The Modified Frailty Index Does Not Predict Mortality After Major Lower Extremity Amputation for Peripheral Arterial Disease in an Asian Population

Ann Vasc Surg. 2020 Nov;69:298-306. doi: 10.1016/j.avsg.2020.05.063. Epub 2020 Jun 4.

Abstract

Background: Patients with critical limb ischemia (CLI) who undergo major lower extremity amputation (LEA) have been associated with high one-year mortality rates. Previous western-based studies have identified risk factors that exponentiate these poor outcomes, including nonambulatory status and cardiovascular morbidity. We assessed the effect of frailty, using the modified frailty index (mFI) in a cohort undergoing major LEA for CLI to predict mortality, perioperative complications, and unplanned readmissions in a tertiary institution from Singapore.

Methods: Data on patients who had undergone major LEA from January 2016 to December 2017 were collected retrospectively. Inclusion criteria were below-knee amputations (BKAs) or above-knee amputations (AKAs) performed for peripheral arterial disease-related tissue loss or sepsis only. Patients were categorized into 3 risk groups based on the 11-variable mFI: low mFI, 0-0.27; moderate mFI, 0.36-0.54; and high mFI ≥0.63. Univariate and multivariate analysis was performed using logistic regression analysis.

Results: 211 patients underwent major LEA, of whom 133 (63.0%) had undergone BKA. The mean mFI was 0.41 (range 0-0.81). 84/211 (39.8%) died within 1 year after the procedure, with mortality rates of 25/65 (38.4%), 49/127 (38.6%), and 10/19 (52.6%) in the low-, moderate-, high-mFI categories, respectively. High and moderate mFI had failed to demonstrate an increased risk of mortality when compared with the low-mFI group (P > 0.05). 91/211 (43.1%) patients had perioperative complications, whereas 27/211 (12.8%) patients were readmitted within 30 days of discharge. Myocardial infarction, chronic kidney disease, and atrial fibrillation were found to be predictive of poor outcomes after major LEA.

Conclusions: Frailty as measured with the mFI did not predict outcome after major LEA. This could be due to confounding effects such as high prevalence of renal dysfunction and the constancy of diabetes and peripheral vascular disease in this population that would reduce the differentiation of patients using the mFI.