Elsevier

Journal of Vascular Surgery

Volume 65, Issue 2, February 2017, Pages 431-437
Journal of Vascular Surgery

Clinical research study
Lower extremity arterial disease
Elevated serum phosphate levels are associated with decreased amputation-free survival after interventions for critical limb ischemia

Presented at the 2016 Vascular Annual Meeting of the Society for Vascular Surgery, National Harbor, Md, June 8-11, 2016.
https://doi.org/10.1016/j.jvs.2016.06.097Get rights and content
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Abstract

Objective

Elevated serum phosphate levels have been associated with increased risks of cardiovascular events and death in several patient populations. The effects of serum phosphate on outcomes in patients with critical limb ischemia (CLI) have not been evaluated. In this study, we assessed the effect of abnormal phosphate levels on mortality and major limb events after surgical intervention for CLI.

Methods

A retrospective review was undertaken to identify all patients at a single institution who underwent a first-time open or endovascular intervention for CLI between 2005 and 2014. Patients without recorded postoperative phosphate levels were excluded. Postoperative phosphate levels ≤30 days of the initial operation were recorded, and the mean was calculated. Patients were stratified according to mean phosphate levels (low: <2.5 mg/dL, normal: 2.5-4.5 mg/dL, and high: >4.5 mg/dL). Patient demographics, comorbidities, and operative details were compared in univariate analysis. Multivariable regression and Cox proportional hazard modeling were used to account for patient demographics and comorbid conditions.

Results

We identified 941 patients, including 42 (5%) with low phosphate, 768 (82%) with normal phosphate, and 131 (14%) with high phosphate. Patients with elevated phosphate were younger and had higher rates of congestive heart failure, diabetes, and dialysis dependence. Bypass was more common among patients with normal phosphate compared with high or low phosphate levels. There was no difference in the Wound, ischemia, and Foot infection (WiFi) classification or TransAtlantic Inter-Society Consensus classification among the cohorts. There were significant differences in 1-year mortality (low: 19%, normal: 17%, high: 33%; P < .01) and 3-year mortality (low: 38%, normal: 34%, high: 56%; P < .01) between phosphate cohorts. Major amputation (low: 12%, normal: 12%, high: 15%) and restenosis (low: 21%, normal: 24%, high: 28%) tended toward worse outcomes among patients with elevated phosphate levels but did not reach statistical significance. After adjustment for baseline characteristics, mortality was higher (hazard ratio [HR], 1.7; 95% confidence interval [CI], 1.3-2.2) and amputation-free survival was lower (HR, 1.5; 95% CI, 1.2-1.9) among patients with elevated compared with normal phosphate levels. A subgroup analysis was then performed to assess dialysis and nondialysis patients separately. Patients with elevated serum phosphate levels maintained a significantly higher risk of mortality in each group (dialysis: HR, 1.8; 95% CI, 1.2-2.6; nondialysis: HR, 1.5; 95% CI, 1.04-2.10).

Conclusions

Elevated phosphate levels are associated with increased mortality and decreased amputation-free survival after interventions for CLI. Future studies evaluating the effects of phosphate reduction in patients with CLI are warranted.

Cited by (0)

This work was completed with support from the National Institutes of Health Harvard-Longwood T32 Research Training in Vascular Surgery Grant HL-007734 to S.L.Z. and P.A.S. The National Institutes of Health had no involvement in design, collection, analysis, data interpretation, manuscript writing, or decision to submit this article.

Author conflict of interest: M.L.S. has been paid a consulting fee for Endologix.

The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest.