Coronary arterial tree remodeling in right ventricular hypertrophy

We investigated coronary vascular adaptations occurring in right ventricular hypertrophy (RVH). Six pigs had RVH induced by pulmonary artery stenosis for 5 wk. Three pigs served as controls. At autopsy we made silicone elastomer casts of the right coronary arteries (RCA) and collected morphometric data. We organized the segments and their diameters and lengths into a framework of a modified Strahler's ordering scheme in which the order number of an offspring is increased only if its diameter is greater than the diameters of its parents by a specific amount. The segments of the same order arranged in series are combined into elements. In RVH the total number of orders of vessels was larger than the control by 1; the total number of elements in each order increased greatly, whereas the diameters and lengths of each order decreased somewhat. The total RCA resistance decreased in RVH mainly because the total cross-sectional area (CSA) of every order was increased. Because the diameters of the resistance vessels decreased, this decrease in total RCA resistance was due to a numerical increase in resistance vessels. These findings indicate that new flow channels have been established. In contrast, the RCA was remodeled in that the lumen diameter increased. Pressure-flow curves showed a decrease of coronary resistance in RVH, in agreement with the morphometric findings. We conclude that there is significant remodeling of the coronary arterial vasculature in RVH, and any future analysis of coronary hemodynamics of the right ventricle in hypertrophy must take the morphometric remodeling into account.