Background Serum Troponin I is used routinely as an adjunct to EKG for the diagnosis of myocardial infarction (MI); however, a correlation between marker level and infarct size has yet to be documented in vivo. We report findings from a chronic coronary artery ligation model in the canine (n = 12) in which peak Troponin I is related to infarct size as determined by high-resolution cardiac magnetic resonance imaging. Methods All animals underwent a left anterior thoracotomy to allow for ligation of the left anterior descending artery. Evidence of myocardial infarction, including EKG changes, elevated Troponin I, along with visual reduction in perfusion and wall motion, was noted in all animals. Thirty days after surgical intervention, cine MRI and contrast-enhanced MRI were performed. Dedicated analysis software was used to quantify global infarction size, LV function and to map regions of MI to a 3D model of the left ventricle. Results A linear relationship between infarct extent and peak Troponin I level exists (r = 0.98, P < 0.0001). In addition, we observed a negative trend between infarct extent, peak Troponin I, and ejection fraction. Conclusion The findings of this study indicate that Troponin I and cardiac magnetic resonance imaging provide a more accurate estimation of infarct size than was previously reported using markers with less sensitivity and imaging modalities of lower spatial resolution and viability imaging capability.
Bibliographical noteFunding Information:
This project could not have been completed were it not for the generous support from Lillehei Heart Institute, Richard L. Varco Surgical Research Fellowship, and NIH/NHLBI (R01 HL65394-01). The authors do not acknowledge any financial conflicts of interests in conducting this study. We recognize the following individuals who contributed the completion of the project: Eric Rahrmann, Zach Kastenberg, Tina Gross, and Melinda Hartman.
- Troponin I
- biological markers
- blood immunoassay
- myocardial infarction