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Ann Thorac Surg 2000;69:56-60
© 2000 The Society of Thoracic Surgeons

Original Articles

Early and follow-up angiography in minimally invasive coronary bypass without mechanical stabilization

Inderjit S. Gill, FRCS(C)a, Lyall A. Higginson, FRCP(C)b, Gyaandeo S. Maharajh, MDa, Wilbert J. Keon, FRCS(C)a

a Department of Cardiothoracic Surgery, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
b Department of Cardiology, University of Ottawa Heart Institute, Ottawa, Ontario, Canada

Address reprint requests to Dr Gill, The Cleveland Clinic Foundation, 2500 MetroHealth Dr, Suite H907, Cleveland, OH 44109;
e-mail: gilli1{at}cesmtp.ccf.org


   Abstract
Top
 Abstract
Introduction
 Patients and methods
 Results
 Comment
 References
 
Background. This study was undertaken to assess the early and late outcome of coronary anastomosis constructed on a beating heart without the help of mechanical stabilization.

Methods. All consecutive patients (51) from January 1996 to September 1997 who had bypass done by one surgeon using a left minithoracotomy (39) or median sternotomy (12) on a beating heart with occlusive local snares without mechanical stabilization underwent follow-up angiography early (100%) (within 6 hours) and late (63.5%) at a mean of 9.6 ± 4.48 months (range, 3.3 to 19.1 months).

Results. The cumulative late patency was 95.4% (83 of 87 patients), with two early and two late occlusions. There was no early or late mortality or perioperative myocardial infarction. Two patients (3.9%) developed recurrent angina. Four anastomotic irregularities (4 of 32 patients, 12.6%) have cleared up on follow-up angiography. There was no evidence of late stenosis at the snare sites used for local occlusion.

Conclusions. Minimally invasive coronary bypass is safe and effective. Early angiographic abnormalities should be interpreted with caution and we could not demonstrate any long-term deleterious effects of local snaring.


   Introduction
Top
 Abstract
 Introduction
Patients and methods
 Results
 Comment
 References
 
Since its revival by Benetti [1] and Buffolo [2] and their colleagues, beating heart coronary bypass has seen a major resurgence. It is intuitive that there are substantial advantages if coronary artery bypass can be carried out with equivalent results to conventional methods with a beating heart. However, concerns about the technical accuracy of the anastomosis constructed on a beating heart [3, 4], especially through a "keyhole" and the long-term effects of local "snares" used for temporary occlusion [5], have deterred many surgeons from pursuing it.

The present study was undertaken to define these issues in a consecutive series of selected patients who underwent minimally invasive direct coronary artery bypass grafting (MIDCABG) at the University of Ottawa Heart Institute.


   Patients and methods
Top
 Abstract
 Introduction
 Patients and methods
Results
 Comment
 References
 
All consecutive patients (51) from January 1996 when the MIDCABG program was started, to September 1997, who had undergone bypass done by one surgeon using a left minithoracotomy (39 patients) or median sternotomy (12 patients) on a beating heart constituted our study population. All patients underwent early postoperative angiography. Preoperative characteristics are given in Table 1.


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  		Table 1. Preoperative Profile

 
The operative technique has been described previously [6]. For patients undergoing a minithoracotomy, an 8-cm to 10-cm incision medial to the nipple was made, and the fourth costal cartilage was excised. The rib cage was lifted with a small scapular retractor and the internal thoracic artery (ITA) was harvested up to the second or first intercostal space and divided distally under the fifth rib after partial heparinization (1.5 mg/kg). Adenosine and esmolol usage was abandoned as experience with the procedure grew. We found the response to adenosine and esmolol to be unpredictable and the cost of multiple boluses of adenosine is prohibitive. Ischemic preconditioning and reperfusion was done for 10 minutes if the left anterior descending coronary artery (LAD) was not completely occluded. A 4-0 Prolene pledgetted double-armed suture (Ethicon, Somerville, NJ) was used for "snaring" the LAD, proximal and distal to the anastomotic site. The snares were tightened to achieve a completely bloodless field. The anastomosis was constructed with a single or double 7-0 or 8-0 Prolene (Ethicon) suture. Stabilization was achieved with digital compression or a "peanut" on a Kelly clamp or a small Satinsky partial occluding clamp (Allegiance V. Mueller, McGaw Park, IL). No formal retractor-based stabilization platform was used.

