A Relatively Narrow Complex Tachycardia at a Rate of 180.

I received a text message with this image: "Cardioversion didn't work.  Any thoughts?" What do you think?  The heart rate is 180.I was viewing this on my phone, but I saw what I thought were P-waves.  I could barely see them in lead II:There are probable P-waves at the arrows, but I wasn't certainI texted back: "Could be very fast sinus."There is also a wide QRS at 113 ms and a large R-wave in aVR, so sodium channel blockade is likely.   Common culprits in this situation are tricyclic overdose and cocaine toxicity (remember cocaine not only increases dopamine in central synapses, but is also a local anesthetic (-caine!) due to Na channel blockade.  Both of these also cause seizures. Here is the history:Male in 40's who had seizures and was unconscious.  BP 200/100.  Pupils dilated.  They had already given adenosine 6 mg and 12 mg without effect.  They had already cardioverted at 120 J, then 200 J, which resulted in Ventricular Tachycardia (no tracing recorded).  They then cardioverted at 200 J which resulted in the same ECG was have above, at 185 beats per minute. I suggested esmolol if the heart rate did not improve.  This would treat both SVT or sinus tachycardia. However, the heart rate gradually fell to 120 with fluids and was proven to be sinus tachycardia. Later, he was found to have used cocaine.  There was a good outcome.Comment:Don't forget that sinus tachycardia can be very tricky!  I ha...
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