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Show Journal of Neiim- Oplilhalnwfogy 18( 4): 237- 241, 1998. © 1998 Lippincolt Williams & Wilkins. Philadelphia Retinal Ischemia in Aortic Arch Atheromatous Disease Jose G. Romano, M. D., Viken L. Babikian, M. D., Christine A. C. Wijman, M. D., and Thomas R. Hedges III, M. D. Retinal ischemia is often caused by emboli arising from the cardiac chambers or the common carotid artery bifurcation; the latter are often composed of cholesterol. However, in many patients no lesions are identified after evaluation of these sources of emboli. Two patients were observed who had retinal ischemia and emboli originating from aortic atheromatous plaques that were visualized by transesophageal echocardiography. Cardiac, carotid, and intracranial sources of emboli were excluded. The embolic nature of retinal ischemia was further corroborated by the presence of microembolic signals during transcranial Doppler insonalion of the middle cerebral artery on the side ipsilateral to the symptomatic retina. In patients with Hollenhorst plaques the aortic arch can be a potential source of emboli. Transesophageal echocardiography should be considered in these patients when the initial evaluation does not identify a cardiac or carotid lesion. Key Words: Aortic arch plaque- Retinal embolism- Retinal ischemia. A common cause of transient monocular blindness and retinal artery occlusion is retinal embolism ( 1). Emboli may be composed of calcific material ( 2), fibrin and platelets ( 3), or, more commonly, cholesterol ( Hollenhorst plaques) ( 2,4). The latter often arise from atheromatous plaques at the common carotid artery bifurcation ( 5). However, as many as 50% of asymptomatic patients with Hollenhorst plaques have no evidence of carotid disease ( 6), and in two thirds a source of emboli could not be found after carotid evaluation and precordial echocardiography ( 7). That the aortic arch can be the source of retinal embolism is not well documented ( 8,9). We observed two patients with retinal embolism originating from the aortic arch in whom the diagnosis was established by means of ultrasound and magnetic resonance imaging ( MRI) tests. Manuscript received November 17, 1997; accepted June 16, 1998. From the Departments of Neurology, University of Miami, School of Medicine ( J. G. R.), Miami, Florida; and the Boston University School of Medicine ( V. L. B., C. A. C. W.) and the Departments of Neurology and Ophthalmology, Tufts University School of Medicine ( T. R. H.), Boston, Massachusetts, U. S. A. Address correspondence and reprint requests to V. L. Babikian, M. D., Department of Neurology, Boston University School of Medicine and Boston Veterans Administration Medical Center, 150 South Huntington Avenue, Boston, MA 02130, U. S. A. CASE REPORTS Case 1 A 91- year- old man suddenly lost vision in the lower half of his left visual field. He had no associated ophthalmologic or neurologic symptoms. Medical history included diet- controlled diabetes mellitus and coronary artery disease, for which he took aspirin. There was no history of headache, jaw claudication, neck or shoulder pain, previous transient visual loss, or cerebral ischemic events. On examination 2 days after onset of symptoms, visual acuity was 20/ 70 OD and 20/ 50 OS. There was an inferonasal quadrantic visual defect in the left eye. Retinal infarction in the distribution of the left superior retinal branch artery secondary to an embolus was noted ( Fig. 1 A). General, cardiac, and neurologic examinations were unrevealing. Erythrocyte sedimentation rate was 3 I mm/ hr. A carotid duplex study showed minimal plaque formation at the origins of both internal carotid arteries, causing diameter reductions estimated at less than 30%. Brain MRI showed an old lacunar infarct in the left caudate nucleus. A magnetic resonance angiogram showed normal intracranial arteries and left common and internal carotid arteries. A plaque causing 50% to 70% luminal diameter reduction was detected in the right common carotid artery. A transthoracic echocardiogram ( TTE) showed hy-pokinesis of the left ventricle but no embolic source. A transesophageal echocardiogram ( TEE) showed calcified plaques in the aortic arch and the ascending and descending aorta ( Fig. IB). The largest in the arch was 8 mm thick. No mobile elements were seen. Diffuse left ventricular hypokinesis was again observed, and no intracardiac thrombus was found. A transcranial Doppler ultrasound ( TCD) study performed 7 days after onset of symptoms showed more than 60 microembolic signals in the left middle cerebral artery during a 30- minute recording ( Fig. 1C). No signals were detected on the right side. Microembolic signals persisted in the left middle cerebral artery and were again absent on the right during a repeat TCD study 6 days later. The laboratory's TCD methods have been described in a previous report ( 10). A diagnosis of retinal embolism and infarction was 237 238 J. G. ROMANO ET AL. made. The