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Ann Thorac Surg 2004;78:1878-1879
© 2004 The Society of Thoracic Surgeons

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Correspondence

Reply

Clinic for Cardiovascular Surgery, University Hospital Zürich, Rämistrasse 100, CH-8091 Zürich, Switzerland

oliver.reuthebuch{at}usz.ch

To the Editor:

We appreciate the interesting remarks of Matschke and associates regarding their findings of early graft occlusion using the Symmetry connector device. According to recently published reports [1–3] it appears that the occlusion or high-grade stenosis of saphenous vein grafts in coronary artery bypass grafting procedures done with the use of the Symmetry connector seems to occur at the level of the device, thus confirming our reported findings [4].

The rationale for these alarming observations is still unclear and is the subject of an ongoing debate. Currently, the following explanations are under discussion:

1. Intimal damage occurs during insertion of the vein transfer sheath.
   
2. Because of the particular design of the Symmetry connector, the vein graft has to be implanted perpendicular to the aorta, and any deviation could result in graft kinking and subsequent stenosis. To date, no angiographic data implicating graft kinking as the reason for bypass occlusion have been published.
   
3. The diameter of the orifice of the proximal anastomosis can be reduced as a result of improper determination of vessel diameter and wall thickness or simply by remnants of adventitial tissue.
   
4. The occlusion or stenosis is caused by the thrombogenic Nitinol surface of the connector, an explanation based on the initial results of coronary stenting, which showed acute thrombosis of uncovered Nitinol. A subsequent antiplatelet regimen with clopidogrel bisulfate or ticlopidine hydrochloride could significantly reduce the restenosis rate [5].
   

The anticoagulation protocol described by Matschke and co-workers addresses this potential mechanism of induced thrombogenicity by the Nitinol surface of the connector. In animal studies [6], implanted St. Jude medical connectors showed a complete neointimal covering after only 30 days, with no subsequent progression after 90 and 180 days. These findings suggest that after a period of 30 days, the implanted Nitinol surface might be covered, and thus thrombosis would not occur. However, in our series and in several reports, occlusions developed well beyond 30 days postoperatively, with 1 patient readmitted to the hospital because of angina 31 months after operation. Angiography revealed an occluded proximal connector, which was successfully dilated.

In summary, we believe that antiplatelet therapy is mandatory in patients with connector devices made of Nitinol. We are aware that this regimen addresses only one potential cause of stenosis or occlusion. Because of the convincing results of thrombosis prevention with clopidogrel or ticlopidine after stenting we do not think anticoagulation is necessary after implantation of a Nitinol connector. However, given our findings, we recommend strongly that antiplatelet therapy be continued more than 3 months postoperatively.

References

1. Hornik L, Tenderich G, Minami K, et al. First experience with the St Jude Medical, Inc, Symmetry Bypass System (Aortic Connector System). J Thorac Cardiovasc Surg. 2003;125:414–417[Free Full Text]
2. Traverse JH, Mooney MR, Pedersen WR, et al. Clinical, angiographic and interventional follow-up of patients with aortic–saphenous vein graft connectors. Circulation. 2003;108:452–456[Abstract/Free Full Text]
3. Donsky AS, Schussler JM, Donsky MS, Roberts WC, Hamman BL. Thrombotic occlusion of the aortic ostia of saphenous venous grafts early after coronary artery bypass grafting by using the Symmetry aortic connector system. J Thorac Surg. 2002;124:397–399[Free Full Text]
4. Reuthebuch OT, Kadner A, Lachat ML, Turina MI. Graft occlusion after deployment of the Symmetry Bypass System. Ann Thorac Surg. 2003;75:1626–1629[Abstract/Free Full Text]
5. Schömig A, Neumann FJ, Kastrati A, et al. A randomized comparison of antiplatelet and anticoagulant therapy after the placement of coronary-artery stents. N Engl J Med. 1996;334:1084–1089[Abstract/Free Full Text]
6. Bonilla LF, Sullivan DJ. New approaches for vascular anastomoses. Curr Interv Cardiol Rep. 2001;3:44–49[Medline]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Alexander Kadner Marko I. Turina Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Reuthebuch, O. Articles by Turina, M. I. Search for Related Content PubMed Articles by Reuthebuch, O. Articles by Turina, M. I.