Should the Left Main Be Covered Entirely with Drug-Eluting Stents in Percutaneous Intervention?

Percutaneous coronary intervention (PCI) with balloon angioplasty or bare-metal stents are not adequate procedures in the treatment of the left main (LM) coronary artery disease because they are associated with an unacceptable restenosis rate, which may present as sudden cardiac death. Although coronary bypass surgery is the preferred method of revascularization,¹ PCI with drug-eluting stents (DES) has been performed with promising results.² There are angiographic and technical details in LM stenting that may be extremely important in the acute and long-term results and have already been studied previously, such as the localization of the lesion within the LM,³ the need for intravascular ultrasound (IVUS)⁴ and the technique used to approach the bifurcation.⁵ However, there still remain some questions to be clarified. One of them may be the length of the lesion that should be covered by the stent. We present here the case of a patient with a new lesion in the LM in the segment not covered with the DES in the initial procedure. Case Report. A 60-year-old female with diabetes, hypercholesterolemia and a previous smoking habit was admitted to the hospital with a non-ST-elevation acute coronary syndrome. Cardiac catheterization revealed distal LM disease with severe stenosis of the origin of the right coronary artery (RCA) and normal left ventricular function. Coronary bypass surgery with a left internal mammary graft to the left anterior descending artery (LAD) and a right internal mammary graft to the RCA was performed. Three months after the surgery, the patient complained of chest pain, and a new catheterization showed occlusion of the left internal mammary graft, as well as severe stenosis at the distal anastomosis of the right mammary to the RCA, with the previous lesion in the distal segment of the LM (Figure 1). A second surgical procedure was discouraged, and PCI with DES was indicated. Balloon angioplasty utilizing a 3.5 x 12 mm Taxus^® Express stent (Boston Scientific Corp., Natick, Massachusetts) was performed in the ostium of the RCA. The LM lesion was a Duke type-D bifurcation, and it was treated using the balloon-crushing technique⁶ with a 3 x 12 mm Taxus Express stent from the LM to the circumflex artery, and a 3.5 x 18 mm Cypher™ stent (Cordis Corp. Miami, Florida) from the LM to the LAD. This second stent did not cover the proximal 3 mm of the LM, which was initially disease-free. The procedure was concluded with kissing balloon inflation, and the proximal edge of the balloon of the LAD covered the proximal non-stented segment of the LM (Figure 2), producing an optimal angiographic result (Figure 3). Again 3 months after discharge, the patient was admitted with acute chest pain. The arteriogram showed an absence of in-stent restenosis in the RCA, and 2 stents in the LM. However, there was a severe new lesion in the proximal 3 mm of the LM where the balloon had been inflated, though none of the stents covered that segment (Figure 4). A new 3.5 x 13 mm Cypher stent was deployed, which was postdilated with a 4 x 13 mm Powersail^® balloon (Guidant Corp., Indianapolis, Indiana), with a successful result (Figure 5). Discussion. Left main PCI is technically demanding and can be considered a challenging procedure that should only be attempted by highly experienced interventionalists. There are some special characteristics of the LM artery that render PCI challenging, and these have been studied previously.^3–5 However, some issues are still unresolved. To date, there is no consensus regarding the appropriate length of the LM that should be covered by the stent, and since it is unlikely that a study specifically designed to answer this question will be performed, the data will have to come from observational experiences. Although it is easier to deploy a stent in short lesions, there will always be cases requiring stent placement in the distal LM artery using complex techniques such as kissing inflation. In such cases, if the stent does not cover the proximal segment of the LM, the balloon may activate the restenosis process. Calcification is frequently found at the LM, which frequently makes predilatation and high-pressure postdilatation necessary. Besides this, kissing balloon techniques are recommended in those cases of LM artery PCI where a bifurcation is involved. In the study by Lemos and colleagues,7 restenosis with sirolimus-eluting stents was located within the stent in 70% of lesions, and at the 5-mm segment proximal to the stent in the remaining 30%. Residual dissection after the procedure or balloon trauma outside the stent was identified in 83% of these proximal-edge lesions. Several series of LM stenting with DES have been published previously.^2,8–12 Two facts indicate that an attempt to cover the LM completely was not made in all of the cases. First of all, none of these studies mention it in the methodology, and in most of them, target lesion revascularization was defined as “a repeated intervention to treat luminal stenosis within the stent or in the 5-mm distal or proximal segments adjacent to the stent, including the ostium of the LAD and/or the circumflex”. Distal involvement carries a higher risk of restenosis,^2,3,8,12 and the ostium of the circumflex in particular accounts for about 50% of the restenosis cases in these series. However, although most of the restenosis occurs at the distal site, it has also been found in the proximal edge of the stent. In the study by Park et al,^{2 6} patients suffered angiographic restenosis, all of them with an initial bifurcated lesion. In one of these cases, the restenosis occurred at the proximal edge after kissing-balloon stent placement. In the study by Chieffo et al,⁸ 12 patients developed restenosis, all of them after a process involving the bifurcation. In 3 of these patients, the restenosis affected the ostium of the LM: one after a modified T-technique, another after the culotte technique and the third after the crushing technique. In the remaining four studies, the restenosis was not at the ostium.^9–12 In the present case, the restenosis was also located at the ostium of the LM, just in the 3-mm segment proximal to the stent. Although it may be easy to assume that restenosis could have been prevented if the entire left main would have been covered in the initial procedure, the data available in the literature cannot support this premise. In the six studies analyzed previously, 434 patients were included and restenosis at the ostium was reported only in four cases in two studies, no incidence in the remaining four. In our opinion, the information currently available in the literature is insufficient to recommend the routine coverage of the entire left main artery with a stent, thus additional studies with larger numbers of patients are needed.

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