Intracavitary blood flow dynamics in the systemic right ventricle after atrial switch operation: a shift from transverse to longitudinal systolic pattern.

Failure of the systemic right ventricle (SRV) is based on morphological differences between right and left ventricles (RVs and LVs). RV adaptation to systemic afterload includes increased circumferential myocardial strain with an unknown impact on intracavitary hemodynamics. The study aimed to explore the SRV pattern of intracavitary blood flow, expressed as hemodynamic force (HDF), and its relationship with wall mechanics. 4D Flow MRI was acquired for twelve adults with transposition of great arteries after atrial switch operation (TGA/AS) SRVs and for twelve healthy subjects. HDF was projected onto the apical-basal, lateral-septal and inferior-anterior directions. The ratio of the root mean square between transverse (sum of HDF_{inferior-anterior} and HDF_{lateral-septal}) and longitudinal HDF (HDF_apical-basal) was evaluated (R_RMS). SRVs of patients with TGA/AS showed R_RMS systolic values (0.94 ± 0.19) comparable to LVs (0.85 ± 0.33, p = 0.82), and significantly lower than RVs (1.85 ± 0.51, p < 0.0001). Concomitantly, averaged systolic HDF_apical-basal magnitude (r=-0.77, p = 0.004) and R_RMS systolic values (r = 0.84, p = 0.0007) showed a strong correlation with free-wall circumferential strain (FWCS). During diastole, TGA/AS SRVs had significantly lower HDF_apical-basal than control LVs (p = 0.002), revealing a diastolic R_RMS (0.72 ± 0.19) similar to RVs (0.96 ± 0.25, p = 0.17). In TGA/AS patients, SRVs structural and functional features impact on intracavitary hemodynamics, being different from that of healthy LVs and RVs. During systole, SRVs displayed a HDF shift towards LV, possibly as a result of increased FWCS. Inversely, the SRV diastolic filling appeared to be closely related to ventricular morphology, as suggested by R_RMS comparable to RVs during diastole.