Intravascular ultrasound (IVUS) is being used to assess the significance of a left main coronary artery stenosis (LMCS). However, the cutoff values of IVUS parameters at which to predict a fractional flow reserve (FFR) of 0.75 are unknown.
Methods and Results—
In 55 patients with an angiographically ambiguous LMCS, a pressure guidewire was used to calculate FFR, and IVUS parameters were calculated after automatic pullback. FFR averaged 0.86±0.13 (range, 0.55 to 1.0). IVUS minimum lumen diameter (MLD), minimum lumen area (MLA), cross-sectional narrowing (CSN), and area stenosis (AS) were 3.8±0.61 mm, 7.65±2.9 mm
, 59±13%, and 47±19%, respectively. Regression analysis demonstrated strong correlations between FFR and MLD (
<0.0001) as well as between FFR and MLA (
<0.0001). There were inverse, moderate correlations between FFR and CSN (
<0.0001), followed by those between FFR and AS (
<0.0001). Compared with FFR as the “gold standard,” an MLD of 2.8 mm had the highest sensitivity and specificity (93% and 98%, respectively) for determining the significance of an LMCS, followed by an MLA of 5.9 mm
(93% and 95%, respectively). Based on an FFR <0.75 and an FFR ≥0.75, the 38-month survival and event-free survival estimates (EFSEs) were both 100% and 100% versus 90%, respectively (
We conclude that (1) an IVUS MLD and MLA of 2.8 mm and 5.9 mm
, respectively, strongly predict the physiological significance of an LMCS and (2) among patients with an LMCS, an FFR of 0.75 is a strong predictor of survival and EFSE.