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Predicting Amputation using Local Circulating Mononuclear Progenitor Cells in Angioplasty-treated Patients with Critical Limb Ischemia
Published on: September 22, 2020
Risk stratification in critical limb ischemia: derivation and validation of a model to predict amputation-free
Andres Schanzer1, Jessica Mega, Judith Meadows
1University of Massachusetts, Worcester, Massachusetts 01655, USA. schanzea@ummhc.org
Insights
A new risk score for critical limb ischemia (CLI) patients undergoing bypass surgery accurately predicts amputation-free survival (AFS). This score helps stratify patients into low, medium, and high-risk groups for better clinical decision-making.
Area of Science:
- Vascular Surgery
- Clinical Decision-Making
- Risk Stratification
Background:
- Critical limb ischemia (CLI) patients present heterogeneous risks for mortality and limb loss.
- Endovascular options offer lower procedural risk but potentially inferior durability compared to bypass.
- Improved risk stratification is needed for better clinical decisions and new technology assessment in CLI.
Purpose of the Study:
- To develop and validate a risk stratification model for amputation-free survival (AFS) in patients with CLI undergoing infrainguinal vein bypass.
- To identify key predictors of AFS in this patient population.
- To create a practical tool for surgical decision-making.
Main Methods:
- Retrospective analysis of prospectively collected data from two cohorts: PREVENT III trial (n=1404) and a multicenter registry (n=716).
- Patients underwent infrainguinal vein bypass surgery for CLI.
- A stepwise Cox model identified significant AFS predictors, which were used to create an integer risk score for stratifying patients into three risk groups. Internal and external validation were performed.
Main Results:
- The developed risk score identified significant predictors of AFS: dialysis, tissue loss, age >=75, hematocrit <=30, and advanced coronary artery disease (CAD).
- The model stratified patients into low, medium, and high-risk groups with distinct 1-year AFS rates (86%, 73%, and 45%, respectively).
- Risk stratification performance was consistent across derivation, internal validation, and external validation datasets.
Conclusions:
- A parsimonious risk stratification model, the "PIII risk score," reliably identifies CLI patients at high risk (>50% chance of death or major amputation at 1 year) undergoing surgical bypass.
- This score can aid surgical decision-making for infrainguinal disease.
- The PIII risk score is valuable for clinical trial designs involving the CLI population.
Background:
Patients with critical limb ischemia (CLI) are a heterogeneous population with respect to risk for mortality and limb loss, complicating clinical decision-making. Endovascular options, compared with bypass, offer a tradeoff between reduced procedural risk and inferior durability. Risk stratified data predictive of amputation-free survival (AFS) may improve clinical decision making and allow for better assessment of new technology in the CLI population.
Methods:
This was a retrospective analysis of prospectively collected data from patients who underwent infrainguinal vein bypass surgery for CLI. Two datasets were used: the PREVENT III randomized trial (n = 1404) and a multicenter registry (n = 716) from three distinct vascular centers (two academic, one community-based). The PREVENT III cohort was randomly assigned to a derivation set (n = 953) and to a validation set (n = 451). The primary endpoint was AFS. Predictors of AFS identified on univariate screen (inclusion threshold, P < .20) were included in a stepwise selection Cox model. The resulting five significant predictors were assigned an integer score to stratify patients into three risk groups. The prediction rule was internally validated in the PREVENT III validation set and externally validated in the multicenter cohort.
Results:
The estimated 1-year AFS in the derivation, internal validation, and external validation sets were 76.3%, 72.5%, and 77.0%, respectively. In the derivation set, dialysis (hazard ratio [HR] 2.81, P < .0001), tissue loss (HR 2.22, P =.0004), age >or=75 (HR 1.64, P = .001), hematocrit
Conclusion:
Among patients selected to undergo surgical bypass for infrainguinal disease, this parsimonious risk stratification model reliably identified a category of CLI patients with a >50% chance of death or major amputation at 1 year. Calculation of a "PIII risk score" may be useful for surgical decision making and for clinical trial designs in the CLI population.