There might be a bigger difference between the types of cardiac troponin assays, after a recent JACC analysis found that the type of troponin could help us better understand the kind of damage occurring after a heart attack.
- Cardiac troponin I and troponin T are currently used interchangeably in clinical practice with guidelines assuming they reflect identical myocardial damage.
- Currently, most practices measure one type or the other but not both.
- Early studies have suggested that the cTnI/cTnT ratio may differ between acute necrotic versus chronic or non-necrotic myocardial injury, but that was uncertain till now.
As part of a multicohort validation, researchers examined 9.7k patients who were marked as having no known, chronic, or acute cardiac disease, and then measured their hs-cTnI and hs-cTnT concentrations to see what cTnI/cTnT ratio could tell them about the injury type.
- The cTnI/cTnT ratio proved highest in acute cardiac disease (2.06).
- This was approximately 4-fold greater than the ratio found in patients with chronic disease (0.66) and no known cardiac disease (0.50).
- Incorporating the cTnI/cTnT ratio alongside individual troponin values made it easier to tell between type 1 and type 2 acute myocardial infarction (AUC: 0.73 vs 0.70).
Experimental cardiomyocyte models were also used to replicate the clinical findings, with researchers discovering that mild nonlethal injury produced cTnT-dominant release, while lethal injury led to cTnI-dominant release.
Given that current practice assumes cTnI and cTnT reflect identical pathophysiology, these findings could challenge single-troponin measurement strategies and guideline recommendations that treat the biomarkers as interchangeable.
- The good news is that implementing this information would require minimal additional cost, since physicians can measure both troponins rather than choosing one.
- The ratio’s ability to distinguish type 1 from type 2 MI could also help guide decision-making about invasive coronary angiography versus medical management.
The Takeaway
It seems like a method for better classifying and triaging cardiac damage was under our noses the whole time. On the bright side, thanks to this study, physicians will no longer have to scratch their heads on which assay to use, since the answer is both.
