful situation than most ambulatory settings, demand attention. This may be contrary to current teaching that physicians should base treatment on the lower levels of blood pressure, but life is a compromise. So we may split the difference, shaving a few mm Hg from the top readings. This leaves everybody happy.