Erratic heart rate

Dear Dr. Roach: A couple weeks ago, I had a sudden fast heartbeat with a very irregular and erratic pulse (approximately 150-161) for about six hours, along with a very low blood pressure, ranging from 74/59 to 79/52. I first felt a strange thumping in my neck area. I am treated for high blood pressure with amlodipine, losartan and HCTZ. My BP usually is in the normal range, and I have never had an episode like this. I called my doctor’s office a day later, and he ordered a Holter monitor (I will have it tomorrow). I was feeling some anxiety before this happened, but this has been an entirely new event for me. My other medications include thyroxine. I am 90 years old, in good health, mild arthritis, alert and oriented. What could possibly cause such an episode? — E.P.

Answer: A sudden, fast heart rate without exertion can be caused by anxiety or fright; however, that doesn’t sound like what happened to you. Your report sounds very much as though you had an episode of atrial fibrillation. The atria are the top chambers of the heart, which fill with blood passively from the veins of the body (on the right side) or the lungs (on the left), and contract to fill the ventricles. The right atrium also normally provides the electrical stimulation for the heart. In atrial fibrillation, instead of, say, 60 beats a minute, the atria may put out a thousand impulses a minute. The heart cannot possibly respond to all those impulses (there is a safeguard built into the electrical system), so the heart rate becomes highly irregular and variable. The rate may be normal, but more frequently it is too fast. One of the goals in atrial fibrillation is to control the heart rate, to protect the heart from going too fast. A rate of 160 in a 90-year-old is not safe, and the fact that your blood pressure went down is concerning: I would have considered admitting you to the hospital in this situation, and certainly would have recommended that you be seen and get an EKG at the time.

People with atrial fibrillation also are at risk for blood clots forming in the heart, and these can travel to the brain, causing a stroke.