Table 1. Classification of dual LAD variants.

AIS: Anterior Interventricular Sulcus, LAD: Left Anterior Descending Artery, LMCA: Left Main Coronary Artery, LCS: Left Coronary Sinus, LV: Left Ventricle, RCA: Right Coronary Artery, RCS: Right Coronary Sinus, RVOT: Right Ventricle Outflow Tract, RV: Right Ventricle

Type	Short LAD Origin	Long LAD Origin	Short LAD Course	Long LAD Course
I	LAD Proper	LAD Proper	Originates from the LAD proper and terminates in the proximal AIS	Descends on LV side of the proximal AIS and enters the distal anterior interventricular sulcus
II	LAD Proper	LAD Proper	Originates from the LAD proper and terminates in the proximal AIS	Descends on the RV side of the proximal AIS and reenters the distal AIS
III	LAD Proper	LAD Proper	Originates from the LAD proper and terminates in the proximal AIS	Courses through the intramyocardial septum proximally, and may emerge in the distal AIS or terminate in the apical septum
IV	LMCA	RCA	Originates from the LMCA and terminates in the proximal AIS	Courses along an anomalous prepulmonic course anterior to the right ventricular outflow tract (RVOT) and reenters the distal AIS
V	LCS	RCS	Originates from the left coronary sinus (LCS) and terminates in the proximal AIS	Courses along an anomalous intramyocardial course within the septal crest, emerges epicardially, to enter the distal AIS
VI	LMCA	RCA	Originates from the LMCA and terminates in the proximal AIS	Courses between the RVOT and the aortic root and emerges in distal AIS
VII	LAD Proper	LAD Proper	Originates from the LAD proper and terminates in the proximal AIS	Courses along the LV side of the proximal AIS and reenters the distal AIS
VIII	LMCA	Mid-RCA	Originates from the LMCA and terminates in the proximal AIS	Courses along the inferior wall of the RV and traverses the apex to terminate in the distal AIS
IX	LAD Proper	LAD Proper	Originates from the LAD proper and terminates in the proximal AIS	Courses along the LV side of the AIS, enters the distal AIS and terminates before the apex
X	LMCA	RCS	Originates from the LMCA and terminates in the proximal AIS	Courses along an anomalous prepulmonic course anterior to the RVOT and reenters the distal AIS
XI	RCS	RCS	Originates from the RCS, takes an intramyocardial course within proximal septum and emerges in the proximal AIS	Courses along an anomalous prepulmonic course anterior to the RVOT and reenters the distal AIS
XII	LMCA	RCS	Originates from LMCA that originates in the RCS and terminates in the proximal AIS	Courses anterior to the main pulmonary artery and terminates in the distal AIS
XIII	No Short LAD	LAD Proper LAD Proper	Not applicable	Two long LADs which both leave the AIS and course out to the apex. One of the vessels courses laterally and the other courses medially of the AIS