Episode Details

Atherosclerosis is the foundational pathology of coronary artery disease (CAD). It is a progressive inflammatory disease characterized by lipid deposition within the intima of the arterial wall, triggered by chronic endothelial injury from factors like tobacco smoking, hypertension, hyperlipidemia, and diabetes. The disease progresses through three key developmental stages over several decades:

1. Fatty Streak: The earliest lesions, consisting of lipid-filled smooth muscle cells that appear yellow, starting in coronary arteries by age 20.
2. Fibrous Plaque: Appearing by age 30, lipoproteins transport lipids into the intima, where collagen covers them to form a grayish-white plaque. This narrows the vessel lumen and reduces distal blood flow.
3. Complicated Lesion: The most dangerous stage. Continued inflammation leads to plaque instability and rupture. This triggers massive platelet aggregation and thrombus formation on the exposed arterial wall, which can cause partial or total vessel occlusion.

Collateral circulation—arterial anastomoses that bypass blockages—can develop in response to chronic, slow-developing ischemia, allowing the heart to receive adequate oxygen. However, with acute coronary occlusion or severe spasms, collateral vessels lack the time to develop, resulting in severe ischemia or myocardial infarction (MI).

The 80/20 Core of CAD: Risk Factors and Clinical Variations

CAD is driven by a combination of nonmodifiable and major, modifiable risk factors:

• Lipid Profiles: High low-density lipoprotein (LDL > 130 mg/dL) and total cholesterol (>200 mg/dL) accelerate plaque formation, whereas high-density lipoprotein (HDL, often called 'good cholesterol') protects arteries by transporting lipids back to the liver.
• Hypertension & Diabetes: Shearing stress from high blood pressure (>120/80 mm Hg) directly injures the endothelium. Diabetes increases CAD risk two to four times by altering lipid metabolism and promoting endothelial dysfunction.
• Tobacco & Lifestyle: Nicotine triggers catecholamine release (increasing heart rate and blood pressure), while carbon monoxide injures the endothelium and reduces oxygen transport. Physical inactivity and obesity further exacerbate these risks.
• Demographic & Sex Disparities: CAD risk increases for men over 45 and women over 55. Men typically present with typical MI symptoms and have larger coronary arteries. Women experience onset about 10 years later (partly due to loss of estrogen's cardioprotective effects post-menopause), more often present with atypical symptoms like fatigue or shortness of breath, and suffer from higher post-MI mortality and undertreatment. Genetics contribute 40% to 60% of CAD risk, primarily influencing lipid metabolism.