Ann Thorac Surg 2007;84:1504-1507. doi:10.1016/j.athoracsur.2007.06.006
© 2007 The Society of Thoracic Surgeons
Original Articles: Cardiovascular
New Method of Thermal Coronary Angiography for Intraoperative Patency Control in Off-Pump and On-Pump Coronary Artery Bypass Grafting
Hidehiko Iwahashi, MD, PhD*,
Tadashi Tashiro, MD, PhD,
Noritsugu Morishige, MD, PhD,
Yoshio Hayashida, MD,
Kazuma Takeuchi, MD, PhD,
Nobuhisa Ito, MD,
Hideki Teshima, MD, PhD,
Go Kuwahara, MD
Department of Cardiovascular Surgery, Fukuoka University School of Medicine, Fukuoka, Japan
Accepted for publication June 1, 2007.
* Address correspondence to Dr Iwahashi, Department of Cardiovascular Surgery, Fukuoka University School of Medicine, 7-45-1 Nanakuma, Jonan-ku, Fukuoka, 814-0180, Japan. (Email: iwahashi{at}fukuoka-u.ac.jp).
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Abstract
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Background: We evaluated the effectiveness of a new thermal coronary angiogram system using intraoperative imaging with an infrared camera for coronary artery bypass grafting.
Methods: The thermal coronary angiograms of 51 patients who underwent a total of 107 coronary artery bypass grafts were evaluated. Thermal coronary angiograms were obtained after completing distal anastomoses by the injection of cold saline solution into the vein grafts or free arterial grafts or by reperfusion with warmer blood in the internal thoracic artery grafts. Temperature differences of greater than 0.1°C between the injectant and the epimyocardium resulted in high-contrast images.
Results: Thermal coronary angiograms were obtained from 107 coronary artery bypass grafts; 103 grafts were patent (96.3%), and 2 internal thoracic artery grafts were occluded. After reanastomoses, thermal coronary angiograms were again obtained, and all grafts appeared to be patent. Four grafts did not clearly show hemokinesis because of an intramyocardial segment or circumferential fat surrounding the artery.
Conclusions: Thermal coronary angiograms cannot show hemokinesis clearly in cases with an intramyocardial arterial segment or in patients in whom the grafts are surrounded by fat. Therefore, thermal coronary angiograms are considered to play a valuable role in confirming the success or failure of myocardium revascularization because this diagnostic modality does not interfere with the surgical procedures, is noninvasive, and can be both quickly and easily performed.
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Introduction
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Graft patency control is important in the sequence of coronary artery bypass grafting (CABG). Early graft failure is often associated with technical failure, and it should therefore be avoided as much as possible. We evaluated the effectiveness of a new thermal coronary angiogram system named IRIS-III using intraoperative imaging with an infrared camera for on-pump or off-pump CABG.
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Patients and Methods
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Patients
Between September 1999 and July 2000, thermal coronary angiograms of 51 patients who underwent a total of 107 CABGs were evaluated. Twenty-four patients (mean age, 61.5 years; 19 men and 5 women) who had 46 grafts underwent on-pump CABG, and 27 patients (mean age, 65.7 years; 19 men and 8 women) who had 61 grafts underwent off-pump CABG.
Methods
A new thermal coronary angiogram system using intraoperative imaging with an infrared camera for CABG named IRIS-III (Thermatrek, Dusseldorf, Germany) has been used since September 1999. This system consists of two mobile parts, a camera and a console. The console contains a video recorder and control unit. The camera unit contains an infrared imager, a charge-coupled device camera, and two monitors (Fig 1). The console can be placed anywhere. As a result, the camera unit is easily placed over the heart from the surgeon’s side or the anesthesiologist’s side. Thermal coronary angiograms were obtained after completing distal anastomoses by the injection of cold saline solution (30°C, 3 to 5 mL) into the vein grafts or free arterial grafts or by reperfusion with warmer blood (about 5 seconds) in the internal thoracic artery (ITA) and gastroepiploic artery graft after epicardial cooling by sprinkling cold saline solution (30°C, 1 to 2 mL).
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Fig 1. A new thermal coronary angiogram system using intraoperative imaging with an infrared camera for coronary artery bypass grafting named IRIS-III (Thermatrek, Dusseldorf, Germany). This system consists of two mobile parts, a camera and a console. The console contains a video recorder and control unit. The camera unit contains an infrared imager, a charge-coupled device camera, and two monitors.
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The temperature of warmer blood is about 37°C during on-pump or off-pump CABG. Temperature differences of greater than 0.1°C between the injectant and the epimyocardium resulted in high-contrast images [1]. Thermal coronary angiograms were performed immediately after distal graft anastomoses but before protamine was given in all cases.
