Ann Thorac Surg 2003;75:1434-1436
© 2003 The Society of Thoracic Surgeons
Original article: cardiovascular
Pitfalls and key lessons with the symmetry proximal anastomotic device in coronary artery bypass surgery
Thierry P. Carrel, MDa*,
Friedrich S. Eckstein, MDa,
Lars Englberger, MDa,
Stefan Windecker, MDb,
Bernhard Meier, MDb
a Clinic for Cardiovascular SurgeryUniversity Hospital, Berne, Switzerland
b Division of Cardiology, University Hospital, Berne, Switzerland
Accepted for publication November 14, 2002.
* Address reprint requests to Dr Carrel, Clinic for Cardiovascular Surgery, University Hospital Berne, CH-3010 Berne, Switzerland.
e-mail: thierry.carrel{at}insel.ch
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Abstract
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BACKGROUND: Increasing practice of less-invasive coronary artery bypass surgery has generated a revival of automated methods to facilitate the creation of vascular connections during coronary artery bypass grafting procedures.
METHODS: We have reviewed our clinical experience with 107 patients who received at least one proximal Symmetry aortic connector from St. Jude Medical Anastomotic Technology Group (St. Paul, MN) to connect a saphenous vein graft to the ascending aorta, in whom the minimal follow-up is 6 months. Seventy-five patients were part of an observational study, and 32 patients were enrolled in a prospective randomized study to compare the anastomotic device with the conventional suture technique. Key lessons and pitfalls observed during loading and deployment as well angiographic findings are presented.
RESULTS: Hospital mortality was 0.9% (1/107); a 76-year-old woman suffered from cerebral complications and died after combined coronary artery bypass grafting and aortic valve replacement. Two connectors had to be removed because of leakage and one because of incomplete deployment. The residual 104 grafts connected to the ascending aorta were patent at the end of the operation (mean flow, 72 ± 29 mL/min). Fourteen patients from the prospective study have received 6 months of angiographic assessment so far. Forty-two grafts have been evaluated: all IMA grafts (n = 14) are patent. Four radial artery grafts have been studied: three are patent and one is occluded. Twenty-four vein grafts have been assessed: 11 were hand-sewn and 13 were connected to the aorta with the proximal connector system. Patency rate is not different between the two techniques, but there is an incidence of 38% (5/13) stenosis in the proximal vein graft segment in those patients with a proximal connector. No proximal hand-sewn anastomosis shows any significant stenosis.
CONCLUSIONS: The use of proximal devices allows ultra-fast connection of a bypass graft to the aorta. The handling of this device is simple, manipulations on the ascending aorta are minimized, and hemostasis is perfect. However, because stenoses have been observed in the vein graft close to the connector site, mid- and long-term patency rates have to be assessed in large prospective trials.
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Introduction
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| Dr Carrel discloses that he has a financial relationship with St. Jude Medical.
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The vascular anastomoses in coronary artery bypass grafting (CABG) are currently performed using running polypropylene sutures. This requires a good level of skill, a substantial learning curve, and a certain amount of time. Recently, major efforts have been focused on the development of innovative revascularization techniques to minimize general trauma due to extracorporeal circulation, reduce neurologic complications, and accelerate patient recovery [1–4].
Whereas stabilization systems have played a major role in enabling safe coronary anastomoses on the beating heart, another technology likely to have a great potential on the adoption of off-pump coronary artery bypass grafting (OPCAB) has been the development of devices that allow ultra-fast connection of a saphenous vein graft with the ascending aorta and with the target coronary arteries [5–9].
Currently, several anastomotic devices are available for research or clinical routine. Since St. Jude Medical (St. Paul, MN) received CE market and FDA approval in May 2001, more than 30,000 Symmetry Aortic Connector Systems have been used worldwide, but there is no consistent information about patency rate. This paper describes briefly some key lessons and pitfalls observed during loading or deployment of this device, emphasizes the most important intraoperative steps, and present some angiographic findings after a follow-up of 6 months.
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Patients and methods
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Loading and deployment of the aortic connector
The Symmetry aortic connector is made of nitinol. The diameter of the vein graft has to be assessed carefully to match with the most appropriate size of connector system. The vein is slid over a transfer sheet that facilitates the loading process on the release tube. Care must be taken that the vein is adequately humidificated. The saphenous vein graft is cleaned from adventitial tissue, and the hooks of the connector are pierced through the wall of the vein to prevent dislocation of the graft during deployment. The system uses a unique aortic cutter with a rotating blade that creates a perfectly round hole in the aortic wall. To avoid the formation of intimal flaps, the blade should be maintained at a 90° angle in the aorta during cutting. Neither creating the neo-ostium nor delivering the device require tangential clamping of the aorta. The optimal mean arterial pressure during delivery is around 50 to 60 mm Hg (systolic pressure ideally not > 100 mm Hg). The device should not be delivered during instillation of cold cardioplegia because the nitinol alloy would not expand properly in a cold environment. Delivery takes less than 10 seconds, and a perfect hemostasis is obtained instantaneously. In case of anastomotic leakage, placement of an adventitial extra stitch can be performed but is not recommended by the company.
Clinical experience
We present our clinical experience with 107 patients who received at least one proximal Symmetry aortic connector to perform the proximal anastomosis between a saphenous vein graft and the ascending aorta, in whom the minimal follow-up is 6 months. Seventy-five patients were part of an observational study: 69 underwent isolated CABG and 6 patients received combined CABG and valve surgery. Thirty of 69 isolated CABG procedures were performed using the off-pump technique.
