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Imaging of post-mortem coronary arteries by 30 MHz intravascular ultrasound
C Borst1, L H Savalle, P C Smits
1Heart Lung Institute, University Hospital, Utrecht, The Netherlands.
Insights
Intravascular ultrasound can guide plaque ablation in older coronary arteries by identifying the echolucent zone. This landmark is often absent in younger arteries, limiting guided ablation effectiveness.
Area of Science:
- Cardiovascular Imaging
- Medical Ultrasound
- Interventional Cardiology
Background:
- Intravascular ultrasound (IVUS) is used for imaging atherosclerotic arteries.
- Plaque ablation techniques require precise guidance.
- The echolucent zone in the three-layered ultrasound appearance of muscular arteries may serve as a boundary for ablative angioplasty.
Purpose of the Study:
- To assess if the echolucent zone in coronary arteries is a reliable boundary for halting transluminal ablative angioplasty.
- To determine the influence of age on the visibility of the echolucent zone in coronary arteries.
Main Methods:
- Epicardial coronary arteries from four post-mortem hearts (aged 22, 31, 56, 82 years) were scanned using a 30 MHz intravascular ultrasound catheter.
- 419 images were analyzed to score the presence of a distinct echolucent zone as a percentage of the wall circumference.
- Ultrasound images were compared with corresponding microscopic sections.
Main Results:
- The median echolucent zone scores were 0%, 0%, 10%, and 75% for the 22, 31, 56, and 82-year-old hearts, respectively.
- A distinct three-layered appearance was largely absent in younger hearts but identifiable in the 82-year-old heart.
- Neither medial elastin nor medial thickness explained the absence of the echolucent zone.
Conclusions:
- 30 MHz intravascular ultrasound can adequately guide transluminal plaque ablation in older coronary arteries (e.g., 82-year-old) due to a discernible echolucent zone.
- Guided ablation may fail in younger hearts due to the limited presence of this echolucent zone landmark.
- Further research is needed to determine if the presence or absence of the echolucent zone is definitively related to age.
Abstract:
Intravascular ultrasound cross-sectional imaging of the atherosclerotic artery may be employed to guide plaque ablation by spark erosion, atherectomy, laser irradiation or other means. To assess whether in the coronary artery the echolucent zone of the three-layered ultrasound appearance of muscular arteries might be a reliable boundary to halt transluminal ablative angioplasty, epicardial coronary arteries were scanned under pressure over a distance of 4-8 cm at 1 mm intervals. A 5.2F catheter with a 30 MHz transducer rotating at 600 RPM was used. In 419 images from four post-mortem hearts, aged at death 22, 31, 56 and 82 years, the presence of a distinct echolucent zone was scored as percentage of the wall circumference. The median scores were 0%, 0%, 10% and 75%, respectively. In the three youngest hearts, the three-layered appearance was largely absent. In the 82 year old heart, in contrast, the three-layered appearance could generally be identified. Within subjects, the presence of an echolucent zone was variable in location. Qualitatively, neither abundant medial elastin tissue nor a reduced medial thickness could explain the absence of an echolucent zone when the ultrasound image was compared to the corresponding microscopic section. The results show that in the 82 year old heart, 30 MHz intravascular ultrasound discrimination of coronary wall layers would be adequate to guide transluminal plaque ablation. In the younger hearts, guided ablation would fail due to the limited presence of a distinct echolucent zone as an ultrasound landmark of the media. Whether the presence or absence of an echolucent zone is related to age remains to be determined.