Between 7 and 10 days after surgery, postoperative angiography was performed in all patients. The results of the thermal coronary angiograms were compared with postoperative angiography. A statistical analysis was performed using Fisher’s exact test. Statistically significant differences were assumed to exist at a value of p less than 0.05.
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Results
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Thermal coronary angiograms were obtained from 107 grafts; 103 grafts were patent (96.3%), whereas 2 ITA grafts were occluded. We found 2 occluded grafts by the IRIS-III in the operation. Immediately after reanastomoses were performed, thermal coronary angiograms were again obtained and all grafts appeared to be patent in the same operation. Therefore, the postoperative angiography was performed in 107 grafts. The results of the thermal coronary angiograms were compared with postoperative angiography. Four grafts did not clearly show hemokinesis because of an intramyocardial segment or circumferential fat surrounding the artery. In four grafts, we could see clear images produced by the IRIS-III. However, these grafts were subsequently revealed to not be patent by postoperative angiography, which was performed because of the occurrence of early graft thrombosis (Table 1).
The graft patency rate of the IRIS-III was 96.3%. In contrast, the postoperative patency rate for angiography was 95.3%. No significant differences in the total grafts performed were observed between the two groups (Table 2). In addition, no significant differences in the left anterior descending artery area (Table 3), the circumflex artery area (Table 4), and the right coronary artery area (Table 5) graft patency variables were observed between the two groups.
We now have two effective cases of intraoperative thermal coronary angiograms in CABG. In the first case, Iwahashi and colleagues [1] reported that the left ITA was grafted to the obtuse marginal artery. Just after completing the anastomosis, we performed thermal coronary angiography by IRIS-III. The left ITA to obtuse marginal artery appeared to not be patent on thermal coronary angiography. After a reanastomosis at the left ITA to obtuse marginal artery, thermal coronary angiography was again performed and the left ITA to obtuse marginal artery anastomosis was thus found to be patent. The postoperative course was uneventful, and all grafts were patent on postoperative angiography.
In the second case, the left ITA was grafted to the left anterior descending coronary artery. The left ITA to left anterior descending coronary artery was not patent on thermal coronary angiography by IRIS-III because of graft occlusion. Therefore, a reanastomosis was done at a saphenus vein graft to left anterior descending coronary artery; thermal coronary angiography was then reperformed, and the saphenus vein graft to left anterior descending coronary artery anastomosis was subsequently found to be patent (Fig 2).
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Fig 2. (A) The left internal thoracic artery to left anterior descending coronary artery anastomosis was not patent on thermal coronary angiography by intraoperative imaging with an infrared camera because of graft occlusion. (B) After a reanastomosis at a saphenous vein graft (SVG) to left anterior descending coronary artery (LAD), thermal coronary angiography was performed again and the saphenous vein graft to left anterior descending coronary artery anastomosis was subsequently found to be patent (black line).
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Comment
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We evaluated the effectiveness of a new thermal coronary angiogram system (IRIS-III) using intraoperative imaging with an infrared camera for CABG. The graft patency rate of the IRIS-III was 96.3%. In contrast, the postoperative patency rate of angiography was 95.3%. No significant differences in the total graft variables were observed between the two groups. Therefore, a thermal coronary angiogram is considered to be better than a postoperative angiogram. Thermal coronary angiography can be performed just after completing distal anastomoses and we can observe it in real time. In addition, temperature differences of greater than 0.1°C between the injectant and the epimyocardium resulted in high- contrast images. A thermal coronary angiogram does not use the contrast medium. As a result, if the bypass graft is not patent, then a reanastomosis can be performed immediately. Because thermal coronary angiograms do not show clearly hemokinesis because of either the presence of intramyocardial arterial segments or circumferential fat surrounding the artery, another method (eg, flowmeter) would therefore be helpful in such conditions.
Up to now, several studies on intraoperative coronary assessment of anastomotic quality have been reported on the development of techniques to verify graft patency. In one method, intraoperative angiography is the gold standard for assessing anastomotic quality, but this is an invasive method that is also expensive and time-consuming [2]. In a second method, angioscopic evaluation is another alternative to assess the quality of anastomosis [3, 4]. However, it has the potential danger of causing intimal injury, and it is not feasible for in situ grafts and has never had wide acceptance. In a third method, Louagie and associates [5] and Merin and coworkers [6] reported on the use of an electromagnetic flowmeter. The determined values based on such measurements are not absolute. In a fourth method, Sakakibara and colleagues [7] reported using intraoperative echocardiography. However, their method was not very clearly described [8], and this tool is nether cost-effective nor practical [9].
