Introduction In recent years, intravascular ultrasound (IVUS) has evolved as a valuable adjunct to angiography. IVUS allows precise tomographic measurement of lumen area and plaque size, distribution and, to some extent, composition. It is essential in clinic decision making. Myocardial fractional flow reserve (FFRmyo) is a special index of the functional severity of coronary stenosis. Although the application of FFRmyo to assess intermediate coronary lesion is widely performed in some centers in developed countries, its use in China was lagged. Because it is relatively expensive to measure FFRmyo, it will be beneficial to save the expenses and to short operation time if CAG and IVUS criteria could be clinically used as tools to discriminate functional significant of intermediate stenosis.
Materials and methods In 46 lesions of intermediate severity (eg, 40% to 60% diameter stenosis) we assessed 1. by pressure wire: myocardial fractional flow reserve (FFRmyo, index of functional significance), and 2. by IVUS: minimal lumen cross-sectional area (MLA) and percent area stenosis at the lesion site. Receiver operating characteristic curve analysis was performed to establish the best cut-off values of IVUS indexes (ie, MLA and percent area stenosis) that were most predictive of FFRmyo<0.75.
Results FFRmyo in 46 lesions of angiographic intermediate stenosis (49±11%) was significantly lower than it was in angiographic normal artery (0.83±0.15 vs 0.97±0.02, p<0.01). 14 lesions (30%) were functionally critical (eg, FFRmyo<0.75). By regression analysis, percent area stenosis had a significant inverse correlation with FFRmyo (r=−0.68, p<0.01). MLA showed a significant positive relation with FFRmyo (r=0.63, p<0.01). By receiver operating characteristic analysis, we identified a IVUS area stenosis ≥65% (sensitivity 100%, specificity 72%), a minimal lumen cross-sectional area ≤4 mm2 (sensitivity 93%, specificity 77%) to be the best cut-off values to fit with FFRmyo<0.75.
Conclusion IVUS area stenosis ≥65% and minimal lumen cross-sectional area ≤4 mm2 reliably identified functionally critical intermediate coronary stenosis.