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Ann Thorac Surg 2005;79:1738-1742
© 2005 The Society of Thoracic Surgeons

New technology

Early Clinical Results With a Magnetic Connector for Distal Coronary Artery Anastomoses

Calin Vicol, MDa,*, Sandra Eifert, MDa, Martin Oberhoffer, MDa, Peter Boekstegers, MDb, Andreas Knez, MDb, Frank Christ, MDc, Bruno Reichart, MDa

a Department of Cardiac Surgery, Grosshadern Medical Center, Ludwig Maximilians University Munich, Munich, Germany
b Department of Internal Medicine I, Grosshadern Medical Center, Ludwig Maximilians University Munich, Munich, Germany
c Department of Anesthesiology, Grosshadern Medical Center, Ludwig Maximilians University Munich, Munich, Germany

Accepted for publication April 20, 2004.

* Address reprint requests to Dr Vicol, Herzchirurgische Klinik, Klinikum Grosshadern der LMU, Marchioninistr 15, 81377 Munich, Germany (E-mail: calin.vicol{at}med.uni-muenchen.de).


   Abstract
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 Abstract
Introduction
 Patients and Methods
 Device Description
 Delivery Technique
 Results
 Comment
 Disclosures and Freedom of...
 Footnotes
 References
 
PURPOSE: The main goals in the development of an anastomotic device are to reduce the invasiveness of the procedure and to improve graft patency. We analyze our preliminary clinical experience with the Ventrica magnetic vascular positioner (MVP) series 6000 system.

DESCRIPTION: Eighteen distal anastomoses were performed in 11 patients using the MVP.

EVALUATION: The target artery for MVP was left anterior descending in 9 patients, a marginal branch in 4, the first diagonal branch in 3, and the right coronary artery in 2. Graft material was the left internal thoracic artery in 9 patients, saphenous vein in 6, the right internal thoracic artery in 2, and the radial artery in 1 case. Fifteen anastomoses were performed in an end-to-side and 3 in a side-to-side fashion. Predischarge angiography was performed in 10 of 11 patients. There was a patent MVP anastomosis in all patients.

CONCLUSIONS: Distal anastomoses using the MVP were performed successfully in all patients. The procedure is simple. Short-term patency is excellent. Further randomized trials are necessary to determine long-term safety and patency.


   Introduction
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 Abstract
 Introduction
Patients and Methods
 Device Description
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There are at least three categories of distal coronary artery anastomotic devices. These include devices using micromechanical tissue bonding, laser assisted vascular anastomotic techniques, and methods using adhesive bonding. Recently, a new device, the Ventrica magnetic vascular positioner (MVP) series 6000 system based on magnetic coupling, has been developed. We evaluated this new method of creating sutureless end-to-side and side-to-side coronary artery anastomoses using arterial and venous graft material.


   Patients and Methods
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Between May and August 2003, we used the MVP for 18 distal coronary artery bypass anastomoses in 11 patients. There were 7 other hand-sewn anastomoses performed in those 11 patients for a total of 25. Institutional Review Board approval was obtained in advance of the study. Written informed consent was obtained from every patient. Criteria for use of the MVP were a target vessel with a high-grade proximal stenosis, an internal diameter of at least 1.5 mm, and no atherosclerotic plaque at the site of the MVP implantation. The MVP should not be used for patients in whom antiplatelet therapy is contraindicated, nor for patients in whom postoperative magnet resonance tomography is planned.

Preoperative patient data are presented in Table 1.


