Objectives: Intracoronary ultrasonography was used to assess coronary arteries before and after balloon percutaneous transluminal coronary angioplasty (PTCA) to determine whether the mode of coronary atherosclerotic remodeling affects the mechanism of balloon dilation.
Background: Coronary arteries may enlarge or shrink in response to atherosclerotic plaque development. The effect of coronary remodeling on the mechanism of balloon PTCA has not yet been studied.
Methods: Forty-one patients with 47 native de novo coronary artery lesions were studied with a 30 MHz intracoronary ultrasound catheter before and after balloon PTCA. Images were analyzed at the lesion site and the adjacent reference segments. At each site the lumen, vessel, and plaque area and the percent area stenosis were measured. Lesions were separated into two groups based on relative vessel area (lesion vessel area/reference vessel area). A relative vessel area >1.0 defines adaptive enlargement (group 1, n = 25), whereas a relative vessel area < or =1.0 reflects coronary shrinkage (group 2, n = 22). Regression analysis examined whether elastic recoil and the PTCA balloon/vessel area ratio correlated.
Results: After balloon PTCA was performed, both the enlargement and shrinkage groups had similar gains in luminal area (2.3 +/- 1.8 mm2 [mean +/- SD] vs 2.8 +/- 1.7 mm2, p = 0.32), reduction in percent stenosis (-19.2% +/- 11.5% vs -14.4 +/- 12.7, p = 0.18), and final lumen area (4.9 +/- 1.7 mm2 vs 4.7 +/- 1.9 mm2, p = 0.73). However, the mechanism of luminal enlargement was different in each group. Reduction in plaque area was significantly greater in the enlargement group (group 1, -2.0 +/- 1.7 mm2 vs group 2, 0.04 +/- 2.2 mm2; p = 0.001), whereas increased vessel area was more important in the shrinkage group (group 1, 0.8 +/- 1.5 mm2 vs group 2, 2.4 +/- 2.3 mm2; p = 0.009). Positive correlation was seen between elastic recoil and the balloon/vessel area ratio in lesions with vessel enlargement (r = 0.80, p < 0.0001). No such correlation was observed in shrinkage vessels (r = 0.28, p = 0.21 ).
Conclusions: The acute luminal gain after balloon PTCA is similar regardless of the type of coronary remodeling. However, the mode of remodeling affects the mechanism of balloon dilation such that enlargement vessels exhibit plaque compression, whereas shrinkage arteries demonstrate vessel stretch. The post-PTCA elastic recoil correlates linearly to the balloon/vessel area ratio in arteries that have undergone adaptive enlargement.