Management cost of acute limb ischaemia

The role of thrombolysis in acute infrainguinal bypass occlusion: a prospective nonrandomized controlled study

Current treatment of acute infrainguinal bypass occlusion consists of either surgical revascularization or catheter-guided intra-arterial thrombolysis with adjunctive correction of the underlying flow-limiting lesion. In maintaining long-term patency, improving the number of outflow vessels could be of utmost importance. To compare the efficiency of both thrombolysis and primary surgical revascularization and to study the effect of thrombolysis on the number of patent outflow vessels, a prospective nonrandomized study was performed. Between February 2002 and August 2003, 54 patients with 56 occluded bypasses were included. Thirty bypasses were treated with thrombolysis, 26 primarily with surgery. Thrombolysis was successful in 80% of cases, with restoration of patency of the bypass but also with doubling of the amount of patent outflow vessels; surgery was successful in 85.71% of cases. However, in only 60% of the successfully lysed bypasses no adjunctive major surgery was needed. Amputation-free survival was 87.5% 1 year after surgery and 82.6% 1 year after thrombolysis. One year after thrombolysis without adjunctive major surgery, the amputation-free survival was only 39.7%. Therefore, a strategy could be to start with thrombolysis to improve outflow followed by a new bypass, whatever the underlying causative lesions are.

National Audit of Thrombolysis for Acute Leg Ischemia (NATALI): clinical factors associated with early outcome

OBJECTIVE

The National Audit of Thrombolysis for Acute Leg Ischemia (NATALI) database is a consecutive series of patients who underwent intra-arterial thrombolysis to treat acute leg ischemia in one of 11 centers in the United Kingdom. The purpose of the study was to analyze the factors associated with outcome after 30 days.

METHODS

The data were collected over 10 years on standard pro formas, and registration was completed at the end of 1999. Since then, data from each unit have been verified and missing data included when available. Univariate and multivariate analyses were performed, with the outcomes of amputation-free survival (AFS), amputation with survival, and death.

RESULTS

A total of 1133 thrombolytic events were included. Outcome results at 30 days for the entire group were AFS, 852 (75.2%); amputation, 141 (12.4%); and death, 140 (12.4%). Results for the entire group improved from the first half of the database, when AFS ranged from 65% to 75%, to almost 80% for the last few years of the study, although this was not statistically significant. Preintervention factors associated with lower AFS at multivariate analysis included diabetes (P =.002), increasing age (P <.001), short-duration ischemia (P =.027), Fontaine grade (P =.001), and ischemia with neurosensory deficit (P =.004). AFS was improved in patients receiving warfarin sodium at the time of the arterial occlusion (P =.04). Mortality was higher in women (P =.006) and in older patients (P <.001), and in patients with native vessel occlusion (P <.001), emboli (P =.02), or a history of ischemic heart disease (P <.001). Amputation risk was greatest in younger men (P <.001) and in patients with more severe ischemia (P =.02), graft occlusion (P <.001), or native vessel thrombotic occlusion (P =.02).

CONCLUSION

Experienced surgeons and radiologists can achieve an AFS of about 80% in selected patients with acute leg ischemia. Information from the NATALI database can be used in selection of an appropriate intervention in the individual patient.

Microtibial embolectomy

BACKGROUND

microtibial embolectomy is an important technique in cases of limb threatening acute arterial occlusion affecting native crural and pedal vessels. It is particularly useful when thrombolysis is contraindicated or ineffective as in "trash foot".

METHODS

in order to evaluate the efficacy of this technique, a retrospective case note review was carried out for patients undergoing microtibial embolectomy from 1990 to 1999. Data collected included the causes and degree of ischaemia, additional procedures required, vessel patency, limb salvage and complications encountered.

RESULTS

twenty-two limbs underwent exploration of the crural/pedal vessels with ankle level arteriotomies under local anaesthetic in 12 cases, general anaesthetic in nine and epidural in one. The causes of ischaemia were cardiac emboli (8), "trash foot" (7), emboli from aortic and popliteal aneurysms (3) and thrombotic occlusion of crural vessels (4). The vessel patency rate was 69% and limb salvage rate 62% (13/21) up to 5-years follow-up. Six of the seven cases with "trash foot" were salvaged while one required an amputation at 3-months post-operatively. The 30-day mortality was 22% (5/22).

CONCLUSIONS

microtibial embolectomy is effective in acute occlusion of the crural/pedal arteries including cases of "trash foot", offering limb salvage to a worthwhile proportion of cases.

Duplex scan surveillance during the first year after infrainguinal autologous vein bypass grafting surgery: costs and clinical outcomes compared with other surveillance programs

PURPOSE

In this study we assessed the costs and clinical outcomes of duplex scan surveillance during the first year after infrainguinal autologous vein bypass grafting surgery and compared duplex scan surveillance, ankle-brachial index surveillance, and clinical follow-up.

