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].