Every patient at Atlanta Hyperbaric gets his blood pressure taken. Measuring a patient’s blood pressure has become a ritual part of the medical examination since the early twentieth century and it didn’t take long to discover an association between high blood pressure and cardiovascular disease. I find it remarkable that after a hundred years of study, researchers are still discovering fundamental truths about this simple and routine medical test.
English researchers just reported that visit-to-visit variability of a patient’s blood pressure over time may be a stronger risk factor for stroke than average blood pressure. The authors looked at blood pressure measurements from four separate studies of patients who had been carefully checked for many years following a stroke or TIA. Overall, more than 10,000 patients had been followed. The researchers found that a high average systolic pressure was a weaker predictor of subsequent stroke than a large variability in systolic pressure over repeated measurements. The risk of stroke of those with the most variable blood pressure compared to those with the least variable blood pressure ranged from 1.78 to 4.84 across the four study groups.
In a companion study, different classes of anti-hypertensive drugs had different abilities to smooth out this variability in blood pressure. The researchers reviewed hundreds of drug trials for treatment of hypertension and discovered that calcium channel antagonists reduced blood pressure variability but ACE inhibitors and Beta blockers actually increased variability. Perhaps even more importantly, it looked like patients treated with the calcium channel antagonists had fewer strokes.
The authors concluded that, “To prevent stroke most effectively, blood-pressure-lowering drugs should reduce [average] blood pressure without increasing variability; ideally they should reduce both.”
Do these studies mean that physicians should be changing the way they treat and monitor their patients with hypertension? At least physicians need to start looking at this issue. It may not be enough just to reduce average blood pressure anymore.