Figure 4: Hydraulic forces acting on the myocardium.
From: Hydraulic forces contribute to left ventricular diastolic filling
On the left, schematic four-chamber view of the heart where the AV plane region of the left heart is highlighted in red. The left-atrial short-axis area (ASA), the left-ventricular short-axis area at the endocardial border (VSAEndo) and the left-ventricular short-axis area at the epicardial border (VSAEpi) are indicated. During diastole the mitral valve is open and the pressure in the left atrium (LA) and left ventricle (LV) is effectively the same. This pressure generates a force acting perpendicularly to the myocardial wall at each location. On the right side of the figure, the force in the atrium corresponds to FA and the force is the ventricle corresponds to FV. These two forces can be resolved into their components in the longitudinal base-apex direction (FAL and FVL) and in the radial direction (FAR and FVR). The radial components of the hydraulic force, FAR and FVR, are partially counteracted by the presence of the pericardium and the surrounding tissues, and may contribute to radial and torsional movement of the myocardium during diastole. The longitudinal components (FAL and FVL) are the hydraulic forces presented in this study, and they act on the longitudinally oriented projection of FA and FV, as indicated with dashed red lines, which correspond to the largest cross-section of the LV and LA, respectively. This illustrates the reason for choosing the largest short-axis area in the LA and in the LV to estimate the hydraulic force in the apex-base direction in the heart.
