Stent Implantation for Coronary Aneurysm with Edge Stenosis: Angiographic and Intravascular Analysis

ABSTRACT: The incidence of coronary artery aneurysms is about 1–2%, with clinical course dependent on the size of the aneurysm. A case of moderate-size aneurysm in the proximal left anterior descending coronary artery with stenosis at both edges is presented. This was interrogated with intravascular ultrasound (IVUS), and based on the patient’s presentation, a single stent, size-matched 1:1 to the proximal reference, was placed across the aneurysm and both lesions. Post-implantation IVUS demonstrated residual stenosis and minimal change in the “neck” size of the aneurysm. At 4 months, there was no thrombosis or in-stent restenosis, and the aneurysm was almost completely resolved.

Key words: coronary aneurysm, coronary artery disease, intravascular ultrasound, stent

Coronary artery aneurysms are local dilatations exceeding the diameter of the normal vessel segments by at least 1.5 times. These were first recognized post mortem, with a 1.4% incidence in autopsy series.¹ The angiographic incidence of coronary aneurysms ranges from 0.3–4.9%.² In one study of 20 patients, 50% of cases were due to atherosclerosis, 20–30% were congenital and 10–20% were due to Kawasaki’s disease.³ Observational studies and case reports suggest an increasing number of cases occurring after percutaneous interventions, with reported incidences of 5% at 6 months after PTCA,⁴ 10% at 5 months after directional coronary atherectomy (DCA),⁵ 32% at 4 months after Gianturco-Roubin stent placement when steroids and colchicine were used adjunctively post-procedure,⁶ and 5–6% at 6 months after Palmaz-Schatz stenting⁷ or laser angioplasty.⁸ Currently, post-intervention coronary artery aneurysm formation remains an infrequent etiology. Predictors of the formation of coronary aneurysm include the presence of coronary artery dissection at the time of PCI^4,7,9 and the use of oversized balloons.^4,7 The depth of arterial resection was not found to be a predictor for aneurysm formation following DCA.¹⁰ Although there is concern over thrombosis within large aneurysms, the natural history of both de novo and post-intervention coronary aneurysms appears to be benign.⁹ However, there is evidence that angina pectoris and left ventricular dysfunction can occur with coronary artery aneurysms, despite the absence of obstruction.¹¹ Furthermore, discrete coronary aneurysms, unlike diffuse ectasia, are more likely to be associated with severe coronary artery disease.³ This case describes the treatment of a moderate-size proximal left anterior descending (LAD) coronary artery aneurysm that was straddled by significant stenoses with a heparin-coated stent.¹² Case Report. A 65-year-old woman was referred for elective cardiac catheterization. The patient developed increasing exertional dyspnea and fatigue after walking a few blocks beginning 4 months prior to presentation. She denied any chest discomfort, paroxysmal nocturnal dyspnea, orthopnea and edema. Cardiovascular risk factors included age, hypertension, hyperlipidemia and family history of coronary artery disease. She had no prior tobacco use, diabetes, and was on hormone replacement therapy. Physical exam was essentially unremarkable, with no signs of heart failure. A dobutamine stress echocardiogram at an outside clinic suggested inferior and apical hypokinesis at peak exercise. Right heart cardiac catheterization revealed normal right heart pressures, with a cardiac index of 2.2. Left ventricular angiogram demonstrated normal left ventricular ejection fraction with no regional wall motion abnormalities. Coronary angiogram demonstrated an ectatic proximal to mid-LAD artery with a 3–5 mm aneurysm in the mid-LAD. There were moderate-grade stenoses proximal and distal to the aneurysm. The proximal and mid-right coronary artery (RCA) had mild-moderate ectasia with 50% ostial and distal RCA stenoses. At this point, the patient was medically managed with aspirin, ACE inhibitors and intermittent diuretics; however, she remained symptomatic with minimal exertion. She was brought back to the catheterization laboratory with the