<qa>  What is the TIMI frame count?Coronary slow flow CSF phenomenon, which is characterized by delayed coronary opacification in the absence of obstructive epicardial coronary artery disease, is a relatively common finding in patients undergoing routine coronary angiography and is often associated with chest pain. In some patients with CSF, blood flow may be heterogeneously distributed in the three coronary arteries, suggesting the heterogeneously distributed microvascular dysfunction in the myocardium. However, the vessel heterogeneity of Thrombolysis in Myocardial Infarction TIMI frame count TFC has not been fully elucidated. 