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Ann Thorac Surg 1995;59:323-326
© 1995 The Society of Thoracic Surgeons

Postoperative Symptomatic Internal Thoracic Artery Stenosis and Successful Treatment With PTCA

Hani K. Najm, MD, Danielle Leddy, MD, Paul J. Hendry, MD, Jean-Francois Marquis, MD, David Richardson, BSc, Wilbert J. Keon, MD

Divisions of Cardiac Surgery and Cardiology, University of Ottawa Heart Institute, Ottawa Civic Hospital, Ottawa, Canada

Accepted for publication August 2, 1994.


   Abstract
Top
 Footnotes
 Abstract
Introduction
 Material and Methods
 Results
 Comment
 References
 
From 1988 to 1992, 4,182 coronary bypass grafting procedures were performed at the University of Ottawa Heart Institute. The left internal thoracic artery (ITA) was used in 2,913 patients, the right ITA in 79, and bilateral ITAs in 61 for a total of 3,053 patients with ITAs. This study assessed patients requiring angioplasty for symptomatic ITA stenosis after operation. A total of 29 patients (0.95%) with a mean age of 55.3 ± 1.9 years underwent angioplasty for ITA stenosis from 4 days to 34 months after operation (mean, 6.5 ± 1.6 months). Internal thoracic artery stenosis was identified in 18 patients (62.1%) within 3 months after operation. Angina was present in 26 patients (89.7%), a positive stress test in 8 (27.6%), and myocardial infarction in 1 (3.4%). At angiography, a total of 34 stenotic sites were identified in ITA grafts. Angioplasty was successful (<50% residual stenosis) in 31 sites (91.2%). Follow-up was available for 28 of 29 patients (96.6%) at 24.6 ± 2.3 months. Four patients (14.3%) returned with restenosis within 3 months, 2 of whom had successful repeat angioplasty, and 1 required reoperation. Canadian Cardiovascular Society anginal class after angioplasty was less than class II in 84.6% of patients. In conclusion, symptomatic postoperative ITA stenosis is uncommon, occurs most frequently at the site of distal anastomosis, and generally presents within 3 months of operation. It may be safely and effectively treated with angioplasty with a low recurrence rate.


   Introduction
Top
 Footnotes
 Abstract
 Introduction
Material and Methods
 Results
 Comment
 References
 
See also page 327.

Since the introduction of the internal thoracic artery (ITA) as a standard conduit for coronary artery bypass grafting in the early 1970s, many reports [1–8] have proved its efficacy and superiority to other conduit grafts. The advantages include a higher patency rate when compared with vein grafts, more favorable flow characteristics [9, 10], and a relative immunity of the ITA to significant atherosclerosis [11, 12]. Patients with ITA grafts have a greater likelihood of remaining asymptomatic for years after the initial operation [2, 8]. For these reasons, the ITA has become the ``graft of choice'' in most institutions. With all the advantages of using the ITA as a conduit, still there is the occasional patient who presents with cardiac ischemia secondary to ITA stenosis or occlusion after a bypass operation. Options for treatment are limited to optimizing medical therapy, redo operation, or percutaneous angioplasty. The purpose of the study was to retrospectively review our experience with internal thoracic artery grafts and identify risk factors for postoperative stenosis and the efficacy of treatment using percutaneous angioplasty.


   Material and Methods
Top
 Footnotes
 Abstract
 Introduction
 Material and Methods
Results
 Comment
 References
 
During a 60-month period between January 1988 and December 1992, 7 surgeons performed 4,182 coronary artery bypass grafting operations. The left ITA was used in 2,913 (69.7%) cases, the right ITA in 79 (1.9%) and bilateral ITAs in 61 (1.5%) patients for a total of 3,053 patients with ITA grafts.

Operative Details
Standard premedication, anesthesia, and median sternotomy were performed on all patients. The ITA was dissected free from its bed using electrocautery, with branches ligated using hemostatic clips. The distal end of the ITA was prepared and spatulated before grafting. The aorta was cross-clamped and cardiac arrest was attained using 1 L of cold crystalloid cardioplegia at 4°C. Grafts were constructed using reversed saphenous veins and ITAs. The distal anastomosis was constructed using an end-to-side technique with either single or double 7-0 Prolene (Ethicon, Somerville, NJ) stitches, depending on the surgeon's preference. After completion of anastomosis, the clamp was removed and the patient was rewarmed. Proximal vein graft anastomoses were made with 5-0 or 6-0 Prolene, and the pericardium was left open. Routine closure of the sternum and leg wound followed.

