VT and VF During ACS Approximately half of patients with out-of-hospital cardiac arrest with the first rhythm identified as VF and who survive to hospital admission have evidence of acute MI (AMI).S2.2.2-27 Of all out-of-hospital cardiac arrests, >50% will have significant coronary artery le- sions on acute coronary angiography.S2.2.2-27 Of patients hospitalized with AMI, 5% to 10% have VF or sus- tained VT prior to hospital presentation, and another 5% will have VF or sustained VT after hospital arrival, most within 48 hours of admission. A study of patients with non ST-elevation ACS who underwent cardiac catheterization within 48 hours found VT/VF in 7.6% of patients, with 60% of those events within 48 hours Accelerated idioventricular rhythm is a common arrhythmia in patients with acute MI, including patients with ST-segment elevation MI un- dergoing primary percutaneous coronary intervention (PCI). Accelerated idioventricular rhythm is more closely related to the extent of infarction than to reperfusion Sustained VA that occurs in the setting of an ACS is more often polymorphic VT or VF than monomorphic VT. Risk factors for VT/VF include prior history of hy- pertension, prior MI, ST-segment changes at presenta- tion, and chronic obstructive pulmonary disease.S2.2.2-30 A nationwide Danish study found that 11.6% of pa- tients with ST-segment elevation MI who underwent PCI had VF prior to the PCI, and that VF was associ- ated with alcohol consumption, preinfarction angina, anterior infarct location, and complete coronary occlu- sion at the time of coronary angiography.S2.2.2-31 In a select group of patients undergoing primary PCI in a clinical trial, 5.7% developed sustained VT or VF, with two thirds of these events occurring prior to the end of the catheterization, and 90% within 48 hours from the procedure. 