A 62-year-old woman with atrial fibrillation presents with acute right-sided weakness and expressive aphasia. CT head is unremarkable. Which imaging or clinical feature best distinguishes cardioembolic stroke from atherosclerotic large-vessel disease as the mechanism?

Explanation

## Distinguishing Cardioembolic from Atherosclerotic Stroke ### Pathophysiological Basis **Key Point:** Cardioembolic strokes arise from a cardiac source (AF, MI, valve disease) and typically lodge in distal cortical branches, often affecting multiple non-contiguous territories. Atherosclerotic large-vessel disease causes in-situ thrombosis at the site of stenosis, producing single-territory infarction in the distribution of that vessel. ### Imaging and Clinical Comparison | Feature | Cardioembolic | Atherosclerotic Large-Vessel | |---------|---|---| | **Territory involvement** | Multiple non-contiguous territories (different vascular beds) | Single territory (MCA, ACA, PCA, or vertebrobasilar) | | **Infarct pattern** | Scattered, cortical, often bilateral | Territorial, wedge-shaped, often with penumbra | | **Hemorrhagic transformation** | More common (10–15%) | Less common (2–5%) | | **Mechanism** | Embolus from cardiac source | Thrombosis at stenotic plaque | | **Recurrence risk** | High without anticoagulation | High without antiplatelet + statin | | **Vascular imaging (CTA/MRA)** | Normal vessels (emboli lodge distally) | Stenosis or occlusion at proximal vessel | ### High-Yield Discriminator **High-Yield:** **Multiple acute infarcts in different vascular territories** (e.g., MCA territory + PCA territory, or bilateral hemispheres) is the most specific discriminator for cardioembolic stroke. This pattern reflects random lodgment of emboli in different distal branches, a hallmark of cardioembolism. Atherosclerotic disease typically produces single-territory infarction. ### Clinical Pearl **Clinical Pearl:** When you see a patient with acute stroke and imaging shows infarcts in two or more non-contiguous vascular territories, immediately think **cardioembolic source** and search for AF (ECG, telemetry, event monitor), recent MI, valvular disease, or dilated cardiomyopathy. This finding warrants urgent echocardiography and anticoagulation (after hemorrhage exclusion). ### Mnemonic for Cardioembolic Sources: CHADS~2~-VASc **Mnemonic:** **C**ongestive heart failure, **H**ypertension, **A**ge ≥75, **D**iabetes, **S**troke/TIA, **V**ascular disease, **A**ge 65–74, **Sc**sex (female) — though this is primarily for AF stroke risk, it captures common cardioembolic sources. [cite:Harrison 21e Ch 435]