Evaluating cardiac sources of embolic stroke with MRI

The evaluation of patients with stroke includes identifying its etiology in order to appropriately tailor therapy. Currently, the diagnostic work-up includes imaging of the brain, the arteries of the head and neck, the aorta, and the heart. Traditional methods of imaging include magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA), duplex ultrasound, and transthoracic echocardiography (TTE) and/or transesophageal echocardiography (TEE). While echocardiography remains a cornerstone in the field of cardiac imaging, MRI is increasingly able to assess for the most common causes of cardioembolic stroke such as left atrial/left atrial appendage thrombus, left ventricular thrombus, aortic atheroma, cardiac masses and patent foramen ovale. This review will focus on the advantages and limitations of echocardiography and cardiac magnetic resonance (CMR) imaging in diagnosing patients suspected of having an embolic stroke and the role these modalities play in clinical practice today.     

The increasing role of transesophageal echocardiography in unexplained cerebral ischemia

Cerebrovascular disease is a leading cause of morbidity and mortality in the United States. A significant number of cerebral infarctions are due to a cardiac source of embolus. Transesophageal echocardiography (TEE) is being used with increasing frequency to study patients with potential cardiac causes of cerebral ischemia. TEE has a higher sensitivity for detecting left atrial and left atrial appendage thrombi and for visualizing abnormalities of the atrial septum such as patent foramen ovale and aneurysm. Abnormalities of the aorta and native and prosthetic valves can now be clearly identified by TEE. Preliminary data suggest that TEE may influence clinical management in patients with unexplained stroke.     

Contribution of transesophageal echocardiography in the investigation of the atrium in systemic embolism]

Transesophageal echocardiography (TEE) is a semi-invasive examination that provides better images of the atrium than classical transthoracic echocardiography (TTE) due to the anatomical positioning of the captor and the high frequency Doppler apparatus used. We used TEE and TTE to evaluate the incidence of the cardiac origin of emboli in 46 patients with unexplained stroke or transient ischemic attack (TIA): 23 had documented heart disease (mean age 60 years) and 23 had no cardiac disease (mean age 43 years). Among those with existing heart disease, 4% of the anomalies certainly or probably responsible for the emboli in addition to the underlying cardiopathy were detected by TTE versus 37% by TEE (as compared to values reported in the literature: 25% by TTE and 51% by TEE). In particular, 4 abnormalities were better visualized by TEE: left atrial thrombus, especially those located in the auricle (5 TEE versus 1 TTE); spontaneous contrast showing the swirl of blood stagnating in the dilated left atria of patients with mitral valve disease seen in 7-39% of the TIA by TEE as compared to less than 1% by TTE (3 TEE versus 0 TTE); aneurysm of the interauricular septum (AIAS) observed in 5-16% of the TIA by TEE as opposed to 0-1% by TTE (4 TEE versus 1 TTE); patent foramen ovale (PFO) was noted more frequently following injection of a contrast medium when visualized by TEE (19-22%) than by TTE (6-8%) and can explain the passage of a paradoxical embolus (1 TEE versus 0 TTE). The incidences of left atrial thrombus, AIAS and PFO are well correlated with systemic emboli, especially in young adults having experienced an unexplained TIA without underlying cardiopathy. TEE is an easy-to-use and well tolerated technique for detecting the cardiac origin of emboli in unexplained stroke. Whether to opt for a medical or surgical treatment to avoid recurrences is discussed.     

Transesophageal versus transthoracic echocardiography in the evaluation of right atrial tumors

The purpose of this study was to define the contribution of transesophageal echocardiography to the diagnosis of right atrial tumors in a large series of patients with this rare finding. Transesophageal echocardiography (TEE) has been found to be valuable in evaluating patients with intracardiac masses and has been shown ton be superior to transthoracic echocardiography (TTE) in evaluating left heart masses. Between 1989 and 1993, 23 patients with either known tumors elsewhere or right atrial masses that were detected on TTE were evaluated with TEE. TEE studies were performed in the noninvasive cardiology laboratory. All patients were studied with 5 MHz biplane or omniplane transducers. The right atrium was evaluated for the presence, characteristics, extent, and attachment of any masses and for extension of these masses into the great vessels or other cardiac chambers. No complications occurred. Six patients had primary right atrium tumors. In 10 patients the tumors reached the right atrium via the inferior vena cava. Seven patients had malignant secondary tumors. TEE demonstrated three tumors not detected by TTE. Furthermore TEE provided 16 additional findings not seen on TTE. In conclusion, TEE is superior to TTE in the evaluation of right atrial tumors. TEE should be considered in patients with right atrial tumors even when these tumors have been demonstrated with TTE.     

