News - Hypertension Week of October 19, 2003/ Vol. 2 No. 42

Study: Oxygen Flow May Identify Heart Problems in Mildly Hypertensive Patients

Doctors can find out early if their patients with mild hypertension have heart problems by following how much oxygen is circulated through their body with each heartbeat during exercise.

"Our research shows that patients with mild hypertension have some reductions in heart function," said study author Kerry Stewart, director of clinical exercise physiology at Johns Hopkins University. "We need to get their blood pressure under control, even if it is only mildly elevated."

As reported October 17 at the American Association of Cardiovascular and Pulmonary Rehabilitation annual meeting in Kansas City, the researchers studied 99 otherwise healthy people between the ages of 55 to 75 with mild hypertension (130 to 159 mmHg systolic and 85 to 99 mmHg diastolic).

Stewart and his colleagues measured the patients' heart sizes and heart performance at rest through traditional echocardiograms and a newer ultrasound method called tissue Doppler imaging that examines the functioning of the heart's walls. Next, they compared those results with the participants' heart performance during exercise on a treadmill.

The researchers measured oxygen usage during the exercise portion by having the subject breathe through a mouthpiece attached to a valve that measures how much oxygen is used during the test.

Normally there is a sharp increase in oxygen pulse during the first few minutes of exercise. This rise continues with exercise, and the load on the heart also rises as it works harder to meet the body's increased needs for oxygen.

However, the researchers found that subjects who were delivering less oxygen to the body per beat after the first few minutes of exercise also had reduced levels of heart function during the Doppler tests of their hearts at rest.

The study shows that mildly elevated blood pressure can lead to heart pumping disorders if left untreated, and suggests that paying attention to oxygen pulse during exercise may be a useful screening tool for identifying heart problems.

Other sources: Johns Hopkins Medical Institutions