Venous thromboembolism after acute ischemic stroke - A prospective study using magnetic resonance direct thrombus imaging

Background and Purpose - We prospectively evaluated the prevalence and clinical risk factors for venous thromboembolism (VTE) after acute ischemic stroke using magnetic resonance direct thrombus imaging, a highly accurate noninvasive technique that directly visualizes thrombus. Method - 102 unselected patients with AIS receiving standard prophylaxis with aspirin and graded compression stockings (GCS) were sequentially recruited, underwent regular clinical assessments, and were screened for VTE. Results - The prevalence of all VTE, proximal deep vein thrombosis (PDVT), and pulmonary embolism ( PE) after 21 days were 40%, 18%, and 12%, increasing to 63%, 30%, and 20% in patients with Barthel indices (BI) of less than or equal to 9 2 days after stroke (BI- 2 less than or equal to 9). Clinical deep vein thrombosis and PE occurred in 3% and 5% overall; half these events were overlooked by the attending team. The true incidence of clinical events is probably higher because the natural history of subclinical PDVT was modified by screening and anticoagulation. BI- 2 less than or equal to 9 or nonambulatory status 2 days after stroke were the clinical factors most strongly associated with subsequent VTE on univariate analysis. Odds ratios for any VTE and PDVT for BI- 2 less than or equal to 9 versus > 9 were 8.3 ( 95% CI, 2.7 to 25.2) and 8.1 ( 95% CI, 1.7 to 38.3) on multivariable analysis. Conclusion - BI less than or equal to 9 or nonambulatory status around the time of admission identifies a subgroup of acute ischemic stroke patients at very high risk for VTE in whom the current strategy of thromboprophylaxis may be inadequate. Future thromboprophylactic studies should focus on the patients at high risk defined in this study.