Delayed Development of a Giant Coronary Pseudoaneurysm After Stent Placement for Chronic Total Occlusion

Coronary artery aneurysms have been identified in up to 5% of all coronary angiographic studies. Atherosclerotic, congenital, inflammatory, infectious and traumatic (resulting from coronary intervention) are the most common etiologies. Coronary artery aneurysm formation after percutaneous transluminal coronary angioplasty (PTCA) has been reported to occur in 3.9–5.0% of cases.^1,2 Coronary artery aneurysms following interventions are not typically associated with an adverse outcome.² However, the assessment of post-interventional aneurysms is based on angiography, which cannot differentiate true from pseudoaneurysms. Thus, it remains unclear whether true aneurysms and pseudoaneurysms carry a different prognosis and whether they require different therapeutic approaches. The present case describes the development of a large, late-onset coronary pseudoaneurysm that developed after stent implantation for chronic total occlusion (CTO). The use of intravascular ultrasound (IVUS) to assist in the placement of a covered stent and follow-up are described. Case Report. A 42-year-old man was hospitalized with stable angina. His medical history was significant for arterial hypertension, hyperlipidemia and gout. Current cardiovascular medications consisted of a calcium antagonist, simvastatin and allopurinol. His double-master exercise test showed significant ST-segment depression in leads II, III, aVF and V4–6. Coronary angiography was performed and showed CTO in the mid-left anterior descending artery (LAD) and proximal right coronary artery (RCA), and 75% stenosis of the left circumflex artery (LCX). A staged PTCA was planned for this patient. The initial intervention was PTCA of the LAD. After 4 weeks, elective PTCA of the RCA occlusion was carried out following intravenous administration of 10,000 IU heparin (Figure 1A). A 7 French Judkins guiding catheter (JR3.5-SH, Johnson & Johnson, Somerville, New Jersey) and a 0.009 x 0.014´´ guidewire (Neo’s conquest, Asahi Intec, Aichi, Japan) were used. First, a 1.5 mm balloon (Maverick, Boston Scientific/Scimed, Inc., Maple Grove, Minnesota) was used to perform five inflations from the distal to proximal portion of the lesion. An angiogram showed recanalization of the RCA (Figure 1B). Next, a 3.0-mm long balloon (VIVA, Boston Scientific/Scimed, Inc.) was used to perform two inflations (8 atmospheres for 60 seconds and 10 atmospheres for 60 seconds). Two stent implantations (3.5 x 24 mm S670 stent; Medtronic, Minneapolis, Minnesota) were required because a dissection developed at the angioplasty site in the proximal RCA (12 atmospheres for 30 seconds). However, the final angiogram showed no residual stenosis (Figure 1C). The patient was discharged 2 days after the procedure. Post-procedural medication consisted of aspirin 200 mg and ticlopidine 200 mg daily. Ticlopidine was continued for 12 weeks after stent implantation. Three months later, the patient returned for PTCA of the left circumflex artery. Coronary angiography revealed an aneurysm of the RCA, which corresponded to the previously stented segment (Figures 2A and 2B). IVUS (Atlantis; Boston Scientific/Scimed, Inc.) revealed a giant pseudoaneurysm with disruption of the arterial wall at the stented segment (Figure 2C). We sealed the RCA aneurysm by implanting a covered stent (2.5 x 5.0 mm JOSTENT; Jomed, Unterschleissheim, Germany) to prevent the rupture. Polytetrafluoroethylene (PTFE), the graft material in this stent, is sandwiched between two stent layers. Predilation was performed using a 3.5 mm VIVA balloon. The stent was implanted using the same balloon, and post-dilation was performed with a 4.0 mm balloon (CALYPSO X’act; Medtronic), which was inflated to 20 atmospheres for 30 seconds. Final angiogram showed no aneurysm (Figure 3A) and IVUS confirmed that the stent completely covered the site of the aneurysm. The patient was discharged 6 days after the intervention and was treated with aspirin 200 mg and ticlopidine 200 mg daily for 12 weeks. Angiography was repeated 6 months after implantation of the covered stent and showed patency of the stent without extravasation of contrast or evidence of restenosis (Figure 3B). Discussion. The most common definition of coronary aneurysm is a localized dilatation that exceeds the diameter of adjacent normal segments by 1.5 times. Coronary aneurysms most commonly represent localized enlargement of a segment weakened by atherosclerosis. Recently, the development of coronary aneurysms as a complication of catheter-based interventions has been reported. These lesions are believed to develop when the arterial wall is injured by dissection or perforation of the media by balloon angioplasty without violation of the adventitia.