In this PhD thesis, we report that VF is still a common complication of STEMI, with an incidence of 11.6% in the population of Danish STEMI patients who survive to reach the hospital. In this STEMI population, we identified several risk factors associated with VF independent of MI. We identified and confirmed findings from several previous studies and found several risk factors, such as younger age, a family history of sudden death, a TIMI flow grade of 0, the absence of angina, anterior infarction (i.e., VF before PPCI), and inferior infarction (i.e., VF during PPCI) that were associated with VF in a Danish cohort. Furthermore, a history of atrial fibrillation and alcohol intake were identified as novel risk factors for VF. To the best of our knowledge, this study contains data on the largest VF cohort with the longest reported follow-up published; we found that VF mortality is significantly higher within the first 30 days for patients who experience VF before and during PPCI compared with STEMI patients without VF. However, the long-term mortality rates of the three groups are the same. Importantly, our results contradict the previous understanding that VF during PPCI is "benign"; the mortality rate within the first 30 days was as high for patients with VF during PPCI as the mortality rate of patients with VF before PPCI. Finally, although it is difficult to draw clinical implications from a descriptive study, due to the comprehensiveness of Danish death certificates, we reported a high incidence of cardiac symptoms and contact with healthcare professionals based on cardiac symptoms in young SCD patients who died due to CAD, although death was not avoided.