The patients were taken to the intensive care unit, and within 4 to 6 hours underwent postoperative angiography. After discharge, they were seen at our outpatient clinic in 2 weeks and by their respective cardiologists at 3 months. The follow-up is 100% complete. All patients were scheduled for a postoperative angiogram 9 to 12 months after operation.

Statistical analysis
Results are expressed as mean ± standard deviation unless otherwise indicated. Statistical analysis of categoric data were performed using Fisher’s exact test or {chi}2 test and analysis of continuous data were performed using the Student’s t test. A p value of less than 0.05 was considered significant.


   Results
Top
 Abstract
 Introduction
 Patients and methods
 Results
Comment
 References
 
The results are summarized in Table 2. Conduits used were left (ITA) 50, right (ITA) 3, saphenous vein graft (2). The last 9 patients were analyzed separately to determine whether there were any differences in outcomes as experience with MIDCABG was gained. There was a slight reduction in operating room times, and most patients were extubated early in the latter period, but there were no statistical differences between the two groups. The ITA dissection took an average of 40 to 50 minutes. Ischemic preconditioning and reperfusion was done in all patients for 10 minutes and it took an average of 10 to 20 minutes to perform the anastomosis, and at the end flow measurements with the transonic flow probe took 10 minutes. There was also no difference in the outcomes between the sternotomy and thoracotomy groups. The indications for operation were stable angina in 32 patients (62.7%), unstable angina in 17 (33.3%), congestive heart failure in 1 (1.9%), and acute myocardial infarction in 1 patient (1.9%).


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  		Table 2. Results

 
Postoperative complications are listed in Table 3. There was 100% (51 patients) hospital survival with no perioperative myocardial infarctions based new on Q-wave or loss of R-wave on postoperative electrocardiogram or elevation of creatinine kinase-MB fraction.


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  		Table 3. Complications

 
Deep wound infections occurred in 3 patients (5.8%). Two insulin-dependent female diabetic patients developed deep wound infections at the minithoracotomy site. One deep wound infection occurred in an insulin-dependent obese male patient who had a sternotomy.

Two patients (3.9%) developed recurrent angina at a mean of 18 months. Follow-up angiography has revealed progression of disease in the right coronary artery in 1 patient, and the circumflex in the other. Both ITA–LAD anastomoses were intact. One patient had his ITA anastomosed to a diagonal branch. This patient remains asymptomatic.

The incidence of atrial fibrillation, defined as atrial arrhythmias lasting more than 30 minutes on postoperative telemetry, which was conducted on all patients for a mean of 2.7 ± 1.97 days, was 15.7% (8 of 51 patients).

The overall patency of 55 anastomotic sites assessed early was 96.3% (53 of 55 sites). There was one anastomotic occlusion, and one ITA damage in the early part of our experience. The follow-up is 100% complete and there is no late mortality. Two patients developed recurrent angina, as discussed.

Follow-up angiography (Fig 1) has been carried out in 32 of 51 patients (62.7%) to date at a mean of 9.60 ± 4.48 months (range, 3.3 to 19.13 months). Two patients in our early experience underwent reoperation purely for early angiographic stenosis that showed a tight pinch just above the level of the anastomosis. In both instances no anatomic cause could be ascertained. Since then symptomatic patients with anastomotic irregularities on early angiograms have been followed with no reintervention. Four such anastomotic irregularities have cleared (4 of 32 patients, 12.57%; Fig 2).



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  		Fig 1. Follow-up angiogram of first minimally invasive coronary artery bypass grafting patient, 11 months postoperatively.

 


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  		Fig 2. Early angiogram showing patent right internal thoracic artery–marginal anastomosis, which was occluded on follow-up angiography.

 
Two patients (of 32 patients, 6.25%) revealed anastomotic occlusions on planned follow-up angiography. In both instances it is thought to be related to competitive flow. In 1 patient, done through a sternotomy the proximal stenosis ({approx}60%) in the marginal branch was perhaps not critical. This patient had an excellent early angiographic result of his right ITA marginal anastomosis (Fig 3). The other patient had a very small caliber ITA that was used for a very large LAD (> 2.5 mm) and there was gross size mismatch. In 1 patient a new 90% anastomotic stenosis was treated successfully with angioplasty. This patient also had a good early angiographic result. Two patients have persistent 80% stenosis, which has remained unchanged with negative treadmill tests. All 5 patients were asymptomatic at the time of their follow-up angiography.



