In 1978, Wellens and associates analyzed the ECG characteristics of 140 episodes of wide complex tachycardias of which 70 were known to be ventricular and 70 were proven to be supraventricular with aberrant conduction. (Am J Med 6: 27, 1978). They noted certain QRS characteristics that suggested ventricular tachycardia. These are illustrated here.
A right bundle branch block type QRS complexes with either a single upright component (R wave) or qR type complex in lead V1 occurred almost exclusively in patients with ventricular tachycardia. An R wave of smaller voltage than the S wave (an rS complex) in V6 also suggested ventricular tachycardia. In addition, a left bundle branch block type QRS complex with a qR complex in lead V6 occurred only in patients with ventricular tachycardia.