Direct Coronary Stenting Through Left and Right Internal Mammary Artery Grafts

Direct coronary stenting is a new technique that consists of direct stent implantation without balloon predilatation of the target lesion. This strategy is now technically possible because of the improvements in crossing profile, flexibility, safety and crimping of the current generation stents. Several recent studies have shown that direct stenting is feasible, costs less and is quicker to perform compared to the conventional approach of balloon predilatation followed by stenting.1–8 However, there are some potential concerns associated with the new technique, including the possibility for stent dislodgement and embolization, the potential for incomplete stent expansion, and the difficulties in exact stent positioning because of the suboptimal visualization of the distal vessel.1,5,9 These possible disadvantages have limited the application of direct coronary stenting in selected cases. Lesions that are long, occluded, heavily calcified or tortuous are supposed to be unsuitable for direct stenting.1–9 We describe a case of successful direct stenting of two subtotal occlusions, one at the site of the left internal mammary artery (LIMA) graft anastomosis with the native left anterior descending artery (LAD) and the other at the site of the anastomosis between the right internal mammary artery (RIMA) graft and the right posterior descending coronary artery (PDA). To our knowledge, this is the first reported case of successful direct stent implantation for subtotal occlusions through the LIMA and RIMA. Case Report. A 78-year-old male who had undergone coronary artery bypass surgery (CABG) twice presented with unstable angina 10 years after his second operation. The patient was admitted to our department for coronary angiography and potential percutaneous revascularization. Coronary angiography showed total occlusion of the proximal LAD, high-grade stenosis of the distal left circumflex artery (LCX) and total occlusion of the mid-portion of the right coronary artery (RCA). The LIMA graft to the LAD was patent, but there was a subtotal occlusion at the site of the anastomosis with the native LAD. The RIMA graft to the PDA also had a subtotal occlusion immediately proximal to the anastomosis with the native vessel. There was a saphenous vein graft to the obtuse marginal branch, which was occluded. The left ventriculography showed hypokinesia of the inferior wall with an estimated ejection fraction of 45%. The patient was referred for coronary angioplasty of the two anastomotic lesions, within the LIMA and RIMA, with the plan to treat them with direct stenting, as both of them were short (less than 10 mm) and not calcified. At the beginning of the procedure, heparin was administered intra-arterially in a bolus dose of 10,000 units. The anastomotic lesion of the LIMA graft was treated first. A 6 French (Fr) IMA Vector-X guiding catheter (Medtronic AVE, Santa Rosa, California) was positioned at the LIMA ostium through a femoral sheath. A 0.014˝ Choice PT guidewire (Boston Scientific/Scimed, Inc., Maple Grove, Minnesota) supported by an ultrafuse catheter failed to cross the subtotal occlusion and was changed to a 0.014˝ medium Galeo guidewire (Biotronic), which passed through the lesion successfully. A 2.5 x 8 mm BX Velocity stent (Cordis Corporation, Miami Lakes, Florida) was then easily advanced through the LIMA and placed at the lesion site with moderate push. The balloon was inflated once to 12 atmospheres (atm) for stent deployment with a good result. Subsequently, the same IMA guiding catheter was engaged in the RIMA ostium and a 0.014˝ Hi-Torque Standard guidewire (Guidant Corporation, Santa Clara, California) successfully crossed the lesion within the RIMA. A 2.5 x 8 mm BX Velocity stent was then advanced through the RIMA and placed at the target lesion with application of constant pressure and simultaneous mild backward traction of the guidewire. Deployment of the stent was accomplished using 12 atm for 30 seconds. The final angiogram showed a good result. The total procedural time for both lesions was 50 minutes with a total fluoroscopy time of 19.7 minutes. The total non-ionic contrast used was 240 cc. The patient had no complications and was discharged home after 24 hours. At 6-month follow-up, he remained asymptomatic. Discussion. Percutaneous revascularization of the internal mammary artery (IMA) graft has been shown to be a safe and effective treatment for patients returning with symptomatic myocardial ischemia after coronary artery bypass graft surgery and whose primary lesion involves the IMA.10–13 Recently, Gruberg et al. showed very good results in a large series of 174 patients who underwent percutaneous revascularization of the IMA graft.14 In this cohort of patients, 91% of the anastomotic IMA lesions were treated with balloon angioplasty and 9% were treated with stents. Although the in-hospital procedural success and outcome were excellent, the lack of randomization and angiographic follow-up of the patients did not allow for a formal comparison between the two treatment strategies (balloon angioplasty and stenting). In our patient, we decided to perform direct stenting of both anastomotic lesions within the LIMA and RIMA in order to reduce the total procedural time, reduce the utilization of contrast agent, and to decrease the ischemia time during such a complex case. Previous reports have suggested that the new technique of direct stenting without balloon predilatation is safe and feasible in selected lesions and reduces the cost and length of the procedure as well as the radiation exposure time.1–8 Other potential advantages of the new therapeutic approach include reduction of ischemic time, which may be clinically relevant in specific patients, and less extent of vessel injury with subsequent reduced restenotic response.1,4,5,9 Unfortunately, at this point there are no large, randomized studies determining the impact of direct stenting on short- and long-term procedural outcomes. In a large retrospective study, Wilson et al. found that the in-hospital and long-term clinical outcomes in patients undergoing coronary interventions are equivalent, comparing direct stenting with balloon predilatation followed by stenting.9 Very recently, Loubeyre et al. announced the results of a randomized study about direct stenting in acute coronary syndromes.15 Interestingly, they found that direct stenting significantly decreased the risk of distal embolization and no-reflow phenomenon in this selected population. There are still some concerns about this new technique regarding the risk of stent dislodgement from the delivery balloon and embolization while crossing a tight stenosis or advancing the stent through a tortuous vessel. Although both lesions were tight and the LIMA was quite tortuous in our patient, direct stent implantation was successful after using some extra maneuvers. The choice of a very flexible and low-profile stent, such as the BX Velocity, helped a lot in the success of this complex procedure. In addition, the optimal guiding support we had from the 6 Fr IMA guiding catheter was also an important advantage. According to our experience, the success and safety of direct stenting depends on a few simple measures. These include careful selection of guide catheter to have optimal guiding support and the use of premounted stents with low profile and high flexibility, especially for complex lesions. Long (> 20 mm) or heavily calcified lesions are not suitable for direct stenting. In such cases, debulking techniques offer the treatment of choice. However, the severity of stenosis and the site of the lesion (proximal or distal) do not appear to limit the success of direct stenting, except in cases with severe proximal vessel tortuosity. Since the stent/balloon may completely occlude the artery and compromise the distal vessel visualization, the use of landmarks for stent positioning is important. Finally, a gentle approach should be employed when positioning the stent to avoid damage to the leading stent struts. When passage of the stent to the desired position at the lesion site is not possible with moderate pushing and deep intubation of the guiding catheter (while possible and safe), the stent should be removed and the lesion should be predilated. Conclusion. The above case describes the first successful implantation of stents directly to treat lesions within the LIMA and RIMA. We conclude that the new direct stenting technique appears to be safe and feasible in a considerable variety of coronary artery and grafts lesions. Further experience and randomized trials will explore the usefulness of this approach.

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