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  		Fig 3. (A) Early angiogram showing stenosis at typical site just above the hood of the anastomosis. (B) Clearing up of anastomotic irregularity on follow-up angiography.

 
There has been no instance of late stenosis at the snare sites used for local occlusion. The late cumulative patency of 87 anastomotic sites assessed by early and late angiography is 95.4% (83 of 87 sites).


   Comment
Top
 Abstract
 Introduction
 Patients and methods
 Results
 Comment
References
 
The present report was designed to examine two specific issues in minimally invasive operation, that is, anastomotic patency of the ITA–LAD graft constructed through small incisions and the long-term effect of occlusive local snares and the effect of handling of the anastomotic site during the construction of an anastomosis on a beating heart.

A patent ITA–LAD anastomosis is the single most important predictor of long-term survival [7] in patients with coronary artery disease and little compromise on procedures affecting its results will be tolerated. The gold standard cited is the angiographic patency of the ITA–LAD anastomosis constructed on a cardiopleged motionless heart.

The angiographic patency of conventional coronary artery bypass grafting in 27 published series to date was recently analyzed by Mack and colleagues [8]. Although the early and late angiographic patency of most studies exceeded 90%, only a small cohort in each underwent follow-up angiography. Only one study by FitzGibbon and associates [9] reports a comprehensive analysis of 476 consecutive patients receiving left ITA grafts, with 96% of the grafts being studied at less than 6 months, 67% at 1 year, and 26% at 5 years. Graft patency was 95%, 91%, and 80%, respectively.

It must also be borne in mind that a majority of these studies were undertaken before the angioplasty era; therefore, these studies included a disproportionately large number of large caliber vessels, which is well known to influence graft patency favorably [10].

Only two recent studies report early angiographic results after conventional bypass. We reported a 96% patency in 25 consecutive patients [6] and Berger and colleagues [11] reported 645 patients (denominator unknown) who underwent ITA–LAD angiography as a part of a multicenter aprotonin trial (IMAGE) at a mean of 10.8 days. Although graft patency was 98.8%, an additional 7.8% of patients had an anastomotic stenosis of 50% or greater.

The current era of minimally invasive operation has led to an understandably tighter scrutiny of results with a much higher percentage of patients being studied [8]. Our study incorporates 100% early angiographic follow-up and a 63% late follow-up in the same cohort of patients and demonstrated a 95% late patency at 9.6 ± 4.5 months. Some patients have refused follow-up angiography, and some have had logistic delays.

We, as with other investigators [12, 13], question the validity of luminal irregularities seen on very early angiograms. In our early experience 2 patients underwent reoperation for purely angiographic stenosis. Yet no anatomical cause could be ascertained. Since then a policy of wait-and-see was adopted if the patients were clinically well and there have been definite improvements in follow-up angiograms in 12.5% of patients. In all instances the stenosis appeared just above the level of the anastomosis and was not flow restrictive; it could be attributed to spasm caused by intraoperative handling, vessel wall edema, or medial hematoma, which resolved with time.

Damage caused by local occlusion has been claimed to have led to anastomotic occlusion and late deaths [14, 15]. Experimental evidence seems to indicate that occlusive snaring does not lead to endothelial damage or to neointimal hyperplasia [16]. Innovative methods to avoid snaring of the target vessels are evolving [17]. However, no evidence of angiographic damage at the site of local occlusion or neointimal hyperplasia at the anastomotic site due to damage caused by movement during construction of the anastomosis on a beating heart could be found in our study.

The results of beating heart procedures have further improved with the use of various retractor-based stabilization devices. Calafiore and colleagues [18] report results of 177 patients. Early angiography in patients who were studied before the utilization of stabilization devices revealed 7 of 61 occlusions (11.5%), versus 2 of 117 (1.7%) who were operated with the help of stabilization (p = 0.02). Subramanian and associates [19] report on improvement in the patency rate from 89% to 97% (p = 0.05) after the introduction of formal stabilizing devices.

We did not have access to stabilization platforms during the period the study was constructed. Since then we have used either the Cardiothoracic Systems (Cupertino, CA) or Medtronic Octopus (Minneapolis, MN) for stabilization.

