Novel clearance of muscle proteins by muscle cells

Diagnostic and prognostic performance of the ratio between high-sensitivity cardiac troponin I and troponin T in patients with chest pain

Background

Elevations of high-sensitivity cardiac troponin (hs-cTn) concentrations not related to type 1 myocardial infarction are common in chest pain patients presenting to emergency departments. The discrimination of these patients from those with type 1 myocardial infarction (MI) is challenging and resource-consuming. We aimed to investigate whether the hs-cTn I/T ratio might provide diagnostic and prognostic increment in this context.

Methods

We calculated the hs-cTn I/T ratio in 888 chest pain patients having hs-cTnI (Abbott Laboratories) or hs-cTnT (Roche Diagnostics) concentrations above the respective 99^th percentile at 2 hours from presentation. All patients were followed for one year regarding mortality.

Results

The median hs-cTn I/T ratio was 3.45 (25^th, 75^th percentiles 1.80–6.59) in type 1 MI patients (n = 408 ☯46.0%]), 1.18 (0.81–1.90) in type 2 MI patients (n = 56 ☯6.3%]) and 0.67 (0.39–1.12) in patients without MI. The hs-cTn I/T ratio provided good discrimination of type 1 MI from no type 1 MI (area under the receiver-operator characteristic curve 0.89 ☯95% confidence interval 0.86–0.91]), of type 1 MI from type 2 MI (area under the curve 0.81 ☯95% confidence interval 0.74–0.87]), and was associated with type 1 MI in adjusted analyses. The hs-cTn I/T ratio provided no consistent prognostic value.

Conclusions

The hs-cTn I/T ratio appears to be useful for early diagnosis of type 1 MI and its discrimination from type 2 MI in chest pain patients presenting with elevated hs-cTn. Differences in hs-cTn I/T ratio values may reflect variations in hs-cTn release mechanisms in response to different types of myocardial injury.

Appropriateness of indirect markers of muscle damage following lower limbs eccentric-biased exercises: A systematic review with meta-analysis

Purpose

The aim of this review was to (1) characterize the time-course of markers of exercise-induced muscle damage (EIMD) based on the level of maximal voluntary contraction torque loss at 24-48h post-exercise (MVC_loss24-48h), (2) identify factors (e.g., exercise and population characteristics) affecting the level of MVC_loss24-48h, and (3) evaluate the appropriateness of EIMD markers as indicators of MVC_loss24-48h.

Methods

Magnitude of change of each EIMD markers was normalized using the standardized mean differences method to compare the results from different studies. Time-course of EIMD markers were characterized according to three levels of MVC_loss24-48h based on a clustering analysis of the 141 studies included. Association between MVC_loss24-48h levels and participant´s characteristics or exercise type/modalities were assessed. Meta-regressions were performed to investigate the associations between MVC_loss24-48h and EIMD markers changes at <6h, 24h, 48h, 72h and >96h after exercise.

Results

Time-course of EIMD markers recovery differs between levels of MVC_loss24-48h. Training status and exercise type/modality were associated with MVC_loss24-48h level (p<0.05). MVC_loss24-48h was correlated to changes in myoglobin concentration (<6h), jump height (24h) and range of motion (48h) (p<0.001).

Conclusion

As the exercise could differently affect markers as function of the EIMD severity (i.e., MVC_loss24-48h levels), different markers should be used as function of the timing of measurement. Mb concentration should be used during the first hours after the exercise (<6h), whereas jump height (24h) and range of motion (48h) could be used as surrogate for maximal voluntary contraction later. Moreover, training status and exercise type/modality could influence the magnitude of MVC_loss24-48h.

The ratio of cardiac troponin T to troponin I may indicate non-necrotic troponin release among COVID-19 patients

BACKGROUND

Although cardiac troponin T (cTnT) and troponin I(cTnI) are expressed to similar amount in cardiac tissue, cTnI often reach ten-times higher peak levels compared to cTnT in patients with myocardial necrosis such as in acute myocardial infarction (MI). In contrast, similar levels of cTnT and cTnI are observed in other situations such as stable atrial fibrillation and after strenuous exercise.

OBJECTIVE

Examine cTnT and cTnI levels in relation to COVID-19 disease and MI.

METHODS

Clinical and laboratory data from the local hospital from an observational cohort study of 27 patients admitted with COVID-19 and 15 patients with myocardial infarction (MI) that were analyzed with paired cTnT and cTnI measurement during hospital care.

RESULTS

Levels of cTnI were lower than cTnT in COVID-19 patients (TnI/TnT ratio 0.3, IQR: 0.1-0.6). In contrast, levels of cTnI were 11 times higher compared to cTnT in 15 patients with MI (TnI/TnT ratio 11, IQR: 7-14). The peak cTnI/cTnT ratio among the patients with MI following successful percutaneous intervention were 14 (TnI/TnT ratio 14, IQR: 12-23). The 5 COVID-19 patient samples collected under possible necrotic events had a cTnI/cTnT ratio of 5,5 (IQR: 1,9-8,3).

CONCLUSIONS

In patients with COVID-19, cTnT is often elevated to higher levels than cTnI in sharp contrast to patients with MI, indicating that the release of cardiac troponin has a different cause in COVID-19 patients.