Usefulness of lumen area parameters determined by intravascular ultrasound to predict functional significance of intermediate coronary artery stenosis.

BACKGROUND: Coronary artery disease is the leading cause of death in China. Percutaneous coronary intervention is a recent milestone technology for treatment coronary artery disease. However, clinical decision making for patients with intermediate coronary stenosis is still controversial. We designed this study to assess the optimal intravascular ultrasound (IVUS) criteria for predicting functional significance of intermediate coronary lesions.

METHODS: We enrolled 141 patients with 165 intermediate coronary lesions located in vessels with a diameter ≥ 2.50 mm. IVUS of intermediate coronary lesions were performed before intervention. Pressure-derived fractional flow reserve (FFR) was measured at maximal hyperemia induced by adenosine infusion. An FFR < 0.80 was considered as abnormal functional significance.

RESULTS: For the overall 165 lesions, the mean FFR value was 0.84 ± 0.09. The diameter of the stenosis by visual estimation on angiogram was (59.63 ± 11.29)%. Minimum lumen diameter (MLD), minimum lumen area (MLA) and plaque burden (PB) were (2.00 ± 0.36) mm, (3.88 ± 1.34) mm(2), (67.28 ± 9.89)% respectively by IVUS measurements. An FFR < 0.80 was seen in 43 lesions (30.5%). There was a moderate correlation between IVUS parameters and FFR, including MLD (r = 0.372, P < 0.001), MLA (r = 0.442, P < 0.001) and PB (r = -0.172, P < 0.05). MLA was a predictor for FFR as a continuous variable independent of possible confounding variables (P < 0.05), and MLA and PB, were predictors for FFR < 0.80 as binary variables (P < 0.05). The best cutoff value of MLA to predict FFR < 0.80 was < 3.15 mm(2), with a 73.6% diagnostic accuracy; sensitivity 71.4%, specificity 67.0%, AUC = 0.709, and P < 0.001. The cutoff value of the PB to predict FFR < 0.80 was 65.45%; sensitivity 82.6%, specificity 41.2%, AUC = 0.644, and P < 0.01. If both MLA and PB were taken into account, the negative predictive value and the positive predictive value were 88.7% and 64.8% respectively.

CONCLUSIONS: Anatomic measurements of intermediate coronary lesions obtained by IVUS showed a moderate correlation to FFR values. IVUS-derived MLA ≥ 3.15 mm(2) may be useful to exclude FFR < 0.80, but poor specificity limits its applicability for physiological assessment of lesions < 3.15 mm(2). MLA was one of many factors affecting coronary flow hemodynamics. Both MLA and PB should be taken into account when determining functional ischemia.