A 52-year-old woman is found unresponsive and pulseless shortly after returning from lunch. What is the most likely cause of her cardiac arrest?

• A. Pulmonary embolism
• B. Coronary heart disease
• C. Aortic dissection
• D. Cardiomyopathy

Answer: (B)

In adults, sudden cardiac arrest most often stems from coronary heart disease causing acute myocardial ischemia and a life-threatening arrhythmia. When a plaque in a coronary artery ruptures, a clot can abruptly occlude blood flow to the heart muscle, leading to ischemia. That electrical instability frequently produces ventricular fibrillation, which causes the heart to stop beating effectively and a pulseless collapse. In a 52-year-old who becomes unresponsive and pulseless, this ischemic pathway is the most common mechanism, making coronary heart disease the likeliest cause. Pulmonary embolism, aortic dissection, or cardiomyopathy can cause sudden collapse too, but their typical signs and presentations are less consistent with this scenario. The immediate steps are high-quality CPR and defibrillation as needed, with rapid evaluation for myocardial ischemia.