Aortic Elasticity and Left Ventricular Function after Arterial Switch Operation: MR Imaging-Initial Experience

Purpose: To prospectively assess aortic dimensions, aortic elasticity, aortic valve competence, and left ventricular (LV) systolic function in patients after the arterial switch operation (ASO) by using magnetic resonance (MR) imaging. Materials and Methods: Informed consent was obtained from all participants for this local ethics committee-approved study. Fifteen patients ( 11 male patients, four female patients; mean age, 16 years +/- 4 [ standard deviation]; imaging performed 16.1 years after surgery +/- 3.7) and 15 age- and sex-matched control subjects ( 11 male subjects, four female subjects; mean age, 16 years +/- 4) were evaluated. Velocity-encoded MR imaging was used to assess aortic pulse wave velocity (PWV), and a balanced turbo-field-echo sequence was used to assess aortic root distensibility. Standard velocity-encoded and multisection-multiphase imaging sequences were used to assess aortic valve function, systolic LV function, and LV mass. The two-tailed Mann-Whitney U test and Spearman rank correlation coefficient were used for statistical analysis. Results: Patients treated with the ASO showed aortic root dilatation at three predefined levels ( mean difference, 5.7-9.4 mm; P <= .007) and reduced aortic elasticity ( PWV of aortic arch, 5.1 m/ sec +/- 1.2 vs 3.9 m/sec +/- 0.7, P = .004; aortic root distensibility, [2.2 x 10(-3)] . mm Hg-1 +/- 1.8 vs [4.9 x 10(-3)] . mm Hg-1 +/- 2.9, P < .01) compared with control subjects. Minor degrees of aortic regurgitation (AR) were present (AR fraction, 5% +/- 3 in patients vs 1% +/- 1 in control subjects; P < .001). Patients had impaired systolic LV function (LV ejection fraction [LVEF], 51% +/- 6 vs 58% +/- 5 in control subjects; P = .003), in addition to enlarged LV dimensions (end-diastolic volume [EDV], 112 mL/m(2) +/- 13 vs 95 mL/m(2) +/- 16, P = .007; end- systolic volume [ESV], 54 mL/ m(2) +/- 11 vs 39 mL/m(2) +/- 7, P < .001). Degree of AR predicted decreased LVEF (r = 0.41, P = .026) and was correlated with increased LV dimensions (LV EDV: r = 0.48, P = .008; LV ESV: r = 0.67, P < .001). Conclusion: Aortic root dilatation and reduced elasticity of the proximal aorta are frequently observed in patients who have undergone the ASO, in addition to minor degrees of AR, reduced LV systolic function, and increased LV dimensions. (C) RSNA, 2008