By far the most common supraventricular arrhythmia is AF, which occurs in 8% to 22% of patients with STEMI, with higher rates in elderly patients and those with HF and hyper- tension. In a contemporary study, the incidence of new-onset AF during hospitalization was 6.3%.497 New-onset AF was significantly associated with shock, HF, stroke, and 90-day These observations mirrored those seen in earlier The cumulative incidence of AF among MI survivors with EF 0.40 over approximately 2 years of follow-up approaches 30%.500 Management of AF during hospitalization for STEMI is based on the usual considerations of rhythm versus rate con- trol and the indications for anticoagulation according to cur- For hemodynamically unstable patients or those with ongoing ischemic symptoms, treatment should be implemented according to the 2010 Advanced Cardiac Life Support guideline for management of unstable supra- If medical treatment is unsuccessful, synchronized, direct current cardioversion may be indicated. Provision of anticoagulation in the context of DAPT creates additional challenges related to the risk of bleeding (Section 9.7). 9.5.4. Bradycardia, AV Block, and Intraventricular Conduction Defects 9.5.4.1. Pacing in STEMI: Recommendation Class I 1. Temporary pacing is indicated for symptomatic bradyarrhythmias unresponsive to medical treat- ment. (Level of Evidence: C) Sinus bradycardia is common early after STEMI, particularly with inferior location. It is mediated through increased vagal tone, is usually self-limited, and gener- ally requires no treatment. It may be necessary to withhold beta blockers until the bradycardia resolves. Symptom- atic or hemodynamically important sinus bradycardia should be treated with atropine or temporary pacing if not The development of AV block and intraventricular conduc- tion delays is associated with the extent of infarction. The incidence of abnormal conduction has decreased substantially in the reperfusion era. 