Acute Limb Ischemia Surgical Options
Can a surgical approach achieve a higher limb salvage rate, or is thrombolysis a safer and less invasive procedure?
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Acute limb arterial thrombosis is both limb and life threatening. Treatment options include surgical intervention and thrombolysis. Many surgeons still consider surgery to be the best treatment option, despite reports of high mortality (20% to 30%) and morbidity.1-3 Limb salvage rates are as low as 60%.1,4 Because of these statistics, many physicians favor the alternative approach of intra-arterial thrombolysis. Proponents of thrombolysis have been criticized for the lack of studies involving controls or standardized reporting practices. The Society of Cardiovascular and Interventional Radiology has recently published a document outlining the reporting standards for acute limb ischemia studies, which should help to clarify the results of future studies.5
In 1996, Weaver et al randomized patients with subacute symptoms attributable to thrombotic native artery occlusion to undergo either thrombolysis or surgery, and found that surgery was more effective as well as more durable.6 Other randomized studies suggest that thrombolysis may be a more beneficial treatment plan, although the optimal approach has not been established.7 A recent Cochrane review suggests that there was no difference between surgery and thrombolysis at 1 year.8 The study by Weaver et al led to a retrospective review of the surgical outcomes for acute limb-threatening ischemia in Leicester, UK.9
Pemberton et al reviewed the case histories of all patients with acute limb-threatening ischemia who were admitted to a dedicated vascular unit over a 6-year period. Ischemia was defined as per the ad hoc committee on reporting standards of the Society for Vascular Surgery/North American Chapter, International Society for Cardiovascular Surgery. Exclusion criteria included patients whose limbs were deemed unsalvageable and those with a history of trauma or previous reconstruction.
The interventionalists performed preoperative imaging using arteriography or color-duplex ultrasound. Unless imaging dictated otherwise, the patients underwent initial thrombectomy through an appropriate vessel arteriotomy. Following successful thrombectomy (determined by completion angiography and the appearance of the limb), the patients received an intravenous heparin infusion before the introduction of warfarin therapy 2 days later.
When patients’ inflow could not be restored, the physician performed revascularization, usually in the form of a crossover graft. In cases of failed distal thrombus retrieval, on-table arteriography was used to determine a vessel for immediate distal reconstruction. If the physician was unable to identify a continuous vessel, he would infuse 100,000 units of streptokinase in 100 mL of normal saline over 30 minutes into the popliteal or crural vessel, using an occlusive clamp applied proximally. The interventionalist either repeated this treatment or performed subsequent arterial reconstruction, depending on the postthrombolysis arteriogram. Patients were returned to the OR postoperatively for the following reasons: (1) concern regarding limb viability; (2) to undergo fasciotomy; (3) further thrombectomy; (4) reconstruction; or (5) amputation.
The study comprised 174 patients with a median age of 74 years (range: 29 to 92 years). There was an equal gender distribution (89 male, 85 female). All patients were admitted with native-vessel, limb-threatening ischemia thought to be salvageable. Of these, 132 patients (145 limbs, 76%) were admitted with acute lower limb ischemia and 42 (42 limbs, 24%) presented with upper limb ischemia. In terms of comorbidity, 25 patients (14%) were diabetic, 72 (41%) had a history of ischemic heart disease, and 28 (16%) had a history of a previous cerebrovascular event.
Pemberton et al identified a potential source of embolization in 107 patients (61%) and obtained preoperative duplex ultrasound imaging in 48 patients who presented with lower limb ischemia (36%). The median duration of ischemia was 14 hours (range, 1-336 hours); 47% presented with a history that lasted less than 12 hours. In patients with lower limb ischemia, the femoral pulse was absent in 32%. Most patients (135 of 174, 78%) had some form of neurological deficit at presentation (72% of upper limb patients and 80% of lower limb patients).
The surgeon performed either embolectomy or thrombectomy in 153 patients (89%) including all upper limbs, with immediate limb salvage in 110 cases (71%). Twenty-one patients (11%) underwent immediate vascular reconstruction (Table 1). After unsuccessful embolectomy/thrombectomy, the surgeon performed a further intervention in 36 patients. This treatment consisted of thrombolysis only in 22 patients, vascular reconstruction only in eight, and both thrombolysis and reconstruction in six patients (Table 2). There was radiological evidence of improvement in 19 of the 28 patients who received thrombolysis (68%), which significantly increased the chance of limb salvage (chi-squared test=7.83, degree of freedom=2, P<.02). There were no complications of thrombolysis.
Subsequently, 26 patients (15%) were returned to the OR; 14 required further embolectomy/thrombectomy, five underwent fasciotomy, and seven needed vascular reconstruction. In the first 30 postoperative days, 19 patients (9%) underwent an amputation of the affected limb.
