Table 2. Outflow tract VAs origin based on QRS pattern. ECG differentiation of a RVOT from a LVOT origin VAs is based on the R/S precordial transition.[32,33].

LBBB = left bundle branch block; LCC = left coronary cusp; RCC = right coronary cusp; AMC = aorto-mitral continuity.

Right ventricle	BBB	Axis	Precordial transition	V1	V6	other
RVOT septal	LBBB	Inferior	≤ V3	rS	R	(-) polarity of lead I in anterior and leftward location; (+) polarity in posterior and rightward location; multiphasic polarity in midway location.
RVOT free-wall	LBBB	Inferior	≥ V3	rS	R	(-) polarity of lead I in anterior and leftward location; (+) polarity in posterior and rightward location; multiphasic polarity in midway location. Notching in lead II, III and aVF.
LCC	LBBB	Inferior	≤ V2	QS/QR	R
RCC	LBBB	Inferior	≥ V3	Multiphasic “M” or “W”	R
AMC	“RBBB”	Inferior	≤ V3	qR	R