Novel clinical method to quantify diastolic dysfunction: Enabling patient-specific left ventricular relaxation rate, minimum pressure and filling pressure

Background Left ventricular (LV) diastolic function reflects three core components; rate of relaxation, restoring forces, and filling pressure (LVFP). Current method for grading diastolic dysfunction (DD), however, is based only on estimated LVFP in combination with mitral velocities. Purpose The aim of this study was to investigate how current grading of DD reflects the three core components of LV diastolic function; rate of relaxation, restoring forces, and LVFP. Methods The study was performed in a dataset of n=24 patients with dyssynchronous heart failure (HF). Echocardiography, including grading of DD was performed according to current EACVI guidelines.1 In addition, LV relaxation was measured as time constant τ of LV isovolumic pressure decay, restoring forces as minimum PLV (minPLV) and LVFP as pre-atrial contraction pressure (pre-A PLV). These parameters were obtained using a non-invasive method for LV diastolic pressure estimation (NiDiP) recently published by Smiseth, Fernandes et al.2 Accordingly, Pre-A PLV was estimated as the sum of minPLV and the maximum atrio-ventricular pressure drop (∆PA-V). MinPLV was estimated by a linear regression encompassing left atrial reservoir strain, arterial systolic pressure, body mass index, and an estimate of the time constant of LV relaxation (τ) (Figure 1). ∆PA-V was computed by a simplified Navier-Stokes momentum conservation equation. Estimated LVFP, minimum PLV and τ were compared against DD classification. Results There was a significant distinction between the DD grading groups (Grade I and combined Grades II and III) quantified non-invasively. The estimates of LV filling pressure, minimum LV pressure, and the LV relaxation τ mirrored the expected directional trends across guideline-based DD categories, confirming physiological consistency of the methodologies (Figure 2). Furthermore, the novel methodology preserved known invasive cut-off values for DD, namely an LV filling pressure of 15 mmHg and a τ of 48 ms, demonstrating alignment with established haemodynamic thresholds. Patients classified with more advanced DD showed, as expected, more elevated LVFP. In addition, advanced DD was associated with further prolongation of τ and further increase in minPLV, reflecting more marked impairment of LV relaxation and restoring forces. These trends remained robust despite inter-patient heterogeneity typical in LBBB desynchrony. Conclusion The study shows feasibility of using the novel method for non-invasive quantification of LV relaxation, restoring forces and LVFP in a HF population. Higher grade of DD by the conventional approach was associated with more marked impaired LV relaxation and higher diastolic pressures, indicating consistency between the two approaches. Future studies in different HF phenotypes should explore if including τ and minPLV provides clinical utility when assessing HF patients.