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Published on: February 16, 2016
Relation of Thrombolysis in Myocardial Infarction Frame Count to Invasively Measured Coronary Physiologic Indexes
Tatsuro Yamazaki1, Yuichi Saito2, Daichi Yamashita1
1Department of Cardiovascular Medicine, Chiba University Graduate School of Medicine, Chiba, Japan.
Insights
The thrombolysis in myocardial infarction frame count (TFC) is not a reliable indicator for diagnosing coronary microvascular dysfunction (CMD). This study found corrected TFC (cTFC) did not correlate well with invasive measures like coronary flow reserve (CFR) or index of microcirculatory resistance (IMR).
Area of Science:
- Cardiology
- Vascular Physiology
- Diagnostic Imaging
Background:
- International guidelines suggest elevated thrombolysis in myocardial infarction frame count (TFC) indicates coronary microvascular dysfunction (CMD).
- The diagnostic accuracy of TFC, specifically corrected TFC (cTFC), for invasively confirmed CMD remains uncertain.
- Invasive assessment of coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) are gold standards for CMD diagnosis.
Purpose of the Study:
- To evaluate if a corrected TFC (cTFC) cutoff of >25, as per guidelines, accurately identifies coronary microvascular dysfunction (CMD).
- To assess the correlation between cTFC and invasive physiological parameters (CFR, IMR) in patients without significant epicardial coronary artery disease.
Main Methods:
- 137 patients without significant epicardial lesions underwent invasive coronary physiological assessment using thermodilution in the left anterior descending artery.
- Corrected TFC (cTFC) was measured from coronary angiography.
- Coronary microvascular dysfunction (CMD) was defined by abnormal CFR (≤2.0) and/or IMR (>25).
Main Results:
- A corrected TFC (cTFC) >25 was present in 24.8% of patients, while CMD was diagnosed in 23.3%.
- No significant difference in CMD rates was observed between patients with and without cTFC >25.
- cTFC showed weak correlations with mean transit time and IMR, but no significant correlation with CFR; receiver operating characteristic analysis indicated poor diagnostic ability.
Conclusions:
- In patients without obstructive epicardial coronary artery disease, corrected TFC (cTFC) is not diagnostic for coronary microvascular dysfunction (CMD).
- Neither cTFC as a continuous variable nor the guideline-suggested cutoff of 25 effectively identifies abnormal CFR or IMR.
- The findings do not support the use of cTFC for evaluating coronary microvascular dysfunction.
Abstract:
In the international guidelines, higher thrombolysis in myocardial infarction frame count (TFC) is indicated as evidence of coronary microvascular dysfunction (CMD). However, the association of TFC with invasively measured coronary physiologic parameters such as coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) remains unclear. Patients without significant epicardial coronary lesions underwent invasive coronary physiologic assessment using a thermodilution method in the left anterior descending artery. Corrected TFC (cTFC) was evaluated on coronary angiography. The cut-off values of CFR and IMR were defined as ≤2.0 and >25, and patients with abnormal CFR and/or IMR were defined as having CMD. This study aimed to assess whether cTFC >25, a cut-off value in the guidelines, was diagnostic of the presence of CMD. Of the 137 patients, 34 (24.8%) and 32 (23.3%) had cTFC >25 and CMD, respectively. The rate of CMD was not significantly different between patients with and without cTFC >25. cTFC was weakly correlated with at rest and hyperemic mean transit time and IMR, whereas no significant correlation was observed between cTFC and CFR. The receiver operating characteristic curve analysis showed the poor diagnostic ability of cTFC for abnormal CFR and IMR and the presence of CMD. In conclusion, in patients without epicardial coronary lesions, cTFC as a continuous value and with the cut-off value of 25 was not diagnostic of abnormal CFR and IMR and the presence of CMD. Our results did not support the use of cTFC in CMD evaluation.
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