 The AGNES case-control set consists of individuals with a first acute ST-elevation myocardial infarction. AGNES cases have ECG- registered ventricular fibrillation occurring before reperfusion therapy for an acute and first ST-elevation myocardial infarction. AGNES controls are individuals with a first acute ST-elevation myocardial infarction but without ventricular fibrillation. All cases and controls are recruited at seven heart centers in The Netherlands. The investigators exclude individuals with an actual non-ST-elevation myocardial infarction, prior myocardial infarction, congenital heart defects, known structural heart disease, severe comorbidity, electrolyte disturbances, trauma at presentation, recent surgery, previous coronary artery bypass graft or use of class I and III antiarrhythmic drugs. Individuals who develop ventricular fibrillation during or after percutaneous coronary intervention are not eligible. Furthermore, because early reperfusion limits the opportunity of developing ventricular fibrillation, potential control subjects undergoing percutaneous coronary intervention within 2 h after onset of myocardial ischemia symptoms were not included. This time interval is based on the observation that 90 of cases develop ventricular fibrillation within 2 h after onset of the complaint of symptoms. 