A 60 yo male came into Midtown a few days ago for generalized weakness. He was hemodynamically stable and the EKG above was obtained. With an irregularly irregular wide complex tachycardia like this our differential is fairly short…
1) A-fib or MAT with aberrant conduction (aka a bundle branch block)
2) A-fib or MAT with conduction via accessory pathway (aka WPW)
3) A-tach or A-flutter with variable block and aberrant conduction
4) A-tach or A-fluter with variable block and accessory pathway
So how do we tell the difference? And does it matter, or should we just treat them all the same to avoid making mistakes? In the unstable patient electricity is always the answer, but in stable patients you can go in a few different directions.
If you felt confident that this was Afib/Aflutter with aberrancy you might consider rate control with a nodal blocking agent, but you risk dropping their BP with diltiazem or metoprolol, and if this is in fact Afib with WPW nodal blocking agents could cause increased conduction through the accessory pathway initiating Vfib.
if you think this is WPW procainamide is your first line choice. In theory this will only slow conduction through the accessory pathway, but in reality there is also a high likelihood you will convert the patient back to a sinus rhythm. This could cause an embolic event just like electrical cardioversion. Also this is a high stakes scenario and it is hard for me to reach for a drug I have only given a handful of times.
My thought is unless you have a good reason not to shock, synchronized cardioversion is the way to go for all wide complex irregular tachycardias. In a high stakes situation, it’s good to stick to what you are most comfortable with. For me, that’s 0.15 mg/kg of etomidate, and 100-150J of synchronized cardioversion. Of course there are always exceptions and a good history from the patient might change the direction I go in, but when it doubt… shock! Curious to hear everyone’s thoughts…