Background . We report our experience with the Perma-Flow aortocoronary-right heart graft in 15 patients in whom autologous conduits were not available.

Methods . Fifteen patients received 39 coronary anastomoses-10 to left anterior descending coronary artery branches, 15 to circumflex coronary artery branches, and 14 to branches of the right coronary artery. Early angiography was done in 11 patients.

Results . One patient died on postoperative day 17 of multiorgan failure. The graft was patent at postmortem examination. Of 30 coronary anastomoses at risk, 24 were patent. Three connections to the left anterior descending system were occluded in patients with an additional internal mammary artery graft to the same coronary system, and three connections to the circumflex system were occluded in patients with a history of major posterior infarction. Three of five distal anastomoses to the right atrial appendage were occluded, whereas all six connections to the superior vena cava were patent. None of the patients had shown recurrent angina at a mean follow-up of 10.9 months (range, 2−39 months).

Conclusions . The synthetic Perma-Flow coronary graft appears to be a safe alternative in patients in whom arterial or venous conduits are not available. Competitive flow may lead to anastomotic occlusions. The appropriate site for the distal arteriovenous fistula seems to be the superior vena cava.

 

 

Many cardiac surgical institutions in the Western world are seeing an increasing number of patients who are referred for redo procedures for failed aortocoronary bypass grafts or who have had complete saphenectomies for other reasons. In most cases, arterial grafts including the gastroepiploic artery, the epigastric artery, and the radial artery serve well as alternatives [1] [2] [3] . When no arterial or venous conduits are available, bovine internal mammary arteries and polymer grafts have been used, but early and long-term patency has not proved satisfactory.

Recently, an expanded polytetrafluoroethylene graft has been developed for use in aortocoronary bypass procedures [4] . The tube graft, which has a lumen of 5 mm, is implanted in order to create a fistula between the aorta and the right atrial or the superior vena cava. A Venturi valve at the distal end functions as a flow resistor by maintaining a continuous but diminished blood flow from the aorta across the coronary branches to the superior vena cava or right atrium, thus preventing early graft thrombosis.

We [5] and others [6] [7] have reported initial success with the use of this Perma-Flow prosthesis in the aortocoronary-right heart position in patients in whom alternatives were not available. This report describes the technique for creating the side-to-side anastomoses to the various branches of the coronary tree and summarizes our experience with our first 15 patients.

During the past 3 years, 2,456 coronary artery bypass grafting procedures have been performed at our institution. Of these, 348 (14.2%) were the second, third, or fourth surgical procedure. In general, all patients received either one or two single internal mammary artery grafts; gastroepiploic artery grafts, radial artery grafts, or saphenous vein grafts were added if necessary. The inferior epigastric artery has not proved a reliable conduit in our hands. If angiographic evaluation demonstrated insufficient collateralization in the palmar tree, we did not use the radial artery . [Figure 1] Similarly, if a patient had a previous upper laparotomy, the gastroepiploic artery was not used. In 15 patients, we applied the Perma-Flow prosthesis (Baxter Europe, Munich, Germany) exclusively (n = 3) or in combination with the left internal mammary artery (n = 12) . [Table 1] In 1 patient, use of the prosthetic coronary graft was combined with aortic valve replacement.

After induction of general anesthesia, the patient was placed in a supine position. A standard median sternotomy was performed, and, if it was to be used, the left internal mammary artery was harvested. Systemic heparinization was achieved with heparin sulfate, 400 U/kg, and cardiopulmonary bypass was instituted with an aortic cannula and a two-stage right atrial cannula. Except for patient 9, all procedures were performed under normothermic conditions. Ventricular fibrillation was electrically induced, and the distal ascending aorta was clamped. Myocardial protection consisted of an initial infusion of 1,000 mL of Bretschneider's solution through the aortic root and infusions every 30 minutes if necessary.