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  		Table 1. Preoperative Patient Characteristics
 
In all cases an antiplatelet regimen was used. For the first 8 patients, intravenous tirofiban (Aggrastat MSD, Haar, Germany) was administered 1 hour before the MVP implantation as a 3-minute bolus of 15 µg/kg. That was followed by a continous infusion of 10 µg/kg until terminated 2 hours after MVP deployment. Sufficient heparin was given to keep the prothrombin time above 60 seconds. A loading dose of 300 mg clopidogrel (Plavix; Sanofi-Synthelabo, GmbH, Berlin, Germany), was given early postoperatively, then 75 mg daily. Because of 1 significant postoperative bleeding episode, after the first 8 patients, we changed the antiplatelet regimen to our current protocol of 150 mg clopidogrel before operation, then a long-term course of 75 mg clopidogrel and 100 mg aspirin daily.

Surgery was performed using cardiopulmonary bypass with cardioplegic arrest.

Data are presented as the mean ± SD.


   Device Description
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 Abstract
 Introduction
 Patients and Methods
 Device Description
Delivery Technique
 Results
 Comment
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 Footnotes
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The MVP was developed by Ventrica (Fremont, CA). The system consists of six magnetic clips mounted on two delivery devices (Fig 1). 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 target coronary artery by applying one magnetic clip inside and two outside the arteriotomy. The other delivery device forms an identical port at the selected anastomotic site on the bypass graft. 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 is intended for vessels with an internal diameter between 1.5 and 2.0 mm; model 6200 is for vessels with an internal diameter of more than 2.0 mm. A 4.0 or 5.0 sizer for gauging arteriotomy length is provided with the anastomotic system. Each delivery device consists of a positioning handle for the magnetic clips and a deployment handle. Deployment of the magnetic clips is activated by squeezing the triggers of the deployment handle.



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  		Fig 1. The magnetic vascular positioner anastomotic device. (a) Delivery device with deployment handle (left) and positioning handle (right). Three magnetic clips are preloaded on the distal tip of the positioning handle. (b) Magnified clip set consisting of one (oval-shaped) intravascular and two extravascular magnetic clips.

 

   Delivery Technique
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First the anterior and lateral wall of the target coronary artery are exposed by dissection at the site of planned anastomosis. A conventional longitudinal 4 mm long incision is performed. The artery is probed to measure its internal diameter. If a MVP model 6150 will be used, the initial incision length of 4 mm is long enough. For the model 6200, the incision should be extended to 5 mm. The distal end of the delivery device, preloaded with the intravascular magnetic clip, is introduced into the arteriotomy (Fig 2a). The delivery device is carefully held in position so that the edges of the arteriotomy symmetrically cover the surface of the intravascular magnetic clip (Fig 2b). Then, taking care to maintain the position of the intravascular magnetic clip, the deployment handle trigger is squeezed until the two extravascular magnetic clips are deployed (Fig 2c). The delivery device is then disengaged from the magnets and removed from the field (Fig 2d). On inspection of the implanted port, no portion of the intravascular magnetic clip surface should be exposed. Only a minimal amount of tissue is tolerable within the port orifice. If the margins of the arteriotomy are not completely captured between the intravascular and extravascular magnetic clips, or if a significant amount of vascular tissue protrudes into the port orifice, the magnetic clips should be removed using the magnetic attraction to a steel forceps. A fresh port can be implanted or the procedure can be converted to a hand-sewn anastomosis. The entire process is repeated for the graft port. If an end-to-side anastomosis is planned, the graft should be closed at its distal end first using a suture or a titanium hemostasis clip. If a side-to-side anastomosis is planned, the procedure is similar to that outlined for the target coronary artery. Finally, the two ports are brought together magnetically.



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  		Fig 2. Implantation steps of the magnetic vascular positioner into a vessel. (a) Toe of intravascular magnetic clip is inserted into incision up to delivery front leg (arrow). Heel of intravascular magnetic clip is lowered into incision. (b) Tissue is retracted by lifting delivery system shoe out of the incision (arrow), draping tissue over intravascular magnetic clip. Tissue stabilization sheath secures incision edges before deployment of extravascular magnetic clips. (c) Deployment arms then lower extravascular magnetic clips and release intravascular magnetic clip. (d) Delivery system is removed from completed anastomotic port.

