Tricuspid lateral annular systolic velocity (S’ wave)
The systolic velocity of the tricuspid lateral annulus reflects the longitudinal contraction of the RV [18]. S’ wave velocity is obtained in the apical 4-chamber view by aligning the ultrasound beam with the longitudinal excursion of the RV and by placing the tissue Doppler marker on the lateral tricuspid annulus [18, 19]. Like TAPSE, it is an easy obtainable parameter, but it is angle-dependent, and it does not reflect the global systolic function of the RV [18, 19]. A S’ wave value < 9.5 cm/s reflects RV systolic dysfunction [16, 18].
Studies found that decreased TDI systolic velocity of the tricuspid annulus is an independent predictor of either cardiac death [25] or of cardiovascular death and rehospitalizations for HF [26] in patients with LV systolic dysfunction. Damy et al. showed that S’ wave<9.5 cm/s is a strong independent predictor of outcomes in patients with LVEF<35%, while having superior prognostic value when compared to other RV systolic parameters such as FAC and TAPSE [27]. Similar results were found by de Groote et al. [28], who found no prognostic value for TAPSE in patients with LV systolic dysfunction but found that S’ wave<9.7 cm/s is an independent predictor of cardiovascular death, with an enhanced prognostic value when combined with RVEF measured by radionuclide angiography. Meluzin et al. showed that the assessment of both TDI systolic and diastolic velocities of the tricuspid annulus provide an enhanced risk stratification in symptomatic HF with reduced EF. The authors found that both TDI systolic and diastolic velocity were independent predictors of survival and of event-free survival, and that patients with combined peak systolic tricuspid annular velocity<10.8 cm/s and peak early diastolic tricuspid annular velocity<8.9 cm/s had the worst prognosis [29].