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Ann Thorac Surg 1999;68:2185-2189
© 1999 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Arterial patch angioplasty for reconstruction of proximal coronary artery stenosis

^a Departments of Department of Thoracic Surgery, Karolinska Hospital, Stockholm, Sweden
^b Department of Thoracic Radiology, Karolinska Hospital, Stockholm, Sweden
^c Department of Thoracic Anesthesiology, Karolinska Hospital, Stockholm, Sweden

Address reprint requests to Dr Liska, Department of Thoracic Surgery, Karolinska Hospital, S-171 76 Stockholm, Sweden

	Abstract

Top Abstract Introduction Patients and methods Results Comment References

 
Background. Ostium patch angioplasty and reconstruction with an onlay patch consisting of pericardium or the saphenous vein is an alternative surgical technique for patients with proximal coronary artery stenosis. Previously described surgical techniques comprise anterior or posterior approaches. In this article we report our experience of using a segment of the proximal right internal mammary artery as an onlay patch for surgical angioplasty.

Methods. Between June 1997 and April 1999, 18 patients (9 men and 9 women) were subjected to surgical patch angioplasty of the left main coronary artery, 3 patients had an additional angioplasty performed on the proximal right coronary artery. The first 12 patients were operated with a posterior incision technique, and six subsequent patients by a new technique performed through an oblique incision into the left main stem after transsection of the ascending aorta.

Results. All patients had an uneventful postoperative course, and were fully rehabilitated without clinical symptoms of ischemic heart disease at mean follow-up of 10 months (range 1–23 months). Postoperative catheterization after six days showed excellent results with a widely open and funnel-shaped neoostium.

Conclusions. The use of a proximal segment of the right internal mammary artery as an onlay patch for reconstructing proximal coronary artery lesions is safe with no complications. Although the posterior approach may be used to obtain excellent results, transsection of the ascending aorta gives an optimal visualization and mobilization of the left main coronary artery when performing surgical angioplasty.

	Introduction

Top Abstract Introduction Patients and methods Results Comment References

 
Stenosis of the left main coronary artery (LMCA) is an anatomic lesion with a malignant nature and with a highly lethal course when untreated [1]. The preferred treatment of this disorder has traditionally been conventional coronary artery bypass surgery. However, several efforts have been made directly against the pathological lesion in the LMCA by means of endarterectomy and onlay patch angioplasty. The initial experience of these attempts was depressing with a high mortality rate and frequent restenosis at the site of reconstruction [2–5]. Better techniques for cardioprotection and cardiopulmonary bypass inspired Hitchcock and coworkers [6] to revive and modify the angioplasty procedure of LMCA stenosis resulting in excellent outcome, this was followed by others reporting similar results [7, 8]. Dion and colleagues [9], with the largest single experience of the procedure, have further delineated the indications and contraindications and also refined the technique. Principally, a venous or pericardial patch has been used for the angioplasty with acceptable early to midterm results, although there are several reports describing restenosis or thrombosis of LMCA [9–13]. Proximal right coronary artery (PRCA) stenosis has also been successfully reconstructed with the similar technique as an isolated procedure or in combination with LMCA angioplasty [13, 14].

The superiority of internal mammary artery (IMA) grafts versus saphenous vein conduits in conventional coronary artery bypass surgery is indisputable. In particular in contrast to the long-term patency, where the patency of vein grafts is limited by accelerated arteriosclerosis as compared to IMA grafts [15]. Furthermore, differences between segments of the IMA in respect to the endothelial function have been disclosed, ie the proximal part of the IMA is less prone to intimal hyperplasia as compared to the distal portion [16]. The proximal part of the IMA is comparable in size and wall thickness with the saphenous vein. The beneficial characteristics of the IMA in conventional coronary bypass surgery encouraged us to investigate the feasibility of using the proximal part of the right IMA as an onlay patch for the reconstruction of proximal coronary artery stenosis.

In the present study we report our clinical experience with this procedure in 18 patients.

