Intracoronary Brachytherapy for In-Stent Restenosis of the Left Anterior Descending Artery Via the Left Internal Mammary Artery

Intravascular radiation is currently the only Food and Drug Administration-approved modality to treat in-stent restenosis (ISR).^1,2 Multiple clinical trials have shown efficacy of beta-radiation in reducing intimal growth associated with ISR.^3,4 The Galileo centering catheter (Guidant Corporation, Santa Clara, California) uses a balloon centering catheter to deliver a Phosphorus-32 (32P) radiation source to the area of restenosis. The catheter design includes a rapid-exchange lumen and a central lumen with a closed end to isolate the radiation source from the patient. The system is typically delivered over a standard coronary guidewire (0.014–0.018´´ diameter) in a 7 French (Fr) guide catheter. The Galileo Centering Catheter has been examined in the INHIBIT and PREVENT clinical trials.^5,6 Currently, the third generation of the Galileo centering catheter (Galileo III) is used worldwide. This report describes the use of the Galileo III centering catheter for intracoronary radiation in a 6 Fr guide catheter system through a left internal mammary artery (LIMA) bypass graft to perform intracoronary radiation for ISR of the distal left anterior descending (LAD) artery. Case Report. A 62-year-old Asian male with a history of coronary artery disease and non-insulin dependent diabetes complained of 1 week of worsening exertional angina. The patient described pressure-like chest pain that was relieved by rest and sublingual nitroglycerin. The day prior to catheterization, the patient was admitted to another hospital with unstable angina. He was stabilized with intravenous heparin and nitroglycerin and transferred to Cedars-Sinai Medical Center for left heart catheterization and possible coronary intervention. The patient denied symptoms consistent with congestive heart failure. The patient underwent four-vessel coronary artery bypass graft surgery 13 years prior with a right internal mammary artery graft to the posterior descending artery, LIMA graft to the LAD and 2 separate saphenous vein grafts to the first and second left circumflex (LCX) marginal arteries. The patient had previous catheterizations, which had documented closure of both vein grafts. Nine months prior to the present admission, the patient presented with exertional angina not controlled by medical therapy and was treated with percutaneous transluminal coronary angioplasty and stenting of his LCX and LAD arteries. A 2.25 x 13 mm Velocity Hepacoat stent (Cordis Corporation, Miami Lakes, Florida) was deployed in the native LAD via the LIMA, a 2.5 x 18 mm Velocity Hepacoat stent was deployed in the distal LCX and a 3 x 8 mm Velocity Hepacoat stent was placed in the proximal LCX. The patient had been maintained on aspirin, clopidogrel, metoprolol, amlodipine, atorvastatin, glyburide and metformin since the prior stent implantation. His past medical history was also notable for Hepatitis C acquired via blood transfusion at the time of coronary bypass grafting. The patient had no known drug allergies. He did not drink alcohol or use illicit drugs. His family history was unremarkable. On physical examination, the patient was stable, with normal vital signs and no evidence of congestive heart failure or peripheral vascular disease. The electrocardiogram showed non-specific ST segment changes most prominent in the lateral leads. The patient was taken for catheterization upon transfer. Diagnostic catheterization of the native left system revealed 100% stenosis of the LAD in the proximal portion. The LCX was noted to have mild disease, with good flow through both previously placed stents and no evidence of in-stent restenosis. The proximal native right coronary artery was 100% occluded. The right internal mammary artery (RIMA) was widely patent and fed the distal RCA with only mild diffuse disease. The LIMA was moderately tortuous, but widely patent throughout its course and at the LIMA-LAD anastamosis. The distal LAD was found to have severe diffuse in-stent restenosis (Figure1). The patient received a 5,000 Unit bolus of heparin, which achieved an activated clotting time of 298 seconds. Percutaneous coronary intervention was performed using a short (90 cm), 6 Fr internal mammary artery guide catheter (Cordis Corporation) and