A 52-year-old man presents with sudden crushing chest pain and tachycardia. He admits to cigarette smoking, consumption of alcohol, and abuse of illicit drugs. An ECG is consistent with ischemic change in the anteroseptal region of the heart. Laboratory studies show elevated serum levels of CK-MB and troponin I. Serum cholesterol is 240 mg/dL. Which of the following most likely contributed to this patient's condition?