A 72-year-old woman from Mumbai is admitted with acute myocardial infarction complicated by anterior wall akinesis and ejection fraction of 35%. Echocardiography reveals a 2 cm × 1.5 cm sessile thrombus adherent to the anteroapical wall. She is started on dual antiplatelet therapy and anticoagulation. Which of the following best describes the pathological sequence of thrombus formation in this patient's left ventricle?

Explanation

## Pathological Sequence of Left Ventricular Thrombus Formation Post-MI ### Clinical Context This patient has acute anterior MI with wall motion abnormality (akinesis) and reduced ejection fraction—ideal conditions for **mural (wall) thrombus formation**. The thrombus is adherent to the damaged myocardium, not in a coronary vessel. ### Virchow's Triad in LV Mural Thrombosis | Component | Mechanism in Post-MI LV | |-----------|------------------------| | **Endothelial Injury** | Myocardial necrosis → endocardial denudation → exposure of subendothelial collagen and tissue factor | | **Blood Stasis** | Akinetic/dyskinetic wall segment → reduced local blood flow velocity → blood pooling | | **Hypercoagulability** | Acute phase response post-MI → increased tissue factor, thrombin generation | ### Pathological Sequence (Step-by-Step) 1. **Myocardial necrosis** from MI → endocardial damage and denudation 2. **Exposure of subendothelial matrix** (collagen, tissue factor, von Willebrand factor) 3. **Blood stasis** in the akinetic zone (wall doesn't contract → blood pools) 4. **Platelet adhesion and activation** on the denuded endocardium 5. **Fibrin deposition** around aggregated platelets → **mixed thrombus** (platelets + fibrin) 6. **Red blood cells trapped** in the fibrin mesh → **red thrombus** ### Key Point **Key Point:** The PRIMARY pathological mechanism in post-MI LV thrombosis is the **combination of endocardial denudation (from myocardial necrosis) AND blood stasis (from wall motion abnormality)**. Both must be present. ### High-Yield Facts **High-Yield:** - **Incidence:** 5–15% of acute MIs (higher with anterior wall MI and low EF) - **Timing:** Thrombus forms within **24–48 hours** post-MI - **Risk factors:** Anterior wall location, EF < 40%, akinesis/dyskinesis, large infarct size - **Prevention:** Anticoagulation (LMWH, UFH, or direct anticoagulants) for 3 months if thrombus detected ### Mnemonic **Mnemonic: STASIS** — for post-MI LV thrombus formation - **S**ubendocardial denudation (from necrosis) - **T**issue factor exposure - **A**ctivation of platelets - **S**tasis in akinetic zone - **I**ncreased coagulation (acute phase) - **S**equential fibrin and RBC deposition ### Clinical Pearl **Clinical Pearl:** Echocardiography is the gold standard for detecting LV thrombus. Anticoagulation is indicated for 3 months; if thrombus resolves, anticoagulation can be stopped. If thrombus persists, long-term anticoagulation or surgical removal may be needed.