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Case #34

You are on call covering the medicine floors of the hospital. You are in a deep sleep when all of a sudden your pager wakes you up "CODE 99 telemetry, CODE 99 telemetry". You rush out of bed and run to the telemetry floor to asses the situation. You arrive to the floor and can see the nurses setting up the code cart outside of one of the patients room. As you reach the room, one of the nurses hands you this strip and says the patient is unresponsive with no pulse and still in this rhythm on the monitor. What is the Rhythm and what do you do?

Click Here for Larger Image of Telemetry Strip

 

 

This is a great example of what the R on T phenomenon can lead to.

First of all before analyzing the strip, the first thing we do in this situation is run the code! Luckily because she was on a monitored floor, she was not down for long. She was shocked successfully back into sinus rhythm after the second shock before any meds where given, and was kept in sinus rhythm on an amioderone drip. The patient had an Ejection Fraction of 20%, coronary artery disease, ischemic cardiomyopathy and eventually had an ICD placed and did very well.

Now for the rhythm strip. The beginning of the strip the patient is coasting along in Sinus Rhythm. On beat number 5, she has a PVC during the QT interval (r wave on t wave). It is not clearly seen where the PVC happens that it is on the t wave, but looking at the previous QT intervals you can extrapolate that the PVC occurs during the QT interval, there for on the t wave. This PVC is the inciting event which begins the following tachycardia. This tachycardia is wide, it is regular, it is @ a rate of 290's, and is characteristic appearance of Ventricular tachycardia. The next step is to determine if it is monomorphic or polymorphic. All this means simply is if every complex looks like the next one (monomorphic) or if the complexes in the tachycardia look different from each other. In this case, you can easily see the the QRS complex is changing as the tachycardia progresses, making it a polymorphic ventricular tachycardia, which is also known as Torsades Des Pointes. The reason why we take this next step in calling it polymorphic or monomorphic is sometimes the causes of these two types of tachycardias can be very different.

Now looking back after converting the patient back into sinus, why did she develop this rhythm? Given the patient had coronary artery disease, the circuit for the tachycardia was likely around an old scar, and having the R on T (PVC) allowed for some part of the circuit to be refractory and conduct slow enough and other parts to be re-polerized to conduct fast and be just right to sustain the tachycardia. If you can recall that the T-wave represents myocardial repolerization. So having a PVC before repolerization is complete, the situation described develops. The figure illustrates this a little better.

Now in this patients instance, she does not have a fixed unifasicular block, but the PVC creates it and there for allows the tachycardia to be sustained. That is why a "R on T" is of concern because given the right situation, as in this patient, torsades can develop