Detection of left atrial thrombi by two-dimensional echocardiography and surgical correlation in 148 patients with mitral valve disease

Cost-Effectiveness of Echocardiography to Identify Intracardiac Thrombus among Patients with First Stroke or Transient Ischemic Attack

Background and Purpose . Echocardiography to select stroke patients for targeted treatments, such as anticoagulation (AC), to reduce recurrent stroke risk is controversial. The authors' objective was to evaluate the cost-effectiveness of imaging strategies that use transthoracic (TTE) and transesophageal (TEE) echocardiography for identifying intracardiac thrombus in new stroke patients. Methods . Model-based cost-effectiveness analysis of 7 echocardiographic imaging strategies and 2 nontesting strategies with model parameters based on systematic evidence review related to effectiveness of echocardiography in newly diagnosed ischemic stroke patients (white males aged 65 years in base case). Primary outcome was cost per quality-adjusted life year (QALY). Results . All strategies containing TTE were dominated by others and were eliminated from the analysis. Assuming that AC reduces recurrent stroke risk from intracardiac thrombus by 43% over 1 year, TEE generated a cost per QALY of $137,000 (relative to standard treatment) among patients with 5% thrombus prevalence. Cost per QALY dropped to $50,000 in patients with at least 15% intracardiac thrombus prevalence, or, if an 86% relative risk reduction with AC is assumed, in patients with thrombus prevalence of at least 6%. Probabilistic analyses indicate considerable uncertainty around the cost-effectiveness of echocardiography across a wide range of intracardiac thrombus prevalence (pretest probability). Conclusions . Current evidence on cost-effectiveness is insufficient to justify widespread use of echocardiography in stroke patients. Additional research on recurrent stroke risk in patients with intracardiac thrombus and on the efficacy of AC in reducing that risk may contribute to a better understanding of the circumstances under which echocardiography will be cost-effective. Key words: cost-effectiveness; decision analysis; stroke; transesophageal echocardiography; transthoracic echocardiography; diagnostic imaging. (Med Decis Making 2007;27:161—177)

Improved visualization of the left atrial appendage by transthoracic 2-dimensional tissue harmonic compared with fundamental echocardiographic imaging

We compared fundamental and tissue harmonic transthoracic echocardiographic imaging for the delineation of the left atrial appendage (LAA) in 32 subjects. The LAA images recorded in the parasternal short-axis view were divided into 4 segments and 2 observers independently graded for each segment using a visual scoring system ranging from 0 to 3 (0 = no, 3 = clearly visible over the entire length of the segment). For the 128 segments, the averaged segment scores were significantly increased after switching to harmonic imaging (1.32 +/- 0.69 versus 1.60 +/- 0.81 for fundamental and tissue harmonic imaging, respectively; P <.0005 for observer 1, and 1.38 +/- 0.65 versus 1.61 +/- 0.82, respectively; P <.001 for observer 2). In a patient with LAA thrombus, the image contrast of the thrombus was improved in harmonic compared with fundamental imaging. These data suggest that tissue harmonic imaging significantly improves image quality of the LAA.

Left atrial appendage function in mitral stenosis: is a group in sinus rhythm at risk of thromboembolism?

OBJECTIVE

To study the left atrial appendage (LAA) function and potential for embolization in severe mitral stenosis (MS).

BACKGROUND

Patients with MS and atrial fibrillation or in sinus rhythm develop systemic emboli. LAA function has not been well studied in sinus rhythm.

METHODS

Forty consecutive patients with MS (valve area < or =0.7 cm2/m2) were studied. LAA ejection fraction and peak emptying velocity were measured along with other data.

RESULTS

Patients were subgrouped according to LAA Doppler flow pattern. Group I (n=13) in sinus rhythm had biphasic high velocity > or =25 cm/s. Group II (n=13) in sinus rhythm had biphasic low velocity <25 cm/s. Group III (n=14) in atrial fibrillation had multiphasic irregular flow <25 cm/s or no definite flow. The LAA ejection fraction and peak emptying velocity were strikingly different in all groups. They were lower in group II when compared to group I. Group II had intermediate risk for thromboembolism compared to Group I and III as judged by systemic embolization, spontaneous echo contrast, thrombus in left atrium and LAA.

