Association of Summed Rest Score on Technetium-99m Sestamibi With Exercise Capacity and Incident Adverse Outcomes in Hospitalized Patients With Nonischemic Cardiomyopathy: A Retrospective Analysis.

BACKGROUND: In nonischemic cardiomyopathy, the clinical relevance of decreased resting myocardial technetium-99m sestamibi (99mTc-MIBI) uptake regarding exercise capacity and clinical outcomes remains incompletely understood. We investigated whether decreased 99mTc-MIBI uptake is associated with impaired exercise capacity and adverse clinical outcomes in nonischemic cardiomyopathy. METHODS: We retrospectively analyzed 182 patients (mean age 51.4±14.0 years; 27% female) with nonischemic cardiomyopathy and left ventricular ejection fraction <50% who underwent 99mTc-MIBI scintigraphy and cardiopulmonary exercise testing from 2016 to 2023. Myocardial uptake of 99mTc-MIBI was evaluated using the summed rest score (SRS). Exercise capacity was assessed by percentage of predicted peak oxygen consumption (PPVO2), with ≤60% defining impairment. RESULTS: Seventy-four patients (41%) had PPVO2 ≤60% and higher SRS (median: 12 versus 8; P < 0.001). Higher SRS remained significantly associated with PPVO2 ≤60% after adjustment for relevant clinical covariates, including brain natriuretic peptide level, left ventricular ejection fraction, and heart failure duration. Over a median follow-up of 807 days, 23 patients (13%) experienced the composite outcome of all-cause death, ventricular assist device implantation, or heart transplantation. Higher SRS was associated with composite outcomes after adjusting for PPVO2 ≤60%. Among the 4 groups stratified by median SRS of 9 and PPVO2 of 60%, patients with high SRS and low PPVO2 had the highest incidence of adverse events. CONCLUSIONS: Decreased myocardial 99mTc-MIBI uptake was associated with impaired exercise capacity and adverse outcomes in patients with nonischemic cardiomyopathy. Our findings suggest that myocardial injury assessment using 99mTc-MIBI scintigraphy may provide prognostic information complementary to exercise capacity.