Ann Thorac Surg 2002;74:S1395-S1397
© 2002 The Society of Thoracic Surgeons
Supplement: Cardiothoracic Techniques and Technologies
Electron beam coronary angiography to assess patency in the off-pump coronary bypass graft
Fernando M. Jara, MDa*,
Jean Kalush, CTAa,
Mark L. Kahn, MDb
a Department of Surgical Services, McLaren Regional Medical Center, Flint, Michigan USA
b Department of Radiology, McLaren Regional Medical Center, Flint, Michigan, USA
* Address reprint requests to Dr Jara, G-4568 Beecher Road, Flint, MI 48532, USA
e-mail: fernandojara{at}aol.com
Presented at the Eighth Annual Cardiothoracic Techniques and Technologies Meeting 2002, Miami Beach, FL, Jan 23–26, 2002.
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Abstract
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BACKGROUND: Off-pump coronary artery bypass is widely practiced today, with critics questioning patency rates. This study was conducted to determine the feasibility of using electron beam coronary angiography to determine patency in this group of patients.
METHODS: A total of 27 patients from a series of 653 off-pump coronary artery bypass patients were selected at random and, after informed consent, underwent electron beam coronary angiography with an Imatron C150 single slide mode using Ioversol as contrast material injected in an antecubital vein.
RESULTS: A total of 88 bypasses were studied with an average of 3.2 ± 0.7125 grafts per patient, with a mean follow-up of 20.3 months. Four bypasses were occluded.
CONCLUSIONS: Electron beam coronary angiography appears to be a safe, suitable test to demonstrate patency in the off-pump coronary artery bypass graft patient, allowing study of a large group of patients without the risk or discomfort of cardiac catheterization.
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Introduction
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Off-pump coronary artery bypass graft is widely practiced today with multiple reports [1,2] showing its safety and decreased incidence of complications; nonetheless, critics of this technique still question bypass graft patency. The gold standard for determining patency is coronary angiography. However, this is an invasive procedure that is costly, uncomfortable for patients, and not without complications [3]; and most patients who are asymptomatic or who have minimal symptoms would be reluctant to undergo the procedure. A less invasive procedure to determine patency would be a welcome addition not only to answer concern by critics of this procedure, but also for routine postoperative care of coronary artery bypass graft patients.
The major difficulty on imaging the coronary arteries is related to the small caliber of the arteries and rapid motion during the cardiac cycle, combined with patient respirations that make the images blurred and difficult to interpret [4]. Electron beam computed tomography, a cross-sectional imaging method with high temporal and spatial resolution with electrocardiographic triggering, appears to be suitable for coronary imaging [5–7]. In previous studies in which this technique has been compared with cardiac catheterization, accuracy rates have been reported varying from 88.9% to 100%, depending on the location of the bypasses [8, 9].
The purpose of this study was to evaluate contrast medium–enhanced electron beam computed tomographic angiography, single-slide mode with three-dimensional reconstruction, to determine patency for off-pump coronary bypass grafts.
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Material and methods
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Study patients
A total of 27 patients were selected at random from a series of 653 off-pump coronary artery bypass graft patients who underwent operation by a single surgeon between August 1998 and December 2000. In all, 88 bypasses were studied, with an average of 3.2 ± 0.7125 grafts per patient and a mean follow-up of 20.3 months (range 14 to 36 months). All patients selected underwent contrast-enhanced electron beam computed tomographic angiography with three-dimensional reconstruction. Each patient provided informed consent and the institutional review board approved the study.
Technique
An electron beam computed tomographic scanner (ultrafast computed tomographic scanner; IMATRON C-150, San Francisco, CA) was used for all patient. Ioversol was used as contrast material injected into an antecubital vein (total amount 130 mL/patient).To determine optimal contrast flow rate, a peak flow study was performed before angiography. Computed tomographic angiography was performed with 3-mm, single-slide mode with 40% of the ECG gaiting. The injection flow rate was 4 mL/s, with a table increment overlap of 2 mm (2.5 mm was also used according to patient’s breath-holding capability). Injection began and the scanner was started at the proper delay of 12 to 18 seconds. The thickness of the slices was 3 mm and the direction of the scanning superior to inferior, for a total scanning time of 100 milliseconds. The display view was an axial imaging with three-dimensional postprocessing.
The reader was an experienced radiologist who had a diagram of the patient’s surgery describing the location and the number and type of grafts. Patency was assessed based on the graft that could be visualized and reconstructed in its entirety.
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Results
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All patients selected for the study underwent successful electron beam coronary angiography with a single mode and three-dimensional reconstruction, obtaining images as shown in Figure 1.
Four bypasses were considered to be closed (three vein grafts and one right internal thoracic artery). The proximal stump was clearly identified in all vein grafts (Fig 2),
whereas the right internal mammary artery was visualized only proximally. Table 1
shows patency rates by conduit, and Table 2
shows patency rates by location.
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Fig 1. Electron beam coronary angiography of a quadruple bypass 22 months postoperatively. LIMA= left internal mammary artery.
