Sarcopenia in cardiac surgery: Dual X-ray absorptiometry study from the McGill frailty registry.

Background: To determine the prevalence and prognostic value of sarcopenia measured by dual x-ray absorptiometry (DXA) and physical performance tests in patients undergoing coronary artery bypass surgery or heart valve procedures.

Methods: Adults undergoing cardiac surgery were prospectively enrolled and completed a questionnaire, physical performance battery, and a DXA scan (GE Lunar) to measure appendicular muscle mass indexed to height (AMMI). Patients were categorized as sarcopenic based on European Working Group 2 guidelines if they had low AMMI defined as <7 kg/m for men or <5.5 kg/m for women, and low muscle strength defined as 5 chair rise time ≥15 seconds. Cox proportional hazards regression was used to test the association between sarcopenia and all-cause mortality over a median follow-up of 4.3 years.

Results: The cohort consisted of 141 patients with a mean age of 69.7 ± 10.0 years and 21% females. The prevalence rates of low AMMI, slow chair rise time, and sarcopenia (low AMMI and slow chair rise time) were 24%, 57%, 13%, respectively. The 4-year survival rate was 79% in the non-sarcopenic group as compared to 56% in the sarcopenic group (Log-rank P = 0.01). In the multivariable model, each standard deviation of decreasing AMMI and increasing chair rise time was associated with a hazard ratio for all-cause mortality of 1.84 (95% CI 1.18, 2.86) and 1.79 (95% CI 1.26, 2.54), respectively.

Conclusion: Lower-extremity muscle strength and DXA-based muscle mass are objective indicators of sarcopenia that are independently predictive of all-cause mortality in older cardiac surgery patients.