CORONARY ARTERIAL TREE REMODELING IN RIGHT-VENTRICULAR HYPERTROPHY

We investigated coronary vascular adaptations occurring in right ventr icular 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 coll ected 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 di ameter is greater than the diameters of its parents by a specific amou nt. The segments of the same order arranged in series are combined int o elements. In RVH the total number of orders of vessels was larger th an the control by 1; the total number of elements in each order increa sed greatly, whereas the diameters and lengths of each order decreased somewhat. The total RCA resistance decreased in RVH mainly because th e total cross-sectional area (CSA) of every order was increased. Becau se the diameters of the resistance vessels decreased, this decrease in total RCA resistance was due to a numerical increase in resistance ve ssels. These findings indicate that new flow channels have been establ ished. In contrast, the RCA was remodeled in that the lumen diameter i ncreased. Pressure-flow curves showed a decrease of coronary resistanc e in RVH, in agreement with the morphometric findings. We conclude tha t 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 a ccount.