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

BACKGROUND: A hydraulic force generated by blood moving the atrio-ventricular plane is a novel mechanism of diastolic function. The direction and magnitude of the force is dependent on the geometrical relationship between the left atrium and ventricle and is measured as the short-axis atrio-ventricular area difference (AVAD). In short, the net hydraulic force acts from a larger area towards a smaller. It is currently unknown how cardiac remodeling affects this mechanism. The aim of the study was therefore to investigate this diastolic mechanism in patients with pathological or physiological remodeling.

METHODS: 70 subjects (n=11 heart failure with preserved ejection fraction (HFpEF), n=10 heart failure with reduced ejection fraction (HFrEF), n=7 signs of isolated diastolic dysfunction, n=10 hypertrophic cardiomyopathy (HCM), n=10 cardiac amyloidosis, n=18 triathletes and n=14 controls) were included. Subjects underwent Cardiac MR and short-axis images of the left atrium and ventricle were delineated. AVAD was calculated as ventricular area minus atrial area and used as an indicator of net hydraulic force.

RESULTS: At the onset of diastole, AVAD in HFpEF was median -9.2 cm2 versus -4.4 cm2 in controls, p=0.02). The net hydraulic force was directed towards the ventricle for both, but larger in HFpEF. HFrEF was the only group with a positive median value 11.6 cm2 and net hydraulic force was throughout diastole directed towards the atrium.

CONCLUSION: The net hydraulic force may impede cardiac filling throughout diastole in HFpEF, worsening diastolic dysfunction. In contrast, it may work favorably in patients with dilated ventricles and aid ventricular filling.