"Within patient"-dependent outcomes in graft occlusion after coronary artery bypass. SINBA Group

Statin therapy after infrainguinal bypass surgery for critical limb ischemia is associated with improved 5-year survival

OBJECTIVE

Although statin therapy has been linked to fewer short-term complications after infrainguinal bypass, its effect on long-term survival remains unclear. We therefore examined associations between statin use and long-term mortality, graft occlusion, and amputation after infrainguinal bypass.

METHODS

We used the Vascular Study Group of New England registry to study 2067 patients (71% male; mean age, 67 ± 11 years; 67% with critical limb ischemia [CLI]) who underwent infrainguinal bypass from 2003 to 2011. Of these, 1537 (74%) were on statins perioperatively and at 1-year follow-up, and 530 received no statin. We examined crude, adjusted, and propensity-matched rates of 5-year surviva1, 1-year amputation, graft occlusion, and perioperative myocardial infarction.

RESULTS

Patients taking statins at the time of surgery and at the 1-year follow-up were more likely to have coronary disease (38% vs 22%; P < .001), diabetes (51% vs 36%; P < .001), hypertension (89% vs 77%; P < .001), and prior revascularization procedures (50% vs 38%; P < .001). Despite higher comorbidity burdens, long-term survival was better for patients taking statins in crude (risk ratio [RR], 0.7; P < .001), adjusted (hazard ratio, 0.7; P = .001), and propensity-matched analyses (hazard ratio, 0.7; P = .03). In subgroup analysis, a survival advantage was evident in patients on statins with CLI (5-year survival rate, 63% vs 54%; log-rank, P = .01) but not claudication (5-year survival rate, 84% vs 80%; log-rank, P = .59). Statin therapy was not associated with 1-year rates of major amputation (12% vs 11%; P = .84) or graft occlusion (20% vs 18%; P = .58) in CLI patients. Perioperative myocardial infarction occurred more frequently in patients on a statin in crude analysis (RR, 2.2; P = .01) but not in the matched cohort (RR, 1.9; P = .17).

CONCLUSIONS

Statin therapy is associated with a 5-year survival benefit after infrainguinal bypass in patients with CLI. However, 1-year limb-related outcomes were not influenced by statin use in our large observational cohort of patients undergoing revascularization in New England.

Comparison of graft patency, limb salvage, and antithrombotic therapy between prosthetic and autogenous below-knee bypass for critical limb ischemia

BACKGROUND

The autogenous vein is the preferred conduit in below-knee vascular reconstructions. However, many argue that prosthetic grafts can perform well in crural bypass with adjunctive antithrombotic therapy. We therefore compared outcomes of below-knee prosthetic versus autologous vein bypass grafts for critical limb ischemia and the use of adjunctive antithrombotic therapy in both settings.

METHODS

Utilizing the registry of the Vascular Study Group of New England (2003-2009), we studied 1227 patients who underwent below-knee bypass for critical limb ischemia, 223 of whom received a prosthetic graft to the below-knee popliteal artery (70%) or more distal target (30%). We used propensity matching to identify a patient cohort receiving single-segment saphenous vein yet had remained similar to the prosthetic cohort in terms of characteristics, graft origin/target, and antithrombotic regimen. Main outcome measures were graft patency and major limb amputation within 1 year. Secondary outcomes were bleeding complications (reoperation or transfusion) and mortality. We performed comparisons by conduit type and by antithrombotic therapy.

RESULTS

Patients receiving prosthetic conduit were more likely to be treated with warfarin than those with greater saphenous vein (57% vs. 24%, P<0.001). After propensity score matching, we found no significant difference in primary graft patency (72% vs. 73%, P=0.81) or major amputation rates (17% vs. 13%, P=0.31) between prosthetic and single-segment saphenous vein grafts. In a subanalysis of grafts to tibial versus popliteal targets, we noted equivalent primary patency and amputation rates between prosthetic and venous conduits. Whereas overall 1-year prosthetic graft patency rates varied from 51% (aspirin+clopidogrel) to 78% (aspirin+warfarin), no significant differences were seen in primary patency or major amputation rates by antithrombotic therapy (P=0.32 and 0.17, respectively). Further, the incidence of bleeding complications and 1-year mortality did not differ by conduit type or antithrombotic regimen in the propensity-matched analysis.

CONCLUSIONS

Although limited in size, our study demonstrates that, with appropriate patient selection and antithrombotic therapy, 1-year outcomes for below-knee prosthetic bypass grafting can be comparable to those for greater saphenous vein conduit.

Distal anastomotic vein adjunct usage in infrainguinal prosthetic bypasses

OBJECTIVE

Single-segment saphenous vein remains the optimal conduit for infrainguinal revascularization. In its absence, prosthetic conduit may be used. Existing data regarding the significance of anastomotic distal vein adjunct (DVA) usage with prosthetic grafts are based on small series.