CONCLUSION

A subset of mitral stenosis in sinus rhythm at increased risk of embolization can be suspected by Doppler transesophageal echocardiographic LAA flow profile.

Evaluation of left atrial appendage stasis in patients with atrial fibrillation using transesophageal echocardiography with an intravenous albumin-contrast agent

To assess stasis in the left atrial appendage in patients with atrial fibrillation and to identify patients at increased risk for thromboembolism, we performed transesophageal echocardiography with an intravenous albumin contrast agent (Albunex) in 25 patients with atrial fibrillation and in 22 patients in sinus rhythm. We demonstrated that the absence of opacification in the left atrial appendage after Albunex administration implies a high risk of left atrial thrombus and cardiogenic thromboembolism.

Selective uptake of radiolabeled annexin V on acute porcine left atrial thrombi

BACKGROUND

Annexin V is a human phospholipid binding protein that binds to activated platelets in vitro. We sought to determine the potential of this agent for imaging intracardiac thrombi in swine.

METHODS AND RESULTS

Left atrial thrombi were formed by crush injury. In initial nonimaging experiments using intravenous 125I-labeled human annexin V, the mean thrombus/whole blood ratio was 13.4 +/- 4.8 for the entire thrombus using well counting of resected specimens (n = 8). Using intravenously injected 99mTc-labeled human annexin V, the left atrial thrombus/blood ratio by well counting was similar (14.2 +/- 10.6 for the entire thrombus and 26.2 +/- 14.9 for the peak section) (n = 12). The ratio for a control protein, 125I-ovalbumin, was only 1.0 +/- 0.2. 99mTc tomographic imaging was positive (n = 10) or equivocal (n = 2) in all experiments with but negative in 10 controls without left atrial thrombi. By region-of-interest analysis of the tomographic images, the mean left atrial appendage/blood ratio at 2 hours in animals with a thrombus was 3.90 +/- 1.12 compared with 0.84 +/- 0.10 in closed chest controls and 1.01 +/- 0.23 in open chest controls (P < .001).

CONCLUSIONS

We conclude that 99mTc-labeled human annexin V detects acute left atrial thrombi in vivo in swine. The combination of a new thrombus detection agent, annexin V, with a 99mTc label may allow in vivo imaging of thrombi in humans.

Left atrial size--a risk factor for left atrial thrombi in mitral stenosis

In a follow-up study, 77 patients with predominant mitral stenosis were examined to investigate the role of left atrial (LA) enlargement in LA thrombi. Fifteen (19.4%) patients had LA thrombi. Of these, 2 (13.3%) were in sinus rhythm and 13 (86.7%) in atrial fibrillation. Fourteen (93.3%) of the patients with LA thrombi had an LA size > or = 4.8 cm. Only one (6.7%) patient had an LA size of 4.4 cm and was in atrial fibrillation. The median LA size in patients with LA thrombi was 5.2 cm compared with 4.75 cm in patients without LA thrombi (p < 0.01). The relative risk for LA thrombi in patients with an LA size > or = 4.8 cm compared with patients with an LA size < 4.8 cm was 10.0 (95% confidence interval 1.4 to 71.4). It was thus confirmed that LA enlargement > or = 4.8 cm is an independent risk factor for LA thrombi in patients with mitral stenosis.

Relation of thrombus in the left atrial appendage by transesophageal echocardiography to clinical risk factors for thrombus formation

Transesophageal echocardiography provides excellent visualization of the left atrial appendage (LAA). This study was conducted to determine whether specific clinical risk factors could predict the presence of LAA thrombus as demonstrated by transesophageal echocardiography. The most recent 860 transesophageal echocardiographic studies performed at our institution were retrospectively reviewed. The LAA was adequately visualized in 778 patients (90%). For each study, the presence or absence of 5 specific clinical risk factors (mitral stenosis, severe left ventricular dysfunction, left atrial dilatation, atrial fibrillation, or a prosthetic mitral valve) and the presence or absence of LAA thrombi were assessed. One or more clinical risk factors were present in 149 patients, whereas no defined risk factors were noted in 629. Left atrial appendage thrombi were found in 20 of 149 patients with versus 6 of 629 patients without a clinical risk factor (13% vs 1%, p = 0.0001). By logistic regression analysis, mitral stenosis, severe left ventricular dysfunction, and left atrial dilatation were independent risk factors for LAA thrombus formation. Neither atrial fibrillation nor the presence of a mitral prosthetic valve achieved statistical significance as independent risk factors for LAA thrombus. Thus, LAA thrombi occur most often in patients with risk factors for thrombus formation that can be determined by clinical evaluation and transthoracic echocardiography. Transesophageal echocardiography rarely identifies LAA thrombi in patients without such clinical risk factors.