suspected source of emboli was an aortic arch plaque distal to the right and proximal to the left common carotid artery ostia. Case 2 A 67- year- old man had a history of two attacks of transient loss of vision of the right eye. He described both as though a shade were being pulled over the eye. The attacks were 24 hours apart. The first lasted 3 hours and the second lasted 30 minutes. There were no other accompanying neurologic or cardiovascular symptoms. His medical history included hypertension, hyperlipid-emia, chronic renal insufficiency, and diabetes mellitus. Approximately 1 year previously, he had had transient symptoms of vertebrobasilar ischemia for which he was prescribed warfarin. International normalized ratio was 3.0 at the time of present symptoms. Physical examination showed normal visual acuity, visual fields, and pupillary responses. Funduscopic examination of the right eye showed white material in the original segment of the inferior branch retinal artery and an embolus at the first bifurcation of the temporal branch artery ( Fig. 2A). In FIG. 1. Case 1. Funduscopic evaluation of the left eye ( A) shows an ischemic retinal whitening in the superior retina and an embolus in the superior branch retinal artery ( arrow). A visual fixation artifact is to be noted ( curved arrow). A calcified plaque ( arrows) of the ascending aortic arch is seen on transesophageal echocardiogram ( B). Transcranial Doppler ultrasound monitoring ( C) shows a microembolic signal ( arrow) in the left middle cerebral artery. addition, a small embolus was seen in the inferior branch of the retinal artery. Six days later, a new shiny retractile embolus was seen at the second bifurcation of the superior temporal branch retinal artery ( Fig. 2B). On general examination, several toes on both feet appeared blue, and no pedal pulses were found. Cardiac and neurologic examinations were both unremarkable. Erythrocyte sedimentation rate was 34 mm/ hour. A brain MRI showed extensive, chronic, periventricular ischemic changes and bilateral basal ganglia lacunes. Minimal plaque was seen by duplex ultrasound at both common carotid artery bifurcations. A TCD study and magnetic resonance angiography studies indicated moderate bilateral siphon stenoses. Transthoracic echocardiography showed left ventricular hypertrophy and mild dilatation of the aortic root and raised the possibility of debris in the aortic arch. Transesophageal echocardiography showed a large plaque 10 mm in thickness in the ascending aorta; in addition, smaller plaque formation was noted in the arch and descending aorta ( Fig. 2C). A cardiac source of emboli was not found. A TCD study, performed 5 days after onset of symptoms, detected five ./ Neiim- Ophlhulmol, Vol. IS. No. 4, 1998 AORTIC ARCH ATHEROMATOUS DISEASE 239 FIG. 2. Case 2. Funduscopic evaluation of the right eye ( A) shows embolic material in several retinal arteries ( arrows). Six days later ( B), an additional shiny retractile embolus is seen ( arrow). Transesophageal echocardiogram shows a plaque in the ascending aorta ( C). A red colored microembolic signal is detected in the right middle cerebral artery during transcranial Doppler testing ( D). t& ff- :> o- 9| U M ; . • ? • * * D 1 1 •• : . : • • • • ' • . ' • . . • • • : m microembolic signals in the right middle cerebral artery during a 30- minute recording ( Fig. 2D). Microembolic signals persisted a month later. Further evaluation showed progressive renal dysfunction. A diagnosis of cholesterol embolism from aortic arch plaque with involvement of the retinal, renal, and peripheral vascular circulations was made. DISCUSSION The two patients described sought medical attention because of symptoms of retinal ischemia. Transesophageal echocardiograms showed thick, presumably atherosclerotic, plaques in their aortic arches, and in both cases the embolic nature of retinal ischemia was corroborated by the observation of emboli in arterioles of the symptomatic retinas in addition to TCD microembolic signals along the distributions of the affected internal carotid arteries. These findings indicate that aortic arch plaques can be the source of embolism in the retina and can be diagnosed with ultrasound and MRI techniques. Although severe stenoses of the cervical internal carotid artery are considered a common origin of retinal emboli, the latter can also originate from other sources. Previous reports have described external carotid artery disease ( 11), atrial myxomas ( 12), myocardial infarcts with mural thrombus formation ( 13), mitral valve prolapse ( 14), and prosthetic valves ( 15) as sources of embolism. Common carotid artery bifurcation and cardiac lesions were ruled out in our patients. In addition, the J Neuro- Oplilhiilnwl, Vol. IK. No. 4. I99K 240 J. G. ROMANO ET Ah. finding of microembolic signals in the middle cerebral arteries on the symptomatic sides ruled out the possibility of embolism from ophthalmic artery lesions. Furthermore, Hollenhorst plaques arise from aortic or