Abstract Body (Do not enter title and authors here): Background: Atrial fibrillation (AF) is a major risk factor for ischemic stroke. Prior studies have shown that reduced blood flow velocity in the left atrial appendage, measured by the invasive transesophageal echocardiography (TEE) procedure, is associated with higher stroke risk. However, TEE is an invasive procedure with inherent risks. In this study, we aimed to investigate whether transmitral atrial flow velocity (MVA) obtained through the non-invasive transthoracic echocardiography (TTE) technique could also predict the risk of stroke in patients with AF.
Methods: We conducted a longitudinal cohort study of 10,150 patients with paroxysmal AF who underwent TTE to assess MVA. The patients were followed up from January 2010 to December 2021, with the primary outcome being hospitalization for ischemic stroke.
Results: Over a mean follow-up of 4.26±3.52years, 2419 (23.8%) patients developed ischemic strokes (5.59% per 100 person-years). Patients with MVA < 50 cm/s had a higher stroke incidence rate than those with MVA ≥ 50 cm/s (6.57% vs 5.47%, P<0.001). On multivariable analysis adjusting for CHA₂DS₂-VASc score, MVA was independently associated with stroke incidence. Every 10 cm/s reduction in MVA velocity conferred 4% higher stroke risk (adjusted hazard ratio [HR] 0.96 [0.94-0.97], P<0.001). AF patients with MVA < 50 cm/s had a 39% increase in stroke risk compared to those with MVA ≥ 50 cm/s (adjusted HR 1.39 [1.22-1.58], P<0.001). In patients with CHA₂DS₂-VASc score 0 or 1, the stroke incidence increased from 1.33 % to 2.28% when they had MVA < 50 cm/s, which was similar to those with CHA₂DS₂-VASc score 2 points (2.51 %).
Conclusions: Reduced transthoracic MVA independently predicts higher ischemic stroke rates in paroxysmal AF patients. MVA assessment easily enhances risk stratification and could help guide targeted stroke prevention therapies, especially in low-risk patients with CHA₂DS₂-VASc scores of 0 or 1.