EKG of the Week 2016 10-2

This EKG comes courtesy of Dr. Benson and Dr. Hardy.

A 60 year old female presents to the ED complaining of palpitations, chest heaviness, right arm pain and shortness of breath.

V/S: P 210, R 20, BP 140/80, O2 sat 98%.

Her EKG is below.

1.       What is the rhythm?

2.       How would you manage this patient?



The rhythm is SVT.

The patient was treated with adenosine. The repeat EKG is shown below.


The initial EKG demonstrates a narrow complex tachycardia at a very rapid rate. At such a fast rate it may be difficult to tell if the rhythm is regular or irregular. This rhythm happens to be regular and there are no P waves or flutter waves. SVT is the diagnosis.

When the rate is this fast it may be difficult to differentiate SVT from rapid a-fib. History may give you a clue. If the patient has a history of one arrhythmia, that may be a clue that they are having the same arrhythmia again. However, remember that is not 100% accurate as patients can have any arrhythmia. In this scenario, when you are unsure if it is SVT or a-fib, adenosine can be diagnostic. Make sure to watch the rhythm on the monitor as the adenosine is administered. The QRS complexes will disappear and the underlying atrial rhythm will become visible. If the rhythm was SVT you may see no atrial activity or you may see P waves, and the arrhythmia may completely terminate. If it was a-fib, you may now see the fibrillatory waves on the monitor and the tachyarrhythmia will come right back.

Tachyarrhythmias with rates above 200 should raise the concern about the possibility of an accessory pathway (i.e. WPW). If the QRS complex is narrow, you can assume the rhythm is orthodromic and it is safe to administer AV nodal blockers. However, if the QRS is wide you must be concerned about an antidromic tachycardia. In that scenario, procainamide is the drug of choice. AV nodal blockers are contraindicated.

Remember the algorithm below to help diagnose tachyarrhythmias: