3.2 Definition of LBBAP
The definition of LBBAP was described in seven studies and omitted in one. Confirmation of LBBAP was made by comprehensively reviewing the following findings: 1) the only criterion used in all seven studies was paced QRS morphology, presented with a right bundle branch block morphology pattern in lead V1; 2) abrupt shortening of Stim-LVAT (stimulus to peak of the R wave) in leads V5 and V6 was used in four studies; 3) observed left bundle branch potential in pacing leads was used in four studies; and 4) demonstration of the transition from nonselective LBBP to selective LBBP was used in two studies. Only one study used contrast to ensure the location of the lead in the interventricular septum.