390. Compare type I and type II second degree AV block / Causes of grouped impulses July 6th, 2008 by reuben in arrhythmia, bradycardia Back Top Tags: card 389. Describe sick sinus syndrome / Define 1st degree AV block / Define conduction ratio as used to describe 2nd degree AV block 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 Leave a Reply Cancel reply Please post any discussion to the emupdates Reddit page.