Failure of P-Wave Duration as a Surrogate Marker for Left Atrial Enlargement in African Americans: Insights from the Jackson Heart Study.

INTRODUCTION: Electrocardiographic (ECG) criteria for left atrial enlargement (LAE) serve as clinical surrogates for structural and hemodynamic left atrial (LA) overload. Their diagnostic performance compared to echocardiography remains suboptimal, and African Americans are consistently underrepresented in relevant diagnostic accuracy studies. METHODS: We performed a cross-sectional analysis of the Jackson Heart Study (JHS), a large community-based cohort of African American adults (aged 21-94 years). P-wave duration was evaluated as the index test across continuous thresholds using receiver operating characteristic (ROC) curve analysis and area under the curve (AUC) with 95% confidence intervals (95% CI). The main reference standard was echocardiographic LAE defined by American Society of Echocardiography (ASE) sex-specific left atrial (LA) two-dimensional (2D) diameter thresholds (>40 mm in men; >38 mm in women). RESULTS: A total of 3,572 participants were included, of whom 647 (18.1%) met ASE diameter criteria for LAE. Overall discriminatory performance was poor (AUC 0.603; 95% CI 0.580-0.627). At the traditional ≥120 ms threshold, sensitivity (Sn) was 58.3% (95% CI 54.4-62.1%), specificity (Sp) was 56.8% (95% CI 55.0-58.6%), positive likelihood ratio (LR+) was 1.35 (95% CI 1.25-1.46), and negative likelihood ratio (LR-) was 0.73 (95% CI 0.67-0.81), reflecting limited capacity to rule in or out LAE. CONCLUSION: In this cohort, P-wave duration demonstrated poor diagnostic accuracy for diameter-defined echocardiographic LAE. These findings highlight the inadequacy of this ECG criterion as a surrogate marker across a historically underrepresented population. Machine learning models may offer a path forward for higher performance of ECG as a screening tool for LAE in African Americans.