Coronary artery disease narrows the blood vessels that supply the heart with oxygen-rich blood due to plaque buildup. This decreases blood flow and can cause chest pain, shortness of breath, or heart attack. Diagnosis involves physical exams, blood tests, imaging tests like angiograms and stress tests. Treatment includes lifestyle changes like quitting smoking, medication to reduce blood pressure and cholesterol, and procedures like angioplasty, stents or bypass surgery to reopen blocked vessels.