The following is a summary of “Relation of Thrombolysis In Myocardial Infarction Frame Count to Invasively Measured Coronary Physiological Indices,” published in the November 2023 issue of Cardiology by Yamazaki et al. 

In international guidelines, an elevated Thrombolysis In Myocardial Infarction frame count (TFC) indicates coronary microvascular dysfunction (CMD). However, the connection between TFC and invasively measured coronary physiological parameters, such as coronary flow reserve (CFR) and index of microcirculatory resistance (IMR), remains unclear. 

Patients lacking significant epicardial coronary lesions underwent invasive coronary physiological assessment using a thermodilution method in the left anterior descending artery. Corrected TFC (cTFC) was assessed through coronary angiography. Cut-off values for CFR and IMR were defined as ≤2.0 and >25, respectively, with patients exhibiting abnormal CFR and/or IMR classified as having CMD. The primary focus was determining whether cTFC >25, a guideline-recommended cut-off value, indicated CMD presence. Among the 137 patients, 34 (24.8%) had cTFC >25, and 32 (23.3%) had CMD. 

The CMD rate did not significantly differ between patients with and without cTFC >25. cTFC exhibited a weak correlation with resting and hyperemic mean transit time and IMR, while no significant correlation was observed between cTFC and CFR. Receiver operating characteristic curve analysis demonstrated the limited diagnostic ability of cTFC for abnormal CFR and IMR, as well as the presence of CMD. 

In conclusion, in patients without epicardial coronary lesions, cTFC did not serve as a diagnostic indicator for abnormal CFR and IMR or the presence of CMD, either as a continuous value or with a cut-off of 25. Our findings do not support the utilization of cTFC in CMD assessment.

Source: sciencedirect.com/science/article/abs/pii/S0002914923013188