Ann Thorac Surg 1999;67:1244-1245
© 1999 The Society of Thoracic Surgeons
Invited Commentary
Robert W. Emery, MDa
a Cardiac Surgical Associates, PA, 920 East 28th St, Suite 420, Minneapolis, MN 55407, USA,
Invited commentary
"Coronary Artery Bypass Grafting with an Expanded Polytetrafluoroethylene Graft" by Weyland and colleagues represents a single institution’s experience with a unique device to validate the use of prosthetic material in coronary artery bypass graft procedures. The holy grail of bypass procedures is the accomplishment of bypass grafts whose patency lasts the life of the patient. Ideally, because of the tissue disruption and inherent complications involved in harvesting internal conduits as well as individual variability in quality, conduits from "off the shelf" would be valuable. Historically, artificial grafts have only been used in dire situations and have been fraught with early failure rates. The causes of early failure relate to thrombogenicity of the artificial surface or biomaterial and stasis that occurs either because of the long length in a smaller diameter graft or the acute change in diameter when a larger graft is used to bypass a smaller coronary artery. To resolve these problems, flow must be maximized through the bypass graft, which could be expected to diminish the occurrence of stasis.
The development of the Perma-Flow graft represents a new concept to alter the physiology rather than the material of a prosthetic graft by maintaining constant flow. A venturi resistor is placed into the distal graft and a controlled arteriovenous fistula constructed. Coronary arteries are sewn proximal to the resistor in side-to-side fashion. The early and 1-year patency of this graft is nearly equal to that of saphenous veins. Weyand and coworkers confirm this experience indicating that in situations in which inadequate conduit exists, the Perma Flow graft may be of value to achieve complete revascularization. Several important points are raised in this contribution. (1) The venous portion of the graft should be connected to the superior vena cava as opposed to the trabeculated right atrium. (2) Vessels with high-grade rather than moderate-grade stenoses should be bypassed with the Perma Flow to minimize competitive flow. (3) Anatomic configuration is important in maintaining graft—arterial patency. (4) Patency of the arteriovenous fistula correlates with patency of the arterial anastomoses. Thus, the selection of arteries that are to be bypassed by the Perma Flow rather than residual native conduit may need to be revised from present concepts. Larger, more highly stenotic right and anterior descending branch arteries may be the vessels of choice for Perma-Flow use, and smaller, moderately diseased circumflex and the left anterior descending arteries may be more appropriate for residual native conduit.
Since the revitalization of radial artery grafting, the need for such a graft has diminished. In recent trials, the patency of the Perma Flow graft has diminished because this graft has been used in most instances to complete revascularization of smaller vessels rather than to bypass the major coronary arteries. As the Perma Flow graft has been used of late for secondary and tertiary branches, patency can be expected to be somewhat diminished, but nonetheless, the Perma Flow graft remains a viable alternative in patients with inadequate conduits especially as new information improves vessel selection. This device has been approved for use on a limited basis with humanitarian device exemption in patients who have inadequate conduits. Ongoing research in the use of prosthetic grafts, the selection of patients who would benefit, and critical definition of criteria for suitable vessels is warranted.
Related Article
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Coronary artery bypass grafting with an expanded polytetrafluoroethylene graft
- Michael Weyand, Sebastian Kerber, Christof Schmid, Norbert Rolf, and Hans H. Scheld
Ann. Thorac. Surg. 1999 67: 1240-1244.
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