Clinical and echocardiographic characteristics of patients with left atrial thrombus and sinus rhythm; experience in 20643 consecutive transesophageal echocardiographic examinations.

Agmon Y, Khandheria BK, Gentile F, Seward JB. Circulation 2002;105:27-31.

Reviewer: Mark A. Chaney, MD
University of Chicago

Abstract: Left atrial (LA) thrombus is infrequently detected in the presence of sinus rhythm (SR) and, in these cases, is usually associated with additional cardiac pathologies. These investigators sought to determine the clinical and echocardiographic characteristics of patients with LA thrombus and SR to define a high-risk group of patients prone to this uncommon clinical presentation. Their institution's (Mayo Clinic; Rochester, Minnesota) echocardiographic laboratory database was searched to identify patients with LA thrombus, diagnosed by transesophageal echocardiography (TEE), who were in SR during the TEE examination. Of 20,643 consecutive TEE examinations performed during an eleven year period, LA thrombus was detected in 314 patients in 380 TEE examinations. Of these, SR was present in 20 patients (age 69 ñ13 years; 40% men) in 23 examinations (0.1% of all TEE examinations; 6.1% of TEE examinations with LA thrombus). High-risk structural heart disease (severe left ventricular dysfunction or significant left-sided valve disease [predominantly mitral valve disease]), previous documented episodes of atrial fibrillation, or both (structural heart disease and previous atrial fibrillation) were present in 10, 4, and 5 of the 20 patients, respectively. Only one patient with LA thrombus and SR did not have high-risk features. The investigators conclude that LA thrombus is rare in the presence of SR and that patients with LA thrombus and SR constitute a high-risk group characterized by specific structural cardiac abnormalities or previous atrial fibrillation.

Comments: The intraoperative diagnosis of LA thrombus via TEE may have major therapeutic implications. LA thrombus is usually detected in association with atrial arrhythmias and is uncommon in the presence of SR. Thus, the yield of TEE in detecting LA thrombus in unselected patients with SR appears to be low. Using their large echocardiographic laboratory database, these investigators determined the clinical and echocardiographic characteristics of patients with echocardiographically detected LA thrombus who were in SR during the echocardiographic examination. The echocardiography laboratory database at Mayo Clinic was searched to identify all patients with LA (or LA appendage) thrombus diagnosed by TEE between 1988 and 1998 (20,643 examinations). From this group, they identified all patients who were is SR during the TEE examination, and the past medical histories and echocardiographic recordings of these patients were reviewed. A wide variety of "high-risk" features for LA thrombus (valve disease, left ventricular dysfunction, history of atrial fibrillation, etc.) in patients with SR were defined a priori. Only a small percentage of patients with LA or LA appendage thrombi were in SR (20 out of 314, 6%). Of these 20 patients, hypertension was common (85%), as was coronary artery disease (55%) and a history of congestive heart failure (55%). Thrombus was most commonly detected within the LA appendage (75%). Most (75%) had "high-risk" structural heart disease, most commonly mitral valve prosthesis, mitral stenosis, or left ventricular systolic dysfunction. These structural and functional cardiac abnormalities tend to be associated with LA stasis, which may lead to LA thrombus formation even in the presence of SR. Hemodynamically significant mitral stenosis, mitral prosthesis, or severe aortic regurgitation are associated with LA stasis. Mitral regurgitation may decrease LA stasis and protect against LA thrombus formation and aortic stenosis (or aortic prosthesis) usually does not result in significant LA stasis unless accompanied by left ventricular dysfunction. Significant left ventricular systolic and/or diastolic dysfunction predispose to LA thrombus formation via their secondary effects on LA hemodynamics. In 45% of these 20 patients, atrial fibrillation had been previously documented. Previous atrial fibrillation is a high-risk marker for recurrent atrial fibrillation. Transient paroxysms of atrial fibrillation may result in atrial dysfunction during the arrhythmia and after conversion to SR (the phenomenon of atrial stunning), thus predisposing to LA thrombus formation. Subsequently, LA thrombus may be detected in the presence of SR, with or without clear clinical recognition of the preceding atrial arrhythmia. Only one of the 20 patients with LA thrombus and SR did not have any predefined "high-risk" characteristics. Thus, LA thrombus is very rare in the presence of SR. Patients in whom LA thrombus is detected while in SR are characterized by specific cardiac abnormalities, notably significant left ventricular dysfunction, valve disease (predominantly mitral valve disease), or previous episodes of atrial fibrillation. Such information may be useful to the anesthesiologist performing intraoperative TEE when the diagnosis of LA or LA appendage thrombus is uncertain. The diagnosis of LA or LA appendage thrombus must be made with a high level of confidence because therapeutic implications of the diagnosis are substantial, specifically in patients without additional indications for anticoagulant therapy.

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