Abstract
The rate of restenosis after directional coronary atherectomy (DCA) is higher than expected. To elucidate why, the current study used intravascular ultrasound (IVUS) imaging to investigate the mechanism of DCA. An in vitro validation study was performed to determine the accuracy of the measurement of plaque removal by IVUS. DCA was performed in eight human atherosclerotic artery segments. The volume of removed plaque was measured by water displacement and was compared with the volume calculated from IVUS images. A clinical study of DCA was performed in 32 lesions. IVUS was performed in 28 lesions after successful DCA. Measurements of lumen dimensions from digital angiograms before and after DCA were compared with observations of lumen and plaque size from the cross-sectional IVUS images. In the in vitro study, the mean plaque volume removed by DCA was 19.9 ± 8.5 μl. The calculated estimate of removed plaque volume by IVUS was 18.6 ± 7.9 μl and correlated closely with the volume by water displacement ( r = 0.92). The calculated volume of plaque removed from histologic sections was 14.3 ± 6.0 μl and was linearly correlated with plaque volume by water displacement ( r = 0.81). In the clinical study, the angiographic mean minimum lumen diameter increased from 1.0 ± 0.4 to 2.7 ± 0.5 mm and the percentage stenosis decreased from 70% to 19% ( p < 0.0001). The IVUS images before and after DCA showed that the lumen DCA improved from 2.9 ± 1.5 to 7.0 ± 1.5 mm 2 ( p < 0.0001). In addition the vessel cross-sectional area (CSA) increased from 17.1 ± 5.9 to 18.7 ± 5.5 mm 2. The atheroma CSA was reduced from 14.2 ± 5.0 to 11.7 ± 4.8 mm 2. This combined effect of reduction in atheroma CSA and stretching of the outer vessel diameter resulted in an improvement in percentage plaque area stenosis from 83% ± 7% to 61% ± 9%. It is concluded that despite a successful angiographic appearance, DCA removed an average of 2.5 mm 2 from the atheroma, which corresponds to only 18% of the atheroma CSA. The total lumen CSA increased 4.1 mm 2; 61% of the new lumen was created by cutting and removal of plaque, whereas 39% of the new lumen was made by stretching the external wall of the artery. Despite an excellent angiographic result, IVUS imaging reveals that after DCA a significant amount of residual atheroma remains. As in balloon dilatation, a stretching effect is a significant component of DCA.
Highlights
Directional coronary atherectomy (DCA) was developed to address the high incidence of restenosis after percutaneous transluminal coronary balloon angioplasty (PTCA). 15 The underlying hypothesis of this technique is that restenosis may be diminished if a sufficient amount of plaque can be removed
May 1995 AmericanHeartJournal be obtained compared with standard balloon dilatation. 6-9 despite angiographic evidence of a satisfactory acute gain, the rates of restenosis are similar to those after PTCA (27 % to 46%)J°ls The results from the Coronary Angioplasty Versus Excisional Atherectomy Trial (CAVEAT) show a modest improvement in restenosis compared with restenosis after PTCA, but the angiographic restenosis rate for DCA is higher than expected, at 50% .!9 This observation challenges the assumption that removing atheroma will reduce restenosis; an alternative explanation is that the atherectomy device does not remove as much plaque as predicted
Intravascular ultrasound (IVUS) imaging provides a method for obtaining quantitative information about the cross-sectional area (CSA) of the lumenand the atheroma burden. 2°-26B y imaging the narrowed segments with IVUS before as well as after atherectomy, it may be possible to obtain a better understanding of the mechanism of action of DCA
Summary
Directional coronary atherectomy (DCA) was developed to address the high incidence of restenosis after percutaneous transluminal coronary balloon angioplasty (PTCA). 6-9 despite angiographic evidence of a satisfactory acute gain, the rates of restenosis are similar to those after PTCA (27 % to 46%)J°ls The results from the Coronary Angioplasty Versus Excisional Atherectomy Trial (CAVEAT) show a modest improvement in restenosis compared with restenosis after PTCA, but the angiographic restenosis rate for DCA is higher than expected, at 50% .!9 This observation challenges the assumption that removing atheroma will reduce restenosis; an alternative explanation is that the atherectomy device does not remove as much plaque as predicted. 2°-26B y imaging the narrowed segments with IVUS before as well as after atherectomy, it may be possible to obtain a better understanding of the mechanism of action of DCA Intravascular ultrasound (IVUS) imaging provides a method for obtaining quantitative information about the cross-sectional area (CSA) of the lumenand the atheroma burden. 2°-26B y imaging the narrowed segments with IVUS before as well as after atherectomy, it may be possible to obtain a better understanding of the mechanism of action of DCA
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