	Patients and methods

Top Abstract Introduction Patients and methods Results Comment References

 
Between June 1997 and April 1999, 1278 patients were operated with surgical coronary revascularization, 18 patients (1.4%) were subjected to surgical angioplasty of the LMCA and PRCA and were included in the study. The male/female ratio was 9/9, and age averaged 60 years (range 52–73). Seven patients had unstable angina, and 8 patients had experienced previous myocardial infarction. Other patient characteristics and preoperative risk factors are as follows:

Hypertension 10 Hyperlipidemia 8 Diabetes mellitus 2 Smoking 12 Obesity 5 Obstructive lung disease 5 Chronic heart failure 2

Catheterization data
LMCA stenosis were present in 18 patients, the degree of stenosis was 50%–75% in 10 patients and 75%–99% in 8 patients. LMCA stenosis was also associated with PRCA stenosis in 3 patients. The LMCA stenosis involved the ostium in 9 patients, the first third in 5 patients, and was circular in 4 patients, whereas no patient had involvement of the distal bifurcation. The PRCA stenosis engaged the ostium in 2 patients. In one patient there was a nonostial stenosis involving the 4–5 mm proximal segment of the right coronary artery. Evidence of slight to moderate calcifications of the LMCA was seen in 5 patients. Concomitant peripheral coronary artery stenosis was seen in 9 patients; 5 patients with isolated LAD stenosis, and 2 patients with significant lesions in both the LAD and the distal RCA, and 2 patients with stenosis of the LAD and a diagonal branch. One patient with ostial stenosis of both LMCA and PRCA also had a combined aortic valve lesion with sclerotic valves. This patient was previously treated with high dose radiation because of a leftsided mammary cancer. One patient also had a severe mitral valve incompetence. Left ventricular ejection fraction (LVEF) was normal in 17 patients, whereas one patient had a severely depressed left ventricular function with a LVEF of 25%.

Operative procedure
The operations were performed using standard balanced fentanyl anaesthesia. Normothermic (36°C) cardiopulmonary bypass, intermittent cold blood cardioplegia, induced antegradely and repeated retrogradely every 10 minutes, were used in all patients. The left ventricle was vented through a 17 French drainage (Research Medical, Midvale, Utah) inserted through the right pulmonary vein. The right IMA was dissected and to access the proximal part of the right IMA it was necessary to first divide the internal mammary vein proximally. A proximal segment of 4–5 cm was procured for later use as an onlay patch, and special care was taken to preserve the perivascular tissue. This part of the IMA was approximately 4 mm in diameter with a vessel wall substantially thicker and more robust than the usually observed distal portion of IMA. Before aortic cannulation, the ascending aorta was mobilized and extensively dissected from the pulmonary artery. In the first 12 patients we used the posterior approach and technique described by Hitchcock and associates [6] and Ridley and Wisheart [17]. Endarterectomy was not performed, even in the presence of calcified plaques. The IMA was longitudinally divided, and trimmed to fit the incised LMCA and the extension out in the aortotomy of approximately 1–1.5 cm. The IMA onlay patch was sutured to LMCA and free aortic wall with a continuos 6-0 Prolene suture (Ethicon Inc, Sommerville, NJ), the remaining aortotomy was sutured with 4-0 Prolene. The angioplasty of the PRCA was performed through a vertical incision in the aortic wall, and with a small probe in place in the right coronary artery, the incision was further extended approximately 1.0–1.5 cm into the PRCA. An onlay IMA patch was then sutured into place as described above. In the six subsequent patients a new technique was used. The ascending aorta was completely transected approximately 1 cm above the commisures and the pulmonary trunk retracted in a leftward direction. By the discontinuation of the ascending aorta, the aortic root could easily be mobilized in an anterior direction, and thereby excellent exposure of the LMCA displayed. An incision was carried out through the aortic wall extending from a position just medial to the noncoronary commisure, and obliquely into the roof of the LMCA. An IMA patch was sutured into place up to the level of the transverse aortic transsection (Fig 1). The aortotomy was closed with 4-0 Prolene.

