Significance of Mechanical Alterations in Single Ventricle Patients on Twisting and Circumferential Strain as Determined by Analysis of Strain from Gradient Cine Magnetic Resonance Imaging Sequences

Preliminary speckle-tracking echocardiographic studies show that patients with single ventricles (SVs) have significantly decreased twisting and dyssynchrony of twisting. This could be related to abnormal cardiac looping, which leads to hearts that lack helical fiber patterns. The aim of this study was to analyze gradient cine magnetic resonance imaging (MRI) using Velocity Vector Imaging to assess cardiac mechanics. Subjects were 38 patients (aged 8 to 37 years) with SVs of left ventricular (n = 30) and indeterminate (n = 8) type who underwent cardiac MRI. Controls were 14 normal children and adults. Gradient cine MRI sequences close to the apex were subjected to a Velocity Vector Imaging analysis program adapted for MRI. In the control group, mean circumferential strain was -18.02 ± 7.31%, mean dispersion of peak circumferential strain was 44.23 ± 37.14 ms, and average rotation was -7.7 ± 1.38°. The rotation values were negative, or counterclockwise. In patients with SVs, mean circumferential strain was -8.87 ± 7.30%, mean dispersion of peak circumferential strain was 181.55 ± 76.07 ms, and average rotation was -2.6 ± 1.24° (p <0.001). Mean dispersion of the peak of rotation in the control group was 39.6 ± 22.8 ms, compared to 166.5 ± 72.4 ms in patients with SVs. In conclusion, this study showed a dramatic decrease in apical rotation and circumferential strain in the SV group compared to the control group. Strain and rotation mechanics at the apex in patients with SVs showed marked dyssynchrony.