COMPARABLE PROXIMAL AND DISTAL SEVERITY OF INTIMAL THICKENING AND SIZE OF EPICARDIAL CORONARY-ARTERIES IN TRANSPLANT ARTERIOPATHY OF HUMAN CARDIAC ALLOGRAFTS

Previous angiographic observations have characterized transplant ather osclerosis as a generally diffuse and more distally severe disease wit h obliteration of secondary branches. However, it has not been firmly established that the disease is structurally and biologically more sev ere distally. We evaluated this hypothesis with computer-based digitiz ation of subserial segments of the entire perfusion-fixed left anterio r descending coronary artery (100 mm Hg for 1 hour with 10% formaldehy de solution) in 25 allografts at autopsy or explant (19 male and 6 fem ale patients; mean age = 50 years, range 16 to 66; mean implant durati on = 490 days, range 3 to 1610). The area, thickness, circumference of the intima and media, and the relative and absolute luminal narrowing were evaluated in a mean of 10 left anterior descending coronary arte ry sections per allograft. The percentage of luminal narrowing (intima l area/[intimal area + luminal area] x 100) was similar between proxim al and distal segments of the left anterior descending coronary artery (45% versus 41%, p > 0.05), and the mean absolute intimal thicknesses (in millimeters) of proximal and distal segments of the left anterior descending coronary artery also were not different (0.32 versus 0.22, p > 0.05). In addition, the 95% confidence intervals for intimal thic knesses of proximal and distal segments were comparable. Because the a bsolute arterial size of proximal segments is naturally larger than th at of distal segments (external diameter 9.37 versus 6.79, p < 0.0001) , an appearance of progressive tapering may be visualized angiographic ally, even though the biologic severity of the disease is geographical ly uniform. Similarly, observations of obliterated secondary branches in distal segments may result from naturally smaller distal luminal ar eas which may be occluded by less intimal thickening than would be req uired proximally. These data emphasize that transplant atherosclerosis is biologically uniform from proximal to distal locations. Etiologic and pathogenetic studies on proximal or distal segments should be equa lly informative.