Don: Um, Yaël? Isn't a normal heart rate somewhere between sixty to one hundred      beats per minute?

Yaël: That's right, Don. Why?

D: This would be the one time you don't correct me. My heart rate is only forty-four      beats per minute. That means I have bradycardia. Oh, Yael, I may be dying.

Y: Hold up. Yes, bradycardia is the term for a heart rate slower than about sixty beats      per minute, but bradycardia doesn't necessarily mean you're not in perfectly good      health. In well-conditioned athletes, bradycardia is a result of being in such good      shape that the heart beats more efficiently, and so it doesn't need to beat as quickly.      An athlete may have a heart rate as slow as thirty and not show any signs of      problems. Also, deep relaxation, such as sleep, slows the heart down.

D: Yeah, yeah. Tell me about the bad news.

Y: Well, bradycardia can also be caused by certain medications, by other disorders      such as hyperthyroidism, and by dysfunction of the sinus node. I don't mean the      hollow space behind your nose, but the node inside your heart. The sinus node      powers your heart by electrical impulses. Dysfunction of the sinus node then can      cause the heart to beat too slowly to keep up with your body's need for blood.      Lightheadedness, weakness, and fainting are symptoms that a heart may be beating      too slowly. In such cases, doctors will remove problem medications, correct the      underlying disorder, or insert a pacemaker that fills in for the sinus node. If      symptomatic bradycardia goes untreated, it could lead to death, but that's easy      enough to prevent--just go see your doctor.  

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