METHODS

In a clinical study, 293 patients (mean age, 70.1 years; 58.7% men) with peripheral arterial disease were observed in a duplex scan surveillance program after infrainguinal autologous vein bypass grafting surgery. Costs were calculated from the health care perspective for surveillance and subsequent interventions from 30 days to 1 year postoperatively. All costs are presented in 1995 US dollars per patient. In a simulation model, we estimated the costs and amputations of duplex scan surveillance, ankle-brachial index surveillance, and clinical follow-up conditional on the indication for surgery. The main outcome measure was the incremental cost per major amputation per patient avoided during the first postoperative year.

RESULTS

Duplex scan surveillance was the least expensive ($2823) and resulted in the fewest major amputations (17 per 1000 patients examined), compared with ankle-brachial index surveillance ($5411 and 77 amputations per 1000 patients) and clinical follow-up ($5072 and 77 amputations per 1000 patients). In patients treated for critical limb ischemia, duplex scan surveillance was the least expensive ($2974) and resulted in the fewest major amputations (19 per 1000 patients). Under all surveillance programs, 13 major amputations per 1000 patients treated for intermittent claudication were performed, and clinical follow-up had the lowest costs ($1577). In a sensitivity analysis that assumed that duplex scan surveillance could have avoided six major amputations per 1000 patients treated for intermittent claudication compared with the other programs, duplex scan surveillance had an incremental cost of $80,708 per major amputation per patient avoided compared with clinical follow-up.

CONCLUSION

Duplex scan surveillance is highly effective for patients treated for critical limb ischemia, leading to a reduction of major amputations and consequently to a reduction in costs compared with other surveillance programs. In patients treated for intermittent claudication, the evidence supporting duplex scan surveillance is less firm, but if duplex scan can avoid six major amputations per 1000 patients examined, the incremental costs are justified.

Quantitative evaluation of selective thrombolysis techniques: influence of catheter characteristics and delivery parameters

Here, we evaluate in vitro the site-specific delivery ability of thrombolysis catheters and compare continuous infusion (CI) and periodic injection (PI) protocols with reference to this parameter. Thrombotic occlusion was simulated by placing a porcine blood clot proximal to an eccentric stenosis in a flow phantom. Iodinated contrast agent was used as the marker. Part I-Evaluation of thrombolysis catheters: four CI and three PI catheters were tested. The marker was delivered as an infusion at 1 ml/min for 1 min (CI), or as two 0.25 ml boluses 30 sec apart (PI). Iodine content of the clot was then estimated with x-ray fluorescence spectrometry. This value as a ratio of the delivered dose was defined as the targeting efficiency. Part II-Evaluation of thrombolysis protocols: CI and PI were compared. The marker was delivered for 3 or 5 min using one of seven protocols. The iodine content of both clot and effluent were estimated. Among PI catheters, the Jet-Lysis catheter proved to be the best (P = 0.02). The EDM catheter had the lowest targeting efficiency in the CI group (P = 0.01). With CI, median iodine recovery dropped from 0.21 (95% confidence interval: 0.08, 0.25) for 1 min to 0.13 (0.05, 0.16) for 3 min and 0.07 (0.03, 0.10) for 5 min; for PI the values remained unchanged. The fraction lost in the effluent increased with the duration of regimen with both CI (P = 0.014) and PI (P = 0.004). Reducing the rate of infusion or the bolus frequency resulted in major improvements with respect to this parameter (P = 0.005). For CI, the targeting efficiency increased as well (P = 0.03). We conclude that currently used thrombolysis protocols do not fully exploit the delivery advantage offered by CI or PI. Fortunately, simple modifications offer the possibility of overcoming these drawbacks.

Assessing clot lysis strategies using a simplified mathematical model

This paper attempts to describe lysis of a clot by infusion of lytic agent using a simple geometrical approach, in which the rate of clot lysis is assumed proportional to the exposed surface of the clot and the concentration of lytic agent. Six simple realizations (a)-(f) of this basic model are developed which account for the dependence of clot lysis time on five different clot geometries. In all six cases the clot is initially described as a uniform cylinder which totally occludes a vessel. In model (a) lysis proceeds as an advancing front at the proximal face of the clot. In model (b) lysis proceeds radially outwards from the central axis of the vessel while in model (c) lysis occurs radially inwards from the surface adjacent the wall, of the cylinder. In models (d) and (e) it is assumed that the clot breaks into a uniform spherical and cylindrical fragments, respectively, while model (f) uses the spherical fragment model combined with a lytic agent concentration which decreases with time. The validity of the models was assessed using previously published data from 76 patients in whom lysis time and clot size were recorded. Least squares linear regression analysis based on the six model equations yielded highly significant correlation coefficients r2 of 0.457, 0.412, 0.412, 0.495, 0.469, 0.663 for models (a)-(f), respectively. The results suggest that when a constant lytic agent concentration is assumed, no single geometry accounts for significantly more variation than any other, but that a combination of varying lytic agent concentration and clot geometry significantly influences clot lysis time and accounts for much of the observed variation.