The quest for determination of standard reference values of right ventricular longitudinal systolic strain: a systematic review and meta-analysis

Right ventricular function is strongly associated with clinical outcomes in many conditions, and the evaluation of right ventricle (RV) structure and function in patients with cardiopulmonary disorders is an essential component of clinical management. The objective of this study was to determine the normal ranges of right ventricular longitudinal strain (RVLS) measurements derived by two-dimensional (2D) speckle tracking echocardiography (STE) through a systematic review and meta-analysis. A systematic review was performed using PubMed, Cochrane, ClinicalKey, and CINAHL. Search terms covered the concepts of right ventricle, strain, speckle-tracking, and 2D echocardiography with additional filtering for humans and adults over the last decade. The RV four-chamber longitudinal strain (RV4CLS), RV free wall longitudinal strain (RVFWLS), and free wall longitudinal segmental strain values of healthy individuals without cardiopulmonary diseases from 28 studies were assessed. Weighted means were estimated using random-effects models in a meta-analysis. The results show for RV4CLS -24,91%[CI - 25.94; - 23.88, I-2 98%], for RVFWLS -27.63%[CI - 28.78; - 26.48, I-2 98%], for basal RVFWLS -26.65%[CI - 30.57; - 22.73, I-2 99%], mid RVFWLS -27.61%[CI - 30.99; - 24.22, I-2 99%] and apical RVFWLS -24.54%[CI - 26.70; - 22.38, I-2 98%]. This systematic review and meta-analysis showed longitudinal strain values of 2D STE derived RV. No clear reference value for RV strain can be distilled from the literature search due to high statistical heterogeneity between the studies. However, all results of our analysis suggest that the lower reference values for RVLS in the current recommendations with a cut-off value of - 20% is underestimated.