Undetermined stroke with an embolic pattern—a common phenotype with high early recurrence risk

<div><p></p><p><i>Introduction.</i> Undetermined strokes with an embolic pattern (USEP) represent a common phenotype. We assessed their frequency and compared USEP with cardioembolic stroke with a known source and non-cardioembolic stroke etiology.</p><p><i>Methods.</i> Study patients were 540 consecutive ischemic stroke patients admitted to Helsinki University Hospital with primary end-point of recurrent stroke in a 21-month follow-up. Cox regression adjusting for CHA<sub>2</sub>DS<sub>2</sub>-VASc and anticoagulation estimated the risk of USEP on recurrent stroke.</p><p><i>Results.</i> A total of 229 (42.4%) patients had a non-cardioembolic stroke etiology, 184 (34.1%) had a cardioembolic stroke with a known source, and 127 (23.5%) were classified as USEP. USEP patients had less diabetes and prior TIA, with more severe symptoms than the non-cardioembolic stroke cases. They were younger, had fewer comorbidities, and less severe symptoms than the cardioembolic stroke patients. Cumulative risk of recurrent stroke was 10.0% (95% CI 4.1%–15.9%) for USEP, 5.0% (1.1%–8.9%) for cardioembolic strokes, and 5.0% (3.0%–7.0%) for non- cardioembolic strokes (<i>P</i> = 0.089). USEP associated with a higher risk of recurrent stroke compared to non-cardioembolic strokes (hazard ratio 2.36, 95% CI 1.02–5.47; <i>P</i> = 0.046) and cardioembolic stroke with a known source (1.83, 1.07–3.14; <i>P</i> = 0.028).</p><p><i>Conclusions.</i> Despite their younger age and more favorable risk factor profile compared with other phenotypes, USEP exhibited a high risk of stroke recurrence.</p></div>