Thirty-two patients were enrolled in a prospective randomized study to compare the anastomotic device (n = 15) with the conventional suture technique (n = 17). According to the study protocol, these patients were operated on with the aid of extracorporeal circulation in moderate hypothermia. Conventional suture of the vein graft to the ascending aorta was performed with a running 6.0 polypropylene suture during tangential clamping of the aorta. Mean time to perform the suture was 4.5 ± 2 minutes. In the connector group, loading was performed while the internal thoracic artery (ITA) was prepared. Loading time was 2.5 minutes and deployment never required more than 15 seconds. Intraoperative flow through the grafts was assessed with the transit time method (Medi-stim Inc, Oslo, Norway) after weaning from extracorporeal circulation. Angiographic follow-up at 6 months is available so far in 10 of 75 patients from the observational group and in 14 of 32 patients from the randomized study. Key lessons and pitfalls observed during loading and deployment as well as angiographic findings are presented.
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Results
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Hospital mortality was 0.9% (1/107); a 76-year-old woman suffered cerebral complications and died after combined CABG and aortic valve replacement. Two connectors had to be removed because of leakage and one because of incomplete deployment. All grafts connected to the ascending aorta were patent at the end of the operation (mean flow, 72 ± 29 mL/min).
Postoperative angiogram was obtained in 10 of 75 patients from the observational study group; 1 of them suffered from recurrent angina 6 months after the operation. In 2 of 10 patients, a stenosis was observed in the first 2 cm of the vein graft distal to the connector, but no hand-sewn anastomosis showed any stenosis. The patient suffering from angina had both saphenous vein grafts connected to the ascending aorta with the aortic connector occluded despite excellent intraoperative flow (47 mL/min to the marginal branch and 52 mL/min to the posterior descending branch).
Fourteen patients from the prospective study group so far have received a 6-month angiogram; 42 grafts have been evaluated. All IMA grafts (n = 14) are patent. Four radial artery grafts and 24 vein grafts have been assessed. Three radial grafts are patent and one is occluded. Of the 24 vein grafts, 11 have been anastomosed with a running suture and 13 anastomosed with the proximal connector system. Patency rate is not different between the two techniques (one occlusion in each group), but there is an incidence of 38% (5/13) stenosis from 30% to 90% in the proximal vein graft segment in those patients who received the proximal connector (Figs 1, 2).
No hand-sewn anastomosis shows any significant stenosis. Three of five stenoses have been successfully dilated and a stent has been implanted in 2 patients. In 1 patient, the native right coronary artery was dilated.
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Fig 1. Six-month postoperative angiogram showing a typical stenosis at the site of the saphenous vein graft-to-aorta connection (so-called "in connector" stenosis, in analogy to the in-stent stenosis).
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Fig 2. Six-month postoperative angiogram showing a significant stenosis located distally from the aortic connector.
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Comment
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Recent developments in less-invasive coronary artery bypass surgery have been driven by the introduction of new technologies that facilitate precise surgical maneuvers on the beating heart within a confined space. Such technologies include coronary stabilizer systems, cardiac positioning vacuum-assisted devices, and telemanipulative technologies [1–3]. Despite these developments, standard suturing techniques still use running polypropylene material. Sometimes, the limited approach to the chest cavity limits the surgeon’s ability to perform complete revascularization with high-quality anastomoses. Proximal (aortic) and distal (coronary) anastomotic devices that allow ultra-fast and precise connection of vessels together may have the potential to boost minimal invasive coronary surgery. Ideal characteristics of such devices would include applicability to all potential graft conduits and all sizes of coronary arteries, interchangeable proximal/distal sequence of the anastomoses, and safe bail-out in case of device malfunction.
This type of connector system allows for the reduction of aortic manipulations, and complete hemostasis is immediate. Intraoperative flow rate through the graft is very satisfying. However, there are some concerns when the aortic connector system is used. The proximal anastomosis has to be performed first; this is not common to all surgeons. Furthermore, a bulldog clamp has to be used to clamp the graft once the anastomosis has been performed. This may damage the endothelium of the graft, especially when the latter is clamped under arterial pressure. The site of the proximal anastomosis is critical. The take-off angle of the vein graft out of the aorta must be 90°, and kinking of the graft should be avoided. The estimation of the definitive length of the saphenous vein graft is important in any CABG procedure, of course but, especially when the proximal anastomosis is performed first. Once the mediastinal tissue or the pericardium has been closed, the final position of the vein graft is difficult to predict.
Recently, Donsky and associates [10] described two cases of acute thrombotic occlusion of the aortic ostia after mechanical connection using the St. Jude device. They hypothetized that this complication may have a similar pathophysiology to that seen in acute stent thrombosis. Increasing use of aggressive antiplatelet agents dramatically reduced the incidence of this complication. The best postoperative medical treatment is still unclear when connectors have been used; whereas some centers have adopted clopidogrel 75 mg daily as a routine for the first 3 months, others still maintain a more classic approach with aspirin 300 mg. We have some concerns regarding the long-term (stenosis-free) patency rate of bypass grafts connected to the ascending aorta using the Symmetry anastomotic device.
Therefore, large prospective randomized trials are required to validate this and other types of anastomotic devices. After intensive deliberation, we decided to interrupt this prospective randomized study for the following reasons. (1) Recruitment of the patients was difficult, because independently of the information received, a majority of the patients wanted to receive the most modern technology. (2) The rate of stenosis observed was not acceptable, similar to that observed in the early days of intracoronary stenting. (3) The new generation of St. Jude proximal connectors that eliminate the major disadvantages of the present device (sliding of the vein over the delivery device, take-off angle of 90°) have been released for investigational purposes.
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References
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Abstract
Introduction
