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Ann Thorac Surg 2006;82:1452-1456
© 2006 The Society of Thoracic Surgeons
a Department of Cardiac Surgery, Grosshadern Medical Centre, Ludwig-Maximilians-University München, München, Germany
b Department of Internal Medicine I, Grosshadern Medical Centre, Ludwig-Maximilians-University München, München, Germany
Accepted for publication April 27, 2006.
* Address correspondence to Prof Dr Calin Vicol, Herzchirurgische Klinik und Poliklinik, Klinikum Grosshadern der LMU München, Marchioninistr. 15, 81377 München, Germany (Email: calin.vicol{at}med.uni-muenchen.de).
| Abstract |
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METHODS: Eighteen distal anastomoses were performed by using the MVP, and 18 with a hand-sewn technique were completed in 11 patients. The target arteries for the MVP anastomosis were the left anterior descending in 9 patients, a marginal branch in 4, a diagonal branch in 3, and right coronary artery in 2. The left internal thoracic artery was used as graft in 9 patients, saphenous vein in 6, right internal thoracic artery in 2, and radial artery in 1.
RESULTS: Coronary angiography was performed at discharge and after a complete follow-up of 19 ± 3.5 months. Patency at follow-up was 83.3% (15/18) for MVP anastomoses and 100% (18/18) for hand-sewn anastomoses. All occluded MVP anastomoses were performed with small-size devices. In one patient, a high-grade left main stenosis was overestimated. Competitive flow may be suspected in this case as a cause of graft occlusion. No deaths occurred during hospital stay or during follow-up. Freedom from reintervention was 100%.
CONCLUSIONS: The MVP is the only mechanical connector for distal anastomoses applicable for all kind of grafts, for all coronary artery locations, and with both end-to-side and side-to-side technique. Mid-term patency of MVP anastomoses is acceptable but inferior to the patency of hand-sewn anastomoses. Occlusion of MVP supplied grafts may be produced by small device size.
| Introduction |
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Five true DADs were investigated in clinical trials after successful short-term animal experiments: the magnetic vascular positioner (MVP) (Ventrica, Inc, Fremont, CA) [13], St. Jude Medical Anastomotic Technology Group Coronary Connector System (St. Jude Medical, Inc, St. Paul, MN) [4, 5], Automated Anastomotic Distal Device (Bypass, Herzlia, Israel) [6], Converge Anastomotic Coupler (Converge Medical, Inc, Sunnyvale, CA) [7], and C-Port System (Cardica, Inc, Redwood City, CA) [8].
Because short-term results after using the DADs were not convincing, the long-term patency of DAD-supported anastomoses was questioned. Our study addressed mid-term angiographic results for a sutureless device used for distal anastomoses in coronary surgical procedures.
| Patients and Methods |
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The MVP system consists of six magnetic clips mounted on two delivery devices. Each delivery device is preloaded with one intravascular and two extravascular magnetic clips. One delivery device is used to create an anastomotic port in the graft by applying one magnetic clip inside and two outside the anastomotic incision (Fig 1A). The other delivery device forms an identical port at the selected anastomotic site on the target coronary artery (Fig 1B). As the two ports are brought together, the clips' magnetism causes coupling of the two ports, creating the anastomosis. The MVP is available in two sizes: model 6150 (small device size) is intended for vessels with an internal diameter of 1.5 to 2.0 mm, and model 6200 (bigger device size) is for vessels with an internal diameter of more than 2.0 mm. The detailed delivery technique was presented in a previous publication [1].
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The MVP was used for 18 distal coronary artery bypass anastomoses in 11 patients. Eighteen distal anastomoses were also performed using the conventional hand-sewn technique. MVP-related operative patient data are presented in Table 1. No patients died, and no myocardial infarctions or major complications occurred related to the MVP anastamosis.
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Angiographic follow-up was 19 ± 3.5 months (range, 13 to 25 months) postoperatively. Coronary artery bypass grafts were evaluated by a cardiologist and a cardiac surgeon. To analyze changes of the luminal diameter of grafts and coronary arteries, the size of angiography catheters and sternal wires at serial examinations were measured. These figures were then used to compensate for differences in magnification.
Anastomotic patency and function were evaluated by a qualitative angiographic analysis. We used the thrombolysis in myocardial infarction (TIMI) flow grade assessment as described by Gibson [9] and defined as follows: grade 0 no perfusion, specifically no antegrade flow beyond the MVP anastomosis corresponding to an anastomotic occlusion; grade 1, penetration without perfusion; grade 2, partial perfusion; and grade 3, complete perfusion and proven optimal anastomotic flow beyond the MVP anastomosis.
The distribution of flow from the graft through the MVP anastomosis to the target coronary artery was analysed while contrast medium was injected through the graft [10]. Absence of competitive blood flow was indicated by opacification of the grafted coronary artery up to the proximal stenosis. The presence of mild competitive flow was indicated by opacification of the grafted coronary artery without retrograde flow of the contrast material up to the proximal stenosis. Presence of true competitive flow was indicated by absence of opacification of the grafted coronary artery and retrograde opacification of the distal segment of the graft near the MVP anastomosis. In case of true competitive flow, proximal stenosis of the involved coronary artery was reevaluated on preoperative coronary angiography. Data are presented as percentages and means ± standard deviation.
| Results |
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All patients underwent control coronary angiography 19 ± 3.5 months (range, 13 to 25 months) postoperatively (Table 2). Patency was 83.3% (15/18) for MVP anastomoses and 100% (18/18) for hand-sewn anastomoses. All patent MVP anastomoses showed a TIMI grade 3.
