Capillary Perfusion and Wall Shear Stress Are Restored in the Coronary Circulation of Hypertrophic Right Ventricle

Abstract

Abstract-It has been shown that right ventricle (RV) hypertrophy involves significant compensatory vascular growth and remodeling. The objective of the present study was to determine the functional implications of the vascular growth and remodeling through a full flow analysis of arterial tree down to first capillary segments. A computer reconstruction of RV branches including the proximal right coronary artery to the posterior descending artery was established based on measured morphometric data in arrested, vasodilated porcine heart. The flows were computed throughout the reconstructed trees based on conservation of mass and momentum and appropriate pressure boundary conditions. It was found that the flow rate was significantly increased in large epicardial coronary arteries in hypertrophic as compared with control hearts but normalized in the intramyocardial coronary arteries and smaller vessels in RV hypertrophy primarily because of the significant increase in number of arterioles. Furthermore, the wall shear stress was restored to nearly homeostatic levels throughout most of the vasculature after 5 weeks of RV hypertrophy. The compensatory remodeling in RV hypertrophy functionally restores the perfusion at the arteriolar and capillary level and wall shear stress in most of larger vessels. This is the first full analysis of coronary arterial tree, with millions of vessels, in cardiac hypertrophy that reveals the compensatory adaptation of structure to function. With the availability of detailed morphometric data on vascular geometry and branching pattern of RV branches in control and RV hypertrophy, a systematic hemodynamic analysis can be performed to investigate the adaptation of structure to function (perfusion). To facilitate the structure/ function analysis, our group has recently developed a computer algorithm 10 that allows full reconstruction of the entire coronary arterial tree down to the arterial capillaries (first capillary segments) from morphological cast and histological data. 1 The computer model facilitates the analysis of the coronary arterial circulation based on detailed anatomical data.Here, a computer reconstruction of the RV branches was implemented down to the capillary level in the right coronary artery (RCA) proximal to the posterior descending artery of control and RV hypertrophy. The detailed morphometric data (ie, vessel diameters, lengths, and numbers) were used to determine the flow throughout the vascular network as well as the wall shear stress. The blood flow was calculated under steady state in arrested, vasodilated pig hearts. The distribution of wall shear stress was studied in the entire coronary arterial tree. One major finding is that RCA flow is significantly increased because of a decrease in vascular resistance primarily attributable to the increase in number of small vessels. Although the flow is increased in large vessels (eg, epicardial), it is normalized in smaller vessels (eg, arterial capillaries and arterioles). The wall shear stress in the majority of vascu...

Two-layer model of coronary artery vasoactivity

“…The high blood pressure that initiates hypertrophy, however, can increase the circumferential stretch of epicardial coronary arteries. This may lead to a drop in SMC contractility, which can be a significant factor for SMC remodeling (13) and possibly coronary neovascularization (11,12,14). Moreover, the differences of mechanical properties and loadings of intima-media and adventitia layers may lead to different structural remodeling between the two layers in response to hypertension (13), which requires further microstructural investigations.…”

Compensatory remodeling of coronary microvasculature maintains shear stress in porcine left-ventricular hypertrophy

“…It was hypothesized that the wall shear stress (WSS) in the larger epicardial arteries is likely to remain elevated at 5 weeks of SVAS, whereas that in the smaller perfusion arterioles should be restored by compensatory vascular growth in this time period similar to right-ventricular hypertrophy (RVH) [22]. To verify this hypothesis, we obtained histological and casting data of the entire coronary vasculature from the left ventricle (LV) in control and SVAS animals in order to fully reconstruct the entire LCx arterial tree down to the first capillary bifurcations for both groups…”

Elevated oxidative stress and endothelial dysfunction in right coronary artery of right ventricular hypertrophy

“…The morphometric data of RCA main trunk, arterioles, and capillaries in RVH suggest outward remodeling in main trunk and increase in numbers of resistance and capillary vessels (12). A hemodynamic analysis showed RCA compensatory adaption during RVH to restore the perfusion at the arteriolar and capillary levels and increase blood flow in the main trunk (10), in proportion to increase in right ventricle (RV) mass (12). The effect of RVH on RCA endothelial function, however, remains unclear.…”