Validation of a modified Frailty Index to predict mortality in vascular surgery patients

Abstract

Background: Patient frailty has been implicated as a predictor of poor patient outcomes; however, there is no consensus on how to define or quantify frailty to assess perioperative risk. A previously described modified Frailty Index (mFI) has been shown to predict adverse outcomes after selected vascular surgical procedures, but no studies to date have compared its utility against other recognized risk indices in specific populations of vascular surgery patients.

Methods: National Surgical Quality Improvement Program data were reviewed for all patients undergoing carotid revascularization, abdominal aortic aneurysm (AAA) repair, and lower extremity revascularization for peripheral arterial disease (PAD) from 2006 to 2012. Patients were then further stratified into "open" and "endovascular" cohorts. The mFI was compared with the Lee Cardiac Risk Index (LCRI) and the American Society of Anesthesiologists (ASA) Physical Status Classification using a receiver operating characteristic area under curve (AUC). The primary end point was 30-day mortality, with a secondary end point of Clavien-Dindo class IV complications.

Results: A total of 72,106 patients were identified in the study period, with 40,931 (56.8%), 20,975 (29.1%), and 10,200 (14.1%) in the carotid, AAA, and PAD populations, respectively. For carotid endarterectomy, mFI demonstrated better discrimination regarding mortality than LCRI and ASA, with an AUC of 0.66 (95% confidence interval [CI], 0.63-0.70; P < .01 vs P = .65 and P = .60, respectively). The open AAA cohort had similar findings, with an AUC of 0.63 (95% CI, 0.59-0.67; P = .02 vs P = .58, and P = .58, respectively). In open PAD patients, mFI was comparable to ASA (AUC, 0.64 [95% CI 0.60-0.69] vs 0.65), with a trend toward better discrimination compared with the 0.60 AUC of LCRI (P = .08). The mFI was a better discriminator of class IV complications than LCRI and ASA after open AAA (AUC for mFI, 0.59 vs 0.56 and 0.55; 95% CI, 0.57-0.61; P < .01) and endovascular AAA repair (AUC for mFI, 0.60 vs 0.59 and 0.57; 95% CI, 0.58-0.62; P = .01). There were no significant differences in discrimination of class IV complications after open or endovascular PAD or carotid endarterectomy.

Conclusions: The mFI was a better discriminator of mortality than other risk indices; however this was only significant for the open cohort. The mFI was also a better discriminator of class IV complications for the open and endovascular AAA repair groups. These data suggest that mFI should be used in place of previously recognized risk indices to define perioperative mortality after open vascular surgery and risk of major complications after aneurysm repair.