Successful Management of an Unruptured Mycotic Coronary Aneurysm

ABSTRACT: Systemic complications of native-valve endocarditis include embolism, abscess formation and development of mycotic aneurysms. To date, only two cases of mycotic coronary aneurysm (MCA) detected by transesophageal echocardiography (TEE) have been reported since 1812. We describe the successful management of infectious mitral valve endocarditis complicated by a MCA involving the left circumflex artery initially detected by TEE. This report illustrates the importance of correlating findings between TEE and coronary angiography, as early detection and prompt management of these rare coronary aneurysms are of paramount importance. J INVASIVE CARDIOL 2007;19:E366–E368 Representing less than 2% of all aneurysms, mycotic aneurysms in the setting of infective endocarditis tend to occur in the cerebral or systemic circulation, with rare involvement of the pulmonary vasculature, aortic root and sinuses of Valsalva.¹ A distinct occurrence is a mycotic coronary aneurysm (MCA) with only 28 cases reported in the international literature since 1812.² Of these, only 2 prior cases of MCA have been diagnosed by transesophageal echocardiography (TEE).^3,4 We describe the successful management of infectious mitral valve endocarditis complicated by a MCA involving the left circumflex artery (LCx) initially detected by TEE. Case Report. An 83-year-old male with a medical history notable only for benign prostatic hypertrophy, an appendectomy and a cholecystectomy was admitted to the hospital with complaints of generalized weakness, fever and watery, nonbloody stools for 3 days. On admission, the patient was tachycardic, normotensive and febrile to 102.6ºF. Physical examination revealed a thin, nontoxic-appearing male with a left conjunctival hemorrhage and bibasilar rales. Cardiac examination demonstrated no visible heaves and a normal left ventricular impulse. A normal S1, physiologically split S2 and a harsh, grade III/IV, holosystolic murmur along the left lower sternal border radiating to the axilla were present. Skin examination revealed multiple, nontender, erythematous macular lesions on the sole of the right foot. An electrocardiogram at the time of admission demonstrated second-degree, Mobitz Type II atrioventricular block. Admission laboratory studies were notable for thrombocytopenia, a mild transaminitis and an elevated Troponin I level. Within 12 hours of admission, four blood culture bottles grew methicillin-sensitive Staphylococcus aureus. Treatment with nafcillin, gentamicin and rifampin were started. A transthoracic echocardiogram (TTE) demonstrated normal left ventricular function, mild mitral regurgitation and normal chamber dimensions. Within 2 days of therapy, the patient developed new-onset slurred speech. Cerebral magnetic resonance imaging (MRI) was notable for multiple focal areas of acute ischemia involving both supratentorial hemispheres in the parietal and occipital regions. By hospital day 6, the patient remained afebrile with improvement in his thrombocytopenia and transaminitis. TEE demonstrated a large, nonmobile mass with central cavitation on the atrial side of the anterior leaflet of the mitral valve (Figure 1A) along with mild mitral valve prolapse with moderate mitral regurgitation. A distinct jet of color Doppler flow across the mitral valve under the area of the vegetation suggested destructive fenestration of the anterior leaflet. Notably, an echolucent circular structure with an eccentric intraluminal focus was seen adjacent to the left atrial appendage, raising the suspicion of a coronary aneurysm (Figure 1B). The aortic valve was trileaflet and sclerotic without obvious vegetation or perivalvular abscess. Cardiac catheterization demonstrated normal right heart filling pressures with non-flow-limiting atherosclerotic disease in the left main, right coronary and left anterior descending arteries (LAD). The proximal LCx contained a large aneurysm with an 80% stenosis at the distal margin of the aneurysm. The remainder of the artery was free of flow-limiting stenoses (Figure 2). On hospital day 8, the patient underwent three-vessel coronary artery bypass, coronary aneurysmectomy, mitral valve replacement and aortic valve exploration. Intraoperative findings included extensive endocarditis of the anterior and posterior mitral valve leaflets with destruction of the anterior mitral valve annulus near the anteromedial commissure. All necrotic tissue was excised and a 29 mm Edwards porcine mitral valve was placed via a transseptal approach. The aortic valve was explored via an anterior aortotomy and was found to be without vegetation. Elevation of the heart revealed a MCA along the proximal portion of the LCx in juxtaposition to the left atrial appendage. The left main coronary artery was oversewn from within the aorta. The LAD artery was ligated