Feasibility of intravascular ultrasound studies: predictors of imaging success before coronary interventions.
BACKGROUND: Intravascular ultrasound (IVUS) is currently used to study lesions during transcatheter coronary therapy. However, before dilation some lesions cannot be reached or crossed with the imaging catheter. HYPOTHESIS: This study seeks to elucidate which factors determine the feasibility of IVUS examination before coronary interventions. METHODS: Accordingly, 100 consecutive patients undergoing IVUS examination before coronary angioplasty were prospectively studied. The clinical and angiographic characteristics of 77 patients with a successful IVUS study (Group A) were compared with those of 23 patients in whom IVUS was attempted but the target lesion could not be interrogated (Group B). The echogenic characteristics of the target lesion [before (n = 77) or after intervention (in 18 patients in Group B)] were also studied. RESULTS: Patients in Group B were significantly older (62 +/- 7 vs. 57 +/- 10 years, p < 0.05) and more frequently had stable angina [8 (35%) vs. 9 (11%), p < 0.05]. The distribution of lesions within the coronary tree and angiographic lesion characteristics including length, eccentricity, calcification, bend location, and the American College of Cardiology/American Heart Association classification were similar in both groups. However, proximal tortuosities (> 45 degrees at end diastole) were more frequently found in Group B [20 (87%) vs. 47 (61%), p < 0.05]. In addition, by quantitative angiography, patients in Group B had smaller arteries (reference diameter 2.8 +/- 0.4 vs. 3.1 +/- 0.4 mm, p < 0.05) and more severe lesions (minimal lumen diameter 0.46 +/- 0.24 vs. 0.65 +/- 0.34 mm, p < 0.05). On IVUS, calcified lesions were more frequently visualized in Group B (61 vs. 38%, p < 0.05). On multivariate analysis, catheter size, baseline minimal lumen diameter, angiographic proximal tortuosities, and lesion calcification on imaging were independent predictors of the feasibility of IVUS studies. CONCLUSIONS: Unsuccessful IVUS studies before intervention occur more frequently (1) in vessels with proximal tortuosities or severe lumen narrowing, (2) in lesions that are calcified on IVUS, and (3) when large imaging catheters are used.