Wide QRS tachycardia

Tachycardia with QRS width of 120 msec or more is taken as wide QRS tachycardia. It is better to consider wide QRS tachycardia as ventricular tachycardia until proved otherwise. Supraventricular tachycardia with phasic aberrancy, antidromic tachycardia in accessory pathway and supraventricular tachycardia with pre-existing bundle branch block are the other types of wide QRS tachycardias. Pseudo S waves and pseudo R’ waves can occur due to P waves occurring immediately at the end of the QRS in a narrow QRS tachycardia, making it an apparently wide QRS tachycardia.

Idiopathic right ventricular outflow tract (RVOT) ventricular tachycardia has a left bundle branch block (LBBB) pattern with inferior axis while left ventricular fascicular tachycardias have right bundle branch block (RBBB) pattern.

Atrial flutter

Atrial flutter can be classified into isthmus dependent and non-isthmus dependent. Non isthmus dependent flutters are the scar related flutters and caval mediated flutters. Isthmus dependent flutter can by typical and reverse typical depending on whether the reentry is counter-clockwise or clockwise. The direction of the less sharper component of the flutter wave is taken as the direction of the wave. If the waves are are positive in inferior leads, it is clockwise loop and if negative, the re-entry loop is counter-clockwise. See this page for illustrations (free full text): Indian Pacing Electrophysiol. J. 2001;1(1):23-31