Canadian researchers measured muscle mass on DEXA and muscle strength (chair lift test) in patients undergoing heart surgery and found that patients with low scores had a three-fold higher risk of death after four years. The finding suggests that measuring muscle mass provides valuable information for the management of high-risk cardiac surgery patients.
“The muscle strength of the lower limbs and [DEXA]Muscle mass based on muscle mass are objective indicators of sarcopenia that are independently predictive of all-cause mortality in elderly cardiac surgery patients, ”wrote lead author Aayushi Joshi of McGill University and colleagues.
Studies using CT scans suggest that low muscle mass is a potentially important risk factor for unwanted outcomes after heart surgery. On the other hand, DEXA offers less ionizing radiation at a lower cost than computed tomography, higher accuracy than bioimpedance, and greater accessibility in most hospitals for routine use in assessing bone density, said the authors.
Despite this appeal, there has not yet been a study examining DEXA-based muscle mass as part of heart surgery, according to the authors. In this prospective study, researchers sought to determine the prevalence and prognostic value of sarcopenia (loss of muscle mass) as measured by DEXA and physical performance tests in patients undergoing heart surgery.
Researchers enrolled 141 patients aged 45 or older (79% male) referred to the Jewish General Hospital in Montreal for coronary artery bypass surgery and / or heart valve repair or replacement procedures between February 2013 and January 2017.
Participants were classified as sarcopenic if they had low appendicular muscle mass on DEXA, defined as greater than 7 kg / m2 for men or greater than 5.5 kg / m2 for women. Low muscle strength was determined by five chair rise times in 15 seconds or more.
Cox proportional hazards regression was used to test the association between sarcopenia and all-cause mortality at a median follow-up of 4.3 years. The primary outcome measure was all-cause mortality up to the last available follow-up period, determined by a combination of medical records, linkage with administrative data sources, and contact with patients or family members.
The prevalence rates of low muscle mass, slow chair rise time, and sarcopenia (low muscle mass and slow chair rise time) were 24%, 57%, 13%. The four-year survival rate was 79% in the non-sarcopenic group compared to 56% in the sarcopenic group.
When sarcopenia was defined as low muscle mass with a cutoff of less than 8 kg / m2 for men and women plus a slow chair rise time, the prevalence of sarcopenia was 28% and it was associated with a Adjusted HR of 2.98.
Classification tree with sarcopenia parameters to predict mortality Algorithm modified to identify sarcopenic patients at increased risk; Classification and Regression Tree Survival Analysis (CART) identified the same chair climb threshold ≥ 15 seconds, but a different appendicular muscle mass index (AMMI) threshold from the American Heart Journal .
“The risk analysis showed that sarcopenia was associated with an approximately three times higher risk of all-cause mortality in patients who had heart surgery,” the researchers wrote.
The researchers suggested an evidence-based clinical approach: start with the chair climb test to screen for physical frailty and sarcopenia. Patients who complete the test in less than 15 seconds are unlikely to be sarcopenic, while those who cannot may be further assessed for muscle mass on DEXA.
The authors noted limitations, namely that the participants were predominantly men – not surprisingly given the higher prevalence of coronary heart disease in men – and that the study was conducted at a single university center. with only one type of DEXA scanner.
“Further research is needed in multicenter cohorts with larger numbers of patients to better define optimal thresholds… and to validate prognostic value with various types of DEXA scanners,” the researchers concluded.
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