Thrombolysis in myocardial infarction frame count with angiographically normal coronary arteries and its relationship to ST-segment depression.

BACKGROUND

The thrombolysis in myocardial infarction frame count (TFC) has been proposed as a simple, reproducible, objective and quantitative method to assess coronary blood flow. However, the TFC in normal coronary arteries has not been investigated in detail. The aim of this study was to determine normal TFC values and investigate their correlation with ST-segment depression during exercise testing (ET).

METHODS AND RESULTS

The TFC was measured in 116 cases with normal coronary arteries who underwent ET. The ST segment was evaluated on 12-lead electrocardiograms at 60 ms after the J-point. Horizontal or downsloping ST-segment depression of > or = 0.5 mm was recorded and the sum of the depressions was calculated. When ST-segment depression > or = 1 mm compared to the level of PR segment on two or more leads was detected, the test was accepted as positive. The TFC for the left anterior descending coronary artery (LAD) was significantly higher than those for the left circumflex coronary artery (LCx) and the right coronary artery (RCA). The TFC of coronary arteries was significantly higher in patients with ET positive (for LAD, 39.5 +/- 10.7 compared with 30.1 +/- 7.6 frames; for LCx, 29.2 +/- 9.3 compared with 23.6 +/- 6.5 frames; and for RCA, 30.7 +/- 11 compared with 23.7 +/- 7 frames; P < 0.001 for overall comparisons). Women had a lower TFC than men in the LAD. Moreover, it was determined that the TFC values for the LAD, LCx and RCA significantly correlated with the sum of ST-segment depression (r = 0.57, r = 0.46 and r = 0.41, respectively, P < 0.001 for overall correlations). It was also determined that the TFC was affected by the proximal diameter of the coronary arteries.

CONCLUSIONS

The results of this study highlight the differences of the TFC in normal LAD, LCx and RCA. In patients with normal coronary arteries, the fact that the TFC is higher in ET-positive than in ET-negative patients may explain false positive results of ET. Sex and coronary artery diameter should be taken into consideration in evaluating the TFC.