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Commentary
Coronary Bifurcation Interventions — Stay on the Highway and Keep it Simple!
November 2009
In current interventional cardiology practice, the treatment of coronary bifurcation lesions remains among the few technically challenging fields. It is estimated that bifurcation lesions comprise 15–20% of all percutaneous coronary intervention (PCI) procedures.1,2 Stenting of a coronary artery narrowing involving a bifurcation may result in a significant angiographic diameter decrease of the ostium of the side branch, mainly due to plaque shift.3–6 Therefore, angioplasty or stenting of the side branch, if appreciated as significant in size, is often performed. Compared to non-bifurcation lesion, these interventions are associated with relatively low procedural success and high complication and restenosis rates despite advances in device technology.2 Therefore, the need for optimal side-branch devices that will result in consistent and sustained clinical benefit compared to the current techniques remains an ongoing challenge to the vascular interventional world.
Valid data on large numbers of patients to test what is the best treatment strategy for bifurcation lesions are lacking. In the meantime, several methods to treat bifurcation lesions have been described and are used according to the patient’s specific anatomy, the operator’s experience and device availability. Conventional approaches, largely based on the operator’s discretion, include stenting the main vessel with provisional intervention on the side branch (provisional strategy) versus deploying stents in both (complex strategy). A variety of approaches including crush, culotte and T-stenting techniques can be employed for side-branch stenting.3 Final kissing-balloon inflations for optimizing stent geometry in both the main and side branches are usually performed, although this is based mainly on in-vitro laboratory findings, and there are no randomized data to evaluate this technique.
The use of bare-metal stents (BMS) in bifurcation lesions is associated with a target lesion revascularization (TLR) rate of 16–38%,6–8 with a tendency toward increased restenosis after stenting of both the main branch and the side branch compared to single-vessel stenting. The introduction of drug-eluting stents (DES) reduced major adverse cardiovascular events (MACE) and TLR rates. The reductions reported in DES registries as compared to historical BMS controls occurred regardless of whether a provisional stenting (MACE: 5.4% vs. 38%; TLR: 5.4% vs. 36%) or complex stenting (MACE: 13.3% vs. 51%; TLR: 8.9% vs. 38%) strategy was undertaken.7–9
In this issue of the Journal, Hakeem et al10 performed a meta-analysis of randomized, controlled trials comparing complex to provisional strategies for coronary bifurcation lesions using DES. Six randomized trials with a total of 1,641 patients were included. Seven-month angiographic follow up was reported in 85% of patients. Routine stenting of both the main vessel and side branch — a more complex strategy — was reported to offer no clinical or angiographic superiority over the more conservative provisional approach to such lesions.
The baseline angiographic characteristics were similar. As observed in many interventional cardiology trials, there was no difference in death, however the incidence of MI was significantly higher in the complex strategy group compared to the provisional strategy group (6.8% vs. 3.6%; RR 1.71 [95% CI, 1.02–2.88]; p = 0.04). Interestingly, at a mean clinical follow up of 10 months and a mean angiographic follow up of 7 months, the rates of TLR (6% vs. 5.3%), stent thrombosis (1.8% vs. 0.8%), main-vessel restenosis (4.9% vs. 5%) and side-branch restenosis (13.8% vs. 13.8%) were similar between the two strategies.
Although the difference in myocardial infarction (MI) were largely due to the higher MI rate in the BBC ONE trial,11 still, there is no advantage with the use of a complex stenting strategy. The complex strategy is also associated with significantly higher contrast volumes and total procedure and fluoroscopy times.3–9,11
An important finding was that while bifurcation lesions have been previously identified as independent predictors of stent thrombosis, especially in the stented side branch12–14 (3.5% with T-stenting technique and 4.5% with crush stenting technique), this rate was significantly lower in the current analysis and was not different between the two groups (1.8% and 0.8%). Whether this is due to better technique or antiplatelet treatment or other factors is unknown.
In this analysis 800 patients were randomized to the provisional stenting arm. In half of these cases, a stent was inserted in the side branch. This was thought to be necessary to obtain an acceptable angiographic result. Sirolimus-eluting stents have been the most extensively studied in this field and showed significantly lower rates of late lumen loss, restenosis and TLR compared to patients treated with paclitaxel-eluting stents.15 The efficacy and safety of newer-generation stents have been demonstrated in multiple trials. However, whether comparable clinical outcomes can be extended to lesion subsets of higher complexity, including bifurcation lesions, needs further investigation. Special stents designed for this subset of coronary lesion are being tested. Another player in the field is the drug-eluting balloon that offers much promise, especially in this scenario, but still has to be evaluated in large-scale studies.
When to intervene on a jeopardized side branch following successful treatment of the main vessel is still an open question. Should the intervention be based on the angiographic stenosis post intervention? The angiographic appearance may exaggerate the real physiological significance of a narrowing. Thus, there may be overuse of side-branch interventions based solely on angiographic assessment. Should we only intervene if flow is impaired, or should we rely on functional-flow measurements? Clearly, the simple approach can become complex if provisional side-branch stenting is performed.
Koo et al, using fractional flow reserve (FFR) to assess jailed side branches, revealed that only 27% of angiographically apparent significant side-branch stenoses were hemodynamically significant when using a FFR value 16 The outcomes were favorable for a FFR > 0.75 in the initial side branch treated conservatively, with no adverse events or target vessel revascularization at follow up. In lesions with a FFR 17
In summary, the meta-analysis presented here confirms that routine stenting of both the main vessel and side branch (complex strategy) offers no clinical or angiographic advantage over a more simple provisional approach. The complex strategy is associated with higher contrast volumes, longer total procedure and fluoroscopy times and is more expensive. Since the complex strategy does not improve the clinical or angiographic outcomes according to the data, the simple strategy can be recommended as a preferred bifurcation stenting technique in the DES era. Our practice for many years in cases of a small-caliber side branch has been to also wire the side branch. But only when there is a significant narrowing in the side branch do we intervene primarily with balloon dilatation, and only if needed, is a stent deployed as well. We typically use a DES when stenting across a bifurcation lesion.
Clinically, when main-vessel narrowing is treated properly, the patient’s symptoms are relieved. Rarely will a side branch lesion cause symptoms. As in many areas of interventional cardiology, we should focus less on lumenology and more on the clinical outcome of the patient. “Keeping it simple” in cases of coronary bifurcation lesions may be the best strategy for our patients.
