Intravascular ultrasound correlates of corrected TIMI framecount.

The TIMI frame count (TFC) is an index of coronary blood flow, and a correction in TFC (CTFC) for left anterior descending artery (LAD) has also been proposed. However, the relationship between TFC and intravascular ultrasound (IVUS) parameters of culprit coronary arteries has not been reported. The aim of this study was to investigate IVUS-derived correlates of TFC before and after stenting, and to assess the validation of its correction for LAD. The study population was comprised of 38 patients with acute coronary syndrome or stable coronary artery disease studied by IVUS before and after stenting (LAD 21, circumflex 8, right coronary artery 9). For LAD, CTFC was calculated by dividing the TFC by 1.7. Preintervention luminal % area stenosis was 82 +/- 12.3%. Pre- and postintervention target lesion lumen areas were 1.8 +/- 0.5 mm2 and 8.5 +/- 0.5 mm2 (P<0.0001), and CTFC were 35.3 +/- 16.8 and 16.9 +/- 4.3 (P<0.0001), respectively. In the 76 IVUS studies, CTFC showed a good correlation to luminal % area stenosis (r = 0.69, P<0.001), and a good and negative correlation to target lesion lumen area (r = -0.70, P<0.001). Postprocedural improvement in CTFC showed a modest correlation to acute lumen gain (r = 0.5, P<0.05). With respect to culprit arteries, pre and postintervention IVUS parameters and CTFC, and net CTFC change after stenting were not different (P>0.05). However, uncorrected TFC of LAD was significantly higher than both the CTFC of LAD and TFC of the other two coronary arteries (P<0.05). We conclude that CTFC is closely correlated to target lesion luminal area and luminal % area stenosis whereas a modest correlation is present between improvement in CTFC and acute luminal gain due to stenting. Results from different coronary arteries with comparable IVUS parameters seem to support the validity of a correction in TFC.