a 0.014´´ Balance wire (190 cm length). Initial balloon angioplasty was performed using a 2.5 x 15 mm Maverick balloon (Boston Scientific/Scimed, Inc., Maple Grove, Minnesota) for 1 minute at 10 atmospheres. The follow-up angiogram showed an excellent result, with no evidence of dissection (Figure 2). Intracoronary brachytherapy was performed using the Galileo III centering catheter. A 2.5 x 32 mm balloon radiation catheter was placed within the stent and intracoronary brachytherapy was delivered for 85 seconds (Figure 3). The patient received a total of 2,000 cGy at a depth of 1 mm. The patient experienced mild episodic angina during the procedure, which resolved after removal of the Galileo III catheter system. The final coronary angiogram showed an excellent result, with TIMI 3 flow in the LIMA and LAD and no evidence of dissection (Figure 4). The patient tolerated the procedure well and there were no complications. The patient was discharged the day after the procedure and remains symptom-free at 6 month follow-up. He will continue to take clopidogrel for 1 year. Discussion. The Galileo centering catheter intracoronary radiation system has been extensively evaluated for safety, efficacy and cost effectiveness.^5–7 The centering catheter allows for precise delivery of radiation to the injury site. The external dimension of the Galileo III catheter system is 1.35 mm (4 Fr) at the shaft of the catheter. The 2.5 mm x 32 mm centering balloon expands to 2.5 mm with 4 atmospheres of pressure, while the minimum diameter of the centering balloon prior to inflation is 1.30 mm (3.9 Fr). This system was used with relative ease via a short 6 Fr internal mammary guide catheter. The internal diameter of the 6 Fr internal mammary guide catheter measures 0.70 inch (1.8 mm). There was no difficulty in maneuvering the Galileo III system in this moderately tortuous LIMA or within the LAD, nor in retrieval of the system following treatment. Possible areas of concern in using this system with a 6 Fr guide catheter are in the advancement and retrieval of the system after brachytherapy. If the hemostatic valve is partially tightened, difficulty may be encountered in the advancement of the dummy wire or radiation source. Passage of the dummy wire should indicate successful ability to reach the area of interest. Significant tortuosity of the LIMA would be the primary source of inability to pass the dummy wire or the radiation source. A stiffer coronary wire with added support may overcome this, but at the risk of “straightening or accordioning” the vessel and causing a reduction in flow.⁸ If the balloon is not fully deflated, there may be significant difficulty removing the system. This could be rectified by ensuring the centering balloon is fully deflated. The primary advantage to using a 6 Fr guide in this case is reducing injury to the LIMA and thereby reducing the possibility of significant intraprocedural complications. Kobayashi et al. have described the use of intracoronary gamma radiation for restenosis in the LAD treated via the LIMA graft.⁹ In 5 patients with distal LAD ISR, there was no delivery failure, nor significant periprocedural complications. The distinct advantage to using the Galileo III system for brachytherapy via the LIMA is in the shorter dwell times for beta-radiation in comparison to gamma-radiation, the decreased dose of radiation to the surrounding tissues, and the decreased need for shielding of the operator. The Beta-Cath 3.5 System (Novoste Corporation, Norcross, Georgia) is another beta-radiation option in the United States. This device is 3.5 Fr, with a recommended guide catheter size of 6 Fr and an internal diameter of 1.7 mm (0.067´´). The manufacturer recommends that internal mammary guide catheters not be used because of possible unintended radiation to other sources or impedance within the guide catheter.¹⁰ To our knowledge, this is the first described case of intra-coronary radiation in the LAD via the LIMA using the Galileo III system. In addition, this was performed with a 6 Fr guide catheter. The recommended guide catheter size from the manufacturer is 7 Fr. Given the dimensions of the Galileo III catheter, it is feasible to consider using the system via large internal diameter 6 Fr guide catheters when using the 2.5 mm centering balloon to treat distal LAD ISR via the LIMA graft.