The Study of Precise Evaluation and Comparison of LVEF on Technetium Scan With Echocardiography in Patients With LBBB (SPECT‐LBBB Study)

Background Left bundle branch block (LBBB) is an indication for cardiac resynchronization therapy (CRT) in patients with severe left ventricular (LV) systolic dysfunction. Accurate estimation of LV ejection fraction (LVEF) by echocardiography is often challenging in LBBB, leading to uncertainty regarding CRT eligibility. Alternative imaging modalities, such as contrast echocardiography (CE) and single‐photon emission computed tomography (SPECT) may provide more reliable LVEF in these cases. Aim This study aimed to compare LVEF estimation by unenhanced trans‐thoracic echocardiography (UE‐TTE), CE, and SPECT in patients with LBBB and significant discrepancy (≥5%) between prior UE‐TTE reports. Methods Sixty patients with LBBB referred for SPECT between May 2022 and May 2023 underwent LVEF assessment with UE‐TTE, CE, and SPECT. Correlation and absolute differences in LVEF estimate across modalities were analyzed. Results LVEF on CE correlated strongly with SPECT ( r = 0.976, r 2 = 0.952) outperforming UE‐TTE ( r = 0.824, r 2 = 0.679). Among patients with LVEF ≤ 35% by UE‐TTE, 13 of 34 had LVEF ≥ 40% on SPECT, compared to only one of 21 by CE. An absolute LVEF difference ≥10% was observed in 40% (SPECT vs. UE‐TTE) and 0.5% (SPECT vs. CE). Conclusion In patients with LBBB and discordant LVEF values on UE‐TTE, secondary evaluation with CE or SPECT improves accuracy of LVEF assessment, potentially optimizing CRT eligibility and clinical decision making.