Paradoxical Arterial Wall Shrinkage May Contribute to Luminal Narrowing of Human Atherosclerotic Femoral Arteries

BACKGROUND: This study was done to assess how local changes in vessel size, together with plaque load, determine luminal narrowing in atherosclerotic arteries. Fifty-one human femoral arteries were analyzed: 32 postmortem and 19 in vivo by 30-MHz intravascular ultrasound. METHODS AND RESULTS: Histological and intravascular ultrasound cross sections were examined every 0.5 cm over an arterial segment 10 to 15 cm long. In each cross section we measured the lumen area and the area circumscribed by the internal elastic lamina (the IEL area). In each arterial segment, the cross section that contained the least amount of plaque was the reference site. For each cross section, the lumen area stenosis was expressed as percent of the lumen area in the reference site. Similarly, the IEL area was expressed as percent of the IEL area in the reference site (the relative IEL area). There was a significant negative correlation between the relative IEL area and the lumen area stenosis percentage (r = -.62, P < .001 for histology and r = -.66, P < .001 for intravascular ultrasound). When lumen area stenosis was less than about 25%, mainly compensatory enlargement was observed. When lumen area stenosis exceeded about 25%, however, mainly a decrease of the IEL area was observed, which is consistent with arterial wall shrinkage. Furthermore, the increase in plaque area does not account for the total loss of luminal area. There was a moderate correlation between an increase in plaque area and reduction of the corresponding lumen area (r = .49 and r = .56 for histology and intravascular ultrasound, respectively). CONCLUSIONS: The decrease in luminal area cannot be attributed to plaque increase alone. Arterial wall shrinkage is a paradoxical mechanism that may contribute to severe luminal narrowing of the atherosclerotic human femoral artery.