Coronary Angioplasty
A total of 29 patients (0.95% of total ITA group at risk) presented with myocardial ischemia postoperatively, which was found to be related to ITA stenosis. Patients were premedicated with aspirin (325 mg daily) for at least 48 hours before the procedure. After sedation, intravenous nitroglycerin administration was started at the onset of the procedure. An 8F sheath was placed in the femoral artery percutaneously and 10,000 units of intravenous heparin was given. Coronary angiography and angioplasty were performed using a standard Judkins approach. After the angioplasty, heparin therapy was maintained for 6 to 36 hours depending on the operator while aspirin administration was continued (325 mg/day) indefinitely.

Angiographic Definitions
All cineangiograms were reviewed by two experienced observers, and digital caliper evaluation of the stenosis was performed. Significant stenosis was defined as a 70% or greater reduction in luminal diameter. Angiographic success referred to reduction of luminal stenosis to less than 50%. Clinical success indicated an angiographic success not complicated by death, myocardial infarction, or the need for repeat bypass graft operation as well as improvement in symptoms of angina. Restenosis referred to a luminal narrowing of 50% or greater at the dilation site.

Follow-up
Patients were interviewed at 3- to 6-month intervals. Information was obtained from medical records and telephone conversation with patients or referring physicians. Exercise treadmill tests and repeat cardiac catheterization were performed in some patients when clinically indicated. Patients were questioned with regard to their symptoms, previous hospitalization, and need for bypass operation.


   Results
Top
 Footnotes
 Abstract
 Introduction
 Material and Methods
 Results
Comment
 References
 
Clinical Characteristics
A total of 29 patients (22 men [75.9%] and 7 women [24.1%]), returned to the Heart Institute with signs of myocardial ischemia and were found by angiography to have ITA stenosis. The average age was 55.3 ± 1.9 years (range, 31 to 69 years). Coronary risk factors included smoking in 12, diabetes in 7, hypertension in 15, positive family history in 11, and hypercholesterolemia in 4. There were 4 patients with single, 6 with double, and 19 with triple-vessel disease undergoing operation.

Operative Details
The left ITA was used for the left anterior descending artery in 24, a marginal artery in 2, and a diagonal in 1 patient. The right ITA was used for the right coronary artery in 2 patients. Sequential grafts were used in 2 patients (left anterior descending artery—diagonal in 1, marginal 1–marginal 2 in 1). The mean number of grafts per patient was 2.6 ± 0.1. Anoxia time was 40.7 ± 2.7 minutes, with a total cardiopulmonary bypass time of 84.5 ± 6.9 minutes.

Postoperative ITA Stenosis
Time of presentation to operation was less than 3 months in 18 patients (62.1%). Symptom status before and after percutaneous transluminal coronary angioplasty (PTCA) is shown in Table 1Go.


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  		Table 1. . Canadian Cardiovascular Society Anginal Classification Before and After Angioplasty
 
The presenting problems were angina in 26 (89.7%) patients, a positive exercise test in 8 (27.6%), and myocardial infarction in 1 (3.4%). One patient was found to have ITA stenosis during a routine cardiac catheterization. At the time of the procedure, 6.9% were asymptomatic or class I, 13.8% had CCS class II symptoms, 37.9% had class III, and 41.4% suffered from class IV symptoms.

A continuous single suture technique was used in 19 (65.5%) patients, whereas double suture technique was used in 10 (34.5%). Sequential grafts were performed in 2 patients: 1 was to the left anterior descending and first diagonal; the second was to the first and second marginal arteries. The average number of grafts per patient was 2.6 ± 0.1. All patients had a left ITA graft and 2 had an additional right ITA graft.

