The interarm blood pressure difference as predictor of cardiovascular events in patients with hypertension in primary care: cohort study.

Objectives of this study were to measure the prevalence of a difference in blood pressure (BP) between arms and determine whether a difference is associated with increased risk of cardiovascular events or death. A prospective cohort study of 247 patients with hypertension was undertaken in one rural general practice in England. The main outcome measures were mean difference in BP between arms and new episodes of myocardial infarction, cerebrovascular event, onset of angina or peripheral vascular disease or death. A total of 57/247 (23%) patients had a mean difference in systolic BP between arms of >or=10 mm Hg and 8/247 (3%) had a mean difference of >or=20 mm Hg. A total of 15/247 (6%) patients had a mean difference in diastolic BP between arms of >or=10 mm Hg. Survival analysis after 4.7 years (range 3.3-5.9) showed a shorter mean survival time without event or death for patients with a difference in systolic BP of >or=10 mm Hg compared with a difference of <10 mm Hg (3.7 (95% confidence interval, 3.2-4.2) versus 4.8 (4.6-5.1) years; P<0.001; hazard ratio 2.5 (1.5-4.2), P=0.001). Difference in systolic BP of >or=10 mm Hg between arms is common in this primary care population and is associated with a shorter survival time to death or new cardiovascular event. Detection of a difference between arms may identify hypertensive patients at increased risk of cardiovascular events. Such an approach would allow more effective targeting of resources in primary prevention strategies.