Optimal ultrasound guided balloon angioplasty

Summary

In the early ’ 90ies an important discrepancy has been shown between angiographic and ultrasound findings after balloon angioplasty, but only in the last years, new strategies of aggressive balloon dilatation based on the ultrasound measurements have been applied. In the CLOUT study, upsizing of the balloon based on the ultrasound measurements was required in 73% of the lesions, ranging from 0.25 mm to 1.25 mm. An even more aggressive strategy was allowed by the availability of coronary stents, allowing focal treatment of the segments of residual lumen narrowing or severe dissection. The balloon was further upsized, matching the media-to-media diameter and, at least in the Milan and Washington experience, high inflation pressures were used. In the Tubingen study, the additional dilatation induced an increase in minimal lumen diameter from 1.95 ± 0.49 mm to 2.21 ± 0.47 mm and a decrease in residual diameter stenosis from 28.3 ± 14.9% to 18.1 ± 14.4%, both p<0.0001. In Washington, ultrasound was used before treatment to select the appropriate balloon and the result was accepted only if the lumen area in the treated segment was ≥ 70% of the reference lumen area and no flow limiting dissections were observed. In 94/242 lesions (39%) these criteria were fulfilled, with a minimal lumen area of 6.0 ± 2.8 mm² and a residual plaque burden of 54 ± 16%. No procedural coronary ruptures or abrupt vessel closure were observed. At a mean follow-up of 8 months, target lesion revascularization was lower in the group treated with PTCA only (7.8%) than in the group crossed-over to stent implantation (12.9%, p<0.08). In Milan, the IVUS guided PTCA strategy was addressed primarily to long lesions (>15 mm) and to lesions located in small vessels (<3.0 mm reference diameter). Balloon angioplasty was initially performed using an angiographically oversized balloon inflated until full balloon expansion was achieved and then an IVUS examination was performed. IVUS success criteria were defined as the presence of a true minimal lumen area ≥ 5.5 mm² or of a minimal lumen cross-sectional area ≥ 50% of the vessel cross-sectional area at the lesion site. In this unfavourable lesion subset, at 5 months clinical follow-up, the cumulative incidence of major adverse cardiac events (death, Q-wave myocardial infarction, target lesion revascularization) was 28%, with an angiographic restenosis rate (≥50% diameter stenosis) of 27%.

These preliminary results from different centers suggest that the procedural success is higher than the success obtained with conventional PTCA in similar lesion subsets and, with the application of stents when needed, similar to the success of elective stenting. Randomized trials are required to establish whether this strategy can improve immediate and long-term results of percutaneous coronary revascularization procedures.