All distal coronary artery anastomoses with the synthetic graft were performed first. Usually we started with branches of the right coronary artery. After elevation of the heart, the coronary vessel was dissected, and an arteriotomy of 4 to 5 mm long was made. The graft was placed in the pericardium around the heart so as to allow for a later anastomosis to the superior vena cava and ascending aorta . [Figure 2] At the appropriate sites, the graft was incised longitudinally, the length of the incision corresponding to the arteriotomy (4 to 5 mm). Thus, the anastomosis could be performed in a diamond-shaped fashion with a running 6−0 polypropylene suture attached to a small needle (Prolene and BB needle; Ethicon, Norderstedt, Germany). This technique keeps the anastomosis open by inherent stretch. The 6−0 suture was chosen because the thickness of the needle and the suture is equal, which minimizes bleeding from stitch sites.

After the completion of all coronary artery anastomoses with the Perma-Flow graft, the left internal mammary artery was anastomosed with the left anterior descending coronary artery or its first diagonal branch if necessary. The aortic cross-clamp was released, and the proximal end of the artificial prosthesis was connected to the ascending aorta. Flow through the graft was and filling of the coronary arteries were visualized. Finally, the distal end of the graft was connected to either the right atrial appendage (n = 6) or the superior vena cava (n = 9) depending on the available length. A completed procedure is shown in . [Figure 3] To maintain a sufficient runoff to the coronary arteries, all patients received at least two distal anastomoses with the Perma Flow (mean number, 2.6 anastomoses). After reperfusion and rewarming, all patients were weaned from cardiopulmonary bypass without difficulty. Mean aortic cross-clamp time was 33.2 minutes and mean duration of cardiopulmonary bypass, 54.3 minutes.

            All patients had an uneventful early postoperative course without electrocardiographic or serologic signs of perioperative myocardial infarction. Blood loss during the first 24 hours averaged 784 mL; no patient required reexploration for bleeding. All patients were extubated and mobilized on the first postoperative day, and 13 of them were discharged to rehabilitation facilities within 10 days after operation. The remaining 2 required a second period of intensive care treatment for imminent multiorgan failure after gastrointestinal complications and laparotomy. One of these patients died on day 17; the aortic and coronary artery anastomoses were patent at postmortem examination. The anastomosis to the right atrium was occluded, as was the Venturi resistor.

Informed consent for early postoperative control angiography was obtained from 11 patients. Angiography was performed between 4 and 12 weeks after operation . [Figure 4] Including the aortic and right heart anastomoses, there were 52 Perma-Flow anastomoses, 30 of them connecting the graft to native coronary arteries. The aortic anastomosis was open in all patients, whereas the right heart anastomosis including the valve was occluded in three instances, all to the right atrial appendage. Runoff was preserved in all 24 patients with a connection to the superior vena cava. Open Perma-Flow-coronary artery anastomoses were found in 24 (80%) of 30 instances.

The distribution of the anastomoses to the branches of the coronary tree is shown in . [Table 2] Of seven anastomoses to the left anterior descending coronary artery system, three were occluded. All were in patients in whom the native left anterior descending coronary artery was grafted with the internal mammary artery, and the Perma-Flow connected to the first diagonal branch. Of 11 anastomoses to marginal branches of the left circumflex system, again three were occluded. All connections to the right coronary system were patent. In addition, seven of eight internal mammary artery grafts were patent; the one oriented to the first diagonal branch was occluded. None of the patients had signs of recurrent angina during follow-up of up to 39 months.

In the past decade, synthetic polymer grafts of various kinds have been used when no alternatives were apparent [8] [9] [10] . However, the resulting patency rate and early mortality did not permit widespread use. The same experience was had with prepared bovine mammary artery [11] . Unsatisfactory patency rates were also obtained with the use of arm veins as alternatives to saphenous vein [12] and with synthetic grafts without valves [13] [14] .

The augmentation of blood flow by inherent arterial shunts is a well-known method in vascular surgery of the lower limbs. This same principle was considered in the Perma-Flow prosthesis by including a Venturi mechanism between the coronary and the caval or atrial anastomosis. The Venturi valve acts as a resistor to control and maintain blood flow from the aorta to the right heart.

