Abstract 13603: Utility of the 6-minute Walk Test in Coronary Artery Disease Screening Before Kidney Transplant

Abstract

Introduction: Coronary artery disease (CAD) screening is a cornerstone of kidney transplant (KTx) evaluation, but existing approaches result in excess testing and low intervention rate. Hypothesis: We hypothesize that aerobic performance, based on a simple office test (the 6-minute walk test, 6MWT), may help risk stratify KTx candidates. Methods: We performed 6MWT in waitlisted patients who were nearing KTx. Results were used for frailty counselling and not for cardiac evaluation. CAD screening was done according to our center protocol: invasive angiogram for patients with long-standing diabetes mellitus (DM) and non-invasive testing for other patients with risk factors and at the evaluating transplant nephrologist’s discretion. We used subdistribution Cox regression and time-dependent receiver operator curve to evaluate time to CAD event (revascularization, myocardial infarction, waitlist removal for CAD, or cardiac death), treating waitlist removal for non-CAD and non-cardiac death as competing events. Results: Of the 360 patients, 200 and 161 patients had 6MWT results <400 meters and ≥400 meters (~4 metabolic equivalents), respectively. Patients with lower 6MWT results were older (59±10 vs 50±12 years) and more likely to be female (54% vs 34%), have DM (61% vs 33%) or known atherosclerotic disease (44% vs 22%), and have had prior cardiac evaluation (72% vs 61%). They were also more likely to exhibit cardiac symptom during 6MWT (36% vs 6%) and more likely to be censored due to waitlist removal for non-CAD reasons (follow-up 391±337 vs 541±277 days). 6MWT was not associated with CAD event (subdistribution hazard ratio 1.00 [0.90-1.10], 1-year area under the curve [AUC] 0.54). 196 patients had invasive (52%) or non-invasive (48%) CAD testing within 6 months of 6MWT: 6MWT did not predict the CAD test result (odds ratio 0.96 [0.81-1.14], AUC 0.54). Of the 94 patients who had concurrent non-invasive CAD testing, the 1-year AUC of 6MWT, symptom (at rest or during 6MWT), AST guidelines, or non-invasive testing for CAD event were 0.64, 0.52, 0.46 and 0.66 respectively. Conclusions: The 6MWT did not perform better in risk stratification for CAD events compared to a symptom- or risk factor-based approach.