Left atrial diameter thresholds and new incident atrial fibrillation in embolic stroke of undetermined source

Background and purpose: We analyzed consecutive patients with embolic stroke of undetermined source (ESUS) from three prospective stroke registries to compare the prognostic performance of different LAD thresholds for the prediction of new incident AF. Methods: We calculated the sensitivity, specificity, positive prognostic value (PPV), negative prognostic value (NPV) and Youden's J-statistic of different LAD thresholds to predict new incident AF. We performed multivariate stepwise regression with forward selection of covariates to assess the association between the LAD threshold with the highest Youden's J-statistic and AF detection. Results: Among 675 patients followed for 2437 patient-years, the mean LAD was 38.5 +/- 6.8 mm. New incident AF was diagnosed in 115 (17.0%) patients. The LAD threshold of 40mm yielded the highest Youden's J-statistic of 0.35 with sensitivity 0.69, specificity 0.66, PPV 0.27 and NPV 0.92. The likelihood of new incident AF was nearly twice in patients with LAD > 40 mm compared to LAD <= 40 mm (HR:1.92, 95%CI:1.24-2.97, p = 0.004). The 10-year cumulative probability of new incident AF was higher in patients with LAD>40 mm compared to LAD <= 40 mm (53.5% and 22.4% respectively, log-rank-test: 28.2, p< 0.001). The annualized rate of stroke recurrence of 4.0% in the overall population did not differ significantly in patient above vs. below this LAD threshold (HR:0.96, 95%CI:0.62-1.48, p = 0.85). Conclusions: The LAD threshold of 40 mm has the best prognostic performance among other LAD values to predict new incident AF after ESUS. The diagnostic yield of prolonged cardiac rhythm monitoring in patients with LAD <= 40 mm seems low; therefore, such patients may have lower priority for prolonged cardiac monitoring.