Should all patients undergo transesophageal echocardiography before electrical cardioversion of atrial fibrillation?

The management of anticoagulant therapy in patients with atrial fibrillation undergoing electrical cardioversion remains controversial, largely because of inadequate studies demonstrating risk or benefit, a relatively inconvenient anticoagulation management strategy and the increasing use of transesophageal echocardiography. Recent investigations into the potential mechanisms involved in the development of thrombus and systemic embolism in patients undergoing electrical cardioversion of atrial fibrillation may provide insight into underlying predisposing factors, with subsequent modification of management strategies. Conventional wisdom suggests that preexisting thrombus is responsible for thromboembolic events after cardioversion. However, development of a thrombogenic milieu after cardioversion, particularly in the left atrial appendage, may also be an important predisposing factor. To protect against both potential mechanisms of embolization, these data support therapeutic anticoagulation for all patients with atrial fibrillation of > 2 days in duration from the time of, as well as after cardioversion for a total of 4 weeks, undergoing cardioversion, even in the absence of thrombus on echocardiography. Therefore, the role of transesophageal echocardiography in this setting should be to enable early cardioversion if atrial thrombus is excluded and to identify high risk patients with atrial thrombi so as to postpone cardioversion and avoid the risk of embolization. Ultimately, however, a controlled, randomized and prospective clinical trial will be required to compare conventional management with a transesophageal echocardiography-guided strategy.

Echocardiographic study of left atrial thrombi in mitral stenosis

Sixty-nine patients with predominant mitral stenosis were examined by echocardiographic means to detect the presence of left atrial thrombi. Forty-nine of these patients were in sinus rhythm and twenty in atrial fibrillation. Four percent of patients in the sinus rhythm group and 45% of those in the atrial fibrillation group had left atrial thrombi. The two risk factors identified for left atrial thrombi in mitral stenosis were atrial fibrillation and left atrial enlargement.

Intracardiac thrombosis diagnosed by echocardiography in childhood: predisposing and etiological factors

Eleven cases of intracardiac thrombi caused by different factors including protein-C deficiency are presented for discussion of the etiology and predisposing factors of intracardiac thrombi during infancy and childhood, and to stress the importance of protein-C deficiency as an etiological factor. Thrombi were localised in the left heart in five patients and right heart in five patients. One patient had both-sided thrombi. Four of our patients had dilated cardiomyopathy, one had mitral valve hypoplasia, and one had pulmonary valvar stenosis as the predisposing factors for thrombus formation. In three patients whose cardiac anatomies were completely normal, we determined protein-C deficiency as an etiological factor of thrombus formation. One of these had congenital protein-C deficiency and the other two had acquired temporary protein-C deficiency due to sepsis. In conclusion we recommend that protein-C deficiency should be investigated as an etiological factor in all cases of intracardiac thrombi irrespective of whether or not another predisposing factor is identified.

The role of transesophageal echocardiography in the detection of left atrial thrombi

Sensitivity of transthoracic echocardiography in the detection of left atrial thrombi, in particular thrombi confined to the left atrial appendage, is surprisingly low (33%-72%). Concerning the detection of left atrial thrombi, transthoracic echocardiography appears as an inadequate technique in patients with suspected cardiogenic embolism with a success rate of only 0.8% in earlier, and about 3% in recent studies. Imaging from the esophagus substantially increases the detection rate for left atrial thrombi, and is the only clinically relevant semiinvasive technique to diagnose thrombi confined to the left atrial appendage. Transesophageal echocardiography has markedly increased the diagnostic power of cardiovascular ultrasound in patients with suspected cardiogenic embolism and/or atrial fibrillation. Meta-analysis of pooled studies using the transesophageal approach in these patients revealed thrombi within the left atrial cavity in about 7% and within the atrial appendage in about 12% of cases.

