Case Report and Brief Review

Detection and Treatment of Coronary Artery Pseudoaneurysms Following Coronary Stent Deployment

Naotsugu Oyama, MD, Kazushi Urasawa, MD, Akira Kitabatake, MD
Naotsugu Oyama, MD, Kazushi Urasawa, MD, Akira Kitabatake, MD
Coronary dissection caused during percutaneous coronary intervention (PCI) can evolve into pseudoaneurysm,1 and can be evaluated with angiography and intravascular ultrasound (IVUS).2–5 Conventional angiography during and after interventional procedures is not necessarily effective in recognizing alternations in the intimal surfaces of the treated lesions.6 Coronary angioscopy is a technique for visualizing the inner surfaces and intraluminal structures, especially the thrombus, which is usually difficult to detect with IVUS.7–9 We report a case of delayed development of a pseudoaneurysm after coronary stenting, which was successfully sealed using a polytetrafluoethylene (PTFE)-covered stent graft and well-evaluated using angioscopy. Case Report. A 53-year-old male with a history of hypertension, dyslipidemia and past smoking history presented with ventricular fibrillation eight years ago. After successful resuscitation, coronary angiography (CAG) revealed severe stenoses in both left anterior descending artery (LAD) and right coronary artery (RCA). Emergency coronary artery bypass graft (CABG) surgery was performed and two saphenous vein grafts (SVG) were anastomosed to the LAD and RCA. Mitral valve replacement (MVR) was concomitantly performed. Six months after the operation, he received a cardiodefibrillator implant. Although he was asymptomatic thereafter, he suffered from chest pain on exertion and was readmitted to our hospital. CAG revealed total occlusion of the proximal LAD, an occluded SVG to the LAD and a patent SVG to the RCA. After stress-induced ischemia was objectively proven with scintigraphy, PCI for occluded LAD was attempted. After a guidewire had successfully crossed the target lesion, we implanted a 4.0 x 23 mm Multilink Tristar stent (Guidant Corporation, Santa Clara Calif.). However, follow-up CAG six months after stent implantation revealed pseudoaneurysms around the proximal LAD (Figure 1A). Considering the potential risk of coronary rupture, we decided to seal the pseudoaneurysm using a PTFE-covered stent graft. The patient was pre-treated with aspirin and ticlopidine, as well as warfarin, for prevention of thromboembolism due to a prosthetic mitral valve. We administered 10,000 units of heparin intravenously before the procedure. After a 0.014-inch Hi-Torque Balance Middle Weight guidewire (Guidant Corporation, Santa Clara Calif.) was crossed to the lesion, we evaluated the pseudoaneurysm with an Atlantis SR Pro imaging catheter (Boston Scientific SciMed Inc. Maple Grove Minn.). CAG showed two pseudoaneurysms at the middle of the stented segment, and IVUS confirmed this finding. IVUS also demonstrated that one of these pseudoaneurysms had a broad connection to the LAD and was 12 mm in length. The outer margin of this pseudoaneurysm was not imaged, as it was beyond the far field of the IVUS probe (Figure 2). We then also performed angioscopy with a Vecmova coronary angioscopic imaging catheter (Clinical Supply Co. Ltd. Gifu, Japan). Angioscopy revealed that a metallic strut of the previously implanted stent was not yet covered by intima. Angioscopy also detected another small aneurysm that was not detected by angiography or IVUS (Figures 3A and 3B). Based on this information, a PTFE-covered stent graft of 3.5mm x 26 mm (JOMED coronary stent graft supreme system, JOMED GmbH, Rangendingen, Germany) was implanted so as to fully cover the opening of all three pseudoaneurysms. The system balloon catheter was dilated up to a pressure of 14 atmospheres and then removed. We performed high-pressure post-dilation with a 4.0 x 20 mm Quantum balloon catheter (Boston Scientific SciMed Inc. Maple Grove Minn.) up to 14 atmospheres to achieve sufficient stent expansion. The procedure was terminated after complete sealing of all the aneurysms was confirmed by CAG (Figure 1B), IVUS and angioscopy. There was no leak of creatine kinase after the procedure. The patient was put on long-term aspirin and warfarin, together with ticlopidine 200 mg twice daily for six months in order to prevent thrombosis. Discussion The reported incidence of coronary aneurysms caused after conventional balloon angioplasty is approximately 4%.10 Deep arterial injury is considered to be the main cause of aneurysm formation after coronary intervention. Injury or resection of media may lead to gradual dilatation and thinning of the vessel wall. The reduced wall thickness and increased stress ultimately cause formation of an aneurysm. Dissection of the coronary artery during the time of percutaneous balloon angioplasty is the major factor related to the occurrence of coronary artery aneurysm.1,10,11 Stent implantation in bailout situations after balloon angioplasty is well accepted, and high pressure balloon inflation is commonly used to optimize the expansion of coronary stents. This technique has been proven to reduce procedural complications, especially subacute thrombosis.12 However, delayed aneurysm formation after stenting has been described in some reports.1,13–17 In our case, mechanical injury during catheter-based therapeutics is the most probable cause of our patient’s coronary pseudoaneurysm which developed at the stented segment six months after the stent index procedure. In addition, anticoagulation treatment may have actively interrupted the natural healing process of the aneurysm affected by mural thrombus formation within the aneurysm. There were several treatment options available to this patient: 1) observation with frequent coronary angiography; 2) surgical resection of the pseudoaneurysms; 3) implantation of autologous vascular graft-coated stents. Obviously, simple observation was inappropriate in this case because large aneurysms had developed in a short period of time and there might have been a risk of spontaneous rupture. Surgical resection was also deemed to be an inappropriate option because the patient had already undergone both CABG and MVR, thus open-chest surgery for a second time might have proved troublesome. Autologous vascular graft-coated stenting has been reported to be effective in sealing off coronary perforation, coronary aneurysm and fistula.18–27 However, long-term patency of the lesions treated with vascular graft-coated stents has not been well established and in this case, furthermore, due to anticoagulation treatment using warfarin and antiplatelet therapy using aspirin and ticlopidine, such treatment would have involved a risk contingent on removal of the patient’s vessels for grafting. PTFE-covered stenting has also been regarded as the therapy of choice for acute coronary rupture, coronary perforation and coronary artery aneurysm.4,5,28–30 This device does not require surgical removal of the vessels and we therefore believe that our decision to use it was the most appropriate and safest strategy in this case. Differentiation of the aneurysmal type is important. True aneurysm formation resulting from the healing of a deep dissection after balloon angioplasty is presumably responsible for low morbidity and mortality.10 The incidence and natural history of coronary pseudoaneurysms are not known because of the inability to diagnose them by conventional angiography alone,31,32 and it can be accurately diagnosed with IVUS or electron beam computed tomography in addition to angiography.33 Unlike the vessel structure of true aneurysms, the fibrous wall of pseudoaneurysms is not continuous with the structure of the adjacent vessel wall and does not contain the normal medial smooth muscle component remnants of the original arterial wall. It has been suggested that for progressive enlargement or eventual rupture, as was considered in our case. In conclusion, detailed information on vessel wall structure and the stent-vessel interaction was clearly visualized by angioscopy. Coronary angioscopy provided useful information on the complex structure of the lesion, which was complementary to that obtained by conventional imaging techniques and pseudoaneurysms were successfully sealed off with a PTFE-covered stent graft.
References
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