936-89 Extent of Coronary Myointimal Proliferation and its Relationship to Resistance Vessel Function in the Cardiac Allograft

Abstract

Transplant coronary arteriopathy is the major obstacle to long-term survival of cardiac allografts and is characterized by myointimal proliferation involving both epicardial conduit vessels and intra myocardial resistance vessels. To evaluate the relationship between conduit disease and resistance vessel integrity, 70 coronary arteries in 58 transplant patients were studied with a 3.5 Fr 30 MHz intravascular ultrasound (IVUS) probe and an 0.018” doppler guidewire. Epicardial conduit disease was characterized by the presence or absence of IVUS discernible intimal thickening, (>500 microns or <500) micronsl in either a diffuse (trilaminar appearance along whole course of studied segment) or a focal (with areas of vessel free of intimal thickening) distribution. Resistance vessel function was assessed by measuring coronary flow reserve (CFR = maximal hypermic/resting blood flow velocity) using intracoronary adenosine (18 mg). (means ± SD): None(n = 12) Diffuse > 500(n = 19) Diffuse < 500(n = 18) Focal > 500(n = 7) Focal < 500(n = 14) CFR 3.1 ± 0.5 3.3 ± 0.4 37 ± 0.7 23 ± 0.6 * 2.8 ± 4 * p < 0.01 vs diffuse There were no differences in the CFR between arteries with (n = 58) and without (n = 12) intimal thickening (3.2 ± 0.6 vs 3.1 ± 0.5; P = NS) or based on the maximal thickness of the intima (<500 microns, 3.2 ± 8 vs >500 microns 3.0 ± 0.7, P = NS). Extensive myointimal thickening can occur without diminishment of the CFR. Focal intimal disease is associated with a significantly more profound effect on microvascular function then classically described diffuse disease. This suggests that typical epicardial transplant arteriopathy can occur without involvement of small vessels.