Ball-valve thrombus obstructing a bioprosthetic mitral valve

We present a patient with a large, left atrial ball valve thrombus that was intermittently obstructing a bioprosthetic mitral valve. The diagnosis was confirmed by transesophageal two-dimensional echocardiogram. The transthoracic study initially had failed to demonstrate the true ball valve nature of the thrombus and instead, suggested two separate mass lesions, one in the left atrium and one in the bioprosthetic mitral valve.

Blue digit syndrome: transesophageal echocardiographic identification of thoracic aortic plaque-related thrombi and successful outcome with warfarin

We describe two patients with blue digit syndrome in whom transesophageal echocardiography was able to identify mobile thrombotic masses attached to the irregular intimal surface of the descending thoracic aorta. These patients were treated with heparin and warfarin and did not have recurrent episodes of peripheral arterial embolization. In this article we discuss the diagnostic and therapeutic approaches in patients with peripheral arterial embolization and blue digit syndrome.

Pitfalls in the echocardiographic diagnosis of intracardiac and extracardiac masses

Transthoracic and transesophageal two-dimensional (2-D) echocardiography remain the procedures of choice for evaluating cardiac mass lesions. Potential errors in diagnosis can be made, however, if the mass lesion's size, shape, mobility, and attachment to other cardiac structures are not clearly delineated. Usually a left atrial myxoma arises from the interatrial septum at the level of the fossa ovalis. Pitfalls in diagnosis occur when the tumor size is very small, or its attachment site is atypical or ill-defined. Atrial thrombi classically reside in an atrial appendage, but can also form in the body of the left atrium. The presence of atrial fibrillation rhythm, enlarged atrial chamber, prosthetic mitral/tricuspid valves, stenotic mitral/tricuspid valves, low cardiac output state, and spontaneous atrial contrast echoes are all features that favor the mass in question being a thrombus. Ventricular thrombi usually occur with poorly functioning ventricles. The diagnosis of ventricular thrombus should be made with great caution if the systolic function is normal, or if the mass has a band or thread-like appearance. A thorough knowledge of normal anatomical variants that can mimic pathological lesions is also important for reaching a correct diagnosis. Last but not least, as in all testing modalities, the patient's clinical picture should be correlated with the echocardiographic findings.

Transesophageal echocardiography

Transesophageal echocardiography has provided a new acoustic window to the heart, the great vessels, and the mediastinum. It provides anatomical, functional hemodynamic, and blood flow information. High-quality visualization of left atrial appendage, thoracic aorta, atrial septum, and mitral valvular apparatus can be obtained readily. We discuss historical and technical aspects of transesophageal echocardiography, anatomical views, and major clinical indications for this procedure. These indications include intracardiac masses, thoracic aortic dissection, endocarditis, prosthetic and native cardiac valve function assessment, as well as its value in the detection of intracardiac source of systemic emboli. Furthermore, the role of transesophageal echocardiography in the assessment of coronary artery and congenital heart disease and as an intraoperative diagnostic and monitoring technique is discussed.

Limitations of transoesophageal echocardiography in patients with focal cerebral ischaemic events

OBJECTIVE

To investigate the detection rate of cardiac sources of embolism by transoesophageal echocardiography in patients with focal cerebral ischaemic events and to relate the echocardiographic findings to other clinical findings.

DESIGN

Prospective study with blinded analysis of the echocardiographic data and subsequent comparison with the other clinical findings.

SETTING

Regional cardiothoracic unit based in a teaching hospital.

PATIENTS

131 consecutive patients with focal ischaemic cerebral events (49 with a transient ischaemic attack, 77 with a cerebrovascular accident, and five with a retinal arterial embolus) referred for echocardiography.

INTERVENTIONS

Full M mode, cross sectional, Doppler, and contrast echocardiography by both the precordial and transoesophageal techniques.

