EKG of the Week

A 78 y/o male c/o palpitations and near-syncope. V/S: Pulse 160, BP 130/80.  The EKG is attached.

1. What is the rhythm?

2. What is the treatment?

A1. Rapid atrial fibrillation with a RBBB

A2. AV nodal blockage (calcium channel blockers or beta blockers)

Wide complex tachycardia should be treated as ventricular tachycardia until proven otherwise. If you are in doubt, treat it as ventricular tachycardia. In one study of 150 patients with wide complex tachycardia confirmed by EP study, 81% had V-tach, 14% had SVT with aberration, and 5% had accessory pathway conduction (Akhtar et al, Wide QRS Complex Tachycardia, Ann Int Med 1988;109:905). Of the 122 patients with V-tach, 35% were incorrectly diagnosed as SVT with aberration. So, don't try to be too smart. Just treat wide complex tachycardia as V-tach.

However, this EKG demonstrates an irregularly irregular tachycardia with a typical RBBB morphology. This represents rapid atrial fibrillation with a RBBB. This is commonly misinterpreted as V-tach. The regularity of the QRS complexes can be helpful in distinguishing ventricular tachycardia from SVT with abnormal conduction and in guiding treatment. Most episodes of ventricular tachycardia and SVT with abnormal conduction are completely or predominantly regular, although some irregularity can be seen with both. Nevertheless, a wide complex tachycardia with an underlying chaotic rhythm (irregularly irregular) is strong evidence of atrial fibrillation with abnormal conduction. The conduction abnormality can result from a preexisting bundle branch block, an acquired bundle branch block (often in an RBBB appearance), or an accessory pathway syndrome.

(Yealy, Delbridge. Dysrhythmias. In Rosen’s Emergency Medicine, 7th ed. Chapter 77, p.1018.)