Protection of the internal mammary artery pedicle with polytetrafluoroethylene membrane.

With increasing frequency, reoperative coronary artery bypass surgery is being performed in the setting of a patent internal mammary artery (IMA) graft. Injury to the IMA graft at reoperation can result in ischemic myocardial injury and cardiac arrest. This descriptive laboratory study examined use of a polytetrafluoroethylene (PTFE) membrane wrap to protect the IMA pedicle during sternal reentry. Six pigs (25-30 kg) underwent median sternotomy and takedown of left and right IMAs. Grafts were implanted in the epicardium by a modified Vineberg procedure. In each animal, one IMA was wrapped circumferentially with PTFE, while the contralateral bare IMA served as the control. Redo sternotomy was performed 3 months later. Severe adhesions between chest wall, myocardium, and bare IMA grafts were encountered in six of six animals. PTFE-wrapped IMAs were easily identified by appearance and by palpation. There was no adherence between PTFE membranes and surrounding tissue, nor was there evidence of cellular infiltration, disruption, or contraction of the membrane. Most notably, PTFE membranes could not be cut or injured with the electrocautery, since they are electrical nonconductors. This study demonstrates that PTFE membrane: (1) is relatively inert and incites minimal surrounding tissue reaction; and (2) is impenetrable to electrocautery injury. Further studies are necessary to determine the impact of PTFE membrane on IMA graft patency and wound infection. PTFE membrane may prove clinically useful in protecting patent IMA pedicles during reoperative cardiac surgery.