Noninvasive Assessment of Repaired Tetralogy of Fallot by Magnetic Resonance Imaging and Dynamic Radionuclide Studies

Background This study was designed to validate the diagnostic accuracy of magnetic resonance imaging (MRI) in evaluating biventricular ejection fraction and to quantify pulmonary regurgitant fraction (PRF) in patients after repair of tetralogy of Fallot. Methods Two hundred and eighty survivors of repaired tetralogy of Fallot aged 42 months to 40 years (mean, 142.2 ± 85.3 months) underwent cardiac MRI, first-pass and gated radionuclide ventriculography (RNV) for the assessment of biventricular function, and PRF after 89.26 ± 42.40 months. The receiver operating characteristic curve analysis was done to quantify the diagnostic accuracy of MRI. Results There was statistically significant agreement between MRI and RNV in evaluating right and left ventricular function. An MRI-derived right ventricular ejection fraction 47.2% or greater than normal was associated with a sensitivity of 92.3% and a specificity of 92.3%. An MRI-derived left ventricular ejection fraction 53.9% or greater than normal was associated with a sensitivity of 93.2% and a specificity of 93.3%. Area analysis indicated that 97.34% (standard error [SE] = 0.0118) and 98.56% (SE = 0.0052) of the time values of right and left ventricular ejection fraction were higher for patients with normal right and left ventricular functions, respectively, compared with abnormal. There was a strong agreement between velocity-encoded and stroke volume-derived PRF [(r = 0.886, p< 0.001; đ = 2.62 ± 1.12, p< 0.0001; r′ = 0.121, p = 0.051; b = 0.96 (SE = 0.012); p< 0.0001; ICC = 0.98, p< 0.0001). Higher PRF was associated with increased indexed right ventricular dimensions and inversely correlated with biventricular ejection fractions. Conclusions The MRI-derived ejection fraction values predictably separate patients with normal ventricular function from abnormal. Velocity-encoded MRI can accurately quantitate PRF in tetralogy of Fallot.