"Snake" shaped vegetation in right coronary artery.

Infective endocarditis is a rare cause of coronary embolism. This can result in myocardial infarction. Prompt identification is necessary as management is different from a regular myocardial infarction. Unlike in regular myocardial infarction, use of thrombolytics in this scenario could result in life-threatening complications and hence not indicated. In a patient who appears to be septic, embolic myocardial infarction should always be in the working differential diagnosis. An early transesophageal echocardiogram and cardiac catheterization could assist in diagnosis and management. We present an interesting case of a 45-year-old man who was admitted with vision loss, fevers and was found to have a non-ST segment elevation myocardial infarction. He had persistent bacteremia and developed systemic emboli. Investigation revealed mitral valve vegetation and a cardiac catheterization showed an interesting "snake"-shaped embolic vegetation in right coronary artery. He was treated with surgery to the mitral valve and antibiotics. In a septic patient with myocardial infarction, possibility of coronary embolism from vegetation should be kept in mind.

Introduction

The most common cause of an acute myocardial infarction is atherosclerotic occlusion of coronary vessels. Coronary embolism is one of the rare causes of non-atherosclerotic causes of myocardial infarction. At autopsy, up to 60% of patients with infective endocarditis were found to have coronary microemboli.[1] The common source of coronary embolism is the cardiac valves. When patients without atherosclerotic disease have coronary embolism they develop severe complications as they do not have the typical collateral supply as seen in atherosclerotic disease patients.[2] Initial treatment of myocardial infarction is similar to the regular myocardial infarction but use of thrombolytics is very controversial and could be detrimental.[3] Surgery to repair or replace the infected valves and prolonged antibiotics are the usual treatment. Multiple cases of coronary embolism have been reported so far. Our case is interesting because the image of the cardiac catheterization was like a “snake” in the right coronary artery.

Case Report

A 45-year-old male with hypertension, diabetes mellitus, end-stage renal disease presented with left eye vision loss and fever. Electrocardiogram showed sinus tachycardia to 120 beats per minute with ST segment depression in lateral leads. Troponins were elevated at 5.64 ng/ mL. Erythrocyte sedimentation rate was 80 mm/hour. Computed tomography (CT) scan of head showed no acute infarcts and CT angiogram of head showed no significant vascular stenosis. Ophthalmology evaluation revealed central retinal artery occlusion. He developed altered mental status and hypotension and magnetic resonance imaging studies showed multiple infarcts in brain suggesting embolic origin. Patient had persistant Methicillin sensitive Staphylococcus aureus-positive blood cultures. Transthoracic echocardiogram was unrevealing but a transesophageal echocardiogram showed large and mobile vegetations on the mitral valve [Figure 1, Video 1]. Cardiac catheterization showed multivessel coronary artery disease affecting ostial left anterior descending, mid left anterior descending and distal right coronary artery. There was a snake-shaped thrombus in the right coronary artery [Figure 2, Video 2] which was most likely embolic from the mitral valve endocarditis. Patient underwent three vessel coronary artery bypass grafting and extraction of vegetations from posterior leaflet of mitral valve. Patient was on nafcillin during his hospital course. He was discharged in a stable condition to a skilled nursing facility on vancomycin, gentamicin and rifampin for a total of 6-week course.

Figure 1

Still image of transesophageal echocardiogram showing the vegetation (arrow) on the atrial surface of mitral valve leaflet

Figure 2

Still image of cardiac catheterization and the arrows point to the “snake” shaped vegetation in RCA

Discussion

Atherosclerosis within coronary arteries is the most common cause of an acute myocardial infarction. Less frequently, it can be caused by non-atherosclerotic conditions such as coronary vasospasm, embolism, congenital coronary artery abnormalities, vasculitis and dissection.[4] Coronary embolization was once frequently caused by endocarditis. In the current antibiotic era, some of the the other implicated associations are dilated cardiomyopathy, atrial fibrillation, plaque from atherosclerosis, cardiac tumors, atrial myxomas, plaque embolism after cardiac catheterization, vasculitis, dissection, vasospasm, congenital coronary anomalies, external obstruction from mycotic aneurysms and aortic abscesses.[4-7] There is an approximate 7% occurrence of coronary embolization in native valve endocarditis.[8] Most embolization occurs to LAD due to favorable anatomy regarding the take off and downward course than the right coronary system and circumflex system which are angled significantly from the main coronary trunk.[5] High suspicion is needed for diagnosis of coronary embolisation as cause of acute myocardial infarction. TEE could help diagnose the endocarditis. Cardiac catheterization is warranted for diagnosis of embolization. Abrupt occlusion on angiography with patency of other vessels, lack of collaterals, and lack of atherosclerotic plaques are important diagnostic findings.[2] Initial management is same as of any myocardial infarction, but use of thrombolytics is more detrimental than beneficial as bleeding risks are very high in these sick patients.[3] Embolic material in this situation is vegetation and not a thrombus like in atherosclerotic occlusion. Hence thrombolytics do not work well and carry a high risk of intracranial and systemic bleeding. Intracranial bleeding is a potential complication most likely due to presence of mycotic aneurysms in brain in systemic endocarditis.[9] Treatment options are percutaneous coronary angioplasty, stent placement, embolectomy and surgery. Stent placement is necessary especially if thrombus is rigid. This could, however, increase the chance of mycotic aneurysm as the thrombus is stuck between vessel wall and stent.[9] Surgery is usually considered high risk because these patients are clinically unstable. Up to 20% operative mortality has been noted in active endocarditis.[10] Ultimate treatment includes a prolonged antibiotic course, replacement of infected valve and removal of embolization source. The main goal of treatment is to prevent further embolic episodes. In a case like ours surgery is the only option as patient had multivessel disease and valve vegetation extraction was done instead of replacement as valve still retained its functionality.

Conclusions

Coronary embolism is a rare cause of myocardial infarction. This cause of myocardial infarction should always be included in the differential diagnosis in a septic patient as the management differs from a regular myocardial infarction caused by atherosclerosis. There are no current guidelines as to what is the appropriate management and treatment options usually differ from case to case. In addition to a prolonged antibiotic course, patients might require coronary revascularization as well as valve surgery. Although there are many case reports on this, our case is interesting due to the shape of the vegetation in the coronary artery.