Among patients with transthyretin cardiac amyloidosis (ATTR-CM), lower skeletal mass index (SMI) and a lower subcutaneous adipose tissue index (SATI) both predict a higher risk of death, according to findings recently published in the European Journal of Heart Failure.
In medicine, loss of skeletal muscle mass is commonly observed as patients become older. In addition, patients with long-term health conditions such as heart failure are also at risk of skeletal muscle mass loss. Existing studies indicate that frailty is a risk factor for poorer outcomes in cardiac amyloidosis (CA), but the role skeletal muscle mass loss plays is not well known.
Investigators conducted a study to determine the relationship between body composition measures and patient outcomes in CA. They recruited adult patients seen at a clinic between January 2001 and August 2021 who had a confirmed diagnosis of CA, including both ATTR-CM and those with the light chain form of the disease.
Read more about ATTR-CM testing and diagnosis
Body composition evaluations were conducted using computed tomography (CT) tools. These allowed researchers to precisely calculate a patient’s SMI and SATI, which were representative of their skeletal muscle mass and fat percentage, respectively. Following these assessments, researchers were able to stratify patients according to different categories of SMI and SATI. In addition, researchers also analyzed the intermuscular adipose tissue percentage (IMAT%) of participants, which measures the amount of fat located within the muscles.
Researchers found that patients who had a low SMI (in other words, low skeletal muscle mass) had a 2-to-2.5 times higher mortality as measured across one year, five years and 10 years. In addition, a medium IMAT% and a medium SATI had around 1.9 times higher mortality as measured across five years and 10 years compared to high IMAT% and SATI levels.
Looking into ATTR-CM specifically, investigators found that a low SATI in ATTR-CM was associated with a higher risk of death. This finding may appear paradoxical, given that high fat percentage is generally associated with poorer heart outcomes. Nevertheless, these results reinforce findings from other studies that a higher percentage of body fat is associated with better outcomes in chronic heart failure, suggesting that fat tissue may be useful as a source of energy.
“Our findings imply that body composition parameters, especially muscle mass and SAT, may have important prognostic value in CA,” the study concluded. “Further research is necessary to understand the underlying mechanisms and potential therapeutic implications in CA.”
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