Decreased diastolic hydraulic forces incrementally associate with survival beyond conventional measures of diastolic dysfunction

Abstract

Decreased hydraulic forces during diastole contribute to reduced left ventricular (LV) filling and heart failure with preserved ejection fraction. However, their association with diastolic function and patient outcomes are unknown. The aim of this retrospective, cross-sectional study was to determine the mechanistic association between diastolic hydraulic forces, estimated by echocardiography as the atrioventricular area difference (AVAD), and both diastolic function and survival. Patients (n = 5176, median [interquartile range] 5.5 [5.0-6.1] years follow-up, 1213 events) were selected from the National Echo Database Australia (NEDA) based on the presence of relevant transthoracic echocardiographic measures, LV ejection fraction (LVEF) ≥ 50%, heart rate 50-100 beats/minute, the absence of moderate or severe valvular disease, and no prior prosthetic valve surgery. NEDA contains echocardiographic and linked national death index mortality outcome data from 1985 to 2019. AVAD was calculated as the cross-sectional area difference between the LV and left atrium. LV diastolic dysfunction was graded according to 2016 guidelines. AVAD was weakly associated with E/e', left atrial volume index, and LVEF (multivariable global R² = 0.15, p < 0.001), and not associated with e' and peak tricuspid regurgitation velocity. Decreased AVAD was independently associated with poorer survival, and demonstrated improved model discrimination after adjustment for diastolic function grading (C-statistic [95% confidence interval] 0.644 [0.629-0.660] vs 0.606 [0.592-0.621], p < 0.001) and E/e' (0.649 [0.635-0.664] vs 0.634 [0.618-0.649], p < 0.001), respectively. Therefore, decreased hydraulic forces, estimated by AVAD, are weakly associated with diastolic dysfunction and demonstrate an incremental prognostic association with survival beyond conventional measures used to grade diastolic dysfunction.

Figure 1

Schematic of hydraulic forces in the left atrium and ventricle. (A) During diastole, a hydraulic force (HF) is generated in the left atrium and ventricle perpendicular to the respective chamber walls, represented by the grey arrows in the left atrium and the left ventricle, respectively. These forces can be resolved into their longitudinal (HF_longitudinal) and radial (HF_radial) components as indicated by the solid black and dashed arrows, respectively. The radial component is counteracted by the pericardium and surrounding tissues whilst the longitudinal component represents the hydraulic force that contributes to the longitudinal motion of the atrioventricular plane during diastole. (B) Due to the larger surface area of the LV compared to the LA in a healthy individual, the LV generates a greater hydraulic force in the longitudinal direction, represented by the two additional red arrows. Abbreviations: AV = atrioventricular; HF = hydraulic force; HF_longitudinal = hydraulic force longitudinal component; HF_radial = hydraulic force radial component; LA = left atrium; LV = left ventricle. Figure adapted from.

Figure 2

Patient inclusion flowchart. This flowchart describes the exclusion criteria of the study cohort.

Figure 3

Measurement of atrioventricular area difference in transthoracic echocardiography. In routine echocardiography, atrioventricular area difference can be calculated as the difference between left ventricular end-diastolic short-axis cross-sectional area and left atrial end-systolic short-axis cross-sectional area. Short-axis cross-sectional area is calculated by circular approximation using left ventricular end-diastolic diameter and left atrial end-systolic diameter measured in a parasternal view. The atrial short-axis and ventricular short-axis areas represent the surface areas which contribute to the generation of hydraulic forces which contribute to the diastolic longitudinal motion of the atrioventricular plane. Abbreviations: Ao = aorta; LA = left atrium; LV = left ventricle; RV = right ventricle.

Figure 4

Survival curves for atrioventricular area difference, E/e’ ratio and diastolic function grading. Kaplan–Meier survival curves for (A) AVAD, (B) E/e’ and (C) diastolic function grading. Each curve is stratified by tertiles, with the respective risk table below each panel. Abbreviations: AVAD = atrioventricular area difference.