COMPENSATORY ARTERIAL ENLARGEMENT IS A COMMON PATHOBIOLOGIC RESPONSE IN EARLY ATHEROSCLEROSIS

BACKGROUND: Human arteries are dynamic conduits that respond to differ ent stimuli by remodeling their structure and size. Arterial dilatatio n has been shown to occur in moderate and advanced atherosclerosis in studies that evaluated only one artery, either coronary, carotid, or s uperficial femoral artery (SFA). The purpose of this study was to quan tify and compare compensatory arterial enlargement throughout the peri pheral vascular system in early atherosclerosis.METHODS: Seventy-two p atients (40 male, 32 female, mean age 67 +/- 12 years) underwent trans cutaneous B-mode ultrasound imaging during routine examinations. Thirt y-nine carotid, 19 aorta, 19 iliac, 23 common femoral (CFA), 21 SFA, a nd 23 popliteal arteries were longitudinally imaged. Eight healthy vol unteers (6 male, 2 female, mean age 27 +/- 2.2 years) had the same art eries evaluated (n = 48). Internal diameter (ID) and external diameter (ED) were measured in disease-free areas and in paired adjacent areas exhibiting increased intima-media thickening (IMT) and small atherosc lerotic plaques. The percent change in ID, ED, IMT, and plaque thickne ss were calculated. RESULTS: There was no observed change in ID or ED in all arteries of the healthy volunteers. When compared with normal v essel segments, all arteries demonstrated a marked decrease in ID and increase in ED in areas of small, hemodynamically insignificant plaque . The aorta had a 6.00% +/- 1.92% increase in ED, which was significan tly less than the percent increase in ED observed in carotid (8.14 +/- 4.5%. P = 0.05), CFA (9.73 +/- 3.54%, P = 0.0001), SFA (9.15 +/- 4.25 %, P = 0.005), and popliteal arteries (9.67 +/- 4.34, P = 0.002). In a ll arteries there was a strong correlation between plaque thickness an d percent change in ED with the best correlation observed in the popli teal artery (R-2 = 0.823, P <0.0001). IMT was significantly increased in all normal vessel segments of the patients when compared with the h ealthy volunteers (P <0.001). CONCLUSION: All peripheral arteries dila te in response to intima-media thickening and early atherosclerotic pl aque formation. This adaptive response occurs at the site of the lesio n to preserve luminal area. The percent change in ED is strongly relat ed to plaque thickness and is greatest in the more distal arteries. Am J Surg. 1998;176:140-143. (C) 1998 by Excerpta Medica, Inc.