What is the most common cause of cardiac arrest in adults?

The most common cause of cardiac arrest in adults is coronary artery disease leading to ventricular fibrillation. This occurs because coronary artery disease involves the narrowing or blockage of the coronary arteries, which supply blood to the heart muscle. Such blockages can lead to ischemia, where the heart muscle does not receive enough oxygen, potentially culminating in arrhythmias like ventricular fibrillation. Ventricular fibrillation is particularly life-threatening as it results in the heart's failure to pump blood effectively, leading to loss of consciousness and death if not rapidly corrected.

While other conditions like pulmonary embolism and myocarditis can lead to cardiac issues, they are not as common as coronary artery disease in the adult population. Pulmonary embolism primarily affects the respiratory system and, while it can lead to cardiac arrest, it does not account for the majority of cases. Cardiomyopathy, which refers to diseases of the heart muscle, can also lead to heart failure and arrhythmias, but again, its incidence is not as prevalent as that caused by coronary artery disease. Thus, the prevalence of coronary artery disease in producing fatal arrhythmias makes it the leading cause of cardiac arrest in adults.