Quality of muscle in the thigh predicts the prognosis in patients with non-ischemic cardiomyopathy

Abstract Background Skeletal muscle atrophy is an independent prognostic predictor for patients with chronic heart failure, and the concept of sarcopenia has garnered scientific attention. Furthermore, the importance of not only muscle mass but also quality of muscle has been pointed out. And a sarcopenia diagnosis is confirmed by the presence of low quality of muscle. However, there is a lack of consensus on the implications of ectopic fat as a quality of muscle for the prognosis in patients with non-ischemic cardiomyopathy. Purpose We investigated whether intramuscular fat (IMF) in the thigh affects the prognosis in patients with non-ischemic cardiomyopathy. Methods We recruited 250 patients who were diagnosed with non-ischemic cardiomyopathy by cardiac catheterization and echocardiographic date between September 2017 and November 2022. Finally, 223 patients enrolled in this prospective study conducted at a single center. Functional status was evaluated by using cardiopulmonary exercise test at baseline. All patients were measured quantity of the percentage of IMF (%IMF) in the thigh using computed tomography scan. Demographic, laboratory and echocardiographic date were collected from the patients’ medical records. Patients were followed up for up to 3 years. Clinical endpoints were cardiovascular death or unexpected rehospitalization because of cardiac events. Results During the follow-up 58 patients had cardiac events. The %IMF was significantly higher in the group with adverse events than without (4.49 ± 4.21 and 3.06 ± 2.39%, respectively; p = 0.001). Spearman correlation coefficient analysis showed a modest correlation between %IMF and exercise tolerance such as anaerobic threshold (Spearman r = -0.367; p < 0.001) and peak oxygen uptake (Spearman r = -0.382; p < 0.001). Patients were divided into 2 groups according to the median values of %IMF. Kaplan-Meier analysis demonstrated that events were significantly higher in the high %IMF group (log-rank p = 0.008). Furthermore, subgroup with left ventricular ejection fraction ≦ 40% or BMI ≧ 22 had a significantly greater frequency of adverse events in the high %IMF group. However, there was no significant difference in %IMF between the groups when divided into two groups at the mean age of this study. Multivariate Cox regression analysis adjusted for left ventricular ejection fraction, estimated glomerular filtration rate, hemoglobin and body mass index found %IMF as an independent factor of adverse events (hazard ratio 1.088; 95% confidential interval 1.024-1.156; p = 0.007). Conclusions In patients with non-ischemic cardiomyopathy, quality of muscle represented by %IMF in the thigh is an independent factor for predicting adverse cardiac events.