View larger version (33K): [in this window] [in a new window]   Fig 1. Arterial patch angioplasty of the LMCA after transsection of the ascending aorta. (A) The ascending aorta is transected and oriented in an anterior direction, the LMCA is exposed by retracting the pulmonary artery to the left. An incision is made from a point medial to the noncoronary commissure into the left coronary ostium. (B) The incision is further extended through the roof of the LMCA, when necessary all the way to the bifurcation of the circumflex artery and the LAD. (C) A trimmed arterial patch consisting of a proximal segment of the right internal mammary artery is sutured with a 6-0 monofilament suture onto the lateral portion of the incised LMCA. (D) The medial part of the incision in the LMCA is closed after retracting the proximal part of the aorta in a caudal direction.

	Results

Top Abstract Introduction Patients and methods Results Comment References

 
Nine patients had concomitant conventional coronary artery bypass surgery; 5 patients with a single LIMA graft to LAD, 2 patients also received a free right IMA graft to the RCA, and 2 patients had sequential grafts to a diagonal and the LAD. Three patients had bilateral ostial angioplasties performed. One patient received a mechanical aortic valve prosthesis, and another one a mechanical mitral valve prosthesis. Soft atheromatous material in the LMCA was found in 7 patients, and dense fibromatous tissue in 3 patients. Calcifications were observed in 8 patients.

All patients had an uneventful postoperative course, with stable hemodynamics and without ischemic ECG changes. Postoperatively there was no significant elevation of enzymatic markers indicating myocardial infarction. The patients were extubated after a mean postoperative ventilator time of 6.6 hours (range 3–15 hours), and with mean postoperative bleeding of 590 ml (range 300–1400 ml). All patients were discharged from the intensive care unit after the first postoperative day. There were no neurological events, respiratory complications, or renal complications postoperatively. Two patients developed a superficial wound infection. On the 6th postoperative day all patients were examined with cardiac cathetherization and coronary angiography, which showed excellent results. The neoostium located at the proximal part of the LMCA was funnel-shaped in all patients. The dimension of the neoostium was substantially wider in patients operated with the posterior approach compared to neoostium reconstructed with the aorta transected (Fig 2). All patients received thromboprophylactic regime, consisting of sodium warfarin and also dalteparinsodium (Fragmin, Pharmacia-Upjohn, Stockholm, Sweden) 5000 IU per day, until the therapeutic level of sodium warfarin was obtained. Two months postoperatively anticoagulation was terminated in all patients excluding those with mechanical valves and the patient was put on a daily dose of 160 mg acetylsalicylic acid.

View larger version (63K): [in this window] [in a new window]   Fig 2. Left coronary artery angiogram demonstrating preoperative LMCA ostium stenosis and postoperative result after surgical angioplasty with an IMA patch. (A) Preoperative (top) and postoperative (bottom) angiogram respectively, following angioplasty with a posterior approach. (B) Preoperative (top) and postoperative (bottom) angiogram respectively, following angioplasty after transecting the aorta.

	Comment

Top Abstract Introduction Patients and methods Results Comment References

 
The LMCA can, from an anatomical standpoint, be divided into three parts, the ostial region, the midsegment, and the distal segment [18]. The most common etiology to LMCA stenosis is arteriosclerosis, and accounts for the vast majority of LMCA stenosis engaging particularly the midpart and distal bifurcation, often associated with two- or three-vessel coronary disease. LMCA stenosis is found in approximately 9% of the patients subjected to coronary artery bypass surgery [19]. Isolated stenosis of the ostial region or the first third of the LMCA is substantially less common with an observed prevalence of approximately 1% [9]. This entity of LMCA stenosis also has a more diversified etiology often related to inflammatory processes of the aortic wall, eg, syphilis, rheumatoid arthritis, and postradiation treatment. In our series of patients, at least two other etiological causes than arteriosclerosis were identified, two patients with rheumatoid arthritis and aortitis, and one patient who had earlier received radiation therapy.