Initially we and others have used the Perma-Flow prosthesis in patients in whom no venous or arterial alternatives were available because of use in previous coronary artery bypass grafting procedures, complete saphenectomies, upper laparotomies, or insufficient collateralization of the palmar tree [5] [6] [7] . However, in their review of the North American experience, Emery and co-workers [7] wrote that the use of the synthetic graft may be expanded because of its proven reliability. In contrast, our experience, demonstrates a slightly higher occlusion rate for the various anastomoses, 20% versus 9.5%, but also suggests that use of the graft is safe and simple.

Some conclusions can be drawn from our findings of patent and occluded anastomoses. First, a connection between the distal end of the graft and the superior vena cava appears better than one to the right atrial appendage. This may be due to the trabeculation of the atrial appendage, which can cause a second resistance to flow after the Venturi valve, and result in thrombosis of the shunt. In addition, these occlusions do not necessarily cause thrombosis of the entire graft, most likely because of sufficient runoff to the coronary tree. Second, in regard to occlusion of coronary connections, a sufficient amount of runoff to the myocardium from the specific branch may be of even greater importance than in arterial conduits. We noted occlusions to the left anterior descending coronary artery system only in patients in whom an arterial anastomosis was performed to this same system. Revascularization of this artery and a major diagonal branch was performed only in patients with substantial proximal branch stenosis. However, it may be important whether these are subtotal or not. Occlusion in the circumflex system occurred only in patients who had a history of major posterior infarction. On the other hand, all anastomoses to the right coronary artery were patent, which suggests sufficient runoff. This finding is consistent with one in a previous report by our group [15] dealing with polytetrafluoroethylene grafts without valves to the right coronary system; these grafts also showed long-term patency.

Polytetrafluoroethylene, as used in this prosthesis as well as in any other vascular setting, expands. This allows a small, but nevertheless considerable amount of elasticity in the longitudinal direction. In a radial direction, the graft displays even more elasticity. Therefore we placed all sequential anastomoses in a diamond-shaped fashion with only a small amount of extra length between the coronary arteries. Because of the inherent tension on the edges, this kind of crossed anastomosis keeps the anastomosis open. The length of the arterial incision is roughly 5 to 6 mm. This corresponds to a graft circumference of 18.4 mm. When we followed these rules, we did not observe distortions of the graft at the anastomotic sites.

In summary, we have demonstrated a satisfactory low mortality rate (6.6%), a very low perioperative infection rate (0% to date), and a sufficiently high patency rate (80%) in the early and intermediate follow-up. None of our patients has recurrent angina or has required a repeat grafting procedure. We agree with Emery and co-workers [7] that use of this graft may be widened in future.

 

 

 

1.Acar C., Jebara V.A., Portoghese M.. Revival of the radial artery for coronary artery bypass grafting. Ann Thorac Surg 1992;54:652−660.

2.Buikema H., Grandjean J.G., van den Broek S., van Gilst W.H., Lie K.J., Wesseling H.. Differences in vasomotor control between human gastroepiploic and left internal mammary artery. Circulation 1992;86:205−209.

3.Canver C.C.. Conduit options in coronary artery bypass surgery. Chest 1995;108:1150−1155.

4.Drasler W.J., Jenson M.L., George S.A.. A unique vascular graft concept for coronary and peripheral application. ASAIO Trans 1988;34:769−772.

5.Schmid C., Weyand M., Kerber S., Breithard G., Scheld H.H.. The use of a Perma-Flow graft for coronary artery bypass surgery. Eur J Cardio-thorac Surg 1996;10:284−286.

6.Emery R.W., Petersen R.J., Baumgard C., Nicoloff D.M.. First clinical use of the Possis synthetic coronary graft. J Cardiac Surg 1993;8:439−442.

7.Emery R.W., Mills N.L., Teijeira F.J.. North American experience with the Perma-Flow prosthetic coronary graft. Ann Thorac Surg 1996;62:691−696.

8.Jones E.L.. Conduits for coronary artery bypass [Key References]. Ann Thorac Surg 1993;55:194−195.

