Clearance of cardiac troponin T with and without kidney function
Vincent Fridén1, Karin Starnberg1, Aida Muslimovic1
1Department of clinical chemistry and transfusion medicine, Sahlgrenska University Hospital, the Sahlgrenska Academy at the University of Gothenburg, SE-41345 Gothenburg, Sweden.
Insights
Clearance of cardiac troponin T (cTnT) is primarily extrarenal at high concentrations post-myocardial infarction. Renal clearance contributes significantly to cTnT elimination at lower concentrations, impacting levels in patients with impaired kidney function.
Area of Science:
- Cardiology
- Nephrology
- Biomarker Analysis
Background:
- Cardiac troponin T (cTnT) is a critical biomarker for diagnosing myocardial infarction.
- The role of kidney function in the clearance of cTnT has not been fully elucidated.
- Understanding cTnT clearance is crucial for accurate interpretation of biomarker levels, especially in patients with renal impairment.
Purpose of the Study:
- To investigate the extent of kidney-dependent clearance of cardiac troponin T (cTnT).
- To determine whether renal function influences cTnT levels, particularly in conditions of varying biomarker concentration.
- To assess the diagnostic utility of kidney function-adjusted cTnT levels.
Main Methods:
- Animal studies involving kidney vessel clamping after cardiac extract injection to simulate myocardial infarction.
- Analysis of cTnT degradation and kidney extraction index in human subjects.
- Infusion studies with controlled cTnT levels and renal vessel clamping in rats.
- Evaluation of cTnT molecular weight distribution in human plasma.
- Clinical assessment in heart failure patients with renal vein catheterization.
Main Results:
- High-concentration cTnT clearance post-myocardial infarction was not significantly affected by kidney function in rats.
- Renal clearance of cTnT became significant at lower concentrations, with renal vessel clamping reducing clearance twofold.
- Over 60% of cTnT in humans had a molecular weight suggesting glomerular filtration.
- The extraction index of cTnT in heart failure patients ranged from 8-19%.
- Kidney function-adjusted cTnT levels improved the diagnostic accuracy for myocardial infarction.
Conclusions:
- Extrarenal clearance mechanisms dominate for high concentrations of cTnT, typical after large myocardial infarctions.
- Renal clearance plays a more substantial role in eliminating cTnT at lower concentrations, as seen in stable elevations.
- Elevated stable cTnT levels in patients with reduced kidney function may be attributed to diminished renal clearance.
Objective:
The extent of kidney-dependent clearance of the cardiac damage biomarker cardiac troponin T (cTnT) is not known.
Methods And Results:
We examined clearance of cTnT after injection of heart extracts in rats with or without clamped kidney vessels. The extent of degradation of cTnT to fragments able to pass the glomerular membrane and the kidney extraction index of cTnT was examined in human subjects. After a bolus injection of rat cardiac extract, simulating a large myocardial infarction, there was no significant difference in clearance of cTnT with or without kidney function. However, a slower clearance was observed late in the clearance process, when cTnT levels were low. When low levels of rat cardiac extract were infused at a constant rate to steady state, clamping of the renal vessels resulted in significant 2-fold reduction in clearance of cTnT. Over 60% of the measured cTnT in human subjects had a molecular weight below 17kDa, expected to have a relatively free passage over the glomerular membrane. The extraction index of cTnT in three heart failure patients undergoing renal vein catheterization was 8-19%. Kidney function adjusted cTnT levels increased the area under the ROC curve for diagnosis of myocardial infarction of the cTnT analysis in an emergency room cohort.
Conclusions:
At high concentrations, often found after a large myocardial infarction, extrarenal clearance of cTnT dominates. At low levels of cTnT, often found in patients with stable cTnT elevations, renal clearance also contribute to the clearance of cTnT. This potentially explains why stable cTnT levels tend to be higher in patients with low kidney function.
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