carotid atherosclerotic plaques, eliminating the possibility of a cardiac source of emboli. The aortic arch has previously been suspected to be the source of retinal emboli in people with the disseminated cholesterol embolism syndrome ( 8,9). Cerebral, cardiac, renal, mesenteric, and peripheral vascular embolism can occur in this context ( 8,9,16,17). Our second patient had clinical or laboratory evidence of retinal, cerebral, and systemic embolism and illustrates the syndrome. The findings in our first patient suggest, however, that retinal embolism from aortic arch plaques can occur in the absence of clinically evident cerebral or systemic embolization. To our knowledge, this has not been recognized in previous studies. Thus, the aortic arch may be the source of isolated retinal embolism and should be studied in patients with nonreveal-ing carotid and cardiac evaluations. Aortic arch atheromas have been increasingly recognized as a potential source for cerebral embolism ( 18). Atheromas more than 4 mm thick, particularly when ulcerated or mobile, have been associated with cerebral infarction ( 19). They are also predictors of recurrent vascular events and are often found in patients with cerebral infarction of undetermined cause ( 20). Until recently, these lesions were missed during the regular evaluation of patients with retinal or cerebral ischemia because available diagnostic tests, such as aortic angiography, were not sensitive enough to detect them. With the development of TEE as a relatively safe ( 21) and effective method of studying the aortic arch ( 22), there has been a growing awareness of the importance of evaluating this arterial segment in patients with retinal or cerebral embolism in whom cardiac and carotid evaluations have been unrewarding. In our patients, TEE helped identify the source of emboli that was suspected from fundus-copic examinations and TCD studies. It is to be noted that technically adequate TTE studies did not permit satisfactory imaging of the aortic arches in either of our patients. This is expected, given the limitations of the technique, and is similar to previous experience with retinal embolism ( 23). The superiority of TEE over TTE in detecting cardioembolic sources has been well documented, with TEE revealing an embolic source in as many as 50% of patients with a negative TTE ( 24,25). Regarding the aortic arch, TTE cannot reliably image this area and often misses atherosclerotic plaques found by TEE ( 22). Thus, a TEE study may be indicated in the patient with retinal ischemia after a nonrevealing work up. Transcranial Doppler ultrasound signals similar to the ones detected in our patients can correspond to in vivo microemboli composed of platelet fibrinogen, cholesterol, or gaseous material ( 10,26). In patients with common carotid artery stenosis these signals have been associated with cerebral ischemia, severe stenosis, and plaque ulceration ( 27- 30). In the cases presented above, their presence identifies the link between aortic arch plaques and retinal emboli. It also indicates that micro-embolism is not a phenomenon of short duration; rather, it may persist for at least a month after a symptomatic event. The finding is consistent with the high risk of recurrent events in patients with large aortic arch plaques. The aortic arch is a potential source of emboli in patients with Hollenhorst plaques. These are associated with significant morbidity and mortality. Although the risk of stroke after transient monocular blindness of all causes is approximately 2% per year ( 31), patients with asymptomatic retinal cholesterol emboli have an annual stroke incidence of up to 8.5% ( 32). The mortality rate is also increased when compared with that in age- and sex-matched control subjects ( 33- 35) and is mostly caused by coronary artery disease and cerebrovascular disease ( 35). Early detection of aortic arch plaques may enable the initiation of appropriate therapy. The optimal treatment of patients with aortic arch atheromatous embolization remains to be defined. Although some early reports suggested that anticoagulation may potentiate cholesterol embolization by preventing adequate thrombosis over the atheromatous plaque ( 36- 38), others have reported the disappearance of mobile elements from aortic arch plaques in anticoagulated patients ( 39- 42). This beneficial effect is most likely related to prevention of thrombus formation over an ulcerated plaque. However, anticoagulation does not exert absolute protection against platelet- fibrin embolization. Laperche et al. ( 43) reported recurrent embolic events in 27% of 15 patients with aortic arch plaques, despite heparin therapy. There is some evidence of stabilization of these plaques and reduction of their emboligenic potential with lipid- lowcring drugs ( 44). Successful aortic end-arterectomy ( 45) or aortic arch replacement ( 46) has also been reported for prevention of recurrent aortic embolization. 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