9.Chard R.B., Johnson D.C., Nunn G.R.. Aortocoronary bypass grafting with polytetrafluoroethylene conduits. Early and late outcome in eight patients. J Thorac Cardiovasc Surg 1987;94:132−134.

10.Suavage L.R., Schloemer R., Wood S.J., Logan G.. Successful interposition synthetic graft between aorta and right coronary artery. Angiographic follow-up to sixteen months. J Thorac Cardiovasc Surg 1976;72:418−421.

11.Mitchell I.M., Essop A.R., Scott P.J.. Bovine internal mammary artery as a conduit for coronary revascularization. Ann Thorac Surg 1993;55:120−122.

12.Stoney W.S., Alford W.C., Burrus G.R., Glassford D.M., Petracek M.R., Thomas C.S.. The fate of arm veins used for aorta-coronary bypass grafts. J Thorac Cardiovasc Surg 1984;88:522−526.

13.Sapsford R.N., Oakley G.D., Talbot S.. Early and late patency of expanded polytetrafluoroethylene vascular grafts in aorta-coronary bypass. J Thorac Cardiovasc Surg 1981;81:860−864.

14.Scheld H.H., Gцrlach G., Moosdorf R., Loskot F., Hehrlein F.W.. PTFE grafts to the right coronary artery following endarterectomy. Herz 1987;12:237−240.

15.Kerber S., Baumbach M., Rahmel A., Weyand M., Scheld H.H., Breithardt G.. Clinical and invasive 7−month follow-up of a patient with a synthetic coronary graft. Int J Cardiol 1995;51:143−147.

 

 

 

 

Background . We report our experience with the Perma-Flow aortocoronary-right heart graft in 15 patients in whom autologous conduits were not available.

Methods . Fifteen patients received 39 coronary anastomoses-10 to left anterior descending coronary artery branches, 15 to circumflex coronary artery branches, and 14 to branches of the right coronary artery. Early angiography was done in 11 patients.

Results . One patient died on postoperative day 17 of multiorgan failure. The graft was patent at postmortem examination. Of 30 coronary anastomoses at risk, 24 were patent. Three connections to the left anterior descending system were occluded in patients with an additional internal mammary artery graft to the same coronary system, and three connections to the circumflex system were occluded in patients with a history of major posterior infarction. Three of five distal anastomoses to the right atrial appendage were occluded, whereas all six connections to the superior vena cava were patent. None of the patients had shown recurrent angina at a mean follow-up of 10.9 months (range, 2−39 months).

Conclusions . The synthetic Perma-Flow coronary graft appears to be a safe alternative in patients in whom arterial or venous conduits are not available. Competitive flow may lead to anastomotic occlusions. The appropriate site for the distal arteriovenous fistula seems to be the superior vena cava.

 

 

Many cardiac surgical institutions in the Western world are seeing an increasing number of patients who are referred for redo procedures for failed aortocoronary bypass grafts or who have had complete saphenectomies for other reasons. In most cases, arterial grafts including the gastroepiploic artery, the epigastric artery, and the radial artery serve well as alternatives [1] [2] [3] . When no arterial or venous conduits are available, bovine internal mammary arteries and polymer grafts have been used, but early and long-term patency has not proved satisfactory.

Recently, an expanded polytetrafluoroethylene graft has been developed for use in aortocoronary bypass procedures [4] . The tube graft, which has a lumen of 5 mm, is implanted in order to create a fistula between the aorta and the right atrial or the superior vena cava. A Venturi valve at the distal end functions as a flow resistor by maintaining a continuous but diminished blood flow from the aorta across the coronary branches to the superior vena cava or right atrium, thus preventing early graft thrombosis.

We [5] and others [6] [7] have reported initial success with the use of this Perma-Flow prosthesis in the aortocoronary-right heart position in patients in whom alternatives were not available. This report describes the technique for creating the side-to-side anastomoses to the various branches of the coronary tree and summarizes our experience with our first 15 patients.

