Abstract 12310: Metabolic Gain Index is Associated With Adverse Clinical Outcomes Independently of Peak VO ₂ in Patients With Heart Failure With Reduced Ejection Fraction Undergoing Cardiopulmonary Exercise Stress Testing

Introduction: Cardiopulmonary exercise stress test (CPET) is an essential prognostic tool in patients with heart failure with reduced ejection fraction (HFrEF) for advanced therapy evaluation. We studied the predictive utility of the metabolic gain index (MGI), which reflects the relative gain of the CPET-estimated stroke volume by the relative change in the product of VO 2 and heart rate (HR) from resting to peak exercise. This novel MGI aims to reflect cardiac reserve function, and, overall prognosis in HFrEF patients. Hypothesis: The MGI is an independent predictor of adverse outcomes in patients with HFrEF. Methods: We reviewed electronic medical records of 843 HFrEF patients (LVEF ≤40%) undergoing CPET from 12/2012 to 9/2020. The MGI was calculated using the formula, [(Peak VO 2 x Peak HR)-(Resting VO 2 x Resting HR)]/(Resting VO 2 x Resting HR). Patients with hypotensive or bradycardia response during exercise were excluded. Primary outcome was the composite of all-cause mortality, LVAD implantation, and heart transplantation. Multivariable Cox proportional hazard models and log rank test were used. For subgroup analysis, patients were stratified by the RER, age, sex, BMI, and beta-blocker use. Results: In our study cohort (mean age 56.2±12.2 years, 73% men, 85% with beta-blockers, mean LVEF 24.8±8.0 %, 16% with BMI ≥35 kg/m 2 , and 75% with RER >1.05), there were 279 (33.1%) patients developed adverse events during median follow up time of 897 days. Lower MGI was independently associated with increased risk of the adverse outcomes with adjustment for age, sex, comorbidities, LVEF, and peak VO 2 (quartile 1 vs 4, hazard ratio 1.83, 95% CI 1.03-3.25, p =0.040, Figure 1A ), especially in patients with RER > 1.05, BMI < 35 kg/m 2 , and without beta-blocker use ( Figure 1B ). Conclusions: Lower MGI is associated with poor prognosis independently of peak VO 2 . The prognostic value of MGI needs to be further corroborated in other multicenter HFrEF cohorts.