Atrial FibrillationDoctors Give an Overview of an Abnormal Rapid Heart Rhythm

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Dr. Morris: Welcome to an MUSC Health Podcast. Hi, this is Dr. Pam Morris, and today I'm interviewing Dr. Marcus Wharton who is Professor of Medicine, and Director of Cardio-electrophysiology at the Medical University of South Carolina. We're talking today about atrial fibrillation, and in my practice, Marcus, I'm noticing that this is a more and more frequent problem. What is atrial fibrillation?

Dr. Wharton: That's a good question, Pam. It's a very common problem, first off, and that's why you see it so commonly in your practice. If you look at the population of people as we get older, it becomes increasingly more frequent. About five percent of the population after the age of sixty-five have atrial fibrillation. And it's an abnormal arrhythmia arising in the upper chambers, or atria of your heart. And it's associated in most, but not all patients but most with rapid palpitations, fluttering, maybe shortness of breath, light headedness, a decrease in your exercise capacity. About twenty-five percent of people though can have atrial fibrillation and never know it. And that in part depends on how fast the lower ventricles, the lower chambers go in response to atrial fibrillation.

Dr. Morris: So this is actually an abnormality of the electrical rhythm of the heart?

Dr. Wharton: It's an abnormally rapid rhythm. It's very chaotic. It's a rhythm going about three hundred to five hundred beats per minute in the upper chamber, in the atrium. Now the lower chambers don't go that fast. If they did, you'd probably pass out, but the upper chambers are going three to five hundred beats per minute. The lower chambers typically in the untreated patient are going about a hundred and fifty, a hundred and sixty beats per minute.

Dr. Morris: And what is the normal heart rate that someone could normally tolerate very well?

Dr. Wharton: Well a normal heart rate in resting sort of situations would be sixty to a hundred beats per minute. With exercise or exertion your heart rate would go up to a hundred and fifty, a hundred and sixty beats per minute. What makes atrial fibrillation, though, different from say a fast heart rhythm with exertion is that with your normal heart rhythm is that your normal heart rate is very regular and predictable. Whereas with atrial fibrillation, given the way that it communicates to the lower chamber causes a very irregular and rapid pulse. And so that's kind of the hallmarks of atrial fibrillation, is that it is what we call irregularly irregular. And that means that it is chaotic. Some fast first, some slow pauses, but because of the rate, and because of the irregularity, patients generally don't tolerate it, and it has a great impact on the quality of life that they experience.

Dr. Morris: I would imagine to that irregularly and the rapidness of the heart rate could effect how well the heart functions.

Dr. Wharton: It does. There's two components to that. One, the rapid rate and the irregularity decrease cardiac function, but also it increases a loss of what we call synchrony between the upper chambers and the lower chambers, so the upper chamber initially contracts, and in a few fractions of a second later the lower chamber of the heart contracts. That gives time for the upper chamber to empty its blood into the lower chamber, and when you do that you maximize the efficiency of the heart. In atrial fibrillation you loose that synchronization between atrial and ventricular events, and that also impairs ventricular function, or how patients feel.

Dr. Morris: So the chambers just don't work as well together as a team.

Dr. Wharton: They don't. Actually it's interesting, the word fibrillation comes from the Latin word fibril

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