During the past 3 years, 2,456 coronary artery bypass grafting procedures have been performed at our institution. Of these, 348 (14.2%) were the second, third, or fourth surgical procedure. In general, all patients received either one or two single internal mammary artery grafts; gastroepiploic artery grafts, radial artery grafts, or saphenous vein grafts were added if necessary. The inferior epigastric artery has not proved a reliable conduit in our hands. If angiographic evaluation demonstrated insufficient collateralization in the palmar tree, we did not use the radial artery . [Figure 1] Similarly, if a patient had a previous upper laparotomy, the gastroepiploic artery was not used. In 15 patients, we applied the Perma-Flow prosthesis (Baxter Europe, Munich, Germany) exclusively (n = 3) or in combination with the left internal mammary artery (n = 12) . [Table 1] In 1 patient, use of the prosthetic coronary graft was combined with aortic valve replacement.

After induction of general anesthesia, the patient was placed in a supine position. A standard median sternotomy was performed, and, if it was to be used, the left internal mammary artery was harvested. Systemic heparinization was achieved with heparin sulfate, 400 U/kg, and cardiopulmonary bypass was instituted with an aortic cannula and a two-stage right atrial cannula. Except for patient 9, all procedures were performed under normothermic conditions. Ventricular fibrillation was electrically induced, and the distal ascending aorta was clamped. Myocardial protection consisted of an initial infusion of 1,000 mL of Bretschneider's solution through the aortic root and infusions every 30 minutes if necessary.

All distal coronary artery anastomoses with the synthetic graft were performed first. Usually we started with branches of the right coronary artery. After elevation of the heart, the coronary vessel was dissected, and an arteriotomy of 4 to 5 mm long was made. The graft was placed in the pericardium around the heart so as to allow for a later anastomosis to the superior vena cava and ascending aorta . [Figure 2] At the appropriate sites, the graft was incised longitudinally, the length of the incision corresponding to the arteriotomy (4 to 5 mm). Thus, the anastomosis could be performed in a diamond-shaped fashion with a running 6−0 polypropylene suture attached to a small needle (Prolene and BB needle; Ethicon, Norderstedt, Germany). This technique keeps the anastomosis open by inherent stretch. The 6−0 suture was chosen because the thickness of the needle and the suture is equal, which minimizes bleeding from stitch sites.

After the completion of all coronary artery anastomoses with the Perma-Flow graft, the left internal mammary artery was anastomosed with the left anterior descending coronary artery or its first diagonal branch if necessary. The aortic cross-clamp was released, and the proximal end of the artificial prosthesis was connected to the ascending aorta. Flow through the graft was and filling of the coronary arteries were visualized. Finally, the distal end of the graft was connected to either the right atrial appendage (n = 6) or the superior vena cava (n = 9) depending on the available length. A completed procedure is shown in . [Figure 3] To maintain a sufficient runoff to the coronary arteries, all patients received at least two distal anastomoses with the Perma Flow (mean number, 2.6 anastomoses). After reperfusion and rewarming, all patients were weaned from cardiopulmonary bypass without difficulty. Mean aortic cross-clamp time was 33.2 minutes and mean duration of cardiopulmonary bypass, 54.3 minutes.

            All patients had an uneventful early postoperative course without electrocardiographic or serologic signs of perioperative myocardial infarction. Blood loss during the first 24 hours averaged 784 mL; no patient required reexploration for bleeding. All patients were extubated and mobilized on the first postoperative day, and 13 of them were discharged to rehabilitation facilities within 10 days after operation. The remaining 2 required a second period of intensive care treatment for imminent multiorgan failure after gastrointestinal complications and laparotomy. One of these patients died on day 17; the aortic and coronary artery anastomoses were patent at postmortem examination. The anastomosis to the right atrium was occluded, as was the Venturi resistor.

Informed consent for early postoperative control angiography was obtained from 11 patients. Angiography was performed between 4 and 12 weeks after operation . [Figure 4] Including the aortic and right heart anastomoses, there were 52 Perma-Flow anastomoses, 30 of them connecting the graft to native coronary arteries. The aortic anastomosis was open in all patients, whereas the right heart anastomosis including the valve was occluded in three instances, all to the right atrial appendage. Runoff was preserved in all 24 patients with a connection to the superior vena cava. Open Perma-Flow-coronary artery anastomoses were found in 24 (80%) of 30 instances.

