The Feasibility and Reproducibility of Measuring Myocardial Performance Index Using Two-Dimensional Phase Contrast Imaging in Patients with Congenital Heart Disease.

The myocardial performance index (MPI) integrates systolic and diastolic function to provide a geometry-independent measure of global ventricular performance. Despite its clinical utility, MPI remains underutilized in cardiovascular magnetic resonance (CMR), especially in patients with congenital heart disease (CHD). This study aimed to evaluate the feasibility and reproducibility of MPI measurement using mitral inflow phase-contrast CMR (PCCMR) in children and young adults with both normal cardiac anatomy and CHD, and to explore its relationship with ventricular function. A total of 124 participants, aged 4 to 27 years, who underwent clinically indicated CMR between August 2017 and December 2023, were retrospectively included. The cohort consisted of individuals with normal cardiac anatomy (n = 24), patients with repaired Tetralogy of Fallot (TOF) without significant residual lesions (n = 30), and patients with single-ventricle physiology following Fontan palliation (n = 70). MPI was calculated as (isovolumetric contraction time + isovolumetric relaxation time) divided by ejection time. Left ventricular ejection fraction (LVEF) was determined from standard cine CMR. Inter-reader agreement was excellent (r = 0.81-0.86, P < 0.001). MPI values were comparable between controls and TOF patients (0.32 ± 0.06 vs. 0.27 ± 0.08). In contrast, Fontan patients with systolic dysfunction had significantly higher MPI (0.65 ± 0.14) compared to those with preserved function (0.37 ± 0.05, P < 0.001), irrespective of systemic ventricle type. Additionally, MPI correlated with established prognostic markers for Fontan failure such as dilated volumes and AV valve regurgitation. These findings support PCCMR-derived MPI as a feasible, reproducible, and geometry-independent functional marker that complements other known biometrics such as ejection fraction, valve regurgitation and ventricular volumes, particularly in single ventricle patients.