A cardiologist explains that coronary artery narrowing in people aged 40+ develops silently over years from accumulated plaque and inflammation, with no guaranteed warning signs even for those appearing physically fit and exercising regularly. The real danger lies not in blocked vessels alone but in sudden plaque rupture triggering blood clots that cause acute heart attacks. Warning signs include chest tightness while exerting effort, shortness of breath, unusual fatigue, and radiating pain to shoulders, arms, neck, or jaw—symptoms requiring immediate medical evaluation rather than attributing to age or poor rest.