Myocardial ECV Fraction Assessed by CMR Is Associated With Type of Hemodynamic Load and Arrhythmia in Repaired Tetralogy of Fallot.

OBJECTIVES: The aim of this study was to investigate the extent of diffuse myocardial fibrosis by measuring left (LV) and right ventricular (RV) extracellular volume fraction (ECV) in patients with repaired tetralogy of Fallot (rTOF) and to explore its association with ventricular remodeling, hemodynamic load, and clinical parameters.

BACKGROUND: Focal myocardial fibrosis is prevalent in patients with rTOF. However, little is known about the extent of diffuse myocardial fibrosis and its clinical implications in this population.

METHODS: We measured ECV by pre- and post-gadolinium T1 measurements using a 1.5-T scanner in 84 patients with rTOF (median age 23.3 years). LV ECV was determined by averaging values from 6 short-axis mid-ventricular segments, and RV ECV was calculated by averaging values from the anterior-inferior and the diaphragmatic RV wall segments.

RESULTS: LV ECV above the upper limit of normal (>28%) was observed in 11 patients and for RV ECV (>41%) in 9 patients. LV ECV correlated positively with RV ECV (r = 0.54; p < 0.001). Greater RV ECV was associated with female gender, lower RV mass-to-volume ratio, lower RV outflow tract pressure gradient, and having volume overload as the predominant hemodynamic burden (all p < 0.001). Similar associations were observed with LV ECV. In multivariable analysis, increased LV ECV was independently associated with arrhythmia, adjusting for age and RV mass index (odds ratio: 5.69; p = 0.031).

CONCLUSIONS: In this cohort, LV and RV ECV values were positively correlated, indicating an adverse ventricular-ventricular interaction at the tissue level. Increased ECV was associated with RV volume overload and arrhythmia. These findings may lead to future studies exploring the role of ECV in improving risk stratification and guiding therapeutic interventions.