Q. When doctors interpret a blood pressure reading, should they also consider the heart rate?

I'm a 78-year-old man and have had high blood pressure (under control) for more than 40 years. I frequently monitor my blood pressure at home, resting for five minutes before I take the reading. My blood pressure is often higher when my heart rate is close to its usual resting rate (about 50 beats per minute) and lower when my heart is beating faster than that.

Can the body's demands that cause higher blood pressure be partially satisfied by a faster heart rate?

A. First, let me congratulate you on monitoring your blood pressure at home.

This is a great way for you to take control of your high blood pressure, and a good step toward preventing a stroke. Knowing that your blood pressure at home is under consistent control is more important than getting isolated readings at the doctor's office.

You are also resting before taking the reading, and this is important to avoid spuriously high readings that happen when someone rushes around, and then sits down quickly to take a blood pressure reading. (Readers interested in monitoring their blood pressure at home can watch the video below.)

Heart rate and blood pressure are intimately related.

Nerves and hormones constantly monitor and balance the heart rate and blood pressure. It is true that an isolated increase in blood pressure can drop the heart rate a little. But the reflexes that control blood pressure and heart rate are not simple.

Sometimes, both heart rate and blood pressure can fall simultaneously, as happens with a typical fainting episode. Often, both heart rate and blood pressure rise together, such as when you exercise, get angry, or have an overactive thyroid.

I suggest that you write down your heart rate along with your blood pressure, and bring that information to your doctor every time you see him or her.

Heart rate trends can provide useful data on your cardiovascular health.

A consistently low heart rate, like yours, can indicate that some medicines might not be good for you. A consistently high heart rate can suggest that the thyroid be checked.

Harvard Health: Measuring blood pressure at home

There is a right way and a wrong way to measure your blood pressure. In this video, Harvard Heart Letter Editor Patrick Skerrett demonstrates both.

Richard Lee, M.D., Associate Editor, Harvard Heart Letter

(c) 2010 The Medicine Cabinet: Ask the Harvard Experts