The role of transesophageal echocardiography in the diagnosis of ischemic stroke in the elderly

Cardioembolic stroke is quite common (15% of all ischemic strokes) not only in younger patients but also in the elderly. Clinical diagnosis is often difficult. Transthoracic echocardiography (TTE) seems to be the most reliable non-invasive method of examination. Because of the close topographical relationship between heart and esophagus, transesophageal echocardiography (TEE) is particularly suitable to evaluate those cardiac structures (left atrium and appendage) where the embolus can most likely be found. Using TTE and TEE, we studied 62 patients older than 65 years of age (mean age 76 +/- 6), having been affected by ischemic stroke. TEE proved to be clearly superior to TTE in the diagnosis of cardioembolic stroke, without any major complication during the execution of this diagnostic method.     

Transthoracic echocardiography using second harmonic imaging: diagnostic alternative to transesophageal echocardiography for the detection of atrial right to left shunt in patients with cerebral embolic events

OBJECTIVES: We sought to evaluate whether transthoracic contrast echocardiography using second harmonic imaging (SHI) is a diagnostic alternative to transesophageal contrast echocardiography (TEE) for the detection of atrial right to left shunt. BACKGROUND: Paradoxic embolism is considered to be the major cause of cerebral ischemic events in young patients. Contrast echocardiography using TEE has proven to be superior to transthoracic echocardiography (TTE) for the detection of atrial shunting, SHI is a new imaging modality that enhances the visualization of echocardiographic contrast agents. METHODS: We evaluated 111 patients with an ischemic cerebral embolic event for the presence of atrial right to left shunt using an intravenous (IV) contrast agent in combination with three different echocardiographic imaging modalities: 1) TTE using fundamental imaging (FI); 2) TTE using SHI; and 3) TEE. The severity of atrial shunting and the duration of contrast visibility within the left heart chambers were evaluated for each imaging modality. Image quality was assessed separately for each modality by semiquantitative scoring (0 = poor to 3 = excellent). Presence of atrial right to left shunt was defined as detection of contrast bubbles in the left atrium within the first three cardiac cycles after contrast appearance in the right atrium either spontaneously or after the Valsalva maneuver. RESULTS: A total of 57 patients showed evidence of atrial right to left shunt with either imaging modality. Fifty-one studies were positive with TEE, 52 studies were positive with SHI, and 32 were positive with FI (p<0.001 for FI vs. SHI and TEE). The severity of contrast passage was significantly larger using SHI (61.6+/-80.2 bubbles) compared to FI (53.7+/-69.6 bubbles; p<0.005 vs. SHI) but was not different compared to TEE (43.9+/-54.3 bubbles; p = NS vs. SHI). The duration of contrast visibility was significantly longer for SHI (17.4+/-12.4 s) compared to FI (13.1+/-9.7 s; p<0.001) and TEE (11.9+/-9.6 s; p<0.02). Mean image quality improved significantly from FI (1.5+/-0.8) to SHI (2.0+/-0.8; p<0.001 vs. FI) and TEE (2.5+/-0.7; p<0.001 vs. SHI). CONCLUSIONS: In combination with IV contrast injections, TEE and SHI have a comparable yield for the detection of atrial right to left shunt. Both modalities may miss patients with atrial shunting. In young patients with an unexplained cerebrovascular event and no clinical evidence of cardiac disease, a positive SHI study may obviate the need to perform a TEE study to search for cardiac sources of emboli.     