Follow-up data were available for 98% of the patients, for a median time of 26 months (range, 0-104 months). The 30-day salvage rate for lower limb ischemia was 88% and 95% for the upper limb. The 30-day mortality rate was 26% for the lower limb and 21% for the upper limb. At 2 years, the limb salvage rate was 74% and 88% for lower and upper limb, respectively, and the survival rates were 49% and 44%.
Subgroup analysis identified particular factors that increased the risk of 30-day mortality rates. Patients with a New York Heart Association functional cardiac score of 3 or 4 (symptoms with usual activity or at rest) had a significantly higher 30-day mortality rate (chi-squared test=5.282, degree of freedom=1, P=.03). Patients with lower limb ischemia and aortoiliac occlusions had a significantly worse mortality rate than those with distal occlusions (chi-squared test=8.08, degree of freedom=1, P<.005). There was an insignificant trend toward higher 30-day mortality rates in patients with neurological deficits compared to those without (28% vs 17%). The duration of symptoms, a history of claudication, or the use of local anesthetics (n=90), did not affect the 30-day mortality rate.
Because acute limb ischemia poses risk to life and limb, the surgical outcome depends on the speed and completeness of the limb’s revascularization. There is considerable debate regarding the relative risks and benefits of endovascular techniques and immediate surgery. The perceived advantages of catheter-directed intra-arterial thrombolysis include a relatively atraumatic procedure, a gradual rather than sudden reperfusion effect, and direct visualization of the effected vessels.10 Uncontrolled studies have demonstrated that thrombolysis is safe and effective,11-13 but there have been very few prospective randomized studies.6,14,15 Furthermore, until recently, there have been no reporting standards for such studies.5
The TOPAS study, which consisted of 213 patients, showed that there were no demonstrable differences between thrombolysis and surgery in limb salvage or survival.14 This study was limited, however, because 40% of the patients presented with graft occlusions but only 27% (58 patients) were randomized to undergo surgery.
Weaver et al, reporting for the STILE investigators, showed that, in 237 patients with nonembolic native artery occlusions randomized to undergo thrombolysis or surgery, the latter option was more effective and more durable.6 Many of the patients presented with subacute symptoms, however, and only 14% presented within 14 days of the onset of symptoms.
Pemberton et al showed that immediate surgery resulted in limb salvage at 30 days and 2 years (88% and 76%, respectively).9 These statistics compare favorably with other thrombolysis and surgery series.13,16 These investigators recommended initial surgical exploration by experienced vascular surgeons who would be able to proceed to immediate vascular reconstruction and/or on-table thrombolysis when necessary in the event of a failed embolectomy/thrombectomy. Pemberton et al perceived the use of on-table thrombolysis as a valuable adjunct to surgery. This method was used in 18% of cases; 67% were deemed to experience a radiological improvement and a consequent significantly increased chance of limb salvage. As with previous studies, the 30-day mortality rate was high at 25%. These investigators identified a number of factors that conferred an increased mortality risk. Many interventionalists cite these statistics in favor of using endovascular therapies.
A recent Cochrane review identified five trials with a total of 1,283 patients randomized to undergo either surgery or thrombolysis.8 There was no significant difference in limb salvage or death at 30 days, 6 months, or 1 year between surgery and thrombolysis. Although initial thrombolysis was associated with a less-severe degree of intervention, it was associated with an increased risk of stroke, major hemorrhage, and distal embolization at 30 days. The reviewers concluded that neither universal treatment with surgery nor thrombolysis could be advocated based on the available evidence. They recommended that the higher risk of complications associated with thrombolysis should be balanced against the risk that surgery poses to the individual patient.
CONCLUSION AND FUTURE DIRECTIONS
The study by Pemberton et al showed that a surgical approach treating the acutely ischemic leg could achieve a high limb salvage rate, but with a significantly high mortality rate.9 Other investigators have suggested that thrombolysis may be a safer and less invasive option. There are few randomized studies comparing surgery with thrombolysis, however, and the recent Cochrane review suggests that further randomized, prospective trials are required8 with standardized reporting methods and inclusion/exclusion criteria.5 Either initial surgery or initial thrombolysis may play a role in patient treatment based on an individual assessment of the potential risks and benefits.
Ian Loftus, MD, is a lecturer in surgery at the Department of Surgery, Leicester University in Leicester, UK. He may be reached at + 44 1162 523140; email@example.com.
Peter R.F. Bell, MD, is a professor of surgery at the Department of Surgery, Leicester University in Leicester, UK. He may be reached at + 44 1162 523140.
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