COMPENSATORY ENLARGEMENT OF ANGIOGRAPHICALLY NORMAL CORONARY SEGMENTSIN PATIENTS WITH CORONARY-ARTERY DISEASE - IN-VIVO DOCUMENTATION USING INTRAVASCULAR ULTRASOUND

Intravascular ultrasound (IVUS) frequently reveals plaque formation at sites with a normal angiographic appearance. However, whether angiogr aphically normal coronary arteries undergo adaptive expansion in vivo remains uncertain. The authors studied 12 patients (11 men, 1 woman; m ean age fifty-three +/- ten years [mean +/- SD]) with focal coronary s tenosis. Sixty IVUS images from angiographically normal coronary segme nts were analyzed (14 left main, 44 left anterior descending, and 2 le ft circumflex coronary arteries). The mean percent area stenosis was 3 6 +/- 5% and the circular shape factor of the lumen cross section aver aged 0.97 +/- 0.02. Both total arterial area and internal elastic lami na area increased as the plaque area expanded (y = 2.13x + 8.07, r = 0 .87, P = 0.0001; y = 2.06x + 4.57, r = 0.87, P = 0.0001, respectively) , suggesting that for every 1 mm(2) increase in plaque area, the total arterial area increased by approximately 2.13 mm(2) and the internal elastic lamina area increased by approximately 2.06 mm(2). The lumen a rea also increased as the plaque area expanded (y = 1.06x + 4.57, r = 0.68, P = 0.0001), suggesting that for every 1 mm(2) increase in plaqu e area, the lumen area increased by approximately 1.06 mm(2). The medi al area did not correlate with the plaque area (r = 0.15, P = 0.26). T hus, compensatory enlargement precedes development of angiographically detectable coronary atherosclerosis. Furthermore, in early stages of atherosclerosis, arterial enlargement may overcompensate for plaque ar ea. The reduction of the total medial mass does not appear to contribu te to the mechanism of compensatory enlargement.