Vascular Quality Initiative Based Risk Score for Mortality within 3 Years of Revascularization for Chronic Limb Threatening Ischemia in End Stage Renal Disease Patients on Dialysis.

Abstract

The purpose of this study was to create a validated risk score for the outcome of mortality within 3 years of revascularization for chronic limb-threatening ischemia (CLTI) in patients with end-stage renal disease on dialysis (ESRD). Query of the United States based data in the Vascular Quality Initiative (VQI) identified 38,144 patients with ESRD undergoing open surgical or endovascular revascularization for CLTI. Patients were divided into a 2/3 test creation cohort and a 1/3 validation cohort. Time-dependent multivariable Cox regression was performed utilizing variables that had a univariable (P<.05) association with the outcome. Variables with a multivariable P-value < .05 from the above-mentioned regression were included in the risk score and weighted based on their respective regression beta-coefficient on a point scale. Variables with a beta-coefficient of less than .2 were assigned 1 point, and then a point was added for each rise in beta-coefficient at .2 intervals. A cumulative point total was then attributed to each patient based on the individual prevalence of the significant covariates. The mean 3-year mortality rate at each risk score cohort was calculated. The risk score was then applied to the 1/3 validation cohort, who were not utilized for risk score creation, and event rates were compared between the testing and validation cohorts. Testing cohort multivariable significance towards the primary outcome was noted for (P<.01 for all) : supra-inguinal bypass procedure (HR reference) supra-inguinal bypass in combination with simultaneous infra-inguinal artery bypass (HR 1.86) BMI<20 kg/m² (HR 1.32); BMI>35 kg/m² (protective HR .873); advancing age with each decade over age 50 (P<.001 at each decade); history (Hx) of coronary artery disease (CAD) (HR 1.09); Hx of CAD revascularization over 5 years ago (HR 1.12); CAD revascularization less than 5 years ago (HR 1.12); CHF class I (HR 1.20); CHF class II (HR 1.25); CHF class III (HR 1.41); CHF class IV (HR 1.86); COPD no medicines (HR 1.10); COPD on medicine (HR 1.18); COPD on oxygen (HR 1.406); nursing home status (HR 1.11); Prior carotid endarterectomy (CEA) or stenting (HR 1.18); lack of preoperative statin (protective HR .611); Dual antiplatelet at post-procedure DC (protective HR .910); lack of post-procedure antiplatelet (HR 1.67), statin (HR 2.12) and ACE-I (HR 1.26); Asian race (HR 1.25); White race HR (1.28); and unidentified race (HR 1.12). Race HR is relative to the reference of the Black race. There is noted to be a steep escalation in mortality rate with event rates of 25% at risk scores <0 to a 3-year mortality rate over 90% for patients with risk score totals of 17 and higher. The odds ratio of event rate is statistically significant with each rise in the risk score bundle. Sub-analysis involving baseline statin and hypertension revealed significant (P<.001) benefit to statin therapy and ACE/ARB at post-revascularization discharge regardless of preoperative statin status or baseline HTN. A novel validated risk score for mortality within three years of revascularization for CLTI in patients with ESRD has been created. Key modifiable variables associated with significantly enhanced survival are postoperative utilization of statin, antiplatelet, and ACE-inhibitor medications (irrespective of baseline hypertension).