Aims

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.

Methods and results

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.

Conclusions

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.

This study is the first assessment of feasibility and clinical usefulness of an imaging wire. The device used is a 0.018" flexible cable mounting a 30 MHz piezoelectric crystal at the end. The only possible application of the wire in its current configuration is the assessment of balloon expansion with over-the-wire balloon catheters. In this study, 17 lesions were examined in 14 patients. Despite careful removal of the air, no image could be obtained with the balloon deflated or through the shaft of conventional balloon catheters. When the balloon was inflated to 1-4 atm the circular echo-free cross-section of the balloon became visible, surrounded by the dense line of the balloon membrane and by the vessel wall. By examining the stent area at different balloon pressures, it was possible to determine the stent recoil between maximal balloon expansion and lowest balloon pressure allowing a readable ultrasound image. These encouraging preliminary observations confirm the feasibility of the use of an ultrasound guidewire for monitoring balloon expansion during stent implantation. After high pressure inflation, a moderate reduction of the stent lumen was observed during deflation, compatible with the small recoil predicted for the stainless-steel mesh stent used.