Light on wide-QRS tachycardia, part 1: Distinguishing the mechanisms - Physiologic and clinical correlations that clarify a challenging diagnosis

The distinction between wide-QRS ventricular tachycardia (VT) and wide-QLRS supraventricular tachycardia (SVT) is not always readily apparent but is very important. Inappropriate treatment can worsen the patient's hemodynamic status and, in some cases, make the arrhythmia refractory. The differential diagnosis of wide-QRS tachycardia (WQRST) includes VT, SVT with preexisting right or left bundle branch block, SVT with functional bundle branch block, and SVT with ventricular preexcitation. VT is the most common WQRST and is usually a sign of structural heart disease. Left bundle branch block is usually associated with cardiac disease. Right bundle branch block may be associated with heart or lung disease or may be idiopathic.