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Ann Thorac Surg 1998;66:51-55
© 1998 The Society of Thoracic Surgeons

Original articles: cardiovascular

Intraoperative MIDCABG arteriography via the left radial artery: a comparison with doppler ultrasound for assessment of graft patency

Joseph R. Elbeery, MDa, Philip M. Brown, MDa, W. Randolph Chitwood, Jr, MDa

a Division of Cardiothoracic Surgery, East Carolina University School of Medicine, Greenville, North Carolina, USA

Address reprint requests to Dr Elbeery, Division of Cardiothoracic Surgery, East Carolina University School of Medicine, 600 Moye Blvd, Greenville, NC 27858-4354
e-mail: (elbeery{at}brody.med.ecu.edu)

Presented at the Forty-fourth Annual Meeting of the Southern Thoracic Surgical Association, Naples, FL, Nov 6–8, 1997.


   Abstract
Top
 Abstract
Introduction
 Material and methods
 Results
 Comment
 References
 
Background. Minimally invasive direct coronary artery bypass grafting involving beating heart left internal mammary artery to left anterior descending coronary artery anastomoses are performed with increasing frequency. Controversy exists regarding the need for intraoperative assessment of graft patency.

Methods. We designed a technique to perform arteriography of the left internal mammary artery by using left radial artery access and standard fluoroscopy to evaluate patency in the operating room. The last 50 of 87 minimally invasive direct coronary artery bypass grafting operations were evaluated by intraoperative arteriography and Doppler ultrasound. Angiograms were performed by the surgeon and involved cannulation and direct injection of contrast medium into the origin of the left internal mammary artery via the left radial artery.

Results. Total procedure time was less than 15 minutes. No injuries to the left internal mammary artery were identified. Anastomotic occlusions were identified in 4 cases (8%), 2 of which involved sequential diagonal and left anterior descending anastomoses. These were corrected at the time of surgery with 2 cases requiring conversion to standard coronary artery bypass grafting. Qualitative assessment of grafts with Doppler ultrasound failed to definitively identify these occlusions. There were no deaths and no perioperative infarctions.

Conclusion. Intraoperative arteriography of the left internal mammary artery can be performed by the surgeon, and a significant number of anastomotic problems may be identified and corrected by using this technique. Therefore, a 100% early graft patency rate may be attainable.


   Introduction
Top
 Abstract
 Introduction
Material and methods
 Results
 Comment
 References
 
Minimally invasive coronary bypass procedure was first reported by Robinson and associates in 1995 [1]. Since then a number of centers have performed many minimally invasive direct coronary artery bypass grafting (MIDCABG) procedures which generally involve the anastomosis of the left internal mammary artery (LIMA) to the left anterior descending artery (LAD) without cardiopulmonary bypass using local occlusion on the beating heart [2]. The reported short-term results are favorable, and preliminary studies suggest that it is superior to percutaneous techniques [3]. At the same time, however, anecdotal reports of perioperative infarctions and poor outcomes are common [4]. The MIDCABG procedure is technically more difficult to perform because the heart is beating and not asanguinous. The use of mechanical stabilization has decreased the level of difficulty to an acceptable one and allowed for largely reproducible results [5–7]. Because MIDCABG operations are more challenging and because the result of the procedure generally is dependent on a single anastomosis, the importance of early assessment of graft patency is obvious. Intraoperative assessment can be made by noninvasive means using various Doppler ultrasound systems [8], but coronary angiography remains the gold standard. Some centers advocate formal cardiac catheterization and coronary angiography by a cardiologist before hospital discharge [6] or immediately after the operation [9]. Problems with scheduling, lack of reimbursement, and the addition of another invasive procedure to the patient’s hospitalization can make these approaches less than ideal. Intraoperative catheterization via the radial artery obviates most of these concerns and provides angiographic evidence of adequacy of graft flow, graft lie, and anastomotic patency. Intraoperative assessment enables immediate correction of problems and therefore minimizes the risk of an ischemic event in the early postoperative recovery period.

The purpose of this investigation is to demonstrate the utility of the intraoperative radial artery catheterization technique by reporting the results of 50 patients who underwent intraoperative catheterization.


