High BP may ward off ischemia during exercise

During exercise, having a high diastolic blood pressure, which is reflected in the second number of the BP reading, may offer protection from exercise-induced restriction of blood flow to the heart - a condition called myocardial ischemia.

"We demonstrated that patients with high diastolic blood pressure during exercise had less severe exercise-induced ischemia than patients with normal diastolic blood pressure," investigators report in the American Heart Journal.

Dr. Hiroyuki Yamagishi, from Osaka City University Graduate School of Medicine in Japan, and colleagues analyzed data from 469 patients with suspected coronary artery disease who underwent heart imaging studies during exercise. A diastolic blood pressure of at least 90 mmHg at peak exercise was considered high.

Roughly half of the patients had normal diastolic blood pressures during exercise and half had high pressures. No significant differences in number of diseased vessels, the severity of atherosclerosis (clogged arteries) or medications were noted between the groups.

Patients with high diastolic blood pressure during exercise had a higher pressure-rate product than their peers with normal pressure, suggesting that ischemia was attenuated in the former group.

High blood pressure is one of the risk factors for coronary artery disease, the authors explain. Most coronary blood flow to the left ventricle of the heart occurs during diastole (dilation) because the vessels are compressed during systole. Therefore, a high diastolic blood pressure during exercise is hypothesized to have a protective effect on exercise-induced ischemia. The findings of the current study support this theory, the investigators conclude.

SOURCE: American Heart Journal, October 2005.