Other parameters of right ventricular function
The interaction between the RV and the pulmonary circulation unit is reflected in the RV–pulmonary artery coupling (RVPAC), which is usually assessed with right heart catheterization. Several echocardiographic studies used the ratio between TAPSE and PASP as a non-invasive surrogate for the RVPAC, as this ratio reflects the interaction between the shortening of the RV fibres and the force generated by the RV [66-69]. TAPSE/PASP ratio was found to be an independent predictor of cardiac mortality [66] and of major events (cardiac death, heart transplant or LVAD implant) [67] in patients with HF. In a recent study, Ghio et al. enrolled 1663 patients with HF (1123 with reduced LVEF, 156 with mid-range LVEF, 384 with preserved LVEF [4]) and showed that TAPSE/PASP is a powerful, independent predictor of all-cause mortality in all HF patients, regardless of the extent of LV dysfunction [68]. Similar results were found by Bosch et al, in a study that assessed the contribution of RV dysfunction in HF with reduced EF (HFrEF) versus HF with preserved EF (HFpEF); they showed that TAPSE/PASP ratio was an independent predictor of all-cause death and HF hospitalization, with no difference between HFrEF and HFpEF and regardless of LVEF [69].
As innovative echocardiographic techniques become part of the comprehensive assessment of RV performance, some researchers used 2D RV longitudinal strain or 3D RVEF for the non-invasive estimation of RVPAC. One recent study found that the ratio between RVFW strain and PASP independently predicted a composite endpoint of all-cause death and rehospitalizations in patients with HF [68]. Similar results were found by Iacoviello et al., who showed that both RVFW strain/PASP ratio and global RV strain/PASP ratio are independent predictors for all-cause mortality in patients with HF and LVEF<45% [70]. In another study RVPAC was estimated non-invasively using the ratio between 3D RVEF and PASP; the authors found that each 0.5 units decrease in RVEF/PASP ratio was associated with a 65% increase in the hazard of death or hospitalization for HF [59].
Fractional shortening of the RVOT (RVOT-FS) is an index of RV performance which is obtained using M-mode echocardiography in parasternal short axis window at the level of the aortic root. It is calculated as the percentage change in RVOT diameter at end-systole compared to end-diastole [71]. Several studies showed a good correlation between RVOT-FS and other indices of RV systolic performance [72, 73]. Yamaguchi et al. showed that RVOT-FS is an independent predictor of MACE (defined as cardiac death, heart transplantation or hospitalization for HF) in a cohort of patients with LVEF<40%, with a higher rate of adverse outcome in patients with RVOT-FS<20% [74].