   Material and methods
Top
 Abstract
 Introduction
 Material and methods
Results
 Comment
 References
 
Since April 1997, the last 50 of 87 patients who underwent MIDCABG have undergone intraoperative LIMA arteriography. All operations were done by the same surgeon and involved direct harvest of the LIMA through a small (approximately 8-cm) left anterior thoracotomy in the fourth intercostal space. Mammary artery exposure was obtained using commercially available retractors designed for this purpose (United States Surgical Corp, Norwalk, CT, and Cardiothoracic Systems, Inc, Cupertino, CA). All grafts were harvested to the level of the subclavian vein with intact pedicles. Anastomoses were performed directly to the LAD in 45 patients and sequentially to a diagonal and LAD in 5. Operations were done on the beating heart with mechanical stabilization (Cardiothoracic Systems, Inc). A bloodless field was maintained using only a proximal tourniquet and a carbon dioxide humidified blower. The tourniquet consisted of a 3-0 polypropylene suture passed beneath the LAD to encompass a large amount of myocardium as well as the vessel. A Teflon felt pledget and keeper on the epicardium maintained tension on the suture. On completion of the anastomosis or anastomoses and final positioning of the pedicle, flow was checked qualitatively with an Ultrasonic Doppler Flow Detector (model 812; Parks Medical Electronics, Inc) with the proximal tourniquet still in place. Flow was graded as: 0 = no flow; 1+ = poor or questionable signal; and 2+ = satisfactory flow with diastolic augmentation. The proximal tourniquet was then removed and arteriography was performed using the left radial arterial catheter. The catheter was placed sterilely at the beginning of the operation and prepared into the surgical field with the arm extended. Technical details of this technique have been described elsewhere [10]. Briefly, a 4F introducer is exchanged for the arterial catheter with the Soldinger technique. A 4F internal mammary artery catheter (Cordis Europa, the Netherlands) is then inserted over a 0.021-inch guidewire by using fluoroscopic guidance. The catheter is advanced into the aorta and then slowly withdrawn into the subclavian artery with the tip positioned caudally. Small injections of 1 or 2 mL of contrast medium allow visualization and cannulation of the LIMA origin (Fig 1). Once the patient was cannulated, arteriograms were made using a C-arm fluoroscopy unit (model 9400; OEC Medical Systems, Inc) during a forceful injection of 8 mL of contrast material. Images were obtained with anterior-posterior and left anterior oblique views. Hard copies were made from digital images and judged as excellent, satisfactory, or poor by an independent observer.



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  		Fig 1. Intraoperative image demonstrating cannulation of the left internal mammary artery origin and contrast injection opacifying the proximal vessel.

 

   Results
Top
 Abstract
 Introduction
 Material and methods
 Results
Comment
 References
 
Arteriography was performed in 50 patients. Demographic data are presented in Table 1. Average age was 59 ± 11.8 years and 70% of the patients were male. Mean ejection fraction was 55% ± 7.7% (range, 30% to 70%). Operative time including angiography was 2.51 ± 0.88 hours. All patients were extubated in the operating suite or recovery room immediately after the procedure and none required intensive care unit care postoperatively. There were no deaths and no perioperative myocardial infarctions. Two patients (4%) required conversion to sternotomy and cardiopulmonary bypass with both of these secondary to angiographic findings.


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  		Table 1. Demographic Data

 
Angiography was attempted in 51 patients. The radial artery was successfully cannulated in all cases. The LIMA origin was cannulated in 50 (98%) of 51 patients. In 1 case the LIMA could not be cannulated within the predesignated 15-minute time limit. There were no major complications related to the procedure. Minor complications included small hematomas at the insertion site, 2 of which required no treatment, and prolonged bleeding from the site, 1 of which required only direct application of pressure. In no case was there any evidence of catheter injury to the LIMA. All patients had follow-up examinations between 2 and 4 weeks after the operation, and all had palpable radial pulses. No patient had complaints related to the catheterization. There were no perioperative or early postoperative myocardial events or interventions. Results of operation are summarized in Table 2.