Clinical and transthoracic echocardiographic predictors of abnormal transesophageal findings in patients with suspected cardiac source of embolism

BACKGROUND: Approximately 20% of cerebral infarctions are caused by a cardiac source of embolism. Although transesophageal echocardiography (TEE) is a valuable tool for evaluating patients with suspected cardioembolism, its use should be more selective. OBJECTIVE: We attempted to determine whether risk factors derived from the clinical, ECG, and transthoracic echocardiogram (TTE) would make TEE use more selective and increase its yield. METHODS: We retrospectively reviewed the records of 108 patients with suspected embolic stroke who had undergone TEE evaluation. We defined the presence of left atrial appendage spontaneous contrast (LAASC), left atrial appendage thrombus (LAAT), patent foramen ovale (PFO), or intraatrial septal aneurysm (IASA) as TEE endpoints suggestive of cardioembolism. We evaluated the association between the TEE endpoints and (1) age greater than 60 years, (2) the presence of atrial flutter (AFl) or atrial fibrillation (AF) on ECG, (3) left ventricular (LV) dysfunction by TTE (mild, LVEF < 40%; severe, LVEF < 25%), and (4) left atrial (LA) size > 4 cm also determined by TTE. The statistical analysis performed was one-way analysis of variance controlling for interactions between different risk factors and the endpoints. RESULTS The strongest independent predictors for the presence of LAASC or LAAT were age greater than 60 years, presence of AFl/AF, and LV systolic dysfunction. There was no association between any of the risk factors with the presence of PFO or IASA. CONCLUSION: This study demonstrates that clinical characteristics, ECG, and TTE findings can help to better select stroke patients for TEE. Future larger studies are needed to provide more supporting data.     

Role of Echocardiography in Assessment of Cardioembolic Sources: a Strong Diagnostic Resource in Patients with Ischemic Stroke

Purpose of Review

This review will discuss the most frequent sources of cardiac embolism and the role of echocardiography in these different clinical settings, and, in addition, provide suggestions about the choice between transthoracic (TTE) and transesophageal echocardiography (TEE).

Recent Findings

Stroke is the third leading cause of death in industrial countries, and 15–40% of all ischemic strokes are due to cardioembolism. TTE and TEE are cornerstones in the detection of cardioembolic sources and provide fundamental information about the embolic risk and most suitable treatment of these patients, improving long-term outcomes.

Summary

Echocardiography is a widely available, inexpensive, and safe diagnostic tool that is almost free from contraindication, and these elements allow the common use of this technique in almost all the patients with ischemic stroke. The most common cardioembolic sources include left atrial appendage thrombosis during atrial fibrillation; vegetations in infective endocarditis; cardiac masses including left ventricular thrombosis, cardiac tumors, etc.; atherosclerotic plaques; and passageways within the heart serving as conduits for paradoxical embolization, e.g., patent foramen ovale.

     

Comparison of cardiac dimensions by transesophageal and transthoracic echocardiography.

Transesophageal echocardiography (TEE) has advanced rapidly as a valuable cardiovascular diagnostic technique. As the use of TEE increases, so does the importance of well-defined normal cardiac measurements. Presently, few data exist on the accuracy of M-mode TEE-derived measurements. Therefore in 81 adult patients, TEE-derived M-mode measurements were compared with analogous measurements that were made by standard M-mode transthoracic echocardiography (TTE). The TTE and TEE measurements did not differ in aortic root diameter, end-diastolic left ventricular diameter, end-diastolic septal wall versus anterior wall thickness, or end-diastolic posterior wall versus inferior wall thickness. These TEE measurements were within 95% confidence limits of TTE measurements. TEE-derived left atrial diameter (3.5 +/- 0.8 cm) was less than that derived by TTE (3.8 +/- 0.8 cm; p less than 0.001) and fell outside of the 95% confidence interval. TTE left atrial size could be estimated as follows: TTE-derived left atrial diameter = TEE-derived left atrial diameter x 0.6 + 1.5 cm. In conclusion, M-mode measurements of aortic root diameter, left ventricular diameter, and wall thicknesses as derived by TTE and TEE are comparable. TEE-derived left atrial diameter may be used to estimate the left atrial TTE measurement. TEE-derived M-mode measurements are likely to be most useful when results of TTE are technically inadequate.     