METHODS

This is a retrospective cohort analysis derived from the regional Vascular Study Group of New England as well as the Brigham and Women's hospital database. A total of 1018 infrainguinal prosthetic bypass grafts were captured in the dataset from 73 surgeons at 15 participating institutions. Propensity scoring and 3:1 matching was performed to create similar exposure groups for analysis. Outcome measures of interest included: primary patency, freedom from major adverse limb events (MALEs), and amputation free survival at 1 year as a function of vein patch utilization. Time to event data were compared with the log-rank test; multivariable Cox proportional hazard models were used to evaluate the adjusted association between vein cuff usage and the primary end points. DVA was defined as a vein patch, cuff, or boot in any configuration.

RESULTS

Of the 1018 bypass operations, 94 (9.2%) had a DVA whereas 924 (90.8%) did not (no DVA). After propensity score matching, 88 DVAs (25%) and 264 no DVAs (75%) were analyzed. On univariate analysis of the matched cohort, the DVA and no DVA groups were similar in terms of mean age (70.0 vs 69.0; P = .55), male sex (58.0% vs 58.3%; P > .99), and preoperative characteristics such as living at home (93.2% vs 94.3%; P = .79) and independent ambulatory status (72.7% vs 75.7%; P = .64). The DVA and no DVA groups had similar rates of major comorbidities such as hypertension chronic obstructive pulmonary disease, diabetes mellitus, coronary artery disease, and dialysis dependence (P > .05 for all). Likewise, they had similar rates of distal origin grafts (13.6% vs 12.5%; P = .85), critical limb ischemia indications (P = .53), and prior arterial bypass (58% vs 47%; P = .08). The DVA group had a higher rate of completion angiogram performed (55.7% vs 37.5%; P =.002) and were more likely to be discharged on coumadin (53.4% vs 37.1%; P =.01). By multivariable analysis, use of a distal DVA was protective against MALEs (hazard ratio, 0.36; 95% confidence interval, 0.14-0.90; P = .03).

CONCLUSIONS

This contemporary multi-institutional propensity-matched study demonstrates that patients that receive distal anastomotic vein adjuncts as part of infrainguinal prosthetic bypass operations in general have more extreme comorbidities and more technically challenging operations based on level of target vessel and prior bypass attempts. After propensity-matched analysis, the use of a DVA may protect against MALEs in prosthetic bypass surgery and should be considered when feasible.

Predicting functional status following amputation after lower extremity bypass

BACKGROUND

Some patients who undergo lower extremity bypass (LEB) for critical limb ischemia ultimately require amputation. The functional outcome achieved by these patients after amputation is not well known. Therefore, we sought to characterize the functional outcome of patients who undergo amputation after LEB, and to describe the pre- and perioperative factors associated with independent ambulation at home after lower extremity amputation.

METHODS

Within a cohort of 3,198 patients who underwent an LEB between January, 2003 and December, 2008, we studied 436 patients who subsequently received an above-knee (AK), below-knee (BK), or minor (forefoot or toe) ipsilateral or contralateral amputation. Our main outcome measure consisted of a "good functional outcome," defined as living at home and ambulating independently. We calculated univariate and multivariate associations among patient characteristics and our main outcome measure, as well as overall survival.

RESULTS

Of the 436 patients who underwent amputation within the first year following LEB, 224 of 436 (51.4%) had a minor amputation, 105 of 436 (24.1%) had a BK amputation, and 107 of 436 (24.5%) had an AK amputation. The majority of AK (75 of 107, 72.8%) and BK amputations (72 of 105, 70.6%) occurred in the setting of bypass graft thrombosis, whereas nearly all minor amputations (200 of 224, 89.7%) occurred with a patent bypass graft. By life-table analysis at 1 year, we found that the proportion of surviving patients with a good functional outcome varied by the presence and extent of amputation (proportion surviving with good functional outcome = 88% no amputation, 81% minor amputation, 55% BK amputation, and 45% AK amputation, p = 0.001). Among those analyzed at long-term follow-up, survival was slightly lower for those who had a minor amputation when compared with those who did not receive an amputation after LEB (81 vs. 88%, p = 0.02). Survival among major amputation patients did not significantly differ compared with no amputation (BK amputation 87%, p = 0.14, AK amputation 89%, p = 0.27); however, this part of the analysis was limited by its sample size (n = 212). In multivariable analysis, we found that the patients most likely to remain ambulatory and live independently despite undergoing a lower extremity amputation were those living at home preoperatively (hazard ratio [HR]: 6.8, 95% confidence interval [CI]: 0.94-49, p = 0.058) and those with preoperative statin use (HR: 1.6, 95% CI: 1.2-2.1, p = 0.003), whereas the presence of several comorbidities identified patients less likely to achieve a good functional outcome: coronary disease (HR: 0.6, 95% CI: 0.5-0.9, p = 0.003), dialysis (HR: 0.5, 95% CI: 0.3-0.9, p = 0.02), and congestive heart failure (HR: 0.5, 95% CI: 0.3-0.8, p = 0.005).

CONCLUSIONS

A postoperative amputation at any level impacts functional outcomes following LEB surgery, and the extent of amputation is directly related to the effect on functional outcome. It is possible, based on preoperative patient characteristics, to identify patients undergoing LEB who are most or least likely to achieve good functional outcomes even if a major amputation is ultimately required. These findings may assist in patient education and surgical decision making in patients who are poor candidates for lower extremity bypass.