 

   Results
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A mean of 2.3 ± 0.9 distal anastomoses were performed per patient. From a total of 25 distal anastomoses, 18 were achieved using the MVP. In 7 target coronary arteries, the vessel itself was either too small (diameter <1.5 mm) or had an atherosclerotic plaque in the area of the anastomosis. In 1 case, the MVP implantation procedure had to be converted to a conventional hand-sewn procedure because a thick-walled coronary artery prevented proper deployment of the two external magnets. In 2 other cases, we made successful second attempts using a fresh MVP. In both of those cases, difficulty arose because the extravascular magnetic clips failed to release properly at the disengagement phase of the triggering maneuvre. Intraoperatively, MVP anastomoses were hemostatic and patent in all patients. Patency was proved intraoperatively by transit time flow measurement. Mean flow was 70.5 ± 27.6 mL/min.

The target artery for the MVP anastomosis consisted of the left anterior descending in 9 patients, a marginal branch in 4, the first diagonal branch in 3, and the right coronary artery in 2. Graft material for MVP anastomosis was left internal thoracic artery (LITA) in 9 patients, saphenous vein in 6, right internal thoracic artery (RITA) in 2, and radial artery in 1 patient. Fifteen anastomoses were performed in an end-to-side and 3 in a side-to-side fashion. Mean time necessary for a MVP procedure was 13.5 ± 2.9 minutes. Twelve MVP model 6200 and six model 6150 devices were used. In 1 case, a concomitant aortic valve replacement was performed.

Mean aortic cross-clamp time was 72.6 ± 21.9 minutes.

There was 1 postoperative bleeding complication requiring reoperation in the first 8 patients. The mean chest tube drainage for the day of operation for the 8 patients was 1,043.7 ± 1,008.9 mL. The drainage decreased on the second postoperative day to 338.1 ± 182 mL. The antiplatelet regimen was changed in the next 3 patients in hopes of reducing postoperative bleeding. On the new protocol, we observed a reduction in chest tube drainage and in the necessity for blood replacement. The mean drainage on the day of operation was 936.6 ± 453 mL and 155 ± 104 mL on the second postoperative day.

There were no perioperative myocardial infarctions. The mean creatine kinase (CK)-MB activity 6 hours postoperatively was 13.1 ± 3.7 IU/L and 11.8 ± 2.7 IU/L on the first postoperative day. The mean ventilation time postoperatively was 16.5 ± 12hours. There were no recognized neurologic complications. The mean time in the intensive care unit was 50.9 ± 16.8 hours. Angiography (Fig 3) was performed before discharge in 10 cases at 7 to 22 days (10.3 ± 4.6) postoperatively. The MVP anastomosis was patent in all 10 patients. Six of 6 investigated hand-sewn anastomoses were patent. Angiography was contraindicated in 1 patient because of transient renal insufficiency at the time of discharge, and the patient refused follow-up angiography later.



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  		Fig 3. Postoperative coronary angiography in patient 5. (a) Left internal thoracic artery-to-left descending coronary artery. Patent end-to-side magnetic vascular positioner (MVP) anastomosis. (b) Aorto-to-right coronary artery venous graft. Patent MVP end-to-side anastomosis. (c) Sequential venous graft to first diagonal branch and to posterolateral branch. Patent side-to-side MVP anastomosis and end-to-side hand-sewn anastomosis.

 

   Comment
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From the beginning of coronary surgery, anastomoses have been done mainly by means of hand-held sutures. Recently, efforts have been made to perform coronary surgery off-pump, to reduce the size of the incision, and even to perform closed-chest video-assisted procedures. Performing a coronary anastomosis on a beating heart, especially through a limited access, is technically demanding [1]. The procedure is more difficult if it is performed by a totally endoscopic approach. Therefore, there is need for an alternative anastomotic method that might reduce technical difficulty, shorten the procedure time, and improve the hemodynamics and patency of the anastomosis. By the end of 2001, 112 patents for distal coronary anastomosis had been issued [2]. In the past 2 years, however, only four evolved to prototype devices that have been tested in clinical trials [3–6].

