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[Lumen enlargement in coronary angioplasty: qualitative and quantitative analysis of vascular mechanisms with intravascular ultrasound].

The purpose of this study was to determine the mechanisms by which balloon angioplasty increases luminal patency. Therefore serial examinations with intravascular ultrasound before and after coronary balloon angioplasty were performed. Forty consecutive patients (7 female, 33 male, aged 58 +/- 9 years) with 49 dilated lesions were examined with a 3.5 F, 20 MHz mechanical intravascular ultrasound imaging system before and immediately after coronary balloon angioplasty. Quantitative measurements of lumen area, total arterial area, plaque area and arterial stretch were performed in the dilated vessel segments. Plaque reduction accounted for 65% and vessel wall stretch for 35% of the total increase in luminal patency after angioplasty. In 34/49 (69%) lesions plaque reduction and in 15/49 (31%) arterial stretch contributed most (> 50%) of the overall increase in luminal area post angioplasty. in lesions with an ultrasound area stenosis before PTCA larger than the mean value of the group (> or = 87%) plaque reduction contributed a significantly higher percentage to luminal gain as compared to lesions with an area stenosis < 87% (76.5 +/- 25.0 vs 52.7 +/- 29.9, p < 0.05). Conversely, PTCA resulted in a significantly greater amount of vessel walls stretch in lesions with an area stenosis < 87% (47.3 +/- 29.9 vs. 24.4 +/- 24.2; p < 0.05). In lesions with localized dissections (32/49 (65%)) after PTCA as compared to lesions without dissection a significantly greater relative reduction of stenosis (24% +/- 13% vs. 19% +/- 7%, p < 0.05) was found. Plaque reduction and to a lesser extent vessel wall stretch constitute the principal mechanisms responsible for increased luminal patency after balloon angioplasty. The amount of plaque reduction and vessel wall stretch on the overall luminal gain after PTCA is dependent on the size of area stenosis. The presence of localized dissections after angioplasty correlates favorably with a better result.