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  		Table 2. Operation Results

 
Angiographic quality of the roentgenogram was judged to be excellent in 8 cases, satisfactory in 39, and poor in 3. Minor irregularities in the LAD and LIMA were present in 10 cases. All 10 had Thrombolysis in Myocardial Infarction (TIMI) 3 flow and the findings were attributed to spasm (Fig 2). Spasm, when present, was noted in the LAD distal to the anastomosis (8 cases) and in the distal LIMA (2 cases). All 10 patients had normal results on external examination. Significant findings which required intervention were limited to total anastomotic occlusion (TIMI 0 flow). The proximal mammary artery was found to be patent without evidence of injury in all cases. Anastomotic problems were identified in 5 patients (10%), 2 of whom had sequential diagonal and LAD operations. One patient required pedicle repositioning, and 1 required conversion to standard coronary artery bypass grafting because the angle between the anastomoses was too acute. Two other patients with calcified distal target vessels had anastomotic occlusions. One required conversion to sternotomy and cardiopulmonary bypass for successful completion of the anastomosis whereas the other anastomosis was redone with MIDCABG technique. A fourth patient with what appeared to be subtotal occlusion (TIMI 1 flow) but a technically satisfactory anastomosis was found to have a widely patent (TIMI 2) anastomosis when arteriography was repeated with a proximal tourniquet in place. This patient had only a moderate LAD stenosis (~60%) preoperatively. Therefore, of the 50 patients who underwent arteriography, significant anastomotic problems were identified and corrected in 4 (8%). None of these patients exhibited intraoperative hemodynamic or electrocardiographic changes suggestive of a graft problem.



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  		Fig 2. Intraoperative image demonstrating spasm of the left anterior descending coronary artery (A) and resolution of spasm on next injection (B).

 
Doppler ultrasound was performed in all cases as a noninvasive assessment of graft flow. Results are shown in Table 3. To avoid mistaking retrograde for antegrade flow, assessment was made with the proximal tourniquet still in place. Of the 50 patients undergoing arteriography, Doppler flow was 2+ in 44 patients, 1+ in 6 patients, and 0 in none. In the 4 patients with anastomotic occlusion, ultrasound was 1+ in 3 patients and 2+ in 1. In the patient with competitive flow, Doppler flow was 2+. Doppler assessment suggested anastomotic problems in three other grafts found to be widely patent by arteriogram. Therefore the sensitivity of Doppler ultrasound in detecting actual problems was 75% and the specificity was 93.5%. In no case was the Doppler signal consistently 0, even with graft occlusion.


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  		Table 3. Results of Intraoperative Assessment

 

   Comment
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
References
 
The MIDCABG operation continues to be performed with increasing frequency. Although short-term patency rates have been reported to be similar to those for coronary artery bypass grafting via median sternotomy on cardiopulmonary bypass, the beating heart procedure is technically challenging and is associated with a significant learning curve. Most centers performing many of these procedures advocate postoperative catheterization before hospital discharge [6, 9]. The major advantage of formal cardiac catheterization by a cardiologist is the high quality angiographic images and multiple views that are obtained. The disadvantages include lack of reimbursement for a relatively costly procedure that may not be clinically indicated and the potential to miss a silent myocardial event that could occur between operation and catheterization. Another important consideration is the patient dissatisfaction that might occur if a problem is detected during catheterization and a second operation is necessary.

The intraoperative radial artery technique offers several advantages, which include satisfactory image quality and the opportunity for the surgeon to independently perform the procedure. Problems that are identified can then be corrected immediately while still in the operating room. This technique should allow early graft patency to approach 100%. The intraoperative technique is also less expensive than formal coronary angiography with the total cost of equipment being less than $100.00. The disadvantages of the intraoperative examination include the potential for vascular injury to the radial artery, LIMA, or vascular structures in between. Although these disadvantages are a concern, no serious complications were encountered in the study population. The atraumatic design of the internal mammary artery catheter and the forgiving nature of the radial artery make serious injury unlikely. A second limitation of the technique is the inability to obtain cardiac catheterization laboratory quality images. This concern may be alleviated by the future availability of the mobile catheterization laboratory (model 9600; OEC Medical Systems Inc, Salt Lake City, UT), which is reported to produce images comparable with those obtained through formal cardiology studies. Intraoperative images often exhibit changes consistent with spasm, edema, or both, of the LAD and LIMA (Fig 2). Therefore extremely high resolution may make many grafts appear suspicious which will ultimately be widely patent. For simple intraoperative assessment, most C-arm units designed for cholangiography and peripheral vascular angiography should give adequate information on flow and patency.