Most of the distal anastomotic devices are used to perform end-to-side anastomoses [7–9]. Regarding MVP, the first report described the use of only one device per patient for exclusive end-to-side graft-to-coronary artery anastomoses [5]. The MVP device enabled us to perform both end-to-side and side-to-side anastomoses. There was no difference between the two applications concerning time to perform an anastomosis nor in the degree of skill required.

Not all devices can use vein and arterial conduits as graft material equally well. Some systems such as the St. Jude connector are suitable only for vein-to-coronary artery procedures [3]. Using the MVP, we were able to perform LITA and RITA-to-coronary artery, radial artery-to-coronary artery, and saphenous vein-to-coronary artery anastomoses. We saw no difference regarding difficulty or time to perform the anastomosis relating to the choice of graft.

Leakage at the anastomosis was observed in 14.2% to 61.5% of cases [4, 8]. In all of our cases, hemostasis of the anastomosis was complete and independent of graft material or target coronary artery.

Conversion caused by leakage at the connection side to conventionally hand-sewn anastomosis may be an issue with some anastomotic devices [3, 4]. In our experience, we had to convert the MVP procedure in one deployment (5.5%). The reason in this case was that the wall of the target coronary artery was too thick at the site of attempted MVP deployment, preventing proper application of the external magnetic clips. After removing the MVP port, a standard hand-sewn anastomosis was performed without difficulty using the same undamaged arteriotomy.

An important concern regarding distal anastomotic devices, especially for beating-heart procedures, is the time required to perform the anastomosis. Reported data vary widely in this regard (24 seconds to 17.7 minutes) [4, 7]. In our patients the distal anastomoses were performed on pump. Our 13.5-minute mean anastomotic time includes the time to expose and open the target coronary artery and the time to prepare the anastomotic site and open the graft. It encompasses the time to measure and assure precisely correct lengths of the coronary and graft incisions. It also includes the time to deploy the two MVP ports, and finally the time to connect the two ports and to anchor the graft by two tacking stitches. If the procedure is performed off pump, the graft MVP port is established before coronary flow is interrupted, so the anastomotic time in those cases will likely be about half that of the arrested-heart anastomotic times.

Another important consideration in the evaluation of a distal anastomotic device is the amount and severity of the manipulation to which the graft is subjected in order to be loaded onto the deploying system. In some devices, the graft is mounted on a transfer sheet; that might cause endothelial and medial damage [4, 7, 8]. The deployment of MVP ports into the target coronary artery and into the graft is a gentle procedure.

Scheltes and colleagues [2] compared the area of blood-exposed nonintimal surface in conventionally sutured anastomosis with device-created anastomoses. This area is approximately 1.3 mm2 in sutured anastomosis, 80 mm2 in anastomoses created with the Jomed graft connector, 33 mm2 after using the first generation of MVP, and 4.3 mm2 in anastomoses created with the St. Jude connector. The MVP new generation has a modified design of the magnetic clips that reduces the area of blood-exposed nonintimal surface by half. This area is still large and has prompted us to use an aggressive antiplatelet program to prevent acute local thrombosis. Therapy with tirofiban may have contributed to significant postoperative bleeding in our early experience. After changing the tirofiban antiplatelet regimen to clopidogrel, we noted a decrease in mean postoperative chest tube drainage, although it still remained higher than that found in our conventional coronary surgery cases without perioperative antiplatelet therapy.

The MVP device is expensive, and its use may increase the cost of coronary artery surgery, a procedure already limited in some venues by economic constraints. High cost is a generally an issue with all anastomotic devices but as more such devices are manufactured and used, it is hoped the price will be reduced.

