The impact of chronically diseased coronary arteries and stenting on the corrected TIMI frame count in elective coronary angiography and percutaneous coronary intervention procedures

Abstract

The impact of chronic coronary obstructions on resting blood flow in stable cardiac patients and the response to percutaneous coronary intervention (PCI) using the TIMI frame count method has not been well documented. We studied the impact of coronary artery stenosis severity on the corrected TIMI frame count (cTFC) in chronically stenosed coronary arteries. We prospectively and quantitatively determined the impact of stenting on the cTFC during elective PCI.

Methods: In substudy 1, analysis was performed to obtain the mean cTFC for arteries with <50% stenosis (Group A), 51-75% stenosis (Group B), 76-85% stenosis (Group C1), 86-95% stenosis (Group C2) and 96-99% stenosis (Group C3). In substudy 2, the cTFC and quantitative coronary angiography were performed pre- and post-PCI.

Results: In substudy 1, the cTFC increased exponentially beyond a diameter stenosis of 75% (P < 0.01). However there was no significant difference in the cTFC for coronary arteries with <75% stenosis. In substudy 2, the overall pre- and poststenting cTFC was 17.1 +/- 11.7 and 7.8 +/- 2.7 (P < 0.01) and the TFC index [calculated by dividing the mean cTFC for the relevant artery by the mean cTFC for the corresponding coronary artery in a previously derived control group in our laboratory] was 1.6 +/- 1 and 0.7 +/- 0.2 (P = < 0.01), respectively.

Conclusion: We have demonstrated that there was a significant increase in the cTFC when the coronary artery stenosis was more than 75% reflecting significant flow abnormalities at this degree of stenosis in chronically diseased coronary arteries. Following stenting there is a significant improvement in the cTFC, which is better than the cTFC for arteries with normal flow, suggesting early hyperaemia.