A simplified geometric CMR method for reproducible quantification of left ventricular thrombus volume

Left ventricular thrombus (LVT) is a frequent complication after myocardial infarction and is associated with increased risk of systemic embolism and adverse cardiovascular outcomes. However, the relationship between thrombus characteristics and its clinical evolution remains poorly understood, partly due to the lack of standardized and reproducible measurement methods. This study evaluated the feasibility and reproducibility of a simplified geometric CMR approach for standardized LVT volume assessment. This post-hoc analysis included patients from the COVERT-MI trial who underwent cardiac magnetic resonance (CMR) imaging 5 days after reperfusion for ST-segment elevation myocardial infarction. LVT volume was estimated using a simplified geometric method based on three orthogonal measurements (ABC/2 formula). Thrombus morphology, surface area, and insertion circumference were also assessed. Inter- and intra-reader reproducibility were evaluated using Bland-Altman analysis and Cohen's kappa coefficients. Associations with thrombus persistence at 3 months and clinical outcomes at 1 year were explored as secondary analyses. Among 161 patients who underwent baseline CMR, 25 (15.5%) had LVT. The mean estimated thrombus volume was 1.03 ± 1.09 cm³. At 3 months, thrombus regression occurred in 80% of patients. The ABC/2 method showed high reproducibility. Inter-observer reproducibility demonstrated a bias of 0.07 cm³, whereas intra-observer reproducibility showed a bias of 0.03 cm³. Inter-observer correlation was high (r = 0.86, SEE = 0.51 cm³), while intra-observer correlation was excellent (r = 0.99, SEE = 0.15 cm³). Accounting for thrombus shape had minimal impact on volume estimation (mean difference 0.035 cm³). No thrombus characteristic was significantly associated with thrombus persistence, and no cardioembolic events occurred during the 1-year follow-up. A simplified geometric CMR approach based on the ABC/2 formula provides a feasible and highly reproducible framework for estimating LVT volume. Further studies in larger cohorts are needed to determine the clinical and prognostic relevance of quantitative thrombus assessment.