The MVP enables the construction of rapid, precise end-to-side or side-to-side arterial or venous-to-coronary artery anastomosis. The procedure is less demanding technically than the conventional hand-sewn anastomosis and requires only average manual dexterity. Short-term anastomotic patency is excellent. Disadvantages of the new MVP anastomotic device include the initial large blood-exposed, nonintimal surface area, the need for aggressive antiplatelet therapy, and the high cost. Although the MVP is a promising tool, long-term safety and patency need to be determined. Further randomized trials are necessary to determine which patients may benefit most from use of this particular device.


   Disclosures and Freedom of Investigation
Top
 Abstract
 Introduction
 Patients and Methods
 Device Description
 Delivery Technique
 Results
 Comment
 Disclosures and Freedom of...
Footnotes
 References
 
The clinical study for the evaluation of the Ventrica magnetic vascular connector for distal coronary artery anastomoses was not supported financially by the Ventrica company. The devices were not donated by the company; they were acquired by our hospital at the regular market cost in Germany. None of the authors has a financial agreement with the company Ventrica. All authors had full control of the design of the study, methods used, outcome parameters, analysis of the data, and production of the written report.


   Footnotes
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Disclaimer The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.


   References
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 Abstract
 Introduction
 Patients and Methods
 Device Description
 Delivery Technique
 Results
 Comment
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 Footnotes
 References
 

  1. Vicol C, Nollert G, Mair H, et al. Midterm results of beating heart surgery in 1-vessel diseaseminimally invasive direct coronary artery bypass versus off-pump coronary artery bypass with full sternotomy. Heart Surg Forum 2003;6:341-344.[Medline]
  2. Scheltes JS, van Andel CJ, Pistecky PV, Borst C. Coronary anastomotic devicesblood-exposed non-intimal surface and coronary wall stress. J Thorac Cardiovasc Surg 2003;126:191-199.[Abstract/Free Full Text]
  3. Eckstein FS, Bonilla LF, Schaff H. Two generations of the St. Jude Medical ATG coronary connector systems for coronary artery anastomoses in coronary artery bypass grafting. Ann Thorac Surg 2002;74:S1363–7..
  4. Tozzi P, Stumpe F, Ruchat P. Preliminary clinical experience with the Heartflo anastomosis device Thorac Cardiov Surg 2001;49:279-282.
  5. Klima U, Falk V, Maringka M, et al. Magnetic vascular coupling for distal anastomosis in coronary artery bypass graftinga multicenter trial. J Thorac Cardiovasc Surg 2003;126:1568-1574.[Abstract/Free Full Text]
  6. Wolf RK, Alderman EL, Caskey MP, et al. Clinical and six-month angiographic evaluation of coronary arterial graft interrupted anastomoses by use of a self-closing clip devicea multicenter prospective clinical trial. J Thorac Cardiovasc Surg 2003;126:168-178.[Abstract/Free Full Text]
  7. Bar-El Y, Tio FO, Shofti R. An automatic suturless coronary anastomotic deviceinitial results of an animal study. Heart Surg Forum 2003;6:369-374.[Medline]
  8. Heijmen RH, Hinchliffe P, Borst C, et al. A novel one-shot anastomotic stapler prototype for coronary bypass grafting on the beating heartfeasibility in the pig. J Thorac Cardiovasc Surg 1999;117:117-125.[Abstract/Free Full Text]
  9. Solem JO, Boumzebra D, Al-Buraiki J, Nakeeb S, Rafeh W, Al-Halees Z. Evaluation of a new device for quick suturless coronary artery anastomosis in surviving sheep Eur J Cardiothorac Surg 2000;17:312-318.[Abstract/Free Full Text]
  10. Buijsrogge MP, Verlaan CWJ, Gründeman PF, Borst C. Briefly occlusive coronary anastomosis with tissue adhesive J Thorac Cardiovasc Surg 2003;125:385-390.[Abstract/Free Full Text]



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