Routine transesophageal echocardiography for the evaluation of cerebral emboli in elderly patients

BACKGROUND: Approximately 20% of cerebral infarctions are cardioembolic in nature. Transesophageal echocardiography (TEE) is widely regarded as the initial study of choice for evaluating cardiac source of embolism. Although the majority of cerebrovascular accidents occur in elderly patients, the value of TEE in this population is poorly defined. METHODS: We compared 491 patients older than 65 years with suspected embolic stroke or transient ischemic attack (TIA) who had undergone TEE evaluation between April 2000 and February 2004 to an age-, sex-, and time-matched control group that consisted of 252 patients. Studies were reviewed for abnormalities associated with thromboembolic disease. RESULTS: The overall incidence of stroke risk factors was significantly higher in the study than in the control group. However, the four patients with left atrial thrombi had a history of atrial fibrillation. Although ascending and aortic arch sessile atheromata were observed more frequently in the study than control group, there were no significant differences in the incidence of either complex or mobile aortic atheromata. The incidence of atrial septal aneurysm was higher in the stroke/TIA group, but not in association with patent foramen ovale. Finally, there were also no differences in the incidence of spontaneous echocontrast, and/or patent foramen ovale between study and control groups. CONCLUSIONS: We conclude: (1) There is a higher incidence of abnormalities implicated as sources of thromboembolic disease on TEE in elderly patients with cerebral infarctions, but (2) this incidence is driven by the presence of sessile aortic atheroma and atrial septal aneurysm. Until the benefits of specific therapies for these conditions are known, routine TEE in elderly patients with suspected embolic neurological events appears to be unwarranted.     

Transthoracic echocardiographic predictors of left atrial appendage thrombus

Transesophageal echocardiography (TEE) is commonly performed to detect the presence of a left atrial appendage (LAA) thrombus in the setting of an embolic event or before an anticipated electrical cardioversion for atrial fibrillation. The predictive value of transthoracic echocardiographic (TTE) findings in these patients has not been well defined. This study evaluated whether TTE findings can predict LAA thrombi using TEE as the gold standard for the identification of LAA thrombi. From November 1995 to March 2003, 10,753 patients underwent TEE to exclude LAA thrombi after embolic events or before cardioversion. Of these, 3,768 patients had complete TTE examinations performed <2 weeks before undergoing TEE. Demographics, TTE, and cardiac rhythm variables were analyzed using univariate and multivariate logistic regression to identify predictors of LAA thrombi diagnosed on subsequent TEE. LAA thrombi were identified by TEE in 199 patients (5.3%). Several TTE variables predicted LAA thrombi by TEE, including mitral stenosis, atrial fibrillation, tricuspid regurgitation, valvular prosthesis, left ventricular dysfunction, and right ventricular dysfunction. Mitral regurgitation was associated with a reduced risk for LAA thrombi (odds ratio 0.61, p = 0.003). A structurally normal heart in sinus rhythm (n = 247, 6.9%) had a 100% negative predictive value for LAA thrombi. In conclusion, several TTE variables were found to be predictive of LAA thrombi. The likelihood of LAA thrombi being found on TEE was infinitely small in the absence of these variables and the presence of sinus rhythm.     

经食管超声评估风湿性房颤栓塞危险性的价值

目的　探讨经食管超声心动图 (TEE)评估风湿性房颤患者栓塞危险性的价值。方法　 10 6例心房颤动患者分为风湿性房颤组 (n =5 1)和特发性房颤组 (n =5 5 ) ,所有患者同时进行TTE和TEE检查 ,对两组间左房自发性超声对比现象 (leftatrialspontaneousechocontrast,LASEC)的严重程度、LA、LVd、LVs、FS、二尖瓣瓣口面积等进行比较。结果　 10 6例中经TEE检查发现 14个血栓 ,而TTE检查仅发现 4个血栓 ,两组间左房血栓发生率、LASEC的严重程度、LA、FS及二尖瓣瓣口面积均有显著差异 (P <0 0 5 ) ,相关分析显示LASEC与LA呈显著正相关 ,与二尖瓣瓣口面积显著负相关。结论　风湿性房颤患者左房血栓发生率高 ,发生栓塞危险性较大 ,应积极抗凝治疗。TEE对于房颤患者血栓的检测及栓塞危险性的评估较TTE更有优势 ,LASEC、LA、二尖瓣瓣口面积可作为房颤患者左房血栓形成的预示因子。     

Low Incidence of Cerebrovascular Events in Patients with Incidental Atrial Septal Aneurysm

Objectives: The purpose of our investigation was to describe the echocardiographic characteristics of an atrial septal aneurysm (ASA) and associated cardiac abnormalities, to determine whether any echocardiographic characteristics are associated with cerebrovascular events, and to compare the cerebrovascular risk of ASA when it is an isolated and incidental finding with ASA associated with other cardiac abnormalities and diagnostic indications, including a cardiac source of embolus. Methods: In 1605 consecutive patients referred for transesophageal echocardiography during open heart surgery, we identified 78 patients with ASA as an incidental finding (Group I). During the same period, this anomaly was found in 39 of 8014 consecutive patients referred to the echocardiographic laboratory for various diagnostic reasons (Group II). The frequency of cerebrovascular events and ASA characteristics was compared between these two groups. Results: A total of 117 patients with ASA was included in the study: 60 males and 57 females with a mean age of 66.7 ± 9.1 years. There were no significant differences in the echocardiographic characteristics of ASA or associated cardiac abnormalities between these two groups; no intracardiac or ASA associated thrombi were detected in either group. While only 6.4% of Group I had a clinical event, 23% of patients in Group II had a stroke or transient ischemic abnormality. Conclusions: The morphological characteristics of ASA and associated cardiac abnormalities do not distinguish patients at risk for cerebrovascular events. Although the presence of ASA may be a risk factor for embolic strokes, this risk is lower than previously thought .     

Diagnosis of patent foramen ovale by transesophageal echocardiography and association with cerebral and peripheral embolic events.

This study compares the value of transthoracic (TTE) and transesophageal (TEE) color Doppler and contrast echocardiography for detecting a patent foramen ovale (PFO). A total of 238 patients were studied: 74 patients with a history of otherwise unexplained ischemic stroke, transient cerebral ischemic attacks or peripheral embolic events (group A), 48 with a history of similar episodes explained by other cardiac abnormalities (group B), and 116 with no embolic events (group C). A PFO was detected by contrast TEE in 50 of 238 patients (21%) compared with 45 patients (19%) by color Doppler TTE. In a subgroup of 198 patients, TEE results could be compared with TTE findings. No patient had a PFO identified by color Doppler TTE. Contrast TTE detected a PFO in 15 patients (8%) compared with contrast TEE which demonstrated a PFO in 44 of 198 patients (22%) (p less than 0.001). Prevalence of PFO by TEE was 22, 21 and 22% in groups A, B and C, respectively. A PFO was present in 50% of patients aged less than 40 years and otherwise unexplained ischemic stroke; this percentage was higher (p less than 0.05) than corresponding values found in all other groups. Thus, contrast and color Doppler TEE are significantly superior to TTE for detecting PFO. The prevalence of PFO is significantly increased in young adults with otherwise unexplained ischemic stroke.     

Transesophageal echocardiography and unexplained cerebral ischemia: a multicenter follow-up study. The STEPS Investigators. Significance of Transesophageal Echocardiography in the Prevention of Recurrent Stroke.

BACKGROUND: Transesophageal echocardiography (TEE) continues to play a prominent role in the evaluation of patients with unexplained cerebral ischemia. The STEPS Study Group (Significance of Transesophageal Echocardiography in the Prevention of Recurrent Stroke) was established to further examine the clinical significance of TEE findings in patients with suspected cardiac source of embolus and to assess the impact of these findings with respect to specific therapy and the prevention of recurrent events. METHODS: A total of 242 patients from 15 institutions within the United States underwent TEE study for evaluation of unexplained cerebral ischemia. Over a 1-year period, detailed follow-up was obtained with respect to recurrent stroke, transient ischemia attacks, or documented embolic events as well as detailed information concerning nonrandomized antithrombotic therapy. RESULTS: Recurrent stroke occurred in 17 of 132 (13%) of the patients in the aspirin group versus 5 of 110 (5%) of the patients receiving warfarin therapy (P <.02). This decrease in cerebral ischemic events in the warfarin group was noted, despite the higher prevalence of atrial fibrillation and impaired ventricular function in the warfarin group. The selection of antithrombotic therapy appears, at least in part, to have been influenced by the TEE findings. Among patients receiving aspirin, a higher recurrent stroke rate was noted in those with left ventricular enlargement and atherosclerotic aortic plaque. CONCLUSION: Abnormalities are commonly found by TEE in patients with unexplained cerebral ischemia. Patients with left ventricular enlargement and demonstrable aortic plaque on TEE study are at increased risk for