Percutaneous Coronary Intervention for de novo Bifurcation Lesions

Abstract

seem intuitive therefore to avoid stenting such small vessels if possible. However, stenting the main vessel may compromise flow in an SB through plaque shift, thrombus formation, spasm or pinching by stent struts, resulting in the need for SB intervention. The rate of SB occlusion varies from 5% to 26%, and is associated with an adverse outcome. In the NIR Vascular Advanced North American (NIRVANA) study of the NIR stent, SB occlusion was associated with a significantly higher rate of Q-wave (7%) and non-Q-wave (20%) myocardial infarction (MI) compared with patients without SB occlusion (p<0.05). Single stent implantation with PSBS has been found to have the lowest rates of MACE and TLR when compared with more complicated techniques. A recent BMS multicentre study of 186 patients having single stenting with PSBS, in which 34% of patients had SB stenting, showed a seven-month TLR rate of 16% and MACE 23%. Event-free survival was significantly better with this technique when compared with a two-stent strategy of T stenting (75% versus 44%, p<0.05). Similar results have been obtained with the use of DES. At present it is not known when intervention is necessary on an SB compromised by MB stenting. What is known is that the prognosis is favourable. In the study by Pan et al. with a very low rate of cross-over from a one-to a two-stent strategy, SB dissections with thrombolysis in myocardial infarction (TIMI) grade 3 flow were left without additional treatment with no effect on clinical outcome. In addition, studies have shown that >60% of SB that are occluded immediately after SES stenting have spontaneously recanalised at follow-up. The need for intervention on a compromised SB is not reliably assessed by angiography, but fractional flow reserve (FFR) has been shown to be effective in preventing unnecessary stenting of a compromised SB. Koo et al. found that angiographically significant lesions (≥75% stenosed) were only functionally significant in 27% of cases, while all lesions assessed to be <75% stenosed on angiography were functionally insignificant by FFR. In contemporary practice with DES, if the SB is of adequate size (≥2.5mm), and the SB diameter stenosis is >50%, a strategy of two stents should be considered (see Figure 2). A variety of techniques exist to perform the two-stent strategy but the most effective stenting technique remains undefined. T stenting is best reserved for the 25% of lesions where the angle between branches is greater than 70 degrees. When this is not the case, T stenting risks incomplete coverage of the branch ostium or protrusion of the side branch struts into the main vessel, increasing the risk of restenosis. Culotte stenting provides complete lesion coverage but can be technically challenging and time consuming. Unfortunately studies with BMS have failed to demonstrate that this leads to improved clinical outcomes with higher one-year MACE compared with T stenting (86% versus 30%, p=0.004). A small study with DES, however, has shown promising results with a TLR rate of 5% and MACE of 15%, suggesting that the technique needs further evaluation. The related V stenting and kissing stents techniques, which are easy to perform and confer full lesion coverage, are best suited to those lesions where both vessels are of similar calibre. There is less stent deformation and crushing and therefore no requirement for kissing balloon post-dilatation; however, a guide catheter of least 7 French is required. Sharma et al. showed promising results in a retrospective study with SES with in-hospital and 30-day MACE rates of 3% and 5%, respectively, and a TLR rate of 4%. Crush stenting provides complete lesion coverage, particularly of the SB ostium-but this still remains a site for focal restenosis. Pre-dilatation during bifurcation lesion intervention facilitates optimal stent deployment, and reduces the potential for ischaemia so that more time is available to accurately position stents. In addition this also gives information as to how the lesion will behave, such that if plaque shift occurs the strategy can be changed from one of PSBS to a two-stent strategy. The disadvantage is geographical miss, which must be avoided as it is a risk factor for restenosis. After the MB stent has been deployed, high pressure dilatation will facilitate rewiring of the SB. Subsequent balloon inflation of the SB ostium, through the MB stent, will result in angiographically invisible stent deformation which occurs in the MB stent opposite the ostium of the SB. 24 Kissing balloon post-dilatation is recommended to counteract this, and not only optimises the angiographic results but has also been shown to reduce in-hospital MACE, stent thrombosis and TLR. In crush stenting, failure to perform kissing balloon post-dilatation is an independent predictor of TLR (hazard ratio (HR): 4.17; 95% confidence interval (CI): 1.3-14.3; p=0.02), and associated with higher SB restenosis rates compared with those having final kissing balloon post-dilatation (11% versus 38%, p<0.001). In essence, two-stent strategies should always be optimised by kissing balloon post-dilatation.