Key result
Removal of the visceral pericardium from porcine left ventricular slices significantly decreased the opening angle from 53.3 to 27.3 degrees (P<0.05) and decreased LV passive stiffness.
Why the study?
Does the visceral pericardium contribute to the residual stress and passive stiffness of the left ventricle in a porcine model?
Does the visceral pericardium contribute to the residual stress and passive stiffness of the left ventricle in a porcine model?
The visceral pericardium plays a significant role in the residual stress and passive stiffness of the heart, which may have implications for diastolic function in various disease states.
Much attention has been focused on the passive mechanical properties of the myocardium, which determines left ventricular (LV) diastolic mechanics, but the significance of the visceral pericardium (VP) has not been extensively studied. A unique en face three-dimensional volumetric view of the porcine VP was obtained using two-photon excitation fluorescence to detect elastin and backscattered second harmonic generation to detect collagen, in addition to standard light microscopy with histological staining. Below a layer of mesothelial cells, collagen and elastin fibers, extending several millimeters, form several distinct layers. The configuration of the collagen and elastin layers as well as the location of the VP at the epicardium providing a geometric advantage led to the hypothesis that VP mechanical properties play a role in the residual stress and passive stiffness of the heart. The removal of the VP by blunt dissection from porcine LV slices changed the opening angle from 53.3 +/- 10.3 to 27.3 +/- 5.7 degrees (means +/- SD, P < 0.05, n = 4). In four porcine hearts where the VP was surgically disrupted, a significant decrease in opening angle was found (35.5 +/- 4.0 degrees ) as well as a rightward shift in the ex vivo pressure-volume relationship before and after disruption and a decrease in LV passive stiffness at lower LV volumes (P < 0.05). These data demonstrate the significant and previously unreported role that the VP plays in the residual stress and passive stiffness of the heart. Alterations in this layer may occur in various disease states that effect diastolic function.
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Jöbsis et al. (2007) studied this question. Removal or surgical disruption of the visceral pericardium vs. Intact visceral pericardium (before disruption) was evaluated on Opening angle (p=<0.05). Removal of the visceral pericardium from porcine left ventricular slices significantly decreased the opening angle from 53.3 to 27.3 degrees (P<0.05) and decreased LV passive stiffness.
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