Global Longitudinal Strain of the Left Ventricle in Patients with Transposition of the Great Arteries Is Associated with Aortic Elastic Properties and Left Atrial Function—Assessment of a Complex Interplay with MRI

Background: Ventricular function is not only determined by intrinsic ventricular properties but also by a complex loop of loading conditions. In patients with transposition of the great arteries (TGA) the role of atrial impairment, as well as decreased aortic distensibility (AD) as surrogates for disturbed pre- and afterload have recently been acknowledged. However, little effort has been made to investigate preload, afterload, and ventricular properties as a sequalae. Therefore, we aimed to investigate the role of atrial function and AD on systemic ventricular function.

Method: In this analysis, patients with TGA after arterial switch operation (ASO) were studied with a 3-T cine CMR. Ventricular function was defined as global longitudinal strain (GLS) which was assessed by feature tracking. Left atrial reservoir function (LAres) was defined as a surrogate for preload. AD as surrogate for afterload was defined as the distensibility of the ascending aorta. First linear regression analysis was performed to investigate whether there is an effect of LAres and AD on GLS. Then mediation analysis was performed to account for the complex interplay of these three variables.

Results: In the current study, 69 TGA patients (16 [IQR: 11, 21] years, 29% female) were included. Median GLS was −24% (IQR: −29, −20), median LAres was 46% (IQR: 42, 50%), and AD was 4.4 10⁻³ mm Hg⁻³ (IQR: 2.5, 6.7 10⁻³ mm Hg⁻³). Both LAres (β: −0.319, p = 0.005) and AD (β: −0.283, p = 0.013) showed negative association with GLS implying that decreasing atrial and aortic function go alongside with ventricular impairment. GLS, LAres, and AD were not associated with ischemia time during the ASO (p > 0.05 for all). Mediation analysis showed that besides direct effects of LAres and AD on ventricular function there are mediated effects through each other (p < 0.001). While both show large main effects on GLS, 29% of the effect of AD on GLS is mediated by LAres (β: indirect effect of LAres −0.059, 95% CI: −0.145, −0.001).

Conclusion: Left atrial function and aortic bioelasticitiy have relevant influence on systemic ventricular function. Those effects are transduced both directly and indirectly. Therefore, they should not be seen as single entities but rather as a loop incorporating preload, afterload, and intrinsic ventricular properties. Our findings underline the importance to assess global hemodynamic function rather than focusing merely on ventricular properties to unvail the pathophysiological interplay in this complex disease.

Publication History

Article published online:
12 February 2022