intent to interrogate the LAD territory for possible intervention. During the second catheterization, intravascular ultrasound (IVUS; Atlantis 40 MHz, Boston Scientific/Scimed, Inc., Maple Grove, Minnesota) of the LAD artery revealed a 7.2 mm eccentric aneurysm (Figures 1 and 2). The proximal edge of the aneurysm had a moderate stenosis, but there was a significant narrowing with minimal luminal diameter (MLD) of 2 mm and MLA of 3.5 mm2, just distal to the neck of the aneurysm. The proximal and distal reference vessels were measured at 4.0 mm. A 3.5 x 18 mm Bx Velocity Hepacoat stent (Cordis Corporation, Miami, Florida) was deployed across the aneurysm with a maximal inflation pressure of 14 atmospheres (atm); this was post-dilated with a 4.0 x 15 mm Maverick balloon (Boston Scientific/Scimed, Inc.) at 10 atm. Immediate post-procedural angiogram demonstrated decreased flow through the aneurysm and resolution of the stenoses. IVUS showed a moderate decrease in the aneurysm size (from 51.6 mm2 to 49.5 mm2 in maximum vessel area), good stent apposition proximally and distally, and improvement of lumen size (3.5 mm in MLD, and 11.7 mm2 in MLA). The patient did well post-procedure and was discharged the next day. Her symptoms resolved for a short period post-procedure; however, she subsequently developed intermittent chest discomfort over the next few months. Follow-up coronary angiography and IVUS were performed 4 months after the initial intervention (Figures 1 and 2). These revealed a widely patent stent (IVUS MLA and MLD of 9.4 mm2 and 3.4 mm, respectively), TIMI 3 flow in the LAD, with amputation of the coronary aneurysm (IVUS maximum vessel area of 35.7 mm2). She had developed a high-grade mid-left circumflex lesion that was treated with balloon angioplasty and stent placement (3.0 x 16 mm Express² stent; Boston Scientific/Scimed Inc.). Discussion. Aneurysmal dilatation of the coronary arteries leads to sluggish and turbulent blood flow, which is thought to predispose to developing myocardial ischemia. Angiographic signs of impaired flow include delayed antegrade filling (slow flow), segmental back flow (milking) and local dye deposition in the dilated segment (stasis). The presence of non-obstructive fusiform coronary aneurysms has been shown to increase lactate production in the coronary sinus following stress testing by ergometry, either by treadmill testing using the Bruce protocol or bicycle stress testing.¹³ Nitroglycerin did not improve the lactate accumulation, and in fact, aggravated it. The indication and best modality for treatment of coronary aneurysm remain controversial and undefined. Polytetrafluoroethylene (PTFE)-covered stents,^14–17 vein-covered stents¹⁸ and uncovered stents¹⁹ have been successfully used to seal coronary aneurysms. Embolization has been used to treat a congenital coronary artery aneurysm.²⁰ Surgical resection or plication^1,21,22 have also been reported and coronary artery bypass graft surgery has been performed as a treatment.²³ However, discrete coronary aneurysms do not appear to rupture more frequently than non-aneurysmal coronary arteries and their resection may not be warranted,³ as procedure-related cases may spontaneously regress.²⁴ The use of stents to treat complex lesions and highly thrombogenic situations carries a higher risk for subacute stent thrombosis. Heparin-coated stents have the theoretical advantage of providing a local antithrombotic milieu at the lesion site, and this has been corroborated by angioscopic assessment following implantation of these stents.²⁵ However, clinical data demonstrating significant reduction in subacute thrombosis by using heparin-coated stents as compared to bare-metal stents are lacking.^26,27 This may be due to the very low incidence of stent thrombosis in current uncoated stents due to aggressive up-front antiplatelet therapy. The opportunity for complete evaluation and follow-up in this case demonstrates that stent implantation over coronary aneurysm may provide a safe approach. This can be performed either to treat stenosis (as the case presented here), or in an attempt to decrease flow through moderate-size aneurysm with documented ischemia.