Preintervention lesion remodelling affects operative mechanisms of balloon optimised directional coronary atherectomy procedures: a volumetric study with three dimensional intravascular ultrasound

Stereology: a simplified and more time-efficient method than planimetry for the quantitative analysis of vascular structures in different models of intimal thickening

OBJECTIVE

Semiautomatic computer-assisted planimetry is currently the standard morphometric technique in models of intimal thickening. We evaluated stereological point counting as an alternative method for the measurement of cross-sectional vascular areas (lumen, intima, and media) by comparing precision, efficiency, and variance components.

METHODS

Sections from murine atherosclerotic aorta (n = 21), stented rabbit iliac arteries (n = 30), and porcine coronary arteries (n = 30) were analyzed at two institutes using both techniques. To determine reproducibility, porcine arteries were measured twice.

RESULTS

Area measurements showed almost identical means and standard deviations for planimetry and stereology [e.g., intima (mm2): 0.10+/-0.11 vs. 0.12+/-0.12 (mouse), 0.60+/-0.16 vs. 0.60+/-0.15 (rabbit), and 1.92+/-1.52 vs. 1.97+/-1.61 (pig)]. Deming regression and Bland-Altman plots demonstrated a good agreement between both techniques that was not influenced by artery size. Both methods exhibited excellent repeatability, although planimetry (-0.18+/-0.27) was more precise than stereology (-0.17+/-0.47; variance, P < .01, Levene test). In addition, intraoperator variance (error inherent to the technique) was greater for stereology (1.6-15.8% vs. 4.8-33.5%), whereas interoperator variance (error between institutes) was very small for both methods (0.1-0.9% vs. 0.1-1.7%). Indeed, biologic variability was, by far, the most important variance component in all measurements (84-98% vs. 65-95%). Finally, stereology required 20% (mouse; P < .05) to 40% (pig; P < .001) less time to complete analysis.

CONCLUSION

The quantification of vascular structures by planimetry and stereology yielded comparable results in all models of intimal thickening, but stereology proved to be less time-consuming. Therefore, study design may dictate the most appropriate choice of technique.

Comparison of directional coronary atherectomy and stenting versus stenting alone for the treatment of de novo and restenotic coronary artery narrowing

Late lumen loss after directional coronary atherectomy (DCA) is mainly determined by arterial remodeling. We hypothesized that stent implantation after optimal lesion debulking could be an effective approach to reduce restenosis. A total of 753 patients with de novo or restenotic coronary lesions were prospectively randomized to DCA plus stenting (n = 381) or stenting alone (n = 372). The patients were followed for 12 months. Procedural success was achieved in 91.5% versus 97.3% (p = 0.0007) of patients treated with DCA plus stent versus stent alone. Optimal atherectomy (<20% residual stenosis) was achieved in 26.5% of patients. The final minimal luminal diameter and the acute gain were similar in the 2 groups. There was no increase in 30-day major adverse cardiac events in the DCA plus stent group (3.9% vs 2.4%, p = 0.30). The primary end point, angiographic restenosis at 8 months, occurred in 26.7% of patients treated with DCA plus stents and in 22.1% of patients treated with stents alone (p = 0.237). Clinical follow-up to 1 year showed no difference in mortality (1.3% vs 0.8%, p = 0.725), acute myocardial infarction (4.2% vs 3.5%, p = 0.706), and target vessel failure (composite of death, Q-wave myocardial infarction, and target vessel revascularization) (23.9% vs 21.5%, p = 0.487) between patients with DCA plus stents and those with stents alone. This study failed to support the hypothesis that DCA before stenting lowers the angiographic restenosis rate compared with stents alone. At 12-month follow-up, there were no significant differences between the 2 groups in rates of death, reinfarction, or target vessel failure.

Mechanism of lumen enlargement with direct stenting versus predilatation stenting: influence of remodelling and plaque characteristics assessed by volumetric intracoronary ultrasound

OBJECTIVE

To compare the effects of arterial remodelling and plaque characteristics on the mechanisms of direct stenting and predilatation stenting. Direct stenting has become routine in some laboratories and differs technically from predilatation stenting.

METHODS

Pre- and post-interventional volumetric intravascular ultrasound (IVUS) was undertaken in 30 patients with direct stenting and in 30 with predilatation stenting of non-calcified native coronary lesions, using the same stent design and stent length. Lumen, vessel (external elastic membrane (EEM)), and plaque (plaque + media) volumes were calculated. Remodelling was determined by comparing the EEM area at the centre of the lesion with the EEM areas at proximal and distal reference sites. Plaque eccentricity was defined as the thinnest plaque diameter to the thickest plaque diameter ratio. Plaque composition was characterised as soft, mixed, or dense.

RESULTS

All volumetric IVUS changes were similar in the two groups. Pre-intervention remodelling remained uninfluenced after direct stenting, but was neutralised after predilatation stenting. Eccentric lesions responded to intervention by a greater luminal gain owing to greater vessel expansion in direct stenting. Plaque composition influenced luminal gain in direct stenting, the gain being greatest in the softest plaques; in predilatation stenting, luminal gain was equivalent but vessel expansion was greater for "dense" plaque and plaque reduction greater for "soft" plaque.

CONCLUSIONS

In non-calcified lesions, the mechanisms of lumen enlargement after direct or predilatation stenting are significantly influenced by atherosclerotic remodelling, plaque eccentricity, and plaque composition.