The value of left ventricular strain–volume loops in predicting response to cardiac resynchronization therapy

BACKGROUND: Three-dimensional (3D) speckle tracking imaging (STI) allows the simultaneous assessment of left ventricular (LV) strain and volume. We aim to explore the value of LV strain–volume loops in predicting response to cardiac resynchronization therapy (CRT). METHODS: Forty heart failure (HF) patients scheduled for CRT and twenty healthy individuals were enrolled. All subjects received a 3D echocardiography and 3D STI analysis to acquire LV global and segmental principal strain (PS) and volume simultaneously. Values were plotted in a Cartesian system to construct PS–volume loop which was assessed using the two characteristics of the linear fitting curve: the slope and the coefficient of determination (R(2)-S/D coupling). RESULTS: HF patients at baseline showed significantly lower slope and R(2)-S/D coupling of all PS–volume loops than healthy subjects. As for as comparing Segmental PS–Global volume loop at baseline, Midseptal R(2)-S/D coupling was lower and Midlateral slope was higher in CRT responders than in non-responders. For each individual, the abnormal segmental heterogeneity of Midseptal slope and R(2)-S/D coupling were lower than Midlateral was observed only in responders. At follow-up, significant improvements of the Midseptal slope and R(2)-S/D coupling were observed in responders. Midseptal R(2)-S/D coupling at baseline was an independent predictor of CRT response and the cut-off value of 0.55 was recommended with sensitivity of 89% and specificity of 77%. CONCLUSIONS: Analysis of strain–volume loops could provide unique information for predicting response to CRT. Assessment of septal myocardial wasted work at baseline is helpful to improve patient selection for CRT.