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Changing flow pattern of the internal thoracic artery undergoing coronary bypass grafting: continuous-wave Doppler
R Cartier1, O S Dias, M Pellerin
1Division of Cardiovascular Surgery, Department of Surgery, Montreal Heart Institute, Quebec, Canada.
Insights
Continuous-wave Doppler ultrasonography assesses internal thoracic artery graft patency during coronary artery bypass surgery. This technique evaluates blood flow velocity, aiding surgeons in confirming graft viability and myocardial vascularization intraoperatively.
Area of Science:
- Cardiovascular Surgery
- Medical Imaging
- Vascular Physiology
Background:
- Assessing internal thoracic artery (ITA) graft patency intraoperatively is crucial for successful coronary artery revascularization.
- Surgeons currently have limited methods to evaluate ITA graft patency in real-time during surgery.
- Doppler ultrasonography offers a potential non-invasive solution for intraoperative assessment.
Purpose of the Study:
- To evaluate the utility of continuous-wave Doppler ultrasonography for assessing ITA graft patency.
- To analyze changes in blood flow velocity and indices before and after ITA grafting.
- To determine if Doppler flow quantification can provide intraoperative feedback on graft function.
Main Methods:
- Continuous-wave Doppler ultrasonography with an 8 MHz scanning probe was used.
- Measurements included systolic and diastolic frequency shifts (KHz) and the systolic/diastolic frequency index.
- Data were collected from 24 ITA grafts in 15 patients before harvesting and after anastomosis.
Main Results:
- A 40% drop in systolic frequency was observed after harvesting the ITA.
- Mean systolic frequency decreased significantly post-grafting (p < 0.01), while mean diastolic frequency doubled (p < 0.001).
- The diastolic/systolic frequency index increased significantly (p < 0.001), indicating enhanced diastolic myocardial perfusion.
Conclusions:
- Continuous-wave Doppler ultrasonography effectively quantifies ITA bypasses, providing intraoperative physiologic assessment.
- The technique allows surgeons to evaluate ITA graft patency and function before and after coronary artery bypass.
- Observed Doppler changes suggest improved myocardial vascularization during diastole following successful grafting.
Abstract:
Surgeons have limited ability to evaluate intraoperatively the patency of internal thoracic artery graft as a bypass for coronary artery revascularization. We used continuous-wave Doppler ultrasonography to study the velocity of the internal thoracic artery before harvesting and after grafting (scanning probe, 8 MHz). Systolic and diastolic frequency shift (in kilohertz) and systolic frequency/diastolic frequency index were analyzed. Twenty four internal thoracic artery grafts in 15 patients were studied. Fourteen internal thoracic artery grafts were anastomosed to the left anterior descending artery, one to a diagonal artery, and nine to the circumflex artery. The mean systolic frequency before harvesting was 1.19 +/- 0.40 KHz and no significant differences were found between the right and the left internal thoracic artery (right, 1.17 +/- 0.37; left, 1.19 +/- 0.42 KHz). There was a 40% drop in systolic frequency related to the harvesting. Mean systolic frequency decreased after grafting (1.19 +/- 0.40 versus 0.87 +/- 0.32 KHz; p < 0.01) whereas mean diastolic frequency doubled (0.32 +/- 0.12 versus 0.83 +/- 0.4 KHz; p < 0.001) and mean diastolic frequency/systolic frequency index increased from 28% +/- 11% to 101% +/- 39% (p < 0.001), indicating an increased myocardial vascularization during diastole. No significant difference was found between grafted arteries (left anterior descending versus circumflex). All patients had an uneventful postoperative course and no perioperative myocardial infarction was reported. Doppler flow quantification of internal thoracic artery bypasses may give the surgeon an opportunity to evaluate intraoperatively the physiologic features and patency of the internal thoracic artery before and after coronary artery bypasses.