Focal scar and diffuse myocardial fibrosis in patients with history of repaired Tetralogy of Fallot

Background Left and right ventricular (LV and RV) remodelling in repaired tetralogy of Fallot (TOF) is poorly understood. Objectives To identify correlates of focal scar and diffuse fibrosis in patients with history of TOF repair by using cardiac magnetic resonance (CMR). Methods Patients with prior TOF repair underwent CMR including cine imaging to assess ventricular volumes and ejection fraction (EF), T1 mapping to assess LV and RV diffuse fibrosis, and high resolution late gadolinium-enhanced (LGE) imaging to quantify scar size. Structural imaging data were related to clinical characteristics and functional imaging markers. In 40 patients, cine and T1 mapping results were compared to age- and sex-matched controls. Results One hundred and three patients were enrolled (age 28 ± 15 years, 36% women), including 36 with prior PV replacement. Compared to controls, TOF patients showed lower LV and RVEF and higher RV volume, RV wall thickness, and native T1 and ECV values on both ventricles. Scar size related to LVEF and RVEF while LV and RV native T1 related to RV dilatation. On multivariable analysis, scar size and LV native T1 were independent correlates of ventricular arrhythmia. Patients with history of PV replacement showed larger scar on RV outflow tract but LV and RV native T1 were shorter. Conclusions Focal scar and biventricular diffuse fibrosis are detected on CMR after TOF repair. Scar size relates to systolic dysfunction, and diffuse fibrosis to RV dilatation. Both may be implicated in ventricular arrhythmias. The finding of shorter T1 after PV replacement suggests that diffuse fibrosis may reverse.