Left and right ventricular strain-volume/area loops: an evaluation of intra-observer, inter-observer, and test-retest reliability.

Introduction: Recent studies highlight that left ventricular (LV) and right ventricular (RV) strain-volume/area interactions, particularly systolic slope and coupling parameters, carry clinical and physiological relevance. This study evaluated the intra-observer, inter-observer, and test-retest reliability of echocardiographic LV and RV strain-volume/area loops. Methods and results: Twenty-nine healthy adults underwent two transthoracic echocardiograms 2 h apart after standardized preparation. One observer analysed the first scan twice (intra-observer reliability) and the second scan once (test-retest reliability). A second observer analysed the first scan once (inter-observer reliability). Observers were blinded and analysed data independently. Reliability was assessed for systolic (systolic slope [SS], peak strain [PS]) and coupling parameters (early [EarlyU] and late diastolic uncoupling [LateU]), using intra-class correlation coefficients (ICCs) and Bland-Altman analyses. ICCs were generally higher for LV strain-volume than for RV strain-area loops. For LV, intra-/inter-observer and test-retest reliability was good-to-excellent for SS (ICCs: 0.84-0.92), moderate-to-good for PS and EarlyU (ICCs: 0.64-0.85 and 0.60-0.87, respectively), and poor-to-good for LateU (ICCs: 0.48-0.78). For RV, reliability was good for SS (ICCs: 0.78-0.89), poor-to-moderate for PS (ICCs: 0.19-0.59), moderate for EarlyU and LateU (ICCs: 0.53-0.68, and 0.60-0.73, respectively). Systematic bias was minimal. Conclusion: Reliability was superior for LV-based parameters compared to RV. Both the LV and RV loops showed moderate-to-excellent reliability for SS and EarlyU, whilst reliability for PS and LateU varied from poor-to-good. These findings provide a methodological basis for future studies applying strain-volume and strain-area loops.