Angioplasty Results
Percutaneous angioplasty was performed in all patients from 4 days to 34 months after operation (mean, 6.5 ± 1.6 months). At the time of PTCA, 34 stenotic sites in internal thoracic grafts were identified in 29 patients. Thirty-two (94.1%) of these lesions were at the anastomotic site and 2 (5.9%) were in the ITA pedicle. Balloon dilation with the previously described technique was successful (ie, less than 50% residual stenosis) in 31 lesions (91.2%). There was a mean reduction in the diameter of luminal stenosis from 90.1% ± 1.5% to 27.7% ± 4.1%. Failure occurred in 3 patients. In 2 patients, there was either a subclavian artery dissection or large dissection in the ITA. When this was recognized, the procedures was terminated and the patients were managed conservatively with no long-term complications. In the other patient, failure occurred due to inability to cross the lesion with the guidewire. This was believed to be because of excessive tortuosity in the ITA proximal to the stenosis. The procedure was complicated in 3 patients by marked spasm of the ITA, requiring repeated doses of nitrates and calcium-channel blockers. In these patients, the procedure was successfully completed. No vascular complications occurred at the site of femoral artery puncture. One patient suffered a small non–Q-wave myocardial infarction as defined by an increase in creatine kinase level. No patients underwent redo coronary artery bypass grafting, and there were no in-hospital cardiac deaths.

Follow-Up
Follow-up was available in 28 of 29 patients (96.6%) at a mean of 24.6 ± 2.3 months after angioplasty. Before the procedure, 79.3% of patients suffered from class III or IV symptoms. At follow-up, 84.6% of patients had CCS anginal class II or less.

A total of 14 patients (50%) underwent recatheterization after their PTCA. There was evidence of symptomatic restenosis after angioplasty in 4 patients (14.3%) within 3 months of initial PTCA, 2 of whom underwent repeat PTCA with good long-term results. One patient required a redo bypass operation because of restenosis of the ITA graft as well as occlusion of two of three of his saphenous vein grafts with persistent ischemic symptoms. One patient died of glioblastoma.


   Comment
Top
 Footnotes
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
References
 
The use of the ITA as a conduit for coronary artery bypass grafting has stood the test of time and proved to be superior compared with autogenous saphenous vein grafts [2]. The accepted early patency rate is 95% and long-term patency is 85% to 90% [2–5]. Although the majority of ITA grafts achieve long-term patency, some will fail and the patient will present with recurrent myocardial ischemia. In our series, only 0.95% of ITA graft patients presented with symptoms of myocardial ischemia attributable to stenosis or occlusion of the ITA graft. Reoperation for coronary artery bypass carries an increased morbidity and mortality of up to 5% [13]. Therefore, percutaneous angioplasty of ITA graft is an appealing alternative to reoperation. Previous reports of ITA graft angioplasty [14–22] confirmed its feasibility and success. The reported numbers of ITA stenosis tend to be small, which supports the efficacy of grafting using ITA. Other reports emphasized the technique and success rate of the procedure. In this study, other aspects of this pathology can be emphasized.

The first report of ITA graft angioplasty was published in 1984 by Kereikes and colleagues [14], who reported 2 cases: one angioplasty to an ITA distal anastomosis and one to the left anterior descending coronary artery beyond the anastomosis. Both were successful with follow-up of 6 months. Cote and associates [23] in 1987 reported angioplasty of 83 vein grafts and five ITA grafts with overall success rates of 85% and 100%, respectively. Predictors of success of angioplasty included a higher measured balloon/graft ratio, a smaller diameter graft, and a shorter lesion length. In the same year, Pinkerton and co-workers [16] reported 9 cases handled by a femoral approach (Table 2Go). In 1988, Shimshak and colleagues [19] reported percutaneous angioplasty of 26 ITA graft stenoses and 24 coronary artery stenoses beyond the insertion of the ITA graft, utilizing ITA as a conduit. More recently, Dimas and associates [18] from the Cleveland Clinic Foundation reported 27 ITA graft angioplasties with a success rate of 98%, and the latest brief report was in 1992 by Popma and co-workers [20], who reported on 20 patients with a success rate of 83%.