In a fifth method, high-frequency epicardial echocardiography was used to detect anastomotic failures by some authors [10, 11]. However, segmental calcifications on the arteries may cause some artifacts that may complicate an accurate assessment and prolong the investigation time.
In a sixth method, the ultrasound-based transit-time flow has been used as a method to measure graft flow [12]. Intraoperative measurements have been reported to result in a revision of 9.9% of the distal anastomosis constructed during off-pump CABG [13]. However, comparing the intraoperative ultrasound-based transit-time flow and postoperative angiogram, the transit-time flow could not identify any significant lesions in the arterial or vein grafts, and the interpretation of the flow measurement alone should therefore be done cautiously [14].
Falk and coworkers [15] reported that a thermal coronary angiogram was an ideal, noninvasive method to immediately document the success or failure of myocardial revascularization. Friedrich and associates [16] reported a thermal coronary angiogram to be both clinically relevant while also helping to improve the decision making during CABG.
The current models of thermal coronary angiograms need temperature differences between 0.2 and 0.4°C [15]. In contrast, the new thermal coronary angiogram needs only a 0.1°C temperature difference [1]. Therefore, we can use the new thermal coronary angiogram system more easily.
We are presently trying to develop a new system to analyze the blood flow using a thermal coronary angiogram system. If such a system can be developed, then thermal coronary angiograms could thus be performed anywhere. In the near future, it may therefore no longer be necessary to perform postoperative angiograms.
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References
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- Iwahashi H, Tashiro T, Nakamura K, et al. An effective case of intraoperative thermal coronary angiography in coronary artery bypass grafting Jpn J Cardiovasc Surg 2001;30:217-219.
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- Siegel SB, White GH, Colman PD, et al. Intraoperative angioscopy for coronary artery bypass surgery J Card Surg 1995;10:210-220.[Medline]
- Louagie YAG, Haxhe JP, Buche M, et al. Intraoperative electromagnetic flowmeter measurements in coronary artery bypass grafts Ann Thorac Surg 1994;57:357-364.[Abstract]
- Merin G, Elami A, Zucker M. Intraoperative detection of unsuspected distal coronary obstruction by thermal coronary angiography Cardiovasc Surg 1995;6:599-601.
- Sakakibara T, Matsuwaka R, Ishikura F, et al. Intraoperative real-time visualization of coronary arteries by means of power Doppler echocardiography: preliminary experience J Thorac Cardiovasc Surg 1997;113:605-606.[Free Full Text]
- Louagie YAG, Haxhe JP, Jamart J, et al. Doppler flow measurement in coronary artery bypass grafts and early postoperative clinical outcome Thorac Cardiovasc Surg 1994;42:175-181.[Medline]
- Sonmez B, Arbatli H, Tansal S, et al. Real-time patency control with thermal coronary angiography in 1401 coronary artery bypass grafting patients Eur J Cardiothoracic Surg 2003;24:961-966.[Abstract/Free Full Text]
- McPherson DD, Armstrong M, Rose E, et al. High frequency epicardial echocardiography for coronary artery evaluation: in vitro and in vivo validation of arterial lumen and wall thickness measurements J Am Coll Cardiol 1986;8:600-606.[Abstract]
- Hiratzka LM, McPherson DD, Brandt 3rd B, et al. The role of intraoperative high-frequency epicardial echocardiography during coronary artery revascularization Circulation 1987;76:33-38.
- van Son JA, Skotnicki ST, Peters MB, et al. Noninvasive hemodynamic assessment of the internal mammary artery in myocardial revascularization Ann Thorac Surg 1983;55:404-409.
- D’Ancona G, Karamanoukian HL, Salerno TA, et al. Flow measurement in coronary surgery Heart Surg Forum 1999;2:121-124.[Medline]
- Hol PK, Fosse E, Mork BE, et al. Graft control by transit-time flow measurement and intraoperative angiography in coronary artery bypass surgery Heart Surg Forum 2001;4:254-258.[Medline]
- Falk V, Walther T, Philippi A, et al. Thermal coronary angiography for intraoperative patency control of arterial and saphenous vein coronary artery bypass grafts: results in 370 patients J Card Surg 1995;10:147-160.[Medline]
- Friedrich GJ, Jonetzko P, Bonaros N, et al. Hybrid coronary artery revascularization: logistics and program development Heart Surg Forum 2005;8:E258-E261.[Medline]
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Abstract
Introduction
