Coronary Artery Aneurysms

Coronary aneurysms are defined as a localized dilatation that exceeds 1.5 times the diameter of the adjacent segment of artery. Aneurysms can be saccular (transverse larger than the longitudinal axis) or fusiform (longitudinal at least twice the transverse axis). These should be distinguished from coronary artery ectasia in which there is diffuse dilatation involving greater than 50% of the coronary artery. Morgagni described the first case of coronary artery aneurysms in 1761,1 and Munker et al. reported the first antemortem case diagnosed by coronary angiography in 1958.2 The Coronary Artery Surgery Study (CASS) registry of 20,087 consecutive patients undergoing coronary angiography for suspected coronary artery disease is the largest series of patients with coronary aneurysms.3 The CASS registry demonstrates a 4.9% incidence of coronary aneurysms (978 patients), and the right coronary artery is the most frequent vessel involved. Patients with both aneurysms and coronary ectasia were included in this study. The current case report of a coronary aneurysm treated with a stent and subsequent bypass surgery by Bartorelli et al. in this month’s Journal involves a 64-year-old female presenting with a non-Q wave myocardial infarction. Coronary angiography showed a large saccular aneurysm in the proximal left anterior descending (LAD) coronary artery with antero-apical hypokinesis on left ventriculography. The aneurysm was further characterized by intravascular ultrasound (IVUS) that demonstrated slow flow through a 12 x 11 mm aneurysm, with no evidence of coronary atherosclerosis or thrombosis. Coronary Doppler flow analysis showed a reduced coronary flow reserve across the LAD aneurysm. The patient had no clinical or laboratory evidence of autoimmune or infectious illnesses. The patient was treated with a polytetrafluoroethylene (PTFE)-covered JOSTENT (Jomed AB, Helsingborg, Sweden) graft with a good angiographic result, but presented 7 months later with restenosis of the covered stent graft. She was then successfully treated with a minimally-invasive single-vessel coronary artery bypass, with a left internal mammary graft to the LAD. Several questions are raised by this case report: Are coronary artery aneurysms a “real” entity or a variant of atherosclerosis? Congenital coronary artery aneurysms are rare.4 The most common etiology is atherosclerosis, present in 50–80% of cases.3–5 Histologic examinations of coronary aneurysms have revealed findings of arteriosclerosis, such as hyalinization and lipid deposition of the intima, intramural hemorrhage, and inflammatory reactions consistent with the arteriosclerotic process.4 The pathophysiology of aneurysm formation has been postulated to be weakening of the medial layer of the vessel wall, which in part may be due to chronic overstimulation of the vasodilator nitric oxide.4 Coronary aneurysms may occur from trauma (blunt and iatrogenic in the catheterization lab) and are the hallmark of Kawasaki disease.4 In the study by Swaye et al., patients with coronary aneurysms had similar coronary risk factors and no difference in 5-year survival rates compared to those without aneurysms, suggesting that coronary aneurysms are not a distinct clinical entity, but rather a variant of coronary atherosclerosis.3 The lingering question remains the relationship of coronary artery aneurysms and atherosclerosis. Do aneurysms predispose to atherosclerosis or vice versa? Current research and data do not resolve this issue. Even though we do not know which came first, it is clear that when aneurysms are present in the absence of a systemic inflammatory condition, associated atherosclerosis should be suspected. Do coronary artery aneurysms cause ischemia and/or infarction? The majority of coronary aneurysms are asymptomatic. When symptoms occur, angina or infarction are the most common presenting features. Myocardial infarction is the initial presentation in 30–50% of cases.3,6 Aneurysms may be complicated by thrombosis and rupture. Rupture is a rare event with no occurrences in the 978 patients with aneurysms in the CASS database.3 Thrombosis is more common. A postmortem study by Daoud et al. reported the presence of thrombus in 7 of 10 patients with coronary aneurysms.7 Several case reports have also demonstrated myocardial infarctions resulting from thrombosed coronary aneurysms without an obstructive coronary lesion.8,9 Thrombosis and distal embolization are thought to be potential etiologies of the clinical presentation. Swanton et al. have demonstrated reduced coronary blood flow in patients with coronary aneurysms, which may be a potential nidus for clot formation.10 Demopoulos et al. reported ischemic event rates (cardiac death, myocardial infarction, or unstable angina) among 121 patients with concomitant coronary aneurysms and obstructive coronary disease (defined as the presence of > 70% stenosis) versus 115 coronary disease patients with no aneurysms.5 There was no difference in event rates (12.4% vs. 10.4%; p = NS). Even though there is a recognized association between aneurysms and coronary atherosclerosis, the current case illustrates that a non-atherosclerotic coronary aneurysm can cause an ischemic event without an obstructing coronary lesion. What tests should be done to characterize coronary artery aneurysms to make treatment decisions? In the case described by Bartorelli, IVUS and coronary Doppler flow analyses provided further anatomic and physiologic assessment. IVUS has been previously demonstrated by Maehara et al. to distinguish coronary aneurysms from other types of lesions11. In this study, only 27% of 73 patients diagnosed with a coronary aneurysm had definitive evidence of a true aneurysm with an intact vessel wall. The other lesions were pseudoaneurysms, complex plaques, or normal segments adjacent to a stenosis. Coronary flow reserve

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