In conclusion, the MIDCABG procedure is safe and effective. Early angiographic abnormalities should be interpreted with caution and we could not demonstrate any long-term deleterious effects of local snaring of the target vessel.


   References
Top
 Abstract
 Introduction
 Patients and methods
 Results
 Comment
 References
 

  1. Benetti F.J., Naselli G., Wood M., Geffner L. Direct myocardial revascularization without extracorporeal circulation. Experience in 700 patients. Chest 1991;100:312-316.[Abstract/Free Full Text]
  2. Buffolo E., Endrorde J.C.S., Succi A.J., Leao L.E.V., Gallucci C. Direct myocardial revascularization without cardiopulmonary bypass. J Thorac Cardiovasc Surg 1985;33:26-29.
  3. Ullyot D.J. Look Ma, no hands!. Ann Thorac Surgery 1996;61:10-11.[Free Full Text]
  4. Lytle B.W. Minimally invasive cardiac surgery. J Thorac Cardiovasc Surg 1996;111:554-555.
  5. Gundry S.R. Discussion of Pfister A, Zaki S, Garcia JM, et al. Coronary artery bypass without cardiopulmonary bypass. Ann Thorac Surg 1992;54:1085-1093.[Abstract]
  6. Gill I.S., FitzGibbon G.M., Higginson L.A.J., et al. Minimally invasive coronary artery bypass. Ann Thorac Surg 1997;64:710-714.[Abstract/Free Full Text]
  7. Cameron A., Davis K.B., Green G., et al. Coronary bypass surgery with internal thoracic artery grafts—effects on survival over a 15 year period. N Engl J Med 1996;334:216-219.[Abstract/Free Full Text]
  8. Mack M.J., Osborne J.A., Shennib H. Arterial graft patency in coronary artery bypass grafting. Ann Thorac Surg 1998;66:1055-1059.[Abstract/Free Full Text]
  9. FitzGibbon G.M., Kafka H.P., Leach A.J., et al. Coronary bypass graft fate and patient outcome. J Am Coll Cardiol 1996;28:616-626.[Abstract]
  10. Grondin C.M., Castonguay Y.R., Lesperance J., et al. Attrition rate of aorto-to-coronary saphenous veins after 1 year. A study in a consecutive series of 96 patients. Ann Thorac Surg 1972;14:223-231.[Medline]
  11. Berger P.B., Alderman E.L., Schaff H.V. Frequency of early occlusion and stenosis in the left interal mammary artery among patients undergoing CABG through median sternotomy on conventional bypass. Circulation 1997;96(Suppl 1):68.
  12. Calafiore AM. Proceedings of advances in cardiovascular surgical therapeutics symposium X. Washington, DC, October 6–7, 1998.
  13. Mack MJ. Proceedings of advances in cardiovascular surgical therapeutics symposium X. Washington, DC, October 6–7, 1998.
  14. Gundry SR, Razzouk AJ, Bailey LL. Coronary artery bypass with and without the heart lung machine: a case matched 6 year follow-up [Abstract]. Circulation 1996;94(Suppl 1)8:I-52.
  15. Alessandrini F., Gaudino M., Gleieca F., et al. Lesions of the target vessel during minimally invasive myocardial revascularization. Ann Thorac Surg 1997;64:1349-1353.[Abstract/Free Full Text]
  16. Perrault L.P., Menasché P., Bidouard J.P., et al. Snaring of the target vessel in less invasive operations does not cause endothelial dysfunction. Ann Thorac Surg 1997;63:751-755.[Abstract/Free Full Text]
  17. Heijman R.H., Borst C., Van Dalen R., et al. Temporary luminal arteriotomy seal for bypass grafting. Ann Thorac Surg 1998;65:1093-1099.[Abstract/Free Full Text]
  18. Calafiore A.M., Vitolla G., Mazzei V., et al. The LAST operation. Ann Thorac Surg 1998;66:998-1001.[Abstract/Free Full Text]
  19. Subramanian V.A., McCabe J.C., Geller C.M., et al. Minimally invasive direct coronary artery bypass grafting. Ann Thorac Surg 1997;64:1648-1655.[Abstract/Free Full Text]
Accepted for publication June 1, 1999.




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