Related Experiment Videos
Intracoronary ultrasound imaging before and after directional coronary atherectomy: in vitro and clinical
S Nakamura1, D J Mahon, C Y Leung
1Division of Cardiology, University of California, Irvine, Orange 92668, USA.
Insights
Directional coronary atherectomy (DCA) often results in restenosis. Intravascular ultrasound (IVUS) shows that while DCA improves lumen diameter, significant plaque remains, with vessel stretching contributing to the outcome.
Area of Science:
- Cardiovascular Interventions
- Medical Imaging
- Atherosclerosis Research
Background:
- Restenosis rates after directional coronary atherectomy (DCA) are higher than anticipated.
- The precise mechanisms driving DCA outcomes require further investigation.
Purpose of the Study:
- To investigate the mechanism of plaque removal by DCA using intravascular ultrasound (IVUS).
- To validate IVUS accuracy in measuring plaque removal in vitro.
- To compare angiographic and IVUS findings after DCA in clinical settings.
Main Methods:
- An in vitro study validated IVUS plaque volume measurement against water displacement and histology.
- DCA was performed on human atherosclerotic artery segments and 32 clinical lesions.
- IVUS imaging was used before and after DCA to assess lumen dimensions, vessel cross-sectional area (CSA), and atheroma CSA.
Main Results:
- In vitro IVUS plaque volume estimates closely correlated with water displacement measurements (r=0.92).
- Clinically, DCA significantly increased minimum lumen diameter (1.0 to 2.7 mm) and reduced stenosis (70% to 19%, p<0.0001).
- IVUS revealed atheroma CSA reduction (14.2 to 11.7 mm2) and vessel stretching, with 18% of atheroma remaining and 39% of lumen gain from stretching.
Conclusions:
- Despite successful angiographic results, DCA leaves significant residual atheroma.
- Vessel wall stretching is a major contributor to lumen gain after DCA, similar to balloon angioplasty.
- IVUS provides crucial insights into the complex mechanisms and residual disease after DCA.
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 microliters. The calculated estimate of removed plaque volume by IVUS was 18.6 +/- 7.9 microliters 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 microliters 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 mm2 (p < 0.0001). In addition the vessel cross-sectional area (CSA) increased from 17.1 +/- 5.9 to 18.7 +/- 5.5 mm2. The atheroma CSA was reduced from 14.2 +/- 5.0 to 11.7 +/- 4.8 mm2. 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 mm2 from the atheroma, which corresponds to only 18% of the atheroma CSA. The total lumen CSA increased 4.1 mm2; 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.