TIMI frame count: a quantitative method of assessing coronary artery flow

Area of Science:

• Cardiology
• Medical Imaging
• Physiology

Background:

• The Thrombolysis in Myocardial Infarction (TIMI) flow grade is a subjective, categorical measure of coronary blood flow used in angiographic trials.
• Limitations in subjective assessment necessitate objective and quantitative methods for evaluating coronary perfusion.

Purpose of the Study:

• To develop and validate an objective, continuous variable index of coronary blood flow.
• To establish a reproducible method for assessing coronary perfusion beyond the limitations of the qualitative TIMI flow grade.

Main Methods:

• The corrected Thrombolysis in Myocardial Infarction (TIMI) frame count (CTFC) method was developed by counting cineframes for dye transit to distal landmarks.
• The method's reproducibility was assessed, and frame counts were corrected for variations in artery length (e.g., Left Anterior Descending artery).
• CTFC was measured in normal arteries, acute myocardial infarction (MI) culprit arteries post-thrombolysis, and non-culprit arteries.

Main Results:

• The CTFC method demonstrated reproducibility.
• Mean CTFC in culprit arteries post-thrombolysis improved significantly from 90 minutes to 18-36 hours.
• No correlation was found between CTFC improvement and changes in minimum lumen diameter.
• Early post-thrombolysis CTFC in non-culprit arteries was higher (slower flow) than normal but normalized by 1 day.

Conclusions:

• The corrected TIMI frame count (CTFC) is a simple, reproducible, objective, and quantitative index of coronary flow.
• CTFC allows for the standardization of TIMI flow grades and facilitates inter-trial comparisons of angiographic endpoints.
• Disordered resistance vessel function may contribute to reduced coronary flow in the early hours after thrombolysis.