Hydraulic force is a novel mechanism of diastolic function that may contribute to decreased diastolic filling in HFpEF and facilitate filling in HFrEF

Atrioventricular Area Difference Aids Diastolic Filling in Patients with Repaired Tetralogy of Fallot

A hydraulic force aids diastolic filling of the left ventricle (LV) and is proportional to the difference in short-axis area between the left ventricle and atrium; the atrioventricular area difference (AVAD). Patients with repaired Tetralogy of Fallot (rToF) and pulmonary regurgitation (PR) have reduced LV filling which could lead to a negative AVAD and a hydraulic force impeding diastolic filling. The aim was to assess AVAD and to determine whether the hydraulic force aids or impedes diastolic filling in patients with rToF and PR, compared to controls. Twelve children with rToF (11.5 [9-13] years), 12 pediatric controls (10.5 [9-13] years), 12 adults with rToF (21.5 [19-27] years) and 12 adult controls (24 [21-29] years) were retrospectively included. Cine short-axis images were acquired using cardiac magnetic resonance imaging. Atrioventricular area difference was calculated as the largest left ventricular short-axis area minus the largest left atrial short-axis area at beginning of diastole and end diastole and indexed to height (AVADi). Children and adults with rToF and PR had higher AVADi (0.3 cm2/m [- 1.3 to 0.8] and - 0.6 [- 1.5 to - 0.2]) at beginning of diastole compared to controls (- 2.7 cm2/m [- 4.9 to - 1.7], p = 0.015) and - 3.3 cm2/m [- 3.8 to - 2.8], p = 0.017). At end diastole AVADi did not differ between patients and controls. Children and adults with rToF and pulmonary regurgitation have an atrioventricular area difference that do not differ from controls and thus a net hydraulic force that contributes to left ventricular diastolic filling, despite a small underfilled left ventricle due to pulmonary regurgitation.

Diastolic Filling in Patients After Heart Transplantation Is Impaired Due to an Altered Geometrical Relationship Between the Left Atrium and Ventricle

BACKGROUND

The geometrical relationship between atrial and ventricular short-axis cross-sectional area determines the hydraulic forces acting on intracardiac blood. This is important for diastolic filling. In patients undergoing heart transplantation (HTx), the left atrium is often enlarged as a result of the standard surgical technique. We hypothesized that diastolic filling in HTx patients is affected by the surgery altering the geometrical relationship between atrium and ventricle.

METHODS AND RESULTS

This retrospective, cross-sectional study included 25 HTx patients (median age, 52 [range, 25-70] years), 15 patients with heart failure with reduced ejection fraction (median age, 63 [range, 52-75] years), 15 patients with heart failure with preserved ejection fraction (median age, 74 [range, 56-82] years), and 15 healthy controls (median age, 64 [range, 58-67] years) who underwent cardiac magnetic resonance imaging. Left ventricular, atrial, and total heart volumes (THV) were obtained. Atrioventricular area difference at end diastole and end systole was calculated as the largest ventricular short-axis area minus the largest atrial short-axis area. Left atrial minimum volume normalized for THV (LAmin/THV) was larger in HTx patients (median, 0.13 [range, 0.07-0.19]) compared with controls (median, 0.05 [range, 0.03-0.08], P <0.001), whereas left ventricular volume normalized for THV (left ventricular end-diastolic volume/THV) was similar between HTx and controls (median, 0.19 [range, 0.12-0.24] and median, 0.22 [range, 0.20-0.25], respectively). At end diastole, when atrioventricular area difference reached its largest positive value in controls, 11 HTx patients (44%) had a negative atrioventricular area difference, indicating impaired diastolic filling.

CONCLUSIONS

Diastolic filling is impaired in HTx patients due to an altered geometrical relationship between the left atrium and ventricle. When performing cardiac transplantation, a surgical technique that creates a smaller left atrium may improve diastolic filling by aiding hydraulic forces.

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

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.