Wednesday, December 22, 2010

SVT revisited

What is Supra Ventricular Tachycardia? I think that I did a good job explaining it here. The problem that brings this up again is yet another nurse who thinks she needs to school the dumb paramedics.

I was recently training a new paramedic, and I showed him a picture of a Sinus Rhythm at a rate of 180 beats per minute. I told him that he was, for the purpose of this discussion, working at the first aid tent of a marathon, and that this was the presenting rhythm of a marathon runner who was complaining of dizziness. I use this scenario often as a training aid, and this medic, as new medics invariably do, identified the rhythm as PSVT and stated that it should be treated with 6mg of Adenosine. I asked why, and he told me that PSVT is any rhythm that has an origin above the ventricles, and a rate of over 150 beats per minute.

I pointed out to him that while SVT is technically any tachycardia that occurs above the ventricles in a purely literal sense, it is important for clinicians to recognize that what we refer to as PSVT is a dysrhythmia, and that there is not any set heart rate that separates Sinus Tachy from PSVT. The only way to tell the difference is to do a good patient assessment.

A nearby RN overheard, and attempted to tell me why I was wrong, and that 150 bpm is the standard for defining SVT.

I asked her why she felt I was incorrect in saying that the aforementioned marathon runner is probably in Sinus Tachy. This rhythm is a response to the normal metabolic demands of the runner's body. A person taking a stress test has similar responses. (After all, the target heart rate for a stress test is usually over 150 beats per minute)

Instead of answering, the RN tried to tell me that the AHA defines SVT as all tachycardias that originate above the ventricles and have a rate over 150. Sigh. Where does the AHA say that?

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