Differential diagnosis of tachycardia with a typical left bundle branch block morphology

Table 1 Electrocardiographic QRS morphology criteria favoring ventricular tachycardia over supraventricular tachycardia

Authors	Date	Morphology	Criteria favoring ventricular tachycardia
Wellens et al[2]	1978	RBBB-like	Monophasic R in V1
			qR, QS, RS in V1
			rS, QS, qR in V6
			R/S < 1 in V6 (S > R or QS in V6)
			Left axis deviation
			QRS width > 140 ms
Kindwall et al[3]	1988	LBBB-like	R in V1 or V2 > 30 ms
			Any Q wave in V6
			Onset of QRS to nadir of S ≥ 60 ms in V1 or V2
			Notching of downstroke of S in V1 or V2
Akhtar et al[4]	1988		Positive QRS concordance across the precordium
			Extreme left axis deviation (-90° to ± 180°)
		LBBB-like	Right axis deviation
			QRS > 160 ms
		RBBB-like	QRS > 140 ms
Brugada et al[5]	1991		Absence of RS complex in all precordial leads
			R to S interval > 100 ms in ≥ one precordial lead
			Wellens’ morphologic criteria in leads V1 or V6
Vereckei et al[6]	2008		Initial R wave in lead aVR
			Initial r or q wave > 40 ms in lead aVR
			Notch on descending limb of negative onset, predominantly negative QRS in lead aVR
			vi/vt ≤ 1

vi/vt: Ratio of voltage amplitude during initial 40 ms of QRS complex relative to terminal 40 ms in any lead with a bi- or multiphasic QRS complex; LBBB: Left bundle branch block; RBBB: Right bundle branch block.