In the present study, 4 patients underwent anastomotic revision based on angiographic findings. All 4 of these patients received technically satisfactory anastomoses, and noninvasive assessments yielded equivocal Doppler signals. Had angiography not been performed, it is likely that these patients would have suffered a postoperative myocardial event or required a subsequent catheter-based procedure or repeat operation. Because no patient of the 50 studied required an early intervention or suffered a myocardial event, one might assume that intraoperative patency translates to short-term and potentially long-term graft patency. Future studies examining long-term patency will be necessary to validate this assumption, however.

More sophisticated duplex ultrasound technology may improve the sensitivity and specificity over the simple technique described here, but all noninvasive testing is subject to technical problems with equipment, user error, and subjective interpretation. Therefore, angiography remains the gold standard.

On the basis of these results, we suggest that intraoperative arteriographic assessment of MIDCABG grafts be performed in the following circumstances: (1) in any patient with equivocal Doppler flow signals, (2) in any patient with severely diseased native coronary vessels, (3) in all sequential or complex anastomotic cases, and (4) in any case in which the surgeon is not entirely satisfied with the anastomosis. The technique may also be helpful to a surgeon early in the MIDCABG learning curve. We recommend forgoing angiography if an experienced MIDCABG surgeon is completely satisfied with the anastomosis, if there is no severe diffuse LAD disease, and if the Doppler signal is excellent.

In conclusion, intraoperative catheterization can be performed quickly and with technical ease by the surgeon. The technique can be applied to open coronary artery bypass grafting procedures when LIMA flow might be questionable as well as to MIDCABG procedures. It can be applied in virtually any operating room and should allow for early graft patency rates approaching 100%. This technique can add a level of safety and confidence to the new and exciting but technically challenging MIDCABG operation.


   References
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 References
 

  1. Robinson M.C., Gross D.R., Zeman W., Stedge-Larsen E. Minimally invasive coronary artery bypass grafting: a new method using an anterior mediastinotomy. J Cardiovasc Surg 1995;10:529-536.
  2. Subramanian V.A., Sani G., Benetti F.J., Calafiore A.M. Minimally invasive coronary bypass surgery. Multicenter report of preliminary clinical experience [Abstract]. Circulation 1995;92(Suppl 1):645.
  3. Mariani M.A., Boonstra P.W., Grandjean J.G., et al. Minimally invasive coronary artery bypass grafting versus coronary angioplasty for isolated type C stenosis of the left anterior descending artery. J Thorac Cardiovasc Surg 1997;114:434-439.[Abstract/Free Full Text]
  4. Reardon M.J., Espada R., Letsou G.V., Safl H.J., McCollum C.H., Baldwin J.C. minimally invasive coronary artery surgery—a word of caution [Editorial]. J Thorac Cardiovasc Surg 1997;114:419-420.[Free Full Text]
  5. Calafiore A.M., Teodori G., Di Giammarco G., et al. Minimally invasive coronary artery bypass grafting on a beating heart. Ann Thorac Surg 1997;63:S72-S75.
  6. Subramanian V.A. Less invasive arterial CABG on a beating heart. Ann Thorac Surg 1997;63:S68-S71.
  7. Cremer J., Struber M., Wittwer T., et al. Off-bypass coronary bypass grafting via minithoracotomy using mechanical epicardial stabilization. Ann Thorac Surg 1997;63:S79-S83.
  8. Canver C.C., Dame N.A. Ultrasonic assessment of internal thoracic artery graft flow in the revascularized heart. Ann Thorac Surg 1994;58:135-138.[Abstract]
  9. Schaff H.V., Casle D.G., Rihal C.S., et al. Minimal thoracotomy for coronary artery bypass: value of immediate post procedure graft angiography. Circulation 1996;94(Suppl):151.[Abstract/Free Full Text]
  10. Elbeery J., Chitwood W.R. Intraoperative catheterization of the left internal mammary artery via the left radial artery. Ann Thorac Surg 1997;64:1840-1842.[Abstract/Free Full Text]



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