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  		Table 2. . Literature Review
 
The timing of presentation of ITA stenosis is of particular interest. In this study, many patients became symptomatic in the early postoperative period, with 62.1% of patients presenting within 3 months of the initial operation. This supports the hypothesis that the most common cause of failure is a technical problem, as 3 months is not enough time for progression of the disease at the anastomosis or distal to it. Other reports [24, 25] support this clinical observation. Causes of failure of the ITA graft could be related to failure of the anastomosis (94.1% in this study), which could be secondary to construction of an anastomosis of smaller diameter, anastomosis to a rigid or narrowed vessel, fibrointimal hyperplasia, or suboptimal anastomotic technique. It also may be related to narrowing of the ITA pedicle, which is less common (5.9% in this series) due to damage of the conduit that occurs during harvesting, with traction, electrocautery, hemostatic clip, or creation of an intimal flap from probing. To minimize the potential complications, the conduit should be handled with utmost care and any doubts regarding the integrity of the conduit should be rectified at the time of operation, even if that precludes the use of the graft. Another possible cause of failure of the ITA graft is stenosis distal to the anastomosis, which was not encountered in this study. This emphasizes the technical point of taking care to assure optimal placement of the anastomosis along the vessel.

Other reports in the literature have addressed the feasibility of percutaneous angioplasty of ITA graft and the different technical approaches [14–20]. The success rate ranged from 67% in the most tortuous artery to 90% in straightforward cases. In this series, the success rate was 91.2%. There were only three failures, one in which the anastomosis could not be crossed due to tortuosity and redundancy, and two that were due to large intimal dissections. Tortuosity of the pedicle is a technical problem encountered during attempts at ITA angioplasty. It is important that surgeons make an effort to cut the conduit to the appropriate length during the construction of the anastomosis to avoid kinking and tortuosity of the graft, which could compromise graft survival.

Performance of angioplasty in the early postoperative period has been reported to carry no increased risk of complications [18], and this also was found to be the case in this series.

Angiographic follow-up was limited in patients presenting with ITA stenosis at the beginning of this series. In total, 50% of patients underwent repeat cardiac catheterization after PTCA for ITA stenosis. Clinically symptomatic restenosis occurred in 4 cases after angioplasty (14.3%). Two of the patients had successful repeat dilation with no complications and good long-term results. The third patient required a redo bypass operation due to failure of the other grafts. The other patient was treated medically. However, the clinically symptomatic restenosis rate after ITA angioplasty appears lower than the reported restenosis rate after routine native coronary artery angioplasty (30% to 50%) [26, 27]. This suggests that the disease process is different than that of native coronary arteries. The true frequency of symptomatic ITA graft stenosis may be underestimated because not all postoperative patients were catheterized to assess the condition of the ITA graft. Another possible problem is that some patients with symptomatic ITA stenosis may not have returned to the Heart Institute and would have been lost to follow-up. This would also lead to an underestimation of the true rate of ITA stenosis. However, the Heart Institute is the only cardiac tertiary care center in the region, and all postoperative patients generally are referred back with the exception of patients moving out of the area.

In conclusion, symptomatic ITA stenosis is rare after coronary artery bypass grafting. Presentation is usually in the early postoperative period and occurs at the site of distal anastomosis. Patients who present with symptoms soon after coronary bypass grafting should have early angiography to identify ITA stenosis. These lesions are readily amenable to dilation with percutaneous angioplasty with a high success rate and few complications.


   Footnotes
Top
 Footnotes
Abstract
 Introduction
 Material and Methods
 Results
 Comment
 References
 
Presented at the Forty-fifth Annual Meeting of the Canadian Cardiovascular Society, Ottawa, Canada, October 20–24, 1992.

Address reprint requests to Dr Hendry, University of Ottawa Heart Institute, Rm H207, 1053 Carling Ave, Ottawa, Ontario, Canada K1Y 4E9.


   References
Top
 Footnotes
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
 References
 

  1. Lytle BW, Loop FD, Cosgrove DM, Ratliff NB, Easley K. Taylor PC. Long-term serial studies of internal mammary artery and saphenous vein coronary bypass grafts. J Thorac Cardiovasc Surg 1985;89:248–58.[Abstract]
  2. Loop FD, Lytle BW, Cosgrove DM, et al. Influence of the internal mammary artery graft on 10-year survival and other cardiac events. N Engl J Med 1986;314:1–6.[Abstract]
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  6. Geha AS, Baue AE. Early and late results of coronary revascularization with saphenous vein and internal mammary artery graft. Am J Surg 1979;137:456–63.[Medline]
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  8. Loop FD, Irarrazaval MJ, Bredec JJ, Sieggle W, Taylor PC, Sheldon WC. Internal mammary artery graft for ischemic heart disease: effect of revascularization on clinical status and survival. Am J Cardiol 1977;39:516–22.[Medline]
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