Bifurcation lesions remain a challenging topic in interventional cardiology, with multiple approaches and strategies for intervention. Bifurcation lesions account for 15% to 20% of coronary stenoses and significantly increase the complexity of intervention exponentially. The 2011 American College of Cardiology (ACC) guidelines recommend provisional side branch stenting as the initial strategy when the side branch is not large and has mild to moderate disease. If the side branch is large with a high risk of occlusion and a low likelihood of side branch reaccess, then a planned 2-stent strategy is reasonable.

The European Bifurcation Club (EBC) defines a bifurcation lesion as: “A coronary artery narrowing occurring adjacent to, and/or involving the origin of a significant side branch.”¹ This definition is to be used practically, with a significant side branch being one that could incur a significant chance of myocardial injury if occluded during intervention. At least 6 different classifications exist for bifurcation lesions, but the most widely accepted is the Medina classification² (Figure 15-1).

The Medina classification scores the 3 arterial segments of a bifurcation sequentially with a binary 0 or 1, based on the absence or presence of a stenosis greater than 50% of the vessel diameter. The segments assessed are, in order, the proximal main vessel, the distal main branch, and the side branch. For example, a stenosis involving only the proximal main vessel and the side branch ostium would be coded as 1,0,1.

The Medina classification has prevailed due to its simplicity and ease of use, but it eschews numerous other factors, including branch size, lesion length, takeoff angle, disease severity, location at the ostium, degree of calcification, and other anatomic considerations. The challenges of bifurcation percutaneous coronary intervention (PCI) are derived primarily from the sum of these anatomic considerations and may direct the strategy for intervention. Furthermore, such anatomic and technical factors may impact long-term clinical outcomes³ (Figure 15-2).

Although there are numerous classification systems, committing multiple systems to memory may be difficult and potentially nonbeneficial, because few aside from the Medina nomenclature are universally recognized.⁴ Strong arguments can be made for a system that takes into account plaque burden, angle of bifurcation, and lesion and vessel characteristics. However, with such large variability between bifurcation lesions, even complex systems such as those proposed by Movahed have their limitations.⁵ For ease of use, the Medina classification allows for a simple manner of conveying the basic nature of the bifurcation lesion.

The Medina classification also allows one to differentiate between a true bifurcation lesion (Medina 1,1,1; 1,0,1; 0,1,1) and non–true bifurcation lesions. True bifurcation lesions are more technically challenging and have worse clinical outcomes. Furthermore, the Nordic-Baltic Bifurcation Study III showed that the benefit of final kissing balloon inflation (KBI) was primarily limited to true bifurcation lesions.⁶

The technical strategies for bifurcation lesions are numerous and a number of variations on ballooning and stenting have been described. An overview of bifurcation strategy has been described in detail by the EBC using the acronym “MADS” to represent the first stent placed in the bifurcation stenting strategy.⁷ The M (main) represents the stent implantation in the proximal main vessel, A (across) represents stent crossing the side branch ostium, D (distal) represents stent implantation at the distal branch(es), and S (side) represents side branch stented first, with or without protrusion (Figure 15-3). The MADS classification prioritizes the first vessel treated and recognizes that initial stent deployment limits subsequent options. The MADS classification can be used in both the provisional and 2-stent strategies, and most bifurcation techniques will fall under a variant of the classification.

PROVISIONAL VERSUS 2-STENT STRATEGY

Due to the complexity of bifurcation lesions, the simplest approach is often best. Clinical trials have repeatedly shown that a planned 2-stent approach does not improve clinical outcomes compared with provisional stenting. Conversely, planned 2-stent approaches are associated with longer procedures, increased use of contrast, and more procedure-related myocardial infarctions.^8-10

The 5-year follow-up of the Nordic study showed that outcomes after a provisional stenting strategy were at least equal to a planned 2-stent strategy. In the optional side branch stenting group versus the main vessel/side branch 2-stent group, all-cause death was seen in 5.9% versus 10.4% of patients (P = .16) and non–procedure-related myocardial infarction was seen in 5% versus 7.9% of patients (P = .09), respectively.¹¹ Important limitations to this study include the following: it was underpowered given the low rate of adverse events, and only first-generation drug-eluting stents were used.