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Fig 2. Electron beam coronary angiography of a triple bypass 24 months postoperatively. PDA= posterior descending artery.
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Comment
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Coronary artery bypass graft remains the treatment of choice for certain forms of obstructive coronary artery disease. As the population ages with increased comorbities, the risk of cardiopulmonary bypass also appears to increase [10], making off-pump surgery more attractive for certain patient subgroups. However, the question of patency rates have been brought up by critics of the procedure, making the search for an appropriate noninvasive test to visualize bypasses of significant importance, if one is to study large groups of patients without subjecting them to discomfort and the risk of cardiac catheterization. Also, long-term bypass graft patency is a major factor determining the success of revascularization and the rate of survival [11]. It is critical that the status of bypass grafts be accurately assessed; therefore, a less invasive test would be of great help in the postoperative follow-up of coronary bypass patients.
Stress testing [12], radionuclide ventriculography [13], and thallium-201 myocardial perfusion scintigraphy [14] are more commonly used to determine indirectly the status of bypass grafts by noting changes in regional myocardial perfusion or regional wall abnormalities. However, direct visualization of the bypasses would be a more desirable technique. Magnetic resonance imaging has been shown to be a useful noninvasive method to determine bypass graft patency [15]; however, this technique is time consuming, and image resolution is poor at this time.
This study demonstrates the feasibility of using electron beam coronary angiography as a possible study tool to determine patency in patients after coronary bypass graft as the test is well tolerated by the majority of patients, including the elderly, and involves little exposure to radiation. It is also a useful technique for follow-up of either symptomatic or asymptomatic patients, as deterioration of bypass grafts can be detected (Fig 3).
In conclusion, coronary angiography is a promising noninvasive method to assess coronary artery bypass grafts, with some limitations, as it is difficult to evaluate accurately the anastomotic site. A larger series with longer follow-up periods appears to be warranted.
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References
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- Cleveland J.C., Jr, Shroyer A.L.W., Chen A.Y. Off pump coronary artery bypass grafting decreases risk-adjusted mortality and morbidity. Ann Thorac Surg 2001;72:1282-1289.[Abstract/Free Full Text]
- van Dijk D., Nierich A.P., Jansen E.W.L., et al. Early outcome after off-pump versus on-pump coronary bypass surgery. Results from a randomized study. Circulation 2001;104:1761-1766.[Abstract/Free Full Text]
- Jackson J.L., Meyer G.S., Pettit T. Complications from cardiac catheterization: analysis of a military database. Mil Med 2000;165:298-301.[Medline]
- Brundage B.H., Lipton M.J., et al. Detection of patent coronary bypass grafts by computed tomography: a preliminary report. Circulation 1980;61:826-831.[Abstract/Free Full Text]
- Bateman T.M., Gray R.S., Whiting J.S., et al. Prospective evaluation of ultrafast cardiac computed tomography for determination of coronary bypass graft patency. Circulation 1987;75:1018-1024.[Abstract/Free Full Text]
- Dai R, Zhang S, et al. Electron-beam CT angiography with three dimensional reconstruction in the evaluation of coronary artery bypass grafts. Acad Radiol 1998;5:863-7
- Chernoff D.M., Rinchie C.J., Higgins C.B. Electron-beam CT coronary angiography imaging characteristics in normal coronaries. Radiology 1996;201:274.
- Achenbach S., Moshage W., Ropers D., et al. Noninvasive three dimensional visualization of coronary artery bypass grafts by electron beam tomography. Am J Cardiol 1997;79:856-861.[Medline]
- Ha J.W., Cho S.Y., et al. Noninvasive evaluation of coronary artery bypass graft patency using three-dimensional angiography obtained with contrast enhanced electron beam CT. Am J Roentgenol 1999;172:1055-1059.[Abstract/Free Full Text]
- Tuman K.J., McCarthy R.J., Najafi H., et al. Differential effects of advanced age on neurologic and cardiac risks of coronary artery operations. J Thorac Cardiovasc Surg 1992;104:1510-1517.[Abstract]
- Loop F.D. Progress in surgical treatment of coronary arteriosclerosis. Chest 1983;84:611-624.[Free Full Text]
- Zellweger M.J., Lewin H.C., et al. When to stress patients after coronary artery bypass surgery?. J Am Coll Cardiol 2001;37:144-152.[Abstract/Free Full Text]
- Kent K.L., Borer J.S., et al. Effects of coronary artery bypass on global and regional left ventricular function during exercise. N Engl J Med 1978;298:1434-1439.[Abstract]
- Khoury A.F., Rivera J.M., et al. Adenosine thalium 201 tomography in evaluation of graft patency late after coronary artery bypass graft surgery. J Am Coll Cardiol 1997;29:1290-1295.[Abstract]
- Vrachliotis T.G., Bis K.G., et al. Contrast-enhanced breath-hold MR angiography for evaluating patency of coronary artery bypass grafts. Am J Roentgenol 1997;168:1073-1080.[Abstract/Free Full Text]
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Abstract
Introduction
