Antithrombotic Therapy in Peripheral Arterial Occlusive Disease: Peripheral Vascular Reconstructive Surgery
Because of the lack of level I studies, few conclusions can be drawn from the data except that thrombotic or embolic arterial occlusive lesions may be lysed by regional thrombolytic therapy, especially when given within 2 weeks. Chronic thromboatherosclerotic lesions are less responsive than thromboembolic occlusions and usually require adjunctive balloon angioplasty or surgery to prevent rethrombosis. In the latter circumstance, thrombolytic therapy preceding surgery might improve outcomes by clearly defining offending lesions and the distal arterial anatomy, as well as improving outflow and collateral circulation. Thrombolytic therapy appears most useful for distal thromboembolic occlusions in surgically inaccessible small arteries of the forearm, hand, leg, and foot, or in patients who are too ill to undergo surgery. In patients with acute renal or visceral arterial emboli identified at angiography, direct thrombolytic therapy may rarely achieve more rapid reperfusion than surgical thrombectomy. buying antibiotics online
There have been recent reports of intraoperative intra-arterial thrombolytic therapy in patients undergoing thromboembolectomy (level IV to V studies). Streptokinase, urokinase, and rtPA have all been used in varying doses being instilled directly into the distal arterial tree after balloon-catheter embolectomy. Early reports are encouraging and demonstrate angiographic evidence of improved clearance of distal thromboemboli not accessible to catheter thrombectomy with no apparent increase in bleeding complications. Some have found that additional thrombi could be mechanically removed following intra-arterial thrombolytic therapy. Whether this approach will lead to improved limb salvage is unknown. The only randomized trial to date comparing placebo and different dosages of intra-arterial urokinase infusion during lower limb revascularization documented the safety of this adjunct, but could detect no improvement in clinical outcomes (level II).
Peripheral Vascular Reconstructive Surgery
Vein Grafts and Arterial Prostheses
The superior patency of vein grafts is documented by a single level I, multicenter, randomized trial comparing saphenous vein grafts with expanded polytetrafluoroethyl-ene (PTFE) prostheses for lower-extremity arterial reconstructions. The primary patency rate at 4 years for infrapopliteal bypasses with saphenous vein was 49%, significantly better than the 12% patency rate with PTFE bypasses (p < 0.001). While demonstrating clear differences between vein and prosthetic bypasses, this trial is also notable because it documented that even expert surgeons had failure rates that were alarmingly high. More recent series demonstrate improved patency rates with no major differences between reversed and nonreversed’ in situ vein grafts in which the valves are rendered incompetent. In the absence of venous conduits, placement of arterial prostheses may be necessary, and most randomized trials evaluating available materials would indicate that human umbilical vein grafts have slightly better patency than PTFE. The variable patency of all lower-extremity arterial bypasses, regardless of the type of bypass conduit, suggests the need for adjunctive antithrombotic therapy.