Coronary artery bypass grafting is an excellent and safe treatment for LMCA stenosis, but with some potential limitation, such as complete graft depending perfusion because of the progressive occlusion of the coronary ostium, and the risk of arteriosclerotic development of the venous grafts [1, 20]. It also has a theoretical negative effect by perfusing large areas of the myocardium retrogradely [6]. Direct surgical angioplasty of LMCA offers a good alternative by restoring native antegrade flow and also by maintaining access to the distal coronary vessels allowing for percutaneous transluminal coronary angioplasty of peripheral lesions. Technically there have been two principal methods described on how to access the LMCA, the posterior [6, 17], and the anterior approach [7, 8]. The posterior incision has the advantage of avoiding an acute angle of the patch at the junction between the LMCA and the aortic wall, which could possibly cause a stenosis. On the other hand, the posterior approach has the disadvantage of a less good exposure of LMCA. We used the posterior technique in 12 patients. By retracting and rotating the distal part of the ascending aorta in a leftward direction a good exposure throughout the whole LMCA was accomplished. In our six recent operations the ascending aorta was instead transected, which resulted in an excellent visualization of LMCA and also the proximal part of LAD and the circumflex artery. An oblique incision was made in the aortic wall extending into the roof of the LMCA thus avoiding an acute angle of the patch at the ostial junction. A similar approach was described in a case report by Eishi and colleagues [21]. We advocate this approach, because it combines the beneficial properties of both the posterior and anterior techniques. Postoperative angiographic investigation showed a slight difference in appearance, with a larger neoostium when using the posterior approach. The importance of this finding has to be further evaluated. Restenosis of the LMCA has been reported, both with the anterior technique [8, 11, 22] and the posterior technique [8, 13]. Restenosis has evolved regardless of whether a pericardial patch [8, 13] or a saphenous vein patch [8, 11, 22] was used.

The higher patency of the IMA vs the saphenous vein as graft material in coronary bypass surgery is well documented. The IMA resembles coronary arteries in respect to histological, physiological, and fibrinolytic properties far better than autologous pericardium or the saphenous vein [23–25]. Accelerated intimal hyperplasia of vein grafts can be explained by differences in structural stiffness and smooth muscle cell proliferation and migration [24, 25]. To possibly reduce the incidence of restenosis and thrombus formation when reconstructing the LMCA and the PRCA, we used a patch of the right IMA, instead of autologous pericardium or the saphenous vein. Early postoperative catheterization showed excellent results, and clinically no patient had recurrence of angina pectoris in the short- to mid-term perspective. Recurrent angina pectoris has been found to be the most prominent symptom of postoperative restenosis of the LMCA [8, 11, 14, 22]. The use of the distal left IMA as an onlay patch of the LMCA was previously reported in one patient [26], but we believe the distal IMA segment to be insufficient with regard to both dimension and wall structure [16]. Furthermore, anticoagulation might be of importance to prevent early thrombus formation. Anticoagulation with warfarin was therefore initiated postoperatively during a period of two months until complete healing of the suture lines could be expected. In no patient did we encounter such heavy calcifications that we were forced to convert the operation to a conventional coronary bypass procedure. In a few places where the coronary artery wall was calcified, sutures could be placed securely in the adventitial tissue. However, when severe calcification and involvement of the distal bifurcation is present we find the angioplasty procedure hazardous and contraindicated. We do not consider age or limited peripheral coronary lesions as contraindications for surgical angioplasty of LMCA stenosis.

In conclusion, using the proximal segment of the right IMA as an onlay patch in surgical reconstruction of LMCA stenosis and PRCA stenosis was safe and without complications. Early catheterization demonstrated excellent results, long-term patency is still to be evaluated. Clinical follow-up showed no residual symptoms of ischemic heart disease. Although the posterior approach was sufficient for excellent results, transsection of the ascending aorta allows for an optimal visualization and mobilization of the LMCA, with an option to incise the LMCA either in an obtuse or acute angle.

	References

Top Abstract Introduction Patients and methods Results Comment References

 

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