Right Atrial Appendage Thrombosis in a Patient with a History of Myocardial Infarction.

Dear Sir,

A 67-year-old man with a history of cigarette smoking and diabetes suffered inferior and right ventricular (RV) myocardial infarction, for which he was admitted to a hospital and given reteplase. The initial transthoracic echocardiography revealed a right atrial (RA) mass. For further evaluation, he was referred to our hospital 6 days after the myocardial infarction onset. Electrocardiography demonstrated normal sinus rhythm, Q-wave in lead III, and T-wave inversion in the inferior leads. Transthoracic echocardiography revealed mild left ventricular systolic dysfunction (ejection fraction ≈ 45%) with severe hypokinesia in the base and mid-inferior wall and mild hypokinesia in the posterior wall, mild RV enlargement and dysfunction, mild mitral regurgitation, and mild-to-moderate tricuspid regurgitation with a tricuspid regurgitation velocity of 2.5 m/s. In addition, a few frames at late-diastole showed a highly mobile mass in the RA, the attachment site of which was not clear [Figure 1a] [Video 1-2]. Transesophageal echocardiography illustrated a highly mobile tubular mass (36 mm) with an echo-free space in its head that was attached to the RA appendage [Figure 1b] [Video 3-4]. Selective coronary angiography demonstrated significant stenosis in the proximal right coronary artery, the distal left circumflex artery, and the first major diagonal. Given the patient's history, RA appendage thrombosis due to an RA infarction in the setting of an RV myocardial infarction was the most probable diagnosis; he was, accordingly, treated with warfarin. The patient refused revascularization and failed to continue the follow-up.

Figure 1

(a) Apical four chamber view in transthoracic echocardiography indicated a mass in the right atrium (arrow), the attachment site of which is not clear. (b) Bicaval view in transesophageal echocardiography indicates a large tubular mass with an echo-free space in its head that is attached to the right atrial appendage (arrow), suggestive of thrombosis. LA = Left atrium, RA = Right atrium

Atrial arrhythmias such as premature atrial contractions, atrial fibrillations, and atrial flutters are more common when atrial infractions are accompanied by ventricular infarctions.[12] In our case, we received no report regarding the presence or absence of atrial arrhythmias from the referring center.

Most cases of atrial infarctions occur in the setting of coronary artery disease. The largest autopsy-based study to date reported an incidence rate of atrial infarctions of about 16%. The thin wall of the RA results in full-thickness infarctions, which predispose to thrombosis formation. There have been reports of atrial thrombosis formation and subsequent thromboembolism.[123] RA infarctions are more common than left atrial infarctions. The RA appendage is the most common site both for such infarctions and for thrombosis.[123] However, RA infarctions following RV myocardial infarctions are not commonly detected,[4] and thrombosis formation in the RA appendage due to RV myocardial infarctions is rarely detectable. The rare detection of RA thrombosis may be because the RA appendage is not usually visualized in transthoracic echocardiography. Indeed, only when thrombosis becomes large is it likely to be detected in transthoracic echocardiography. It can be concluded that in the setting of RV myocardial infarctions, cardiologists should consider the possible presence of RA infarctions and the probable presence of RA appendage thrombosis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.