Novel MRI Sequences for the Detection of Early Structural and Functional Myocardial Alterations in Patients with Repaired Tetralogy of Fallot: A Pilot Study

Background: Patients with tetralogy of Fallot (TOF) remain at risk for right heart failure and ventricular arrhythmias, which may, in part, be attributed to diffuse fibrosis in the right ventricle (RV). While RV evaluation is challenging by echocardiography, magnetic resonance imaging (MRI) is an established tool to evaluate biventricular cardiac function. The aim of our study was to assess and correlate right and left ventricular (LV) volumetric parameters, the presence of diffuse myocardial fibrosis, and parameters of contractility in patients with repaired TOF.

Methods: This study was approved by the local ethics committee. Patients with repaired TOF and clinically indicated cardiac MRI were included in the study. Cardiac MRI was performed at 1.5 T using the following protocol: (i) steady-state free precession (SSFP) sequences for semiautomatic analysis of RV and LV volume and function, (ii) modified look-locker inversion recovery (MOLLI) for native T1 mapping (nT1) in RV (outflow tract, free wall, inferior wall) and LV (global, free wall, and septum) for detection of diffuse myocardial fibrosis, and (iii) velocity-encoded phase-contrast imaging (tissue phase mapping, TPM) for radial, long axis, and circumferential systolic and diastolic peak velocities and time to peak (TTP) at base, mid, and apex. We used two control groups comprising 25 and 20 healthy volunteers as references for TPM data and nT1 values, respectively.

Results: Seventeen patients with repaired TOF (four females; age 23.5 ± 12.6 years) were included in the study. Patients with TOF showed significantly lower systolic and diastolic peak velocities and altered TTP in most regions of RV and LV compared with healthy volunteers (e.g., long axis peak systolic velocity at RV base: 3.4 ± 1.3 cm/s vs. 6.9 ± 1.5 cm/s, p < 0.001). In those patients with normal RV ejection fraction (n = 5, 29.4%), RV long axis and circumferential peak velocities as well as RV TTP were reduced compared with controls. Global LV nT1 values were significantly higher in patients than in controls (1,028 ± 38 ms vs. 997 ± 22 ms, p = 0.013), while there was no statistically significant difference in nT1 values in segmental comparison. In patients with TOF, there was a significant correlation of shorter diastolic TTP with higher LV lateral nT1, and of longer systolic and diastolic TTP with higher RV inferior nT1.

Conclusion: Abnormalities in systolic and diastolic RV function may be identified earlier by TPM than by standard functional MRI evaluation in patients with repaired TOF. Biventricular diffuse fibrosis appears to be associated with mechanical alterations. Larger cohort studies are warranted to validate our results and understand underlying pathomechanisms.

Publication History

Article published online:
11 February 2025