The distribution of the anastomoses to the branches of the coronary tree is shown in . [Table 2] Of seven anastomoses to the left anterior descending coronary artery system, three were occluded. All were in patients in whom the native left anterior descending coronary artery was grafted with the internal mammary artery, and the Perma-Flow connected to the first diagonal branch. Of 11 anastomoses to marginal branches of the left circumflex system, again three were occluded. All connections to the right coronary system were patent. In addition, seven of eight internal mammary artery grafts were patent; the one oriented to the first diagonal branch was occluded. None of the patients had signs of recurrent angina during follow-up of up to 39 months.

In the past decade, synthetic polymer grafts of various kinds have been used when no alternatives were apparent [8] [9] [10] . However, the resulting patency rate and early mortality did not permit widespread use. The same experience was had with prepared bovine mammary artery [11] . Unsatisfactory patency rates were also obtained with the use of arm veins as alternatives to saphenous vein [12] and with synthetic grafts without valves [13] [14] .

The augmentation of blood flow by inherent arterial shunts is a well-known method in vascular surgery of the lower limbs. This same principle was considered in the Perma-Flow prosthesis by including a Venturi mechanism between the coronary and the caval or atrial anastomosis. The Venturi valve acts as a resistor to control and maintain blood flow from the aorta to the right heart.

Initially we and others have used the Perma-Flow prosthesis in patients in whom no venous or arterial alternatives were available because of use in previous coronary artery bypass grafting procedures, complete saphenectomies, upper laparotomies, or insufficient collateralization of the palmar tree [5] [6] [7] . However, in their review of the North American experience, Emery and co-workers [7] wrote that the use of the synthetic graft may be expanded because of its proven reliability. In contrast, our experience, demonstrates a slightly higher occlusion rate for the various anastomoses, 20% versus 9.5%, but also suggests that use of the graft is safe and simple.

Some conclusions can be drawn from our findings of patent and occluded anastomoses. First, a connection between the distal end of the graft and the superior vena cava appears better than one to the right atrial appendage. This may be due to the trabeculation of the atrial appendage, which can cause a second resistance to flow after the Venturi valve, and result in thrombosis of the shunt. In addition, these occlusions do not necessarily cause thrombosis of the entire graft, most likely because of sufficient runoff to the coronary tree. Second, in regard to occlusion of coronary connections, a sufficient amount of runoff to the myocardium from the specific branch may be of even greater importance than in arterial conduits. We noted occlusions to the left anterior descending coronary artery system only in patients in whom an arterial anastomosis was performed to this same system. Revascularization of this artery and a major diagonal branch was performed only in patients with substantial proximal branch stenosis. However, it may be important whether these are subtotal or not. Occlusion in the circumflex system occurred only in patients who had a history of major posterior infarction. On the other hand, all anastomoses to the right coronary artery were patent, which suggests sufficient runoff. This finding is consistent with one in a previous report by our group [15] dealing with polytetrafluoroethylene grafts without valves to the right coronary system; these grafts also showed long-term patency.

Polytetrafluoroethylene, as used in this prosthesis as well as in any other vascular setting, expands. This allows a small, but nevertheless considerable amount of elasticity in the longitudinal direction. In a radial direction, the graft displays even more elasticity. Therefore we placed all sequential anastomoses in a diamond-shaped fashion with only a small amount of extra length between the coronary arteries. Because of the inherent tension on the edges, this kind of crossed anastomosis keeps the anastomosis open. The length of the arterial incision is roughly 5 to 6 mm. This corresponds to a graft circumference of 18.4 mm. When we followed these rules, we did not observe distortions of the graft at the anastomotic sites.

In summary, we have demonstrated a satisfactory low mortality rate (6.6%), a very low perioperative infection rate (0% to date), and a sufficiently high patency rate (80%) in the early and intermediate follow-up. None of our patients has recurrent angina or has required a repeat grafting procedure. We agree with Emery and co-workers [7] that use of this graft may be widened in future.

 

 

 

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