RESULTS

Precordial echocardiography detected a cardiac abnormality in 72 patients. Transoesophageal echocardiography confirmed all the precordial findings (except left ventricular hypertrophy, which at present cannot be defined with this technique) and detected other abnormalities in a further 20 patients (18 with potential right-to-left shunts and two with valve vegetations). It also showed spontaneous contrast echoes in 27 of 28 patients with a large left atrium and showed atrial thrombus in three. Cardiac abnormalities were clinically detected in 53 patients, all of which were confirmed or documented by echocardiography. In the 78 patients with no clinically detectable cardiac abnormality six had mitral valve prolapse and one had a regional wall motion defect (identified by precordial echocardiography) and 17 had potential right-to-left shunts (11 of which were identified only by transoesophageal echocardiography).

CONCLUSIONS

Transoesophageal echocardiography is more sensitive than precordial echocardiography in detecting potential sources of embolism in these patients. However, except for the detection of a potential right-to-left shunt, the yield in patients with no cardiac abnormality is low. Moreover, the abnormalities detected in those with previously detected cardiac disease merely confirm the clinical diagnosis. Patients with left atrial spontaneous contrast echoes may benefit from anticoagulation but this requires further study. Until more data are available on this feature and on the role of potential right-to-left shunts in this population, the contribution of echocardiography, precordial or transoesophageal, remains limited.

Exclusion of atrial thrombus by transesophageal echocardiography

To determine whether transesophageal echocardiography (TEE) is useful in ruling out the presence of atrial thrombus, we performed TEE in 20 patients immediately before valve replacement or valve repair and within 3 days of an autopsy in one patient. Mitral stenosis was the predominant lesion in three patients, mitral regurgitation was seen in 11 patients, five patients had mitral prosthesis malfunction, one patient had a tricuspid prosthesis malfunction, and one patient had aortic stenosis. Eight patients were in atrial fibrillation. Four patients demonstrated spontaneous contrast in the associated atria. Nine patients were receiving oral anticoagulation. Mean left atrial diameter was 5.3 +/- 1.3 mm. TEE revealed no evidence for atrial thrombus in 18 of the 21 patients; this finding was confirmed by careful inspection of the atria including the appendages. TEE demonstrated a left atrial thrombus in two patients and a right atrial thrombus in another (confirmed at the time of surgery or at autopsy). In all cases transthoracic echocardiography was negative. Our data suggest that TEE is useful in ruling out atrial thrombus, and therefore may be a useful test preceding interventions associated with an increased risk of embolism from the atria such as cardioversion, mitral valvuloplasty, or valve replacement.

Role of transoesophageal echocardiography in evaluation of cardiogenic embolism

OBJECTIVE

To determine the value of transoesophageal echocardiography in the assessment of selected patients at risk of cardiogenic embolism or after it.

DESIGN

Prospective comparison of the results of transoesophageal and transthoracic echocardiography. Transoesophageal echocardiography was performed with a 5 MHz single plane phased array transducer.

SETTING

University teaching hospital.

PATIENTS

100 patients referred for transoesophageal echocardiography after a cerebral ischaemic event or peripheral arterial embolism (n = 63), before percutaneous balloon dilatation of the mitral valve (n = 23), or before electrical cardioversion of atrial fibrillation (n = 14).

RESULTS

Transthoracic echocardiography showed potential sources of embolism in four patients including left ventricular thrombus in two patients (with one false positive), left atrial appendage thrombus (n = 1), and patent foramen ovale (n = 1). Transoesophageal echocardiography showed 59 potential embolic sources in 45 patients including left atrial spontaneous echo contrast (n = 33), left atrial appendage thrombus (n = 13), left ventricular thrombus (n = 5), patent foramen ovale (n = 3), left ventricular spontaneous echo contrast (n = 2), mitral valve prosthesis thrombus (n = 1), mitral valve prolapse (n = 1), and pronounced aortic atheroma (n = 1). Transoesophagal echocardiography showed potential embolic sources in 36/53 (68%) patients with atrial fibrillation compared with 9/47 (19%) patients in sinus rhythm. Percutaneous balloon dilatation of the mitral valve was performed without embolic complications in 18 patients without left atrial thrombi and in three patients with small fixed thrombi in the left atrial appendage. It was cancelled in two patients with large thrombi in the left atrial appendage. Cardioversion was performed without embolic complications in 14 patients without left atrial thrombi.