³ The result is the development of a pseudoaneurysm. Alternatively, a true aneurysm may develop following wash-out of the lipid core of a large plaque in a severely dilated, remodeled coronary artery after angioplasty.⁴ Aneurysms induced by balloon angioplasty may be caused by the use of oversized balloons or excessively high pressure.^1,5 On the other hand, Slota et al.⁶ found there was no association between dissection and the development of aneurysms. The development of coronary aneurysms following stenting is rare because the stent is imbedded and ultimately integrated into the vessel wall, thereby strengthening it. However, reports of aneurysmal formation after stenting do exist. Voigtander et al.⁷ reported the case of a coronary aneurysm that developed after bailout stenting. In that case, a persistent false lumen remained outside the stent that was in continuity with the stent lumen, which gradually enlarged over 6 months. Regar et al.⁸ reported a similar case of aneurysmal formation after bailout stenting. The patient was a 68-year-old man who developed an extensive dissection of his LAD after balloon angioplasty. This aneurysm was treated successfully with a stent. IVUS showed that the aneurysm was caused by a large, patent false lumen that was external to media. In the present case, coronary stenting was successfully performed after moderate coronary dissection occurred following predilation, but a coronary aneurysm was formed at the stented segment despite the excellent angiographic result. Although the trigger to the development of the pseudoaneurysm was a dissection, our case is rare in that the arterial wall rupture occurred at a later stage, despite the excellent angiographic result after initial stent placement. A possible mechanism for the gradual formation of the pseudoaneurysm in this case may include a residual small false lumen of the stented segment due to the incomplete apposition of the stent to the arterial wall leading to thinning and remodeling of the arterial wall, and eventually to the development of the pseudoaneurysm. These findings demonstrate that a coronary aneurysm can form after stenting. Slota et al.⁶ also found that coronary aneurysms can develop after stenting and that there was no difference in the incidence of aneurysms after balloon angioplasty and stent implantation. These data should alert the interventionalist to the potential consequences of incomplete coverage or incomplete apposition of the stent to the arterial wall. IVUS following stent placement for PTCA-induced dissection may have the power to detect the incomplete coverage or incomplete apposition of the stent to the arterial wall, which may not be detected by plain angiography alone. True coronary aneurysms generally are benign, and most cases are thus left untreated.² However, data on the prognosis and treatment of coronary aneurysms following interventions are limited, and no consensus as to the optimal treatment strategy has been reached. The management of coronary pseudoaneurysms is controversial because of their potential for late rupture. The lack of IVUS data explains why the risks and the optimal treatment of small-to-moderate sized coronary pseudoaneurysms are not known. Large pseudoaneurysms that are only partially lined by a thin rim of adventitia may require surgery to prevent rupture. Possible surgical approaches include ligation in combination with bypass grafting or bypass alone.⁹ We identified the aneurysm in our patient as a late giant pseudoaneurysm and decided to treat the patient with a covered stent to prevent aneurysmal rupture. Placement of covered intracoronary stents to avoid surgery was recently reported.^10,11 In our patient, the covered stent interrupted blood flow to the aneurysm and follow-up coronary angiography showed good patency of the covered stent without aneurysm. In summary, we described a case with delayed development of a giant coronary pseudoaneurysm after stent placement for chronic total occlusion despite the excellent angiographic result, which was obliterated with a covered stent. IVUS-guided covered stent placement may be a feasible and effective method to treat coronary artery pseudoaneurysm at the previously stented segment.

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