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The three occluded MVP anastomoses were performed with the small-size device (model 6150). All anastomoses performed with the bigger device (model 6200) were patent and showed no flow restriction. Mild competitive flow was observed in 2 LAD arteries each grafted with LITA by means of MVP. None of these grafts showed a string phenomenon.
Patients 2 and 5 accidentally underwent MRI at 4 and 10 months, respectively, after their coronary procedure. One patient underwent diagnostic MRI because of shoulder pain. During the investigation, he experienced severe chest pain that spontaneously resolved after cessation of the procedure. A coronary angiography the next day showed patency of all three hand-sewn and one MVP anastomosis (Fig 2). A control angiography 9 months later showed all grafts were patent, without changes in the MVP anastomoses.
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| Comment |
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Any device developed to perform coronary artery bypass graft anastomosis has to achieve at least the same results for graft patency as those obtained with the standard hand-sewn technique. Four authors reported 6-month angiographic results: one with the MVP, one with the C-Port System, and two with the St. Jude Medical Coronary Connector. Patency of eight investigated MVP anastomoses was 100 % [11]. Patency of the C-Port Systemsupported anastomoses was 87.5% [8]. Patency of the St. Jude Medical Coronary Connector anastomoses was modest at 70% (7/10), as reported by Carrel and colleagues [4], and 74% (20/27) by Wiklund and colleagues [5].
Overall patency of MVP anastomoses in our study was 83.3% (15/18) at 19 ± 3.5 months after the procedure. Three MVP anastomotic occlusions occurred in one LITA, one RITA, and one radial artery. The small number of patients does not allow us to give definitive conclusions about the influence of graft material on patency or coronary territory. Nevertheless, mid-term patency of MVP anastomoses is comparable to mid-term patency of hand-sewn anastomoses using the radial artery (89%) [13] and vein graft (73.3%) [14], but inferior to the patency if the ITA is used (94%) [10].
Two occlusions of MVP-supported anastomosis occured in the same patient. In this case, the proximal left main stenosis was overestimated on the preoperative coronary angiography. We assume that competitive flow in the native LAD and marginal branch, which were supported by the LITA and RITA, respectively, caused the occlusion of the MVP-supported anastomoses.
Another factor that seems to influence the patency of MVP anastomoses is the size of the device. The three occluded MVP anastomoses in our patients were performed with model 6150, the small-ize device. Neither quality of coronary artery wall, nor diameter at the site of anastomosis, nor coronary artery territory influenced patency in our experience.
There might be some concern about patency of anastomoses created with DAD because of the blood-exposed nonintimal surface of foreign material [15]. Although MVP has a higher blood-exposed nonintimal surface compared with conventional hand-sewn anastomoses, we did not observe any narrowing in the MVP anastomoses during angiography. Flow assessment of the MVP anastomoses using coronary angiography was considered difficult because of the radiopacity of the magnetic clips [11]. TIMI analysis allowed us to make a qualitative assessment of flow measurement through the MVP anastomoses, and all the patent anastomoses showed optimal flow.
Caution should be taken for patients with MVP-supported anastomoses in regards to magnetic field exposure for at least 6 months after the procedure. This precaution is particularly important as MRI becomes more prevalent [3]. Contrary to our indication, 2 patients underwent MRI at 4 and 10 months, respectively, after surgery. Severe chest pain occurred in both patients at the beginning of the MRI investigation and stopped immediately after cessation of the procedure. Angiography in both patients after the MRI incidents demonstrated patent MVP anastomoses. MVP anastomoses were still patent 9 and 11 months later.
MRI techniques might be hazardous for patients with metallic implants because of heating and movement of ferromagnetic objects by magnetic field interactions with MRI systems. The relative risks are proportional to the strength of the static magnetic field, the strength of the spatial gradient, the mass and shape of the object, and its magnetic susceptibility. Obviously, metallic implants such as the MVP clips inside the coronary arteries are sensitive to MRI procedures. We strongly recommend that MRI procedures not be performed in patients with MVP-supported anastomoses.
Limits of the study include the small number of patients. The power of the statistical tests is not sufficient to give indisputable conclusions. Our results may be considered valuable, however, because there is a paucity of data on this topic in the literature.
In conclusion, MVP-DAD is safe, applicable with all kinds of grafts, in any coronary artery position, in end-to-side or side-to-side technique, and has acceptable mid-term patency rates. Hand-sewn graft-to-coronary artery anastomosis remains the gold standard, the mid-term patnency of which was not equalled by the MVP anastomoses in this study. One should remember, however, that although graft patency depends on multiple factors, the quality of the distal anastomosis is one of the most important. The success of the hand-sewn technique is highly related to surgical experience and skill. Anastomotic devices avoid variability of hand-sewn created anastomosis and realize a well-defined graft-to-coronary artery connection. With additional improvements, MVP may have overcome the "human touch" of distal graft connection.
The MVP device obtained CE approval in 2002, and the company, Medtronic, initiated at the same time formalities to obtain the United States Food and Drug (FDA) approval. In 2004, some working groups reported disappointing results with the Symmetry device [16], and the FDA decided to stop the evaluation procedure. As a consequence, Medtronic suspended the production and sale of the MVP at the beginning of 2005. This decision was not dictated by bad results with the MVP device.
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| Acknowledgments |
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