1Universitätsklinikum Bonn Medizinische Klinik und Poliklinik II Bonn, Deutschland; 2Universitätsklinikum Bonn Radiologische Klinik Bonn, Deutschland
BACKGROUND:
The current European guidelines underscore the importance of objective patient evaluation and risk stratification in patient-centered decision-making for valve interventions. However, the guidelines primarily rely on surgical risk scores, which do not consider crucial clinical factors such as frailty. Computed tomography (CT) is a routine part of the pre-interventional workup in patients with aortic stenosis (AS) and allows for body composition analysis, including the assessment of fat-free muscle fraction (FFMF) as an indicator of muscle quality.
AIMS:
This study aimed to assess the correlation between FFMF and inflammation, as well as endocrine disorders, and to investigate the predictive value of FFMF in patients with AS undergoing TAVR.
METHODS:
The study cohort consisted of 789 patients undergoing TAVR between 2017 and 2019. Patient evaluations involved CT scans, with the determination of skeletal muscle area at the L3/L4 level. Using densitometric thresholds, the skeletal muscle area was separated into fatty and lean muscle areas to calculate the FFMF (Figure 1). The cohort was stratified into tertials based on the median percentage of FFMF, defining patients with high, medium, and low FFMF, respectively. Clinical endpoints included one- and five-year mortality following TAVR.
RESULTS:
The study population was 45.5% female and had a mean age of 81.2±6.0 years. According to the CT evaluation 261 (33.1%) patients had a high , 293 (37.1%) patients had a medium, and 235 (29.8%) patients had a low FFMF. Patients with a low FFMF were older (82.3±5.9 vs 81.6±5.6 vs 79.8±6.2 years, p<0.01) and had higher rates of atrial fibrillation (51.9 vs 43.0 vs 36.8%, p=0.003), compared to medium and high FFMF. Regarding body composition, patients with a low FFMF had higher percentage of body fat (28.7±11.2 vs 26.8±9.1 vs 24.2±9.6%, p=0.01) as well as lower percentage of body muscle (30.9±5.3 vs 31.3±4.2 vs 32.7±4.4%, p=0.03). Moreover, a low FFMF was associated with inflammation as indicated by increased levels of C-reactive protein (6.30 vs 4.20 vs 3.10 mg/l, p<0.01) and procalcitonin (0.06 vs 0.05 vs 0.05 µg/l, p=0.01). Endocrinological assessment revealed lower levels of estradiol (6.80 vs 14.70 vs 15.50 pg/ml, p=0.02) and testosterone (0.18 vs 0.48 vs 2.35 ng/ml, p<0.01) as well as higher levels of basal cortisol (8.90 vs 7.70 vs 7.60 μg/dl, p=0.05) in patients with a low FFMF. Regarding clinical outcomes, a low FFMF was associated with increased one-year mortality (23.4%) as compared to a medium (11.6%) or low FFMF (3.8%, p<0.01), Figure 2A. This difference persisted for up to five years after TAVR (p<0.01), Figure 2B. By using ROC curve analysis, FFMF (AUC 0.75, p<0.01) showed the strongest association with one-year all-cause mortality and was superior to the STS-PROM (AUC 0.65, p<0.01) and EuroSCORE II (AUC 0.64, p<0.01). Multivariate regression analysis revealed that a low FFMF (OR: 3.19 [95% CI: 1.64 – 6.22], p<0.01) was an independent predictor of one-year mortality following TAVR.
CONCLUSION:
The CT-derived FFMF is associated with inflammation and endocrinological disorder in patients undergoing TAVR. A low FFMF is a strong and independent predictor of dismal outcomes following TAVR. The assessment of FFMF as an indicator of muscle quality, can be seamlessly integrated into routine pre-interventional CT. This positions FFMF as a promising and objective imaging parameter for predicting outcomes in TAVR patients.
Figure 1: