Discrepancy between angiography and intravascular ultrasound when analysing small coronary arteries

A small reference diameter may be the consequence of high plaque burden and diffuse disease. The reference vessel diameter in small coronary arteries may vary according to the method of measurement used. We endeavoured to confirm the difference between data from examinations conducted using angiography with that revealed by intravascular ultrasound.

Between March 1993 and October 1999, 344 consecutive patients with 419 lesions in small vessels (< or =2.75 mm, Small group) and 953 patients with 1161 lesions in large vessels (Large group) underwent intravascular ultrasound-guided percutaneous transluminal angioplasty in our Institution. The mean difference between the intravascular ultrasound and the angiographic reference diameter (Delta(IVUS-Angio)) was 1.3+/-0.5 mm in the Small group and 1.0+/-0.6 mm in the Large group (P<0.001). There was a stronger correlation between plaque burden and Delta(IVUS-Angio)in the Small group (r=0.80, P<0.001) than in the Large group (r=0.59, P<0.001). An Delta(IVUS-Angio)> or =0.30 mm occurred in 99.5% of cases in the Small group and in 90% in the Large group (P<0.001). An Delta(IVUS-Angio)> or =0.50 mm occurred in 96% of case in the Small group and 80% in the Large group (P<0.001). Predictors of Delta(IVUS-Angio)> or =0.50 in the Small group were: proximal or middle lesion site, vessel type (left anterior descending artery, diagonal and obtuse marginal branches) and female sex. An Delta(IVUS-Angio)> or =1.0 mm occurred in 71% of cases in the Small group and in 49% in the Large group (P<0.001). Predictors of Delta(IVUS-Angio)> or =1.0 mm in the Small group were: proximal or middle lesion site, female sex, and lesion length.

A high percentage of vessels measuring < or =2.75 mm are large vessels with a high plaque burden. This condition is particularly prevalent in females, with lesions in the proximal or middle left anterior descending artery, and in obtuse marginal and diagonal branches.