DESCRIPTION

The rhythm is fairly regular and looks like sinus rhythm, with P waves before each QRS. But if you look closely, you’ll see some irregularity, a phasic speeding up and slowing down of the heart rate a few beats per minute. If you’re particularly astute, you may notice that it speeds up with inspiration, and slows with expiration. This is not a coincidence! Your physiology professor might be able to explain this to you.

HABITAT

Usually NOT in the intensive care unit; this is a restful rhythm, where there is not a lot of adrenergic drive. We see this more in young ‘uns.

CALL

“What’s for dinner?”

RESEMBLANCE TO OTHER ARRHYTHMIAS

Most often this arrhythmia is confused with premature atrial complexes (see below), and can lead to endless arguments between physicians, nurses, and cardiologists about which of the two is present. If the underlying rhythm is perfectly regular and then there is an early beat, it most likely is a premature atrial complex. If you see a phasic speeding up and slowing down of the heart rate you are most likely seeing sinus arrhythmia. In either case treatment doesn’t really change, since in general no therapy is indicated for either arrhythmia. Since therapy and outcome aren’t affected, it makes a very good subject to argue about.

CARE AND FEEDING

Pat the patient on the head and wish him or her a good night.

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