Perspectives and Conclusions
Half of patients with the clinical syndrome of heart failure are presented with preserved ejection fraction. The pathophysiology of HFpEF is complex but increased LV stiffness is proved to play a key role. Additive information about LV stiffness may be helpful in the early diagnosis and management of patients with HFpEF. Determination of LV stiffness has previously relied on invasive cardiac catheterization. The echocardiographic imaging has increasingly been applied recently for non-invasive evaluation of LV chamber and myocardial stiffness. LV chamber stiffness indices such as E/e’/LVEDV, E/SRe/LVEDV, and DPVQ were derived on the basis of the relationship between echocardiographic parameters of LVFP and LV size. However, all these methods are surrogate and lumped measurements, relying on E/e’ or E/SRe for evaluating LVFP. The limitations of E/e’ or E/SRe in assessment of LVFP may contribute to the moderate correlation between E/e’/LVEDV or E/SRe/LVEDV and LV stiffness constant. Even the best validated measurement (DPVQ) is considered unreliable in the individual patient by Kass and Burkhoff themselves. Compared to E/e’/LVEDV and E/SRe/LVEDV, IPVA/IA and FPVA/FA may display better performance in assessing LV chamber stiffness as evidenced by a higher correlation with LV stiffness constant. However, only one study has been conducted in the literature on the exploration and application of IPVA/IA and FPVA/FA, and its accuracy in assessing LV chamber stiffness remains to be confirmed. In terms of echocardiographic indices for LV myocardial stiffness evaluation, the parameters of EMI/DWS, iVP and SWI were proposed. Despite alteration of DWS and its predictive value of adverse outcomes in various populations have been widely validated, it was found that DWS may be better considered as an overall marker of cardiac function performance instead of pure myocardial stiffness. As for the iVP and SWI, the validities of these two indices in assessing LV myocardial stiffness have not been confirmed in invasive studies.
Taken together, it seems that no echocardiography-derived indices could be currently used to reliably and accurately assess LV stiffness despite several parameters were developed. Therefore, the comprehensive evaluation of LV stiffness using all these available parameters may be more accurate and earlier to detect the alterations of LV stiffness. Despite there is a long way to go, indices from STE such as FRe/SRe and PALS have been proved to show good correlations with LVFP and have the potential to become promising indexes for LV stiffness assessment. More echocardiographic indices with higher sensitivities and specificities warrant to be further uncovered to evaluate LV stiffness. Additionally, further cross-sectional and longitudinal studies with large sample size and prospective design of nature are also required to confirm their utilities in different populations and their prognostic values.