391. What determines QRS width in 3rd degree AV block? / Congenital vs. acquired 3rd degree AV block / Most common cause of a pause on ECG July 6th, 2008 by reuben in bradycardia Back Top Tags: card 390. Compare type I and type II second degree AV block / Causes of grouped impulses 392. Features of PACs vs. PVCs Leave a Reply Cancel reply Please post any discussion to the emupdates Reddit page.