A 58-year-old man with a 10-year history of type 2 diabetes mellitus and hypertension presents to the emergency department with acute onset chest pain and dyspnea. His blood pressure is 95/60 mmHg, heart rate 110/min, and respiratory rate 28/min. ECG shows ST elevation in leads II, III, and aVF. Coronary angiography reveals complete occlusion of the right coronary artery with thrombus. Which of the following pathophysiologic mechanisms is MOST likely responsible for the acute thrombotic occlusion in this patient?

Explanation

## Pathophysiology of Thrombosis in Diabetes and Hypertension ### Virchow's Triad and Endothelial Dysfunction **Key Point:** Thrombosis results from the interaction of three factors: blood flow abnormality, vessel wall injury, and blood composition changes (Virchow's triad). In this case, endothelial injury is the primary driver. ### Mechanism of Endothelial Damage in Diabetes and Hypertension Chronic hyperglycemia and hypertension cause: 1. **Endothelial dysfunction** — reduced nitric oxide production, increased oxidative stress 2. **Exposure of procoagulant surfaces** — tissue factor (TF) and von Willebrand factor (vWF) are released from damaged endothelium 3. **Atherosclerotic plaque rupture** — chronic hyperglycemia accelerates atherosclerosis; plaque rupture exposes the lipid core (rich in TF) to circulating blood 4. **Platelet activation and aggregation** — vWF binds to exposed collagen and von Willebrand factor receptors on platelets, initiating the coagulation cascade ### Why This Patient Thrombosed The patient's diabetes and hypertension have caused: - Coronary atherosclerosis with lipid-rich plaque - Plaque rupture → exposure of tissue factor - Tissue factor activates the extrinsic coagulation pathway (Factor VII → X → II → fibrin) - Platelet adhesion via vWF-collagen-platelet interactions - Rapid thrombus formation occluding the artery **High-Yield:** The **extrinsic pathway** (tissue factor-dependent) is the primary initiator of thrombosis in atherosclerotic plaque rupture. Tissue factor is the most potent trigger for coagulation in vivo. ### Coagulation Cascade Overview ```mermaid flowchart TD A[Plaque Rupture]:::outcome --> B[Tissue Factor Exposure]:::outcome B --> C[Factor VII Activation]:::action C --> D[Factor X Activation]:::action D --> E[Factor II Activation]:::action E --> F[Thrombin Generation]:::action F --> G[Fibrin Polymerization]:::action G --> H[Thrombus Formation]:::urgent B --> I[Platelet Adhesion via vWF]:::action I --> J[Platelet Aggregation]:::action J --> H ``` **Clinical Pearl:** Acute coronary thrombosis is almost always preceded by atherosclerotic plaque rupture with exposure of the lipid core (tissue factor-rich) to blood. This is why antiplatelet agents (aspirin, P2Y12 inhibitors) and anticoagulants (heparin, warfarin) are both used in acute MI management — they target different pathways of thrombus formation. [cite:Robbins 10e Ch 4]