Erector Spinae Muscle to Epicardial Visceral Fat Ratio on Chest CT Predicts the Severity of Coronavirus Disease 2019

Abstract

Background: Chest computed tomography (CT) is a valuable tool for diagnosing and predicting the severity of coronavirus disease 2019 (COVID-19) and assessing extrapulmonary organs. Reduced muscle mass and visceral fat accumulation are important features of a body composition phenotype in which obesity and muscle loss coexist, but their relationship with COVID-19 outcomes remains unclear. In this study, we aimed to investigate the association between the erector spinae muscle (ESM) to epicardial adipose tissue (EAT) ratio (ESM/EAT) on chest CT and disease severity in patients with COVID-19.

Methods: We analysed data from 1074 COVID-19 patients enrolled in the Japan COVID-19 Task Force database. The primary outcome was the rate of critical outcomes (requiring high-flow oxygen therapy, invasive ventilator support or death). The incidence of critical outcomes was compared between patients with high and low ESM/EAT ratios.

Results: The low ESM/EAT group (n = 353) had a higher incidence of critical outcomes (13.3% vs. 5.13%, p < 0.001) and mortality (2.55% vs. 0.69%, p = 0.019) than the high ESM/EAT group (n = 721). In multivariable analysis, the low ESM/EAT ratio was associated with critical outcomes (adjusted odds ratio [aOR] 2.11, 95% confidence interval [CI] 1.22-3.66) independently of the known COVID-19 severity factors including age, sex, body mass index (BMI), smoking history, lifestyle-related comorbidities and pneumonia volume.

Conclusion: The low ESM/EAT ratio in COVID-19 patients can be obtained on chest CT and used to predict critical outcomes after disease onset, demonstrating the importance of detailed body composition assessments in COVID-19 practice.

Keywords: COVID‐19; computed tomography; epicardial adipose tissue; erector spinae muscles; obesity; sarcopenia.

FIGURE 1

Process of patient selection in this study. Out of the 1410 COVID‐19 hospitalized patients from the four institutions during the study period, 336 were excluded. Therefore, 1074 patients were included in the analysis, of which 169 had 3 months chest CT analysis.

FIGURE 2

Representative CT images used to measure each muscle and adipose tissue. (A) Representative CT images used to measure erector spinae muscle (ESM) (green) and epicardial adipose tissue (EAT) (pink). (B) Distribution of ESM/EAT ratio and definition of high and low ESM/EAT group (first tertile of values).

FIGURE 3

Relationship between ESM/EAT ratio and disease severity in hospitalized patients with COVID‐19. (A) Comparison of the prevalence of critical outcomes by high and low ESM/EAT. (B) Receiver operating characteristic curve analysis for critical outcome based on ESM/EAT ratio and ESM. (C) Multivariable logistic regression analysis for the association between the critical outcomes and low ESM/EAT ratio and already‐known risk factors of COVID‐19. aOR, adjusted odds ratio; AUC, area under the curve; BMI, body mass index; CI, confidence interval. *, Significant; ***, p < 0.001.

FIGURE 4

Association between ESM/EAT ratio and pneumonia volume. (A) Correlation between ESM/EAT ratios and pneumonia volume. (B) Comparison of pneumonia volume by high and low ESM/EAT. ***, p < 0.001. (C) Correlation between ESM/EAT ratios and residual pneumonia volume at 3 months after onset. (D) Comparison of residual volume at 3 months after onset by high and low ESM/EAT.