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 ( 99m Tc‐MIBI) uptake regarding exercise capacity and clinical outcomes remains incompletely understood. We investigated whether decreased 99m Tc‐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 99m Tc‐MIBI scintigraphy and cardiopulmonary exercise testing from 2016 to 2023. Myocardial uptake of 99m Tc‐MIBI was evaluated using the summed rest score (SRS). Exercise capacity was assessed by percentage of predicted peak oxygen consumption (PPVO 2 ), with ≤60% defining impairment. Results Seventy‐four patients (41%) had PPVO 2 ≤60% and higher SRS (median: 12 versus 8; P < 0.001). Higher SRS remained significantly associated with PPVO 2 ≤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 PPVO 2 ≤60%. Among the 4 groups stratified by median SRS of 9 and PPVO 2 of 60%, patients with high SRS and low PPVO 2 had the highest incidence of adverse events. Conclusions Decreased myocardial 99m Tc‐MIBI uptake was associated with impaired exercise capacity and adverse outcomes in patients with nonischemic cardiomyopathy. Our findings suggest that myocardial injury assessment using 99m Tc‐MIBI scintigraphy may provide prognostic information complementary to exercise capacity.