THE CONTRIBUTION OB TISSUE REMOVAL TO LUMEN IMPROVEMENT AFTER DIRECTIONAL CORONARY ATHERECTOMY

The contribution of tissue removal to lumen improvement after directio nal coronary atherectomy remains controversial. The purpose of this st udy was to validate the intravascular ultrasound measurement of plaque volume and use it to study the contribution of tissue removal to lume n improvement after directional coronary atherectomy. With use of intr avascular ultrasound, 12 human coronary vessels were imaged in vitro. With use of computer-assisted planimetry, the external elastic membran e and lumen cross-sectional areas were manually traced and the plaque + media area was calculated at 1 mm axial intervals. Then, plaque + me dia volume was calculated by Simpson's rule. After imaging, ultrasound measurements of plaque + media volume were compared with histologic m easurements. Similarly, volumetric intravascular ultrasound imaging wa s performed before and after directional atherectomy in 47 patients. I n vitro, the mean plaque + media volume measured by intravascular ultr asound was 134.0 +/- 94.8 mm(3) and compared well with that derived by histology (187.4 +/- 123.8 mm(3), r = 0.96, p <0.001). In vivo, the l umen volume increased from 27.2 +/- 12.3 to 58.7 +/- 30.3 mm(3), and t he mean plaque + media volume decreased from 122.0 +/- 74.0 to 97.5 +/ - 63.5 mm(3). The mean intravascular ultrasound atherectomy index was 76 +/- 23%. In ii of the 47 patients (23.4%), tissue removal alone acc ounted for lumen improvement. Volumetric intravascular ultrasound imag e analysis indicates that the mechanism of directional coronary athere ctomy primarily is tissue removal. As a result, the contribution of ar terial remodeling (expansion and dissection) probably is less importan t.