RV peak systolic annular velocity (S’)
As a conventional RV function parameter, S’ represents the tricuspid annulus’ longitudinal velocity at systole and is easy to estimate, reliable and reproducible . Previous studies show that S’ might be the best predictor of RVEF, and may predict short-term outcome of heart failure. S’ was also questioned whether the displacement of the myocardium or the regional velocities in a single segment can truly represent the entire RV function. However, our observation indicates the accuracy of S’ in assessing RV systolic dysfunction maybe not as good as suggested in prior studies . Using a cutoff of < 10 cm/s, the accuracy (AUC) of S’ in differentiating the severity of RV systolic dysfunction were in the range of 0.58-0.65 in our study; which is apparently lower than previously reported 0.7-0.8 range. Of note, the S’ threshold of RV systolic dysfunction varies considerably between studies while the commonly accepted S’ cutoff for RV dysfunction is < 10 cm/s . In addition, a study showed that S’ detected best at a cut-off value of 8.8 cm/sec in 10 patients with arrhythmogenic RV dysplasia and low RVEF. Another study found that S’ between lateral and septal tricuspid annulus of 7 cm/s was the most accurate means to detect an RVEF cut-off by MRI of 45%. Overall, our data support that S’ is more accurate in cases with mild RV dysfunction as reported previously. The S’ cutoff used in prior studies ranged from 7 cm/s to 11 cm/s , which is about 30 to 40% variation between different studies. This implies a single best cutoff threshold may not exist among different patient cohorts.