DESCRIPTION

The same as sinus rhythm, only faster: by definition, sinus rhythm with a rate over 100. Each QRS is preceded by a proper P wave. If you are seeing rates over 140 in a patient resting in bed, either they’re REALLY sick or it may not be a sinus tachycardia at all (i.e., some sort of supraventricular tachycardia in disguise, see below). On the other hand, if the patient is running on a treadmill or pursued by a carnivore, a sinus tachycardia at 160 may be quite appropriate.

HABITAT

Commonly found where people are frightened, stressed, hurt, or in pain, such as in an Emergency Department or Operating Room, or if you are a medical student presenting a case to the Chief of Service or taking a final exam. The rhythm is often driven by adrenaline, which is why it is never found during mandatory infection control handwashing updates. But you may commonly see this with fevers, trouble breathing, pain, blood loss, or dehydration – anything that fires up the “fight or flight” system and gets the adrenaline pumping. Some medications themselves can speed up the heart rate, like bronchodilators or dopamine. Don’t forget that accidentally omitting someone’s β-blocker can result in fantastic sinus tachycardias!

CALL

“Get these restraints off me!”

RESEMBLANCE TO OTHER ARRHYTHMIAS

Just like with normal sinus rhythm, it is regular, with a P wave before each QRS, only faster. If a patient is resting in bed we normally wouldn’t expect a rapid heart rate, so if one is present it may mean something is going on. If the heart rate gets really fast (140 and up), unless something terrible is happening (like the bed is on fire), it might be a completely different rhythm, such as atrial flutter with 2:1 atrioventricular (AV) block, or a supraventricular tachycardia (see below).

CARE AND FEEDING

Try to identify and treat the underlying problem, such as lowering the fever, giving oxygen, putting out the fire, or turning down the volume of the Led Zeppelin music from the next bed … you get the idea. If that doesn’t work, a little β-blocker (if the patient isn’t in shock), a little sedation, or a little analgesia might help.

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