CONCLUSIONS

Transoesophageal echocardiography detects potential sources of embolism better than transthoracic echocardiography in selected patients at risk of cardiogenic embolism or after it.

Predictors of left atrial thrombus in mitral valve disease

OBJECTIVE

To determine the risk factors for left atrial thrombus (LAT) and the prevalence of thrombi in cases of mitral valve disease whose severity was judged to necessitate surgical intervention.

DESIGN

Hospital record review of all operative cases from 1982 to 1985.

SETTING

A community serving a referral population encompassing 1.5 million people. Only two hospitals in the geographic area performed cardiac surgery, and both hospitals' records were reviewed.

PATIENTS

All 372 patients who underwent either mitral valve replacement or open mitral commissurotomy.

MAIN RESULTS

Twenty-six patients (7%) were noted to have LAT at surgery. Five preselected factors were significantly (p less than 0.05) associated with LAT in univariate analysis: female gender, prior history of embolism, prior anticoagulant therapy, mitral stenosis (MS), and atrial fibrillation (AF). In logistic regression analysis, only MS and AF remained as significant independent predictors of LAT. Mitral stenosis patients in sinus rhythm had a relatively low [2.4 +/- 3.3% (observed +/- 95% confidence interval)] likelihood of having an LAT. Likewise, mitral regurgitation patients in sinus rhythm (n = 139) had an extremely low (0.7 +/- 1.4%) prevalence of LAT. In contrast, MS patients in AF (n = 122) had a prevalence of LAT of 18.0 +/- 6.8%.

CONCLUSIONS

These findings indicate that, overall, LAT in mitral valve disease may be less common than previous studies have suggested. In addition, mitral valve disease patients who remain in sinus rhythm appear to have a low risk of harboring an LAT. Conversely, MS patients, especially those in AF, appear to be at high risk of harboring an LAT. These results may be helpful in formulating strategies for the use of prophylactic anticoagulation in categories of patients with clinically severe mitral valve disease, or perhaps in estimating the likelihood of a cardiac source of embolism in mitral valve disease patients with suspected cerebral or peripheral emboli.

The clinical role of transoesophageal echocardiography

The role of transoesophageal echocardiography (TEE) was evaluated in a consecutive series of 100 procedures performed in 86 patients (age 17-81, mean 56 years). All patients had prior transthoracic echocardiography (TTE). TEE was performed with a 5 MHz phased array transoesophageal transducer with pulsed wave Doppler and colour flow mapping capability. Forty-four per cent of patients received intravenous sedation and 36% received antibiotic prophylaxis. There were no complications of TEE. The TTE and TEE findings were compared. In patients referred for possible cardiac source of embolism, left atrial thrombi were detected in 8/27 TEE studies but in none of 27 TTE studies. In 12 patients with prosthetic valve dysfunction TEE distinguished prosthetic from periprosthetic regurgitation in 9/12 studies compared to 3/12 with TTE. In 11 patients with suspected aortic dissection TEE correctly detected dissection in all seven cases in which the diagnosis was subsequently confirmed, whereas TTE showed only equivocal findings in two cases. Vegetations were detected by TEE in 4/5 studies in patients with proven native valve endocarditis and by TTE in 2/5. No vegetations were detected by TTE or TEE in five studies in patients with proven prosthetic valve endocarditis. Compared with other investigations there were no false positive TEE studies and one possible false negative study. We conclude that TEE is a safe procedure which often provides additional clinical information to transthoracic echocardiography.

Diagnosis of left atrial thrombi in mitral valve disease by coronary arteriography

Arteriographic findings of neovascularity and fistula formation between coronary arteries and left atrium have occasionally been described in association with left atrial thrombosis in patients with mitral valve disease. The validity of these coronary arteriographic findings in diagnosis of atrial thrombi has been evaluated in 112 patients with mitral valve disease. Comparison was made with surgery. The study furnished these diagnostic values: sensitivity 70%, specificity 85%, positive predictive value 72%. Even if this angiographic finding is complementary in diagnosis of atrial thrombosis, its identification during coronary arteriography in patients with mitral valve disease is useful. Its detection could improve diagnostic prediction of thrombosis, especially in patients without previous embolic events or where echocardiography failed to reveal thrombi.