The Coronary Bifurcation Application of the Crush Technique Using Sirolimus-Eluting Stents (CACTUS) trial demonstrated that even in true bifurcation lesions, provisional stenting is effective, with side branch stenting only necessary in one third of cases. Outcomes were similar at 6 months, with no difference in restenosis and similar rates of major adverse cardiac events (15.8% in the 2-stent crush group vs. 15% in the provisional stenting group, P = not significant).⁸ Similarly, other studies have failed to demonstrate a clear advantage to a dedicated 2-stent strategy.

However, considering that the CACTUS trial demonstrated that one third of lesions were true bifurcation lesions requiring 2 stents, a clinical assessment of side branch relevance and lesion characteristics may help tailor the approach for individual bifurcation lesions.

PROVISIONAL STENTING

Even with provisional stenting, the goal for the procedure is to keep both branches open, while optimally stenting the main branch. This is known as the “keep it open” technique. If the side branch is larger than 2 mm, supplies a medium to large myocardial territory, or has significant ostial disease, these characteristics shift the balance toward a 2-wire approach. To that end, if possible, 2 wires should be placed to protect the side branch from closing as a result of stent struts or plaque shifting. Wiring the side branch increases the side branch takeoff angle and displaces the carina, reducing the risk of side branch occlusion during stenting.¹² It also assists in insertion of a second guidewire into the side branch following main branch stenting and can serve as a marker wire in case the side branch does occlude. The absence of a second jailed wire is associated with a greater rate of re-intervention during follow-up. The risk of entrapment or guidewire fracture is small and can usually be treated conservatively.¹³

As long as Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow is maintained in the side branch, clinical outcomes are not improved by kissing balloons or complex dual stent procedures.^8,10,14 If the side branch has TIMI grade 1 or 2 flow, then balloon angioplasty or stenting should be considered and may be guided by functional testing.

USE OF FUNCTIONAL TESTING

When approaching the provisional stenting strategy, it should be noted that without prior side branch involvement, development of a functionally significant stenosis in the side branch is infrequent.^15,16 Carinal shift may lead to angiographic ostial stenosis but does not frequently cause functional impairment as measured by fractional flow reserve (FFR).¹⁷ FFR-guided revascularization is superior to angiographic revascularization in most lesions and may be particularly useful in side branch scenarios, as angiographic stenoses may not be functionally significant by FFR. FFR has been validated in bifurcation lesions and shown to be safe and effective^1,18 (Figure 15-4). Available data suggest that no lesions with quantitative coronary angiography (QCA) percentage less than 75% had an FFR of less than 0.75, whereas only 27% of those with percentage stenosis greater than 75% had physiologically significant disease by FFR (Figure 15-5). FFR is an excellent tool in the provisional stenting strategy to determine whether a side branch needs further intervention.

TECHNIQUE

If either the physiologic or angiographic (either TIMI grade 1 or 2 or QCA stenosis >75%) assessment reveals a significant stenosis in the side branch, the side branch may be rewired, using a hydrophilic wire and possibly a Glider balloon catheter with a low profile and torquable tip to navigate stent struts¹⁹ (Figure 15-6). Once side branch access is obtained, high-pressure balloon inflation may open the stent struts (Figure 15-7). If the resultant flow is TIMI 3 and the side branch is small, then further stenting may be deferred. If the side branch is medium to large or supplies a moderate to large territory, then a stent may be deployed in the side branch with minimal protrusion into the main branch, followed by kissing balloon inflation using noncompliant balloons to complete the procedure (reverse crush or reverse T and protrusion).