proximally and the LCx was ligated distal to the aneurysm. Three bypass grafts were placed: the left internal mammary artery (LIMA) to the mid-portion of the LAD, a reverse-saphenous vein graft (rSVG) to the first obtuse marginal branch and a rSVG to the second obtuse marginal branch. The resected aneurysm measured 4 cm x 2 cm and was sent to pathology for further analysis. Microscopic examination demonstrated an inflammatory infiltrate with diffuse infiltration of gram-positive cocci in clusters (Figure 3). A dual-chamber permanent pacemaker was placed on postoperative day 3 for persistent bradycardia and intermittent heart block requiring external pacing. On postoperative day 6, the patient was discharged home on intravenous oxacillin and rifampin for 8 weeks to be followed by life-long oral antibiotic prophylaxis. Upon follow up 6 months later, the patient remained in good health with persistent first-degree atrioventricular block on electrocardiography. Discussion. Cardiovascular complications of infective endocarditis include congestive heart failure secondary to valvular incompetence, perivalvular abscess, pericarditis, formation of intracardiac fistulae, aortic valve dissection, embolization and mycotic aneurysms. Systemic embolization occurs in 22–50% of patients who are diagnosed with infective endocarditis,⁵ often involving the coronary circulation. Of these, 74% occur in the left coronary circulation, with the LAD being more susceptible.^6,7 A rare occurrence is the development of a MCA. First described by Bourgon in 1812, the majority of coronary aneurysms occur in the setting of atherosclerosis with congenital aneurysms, vasculitides (e.g., Kawasaki syndrome) and connective tissue disorders.⁸ The underlying mechanism of mycotic aneurysm formation includes embolization of septic material to the vasa vasorum, contiguous infection along the arterial wall, direct inoculation of a vessel wall by instrumentation or bacteremic seeding of an existing atheromatous plaque.⁹ Staphylococcus aureus is the primary infectious agent in the majority of cases. Potential complications secondary to mycotic coronary aneurysms include rupture, cardiac tamponade, fistulization, myocardial ischemia or infarction secondary to septic embolization, and sudden cardiac death. The management of endocarditis complicated by cerebral emboli and a MCA proves to be challenging, as the risk of surgical complications are increased and guidance from previous experience is limited. Coronary ligation with resection appears to offer the most uncomplicated approach, assuming viable target vessels exist for grafting. In this case, the patient’s coronary artery disease was limited to the proximal portion of the LCx. Given the proximity of the LAD ostium and distal portion of the left main artery to the infected aneurysm, the proximal LAD was bypassed with a LIMA graft and 2 saphenous veins were grafted to each of 2 obtuse marginal branches. Without appropriate target vessels, the complexity of such a surgical approach increases significantly. Other approaches may have included reconstructing the proximal LCx artery or bypassing only the LCx after resection of the mycotic aneurysm. However, the possibility of persistent infection in the proximal LAD and possibly the left main itself would remain. This case illustrates an unusual presentation of native mitral valve endocarditis complicated by peripheral embolization, coronary aneurysm, and atrioventricular conduction block in a healthy 83-year-old male. Given the limited experience with MCAs, clinical management remains controversial, as the majority of reported cases have been documented post mortem. While coronary aneurysms have been detected by TEE in the past,^10,11 the diagnosis of a MCA by TEE has only been reported twice in the literature since 1812. To our knowledge, we report the third MCA diagnosed by TEE. As evidenced by this case, correlating findings between the TEE and coronary angiogram are of paramount importance in the detection of these rare coronary aneurysms. Early diagnosis, appropriate antibiotic therapy and prompt surgical evaluation remain the mainstay of current therapy. References 1. Mylonakis E, Calderwood SB. Infective endocarditis in adults. N Engl J Med 2001;345:1318–1330. 2. Osevala MA, Heleotis TL, Dejene BA. Successful treatment of a ruptured mycotic coronary artery aneurysm. Ann Thorac Surg 1999;67:1780–1782. 3. Gebuhrer V, Genoud JL, Andre-Fouet X, et al. Coronary artery mycotic aneurysm discovered by transoesophageal echocardiography. Eur Heart J 1997;2:352. 4. Brasselet C, Maes D, Tassan S, et al Extensive mycotic coronary aneurysm detected by echocardiography. Apropos of a case. Arch Mal Coeur Vaiss 1999;92:1229–1233. 5. Bayer AS, Bolger AF, Taubert KA, et al. Diagnosis and management of infective endocarditis and its complications. 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