Association Between Serum Myostatin Levels, Hospital Mortality, and Muscle Mass and Strength Following ST-Elevation Myocardial Infarction.

AIM: This study aimed to evaluate the association between serum myostatin levels, hospital mortality, and muscle mass and strength following ST-segment elevation myocardial infarction (STEMI). METHODS: This was a prospective observational study. Within 48 hours of admission, bioelectrical impedance and handgrip strength were assessed and blood samples collected for myostatin evaluation. Hospital mortality was recorded. A multiple logistic regression model was also constructed, adjusted by parameters that exhibited significant differences in the univariate analysis, to evaluate the association between myostatin levels and hospital mortality. RESULTS: One hundred and two (102) patients were included: mean age was 60.5±10.6 years, 67.6% were male, and 6.9% died during hospital stay. Univariate analysis showed that patients with lower myostatin levels had higher mortality rates. Serum myostatin levels positively correlated with handgrip strength (r=0.355; p<0.001) and appendicular skeletal muscle mass index (r=0.268; p=0.007). Receiver operating characteristic (ROC) curve analysis revealed that lower myostatin levels were associated with hospital mortality at the <2.20 ng/mL cut-off. Multiple logistic regression showed that higher serum myostatin levels were associated with reduced hospital mortality when adjusted by ß blocker use (OR, 0.228; 95% CI, 0.054-0.974; p=0.046). CONCLUSIONS: Serum myostatin concentrations positively correlated with muscle mass and strength in STEMI patients. Further assessment of serum myostatin association with mortality should be conducted using a larger sample and assessing the additive value to the Global Registry of Acute Coronary Events (GRACE) or thrombolysis in myocardial infarction (TIMI) risk scores.

Ultra-short heart rate variability recording reliability: The effect of controlled paced breathing.

BACKGROUND: Recent studies have reported that Heart Rate Variability (HRV) indices remain reliable even during recordings shorter than 5 min, suggesting the ultra-short recording method as a valuable tool for autonomic assessment. However, the minimum time-epoch to obtain a reliable record for all HRV domains (time, frequency, and Poincare geometric measures), as well as the effect of respiratory rate on the reliability of these indices remains unknown. METHODS: Twenty volunteers had their HRV recorded in a seated position during spontaneous and controlled respiratory rhythms. HRV intervals with 1, 2, and 3 min were correlated with the gold standard period (6-min duration) and the mean values of all indices were compared in the two respiratory rhythm conditions. RESULTS: rMSSD and SD1 were more reliable for recordings with ultra-short duration at all time intervals (r values from 0.764 to 0.950, p < 0.05) for spontaneous breathing condition, whereas the other indices require longer recording time to obtain reliable values. The controlled breathing rhythm evokes stronger r values for time domain indices (r values from 0.83 to 0.99, p < 0.05 for rMSSD), but impairs the mean values replicability of domains across most time intervals. Although the use of standardized breathing increases the correlations coefficients, all HRV indices showed an increase in mean values (t values from 3.79 to 14.94, p < 0.001) except the RR and HF that presented a decrease (t = 4.14 and 5.96, p < 0.0001). CONCLUSION: Our results indicate that proper ultra-short-term recording method can provide a quick and reliable source of cardiac autonomic nervous system assessment.