Validation of a Manual Method for Measuring Left Atrial Reservoir Strain Against Automated Speckle Tracking Analysis

<b>Background:</b> Left atrial strain, particularly reservoir strain, has emerged as a sensitive marker of left atrial function and an early indicator of diastolic dysfunction and cardiovascular risk. However, automated left atrial strain analysis is not universally available, particularly in resource-limited settings. In this study, we propose a manual method for calculating biplane left atrial reservoir strain and validate its agreement with automated software in patients with atrial fibrillation and in sinus rhythm. <b>Methods:</b> Echocardiography examinations from 30 patients with atrial fibrillation and 30 patients in sinus rhythm were analyzed. Left atrial reservoir strain was calculated using both an automatic speckle tracking imaging-based algorithm and a manual point-by-point method based on atrial wall delineation. Agreement between methods was assessed using Pearson correlation, Bland-Altman analysis, and intraclass correlation coefficient. <b>Results:</b> Strong correlation and excellent agreement were observed between the two methods in both groups. Pearson correlation coefficients were r = 0.95 (<i>p</i> < 0.0001) in the atrial fibrillation group and r = 0.94 (<i>p</i> < 0.0001) in the sinus rhythm group. Bland-Altman analysis showed narrow limits of agreement, particularly in the atrial fibrillation group. The intraclass correlation coefficient was 0.95 in atrial fibrillation and 0.92 in sinus rhythm, indicating excellent reliability. The standard error of measurement and minimal detectable change were low in both groups. <b>Conclusions:</b> Manual measurement of left atrial reservoir strain is feasible, reproducible, and demonstrates excellent agreement with automated software. It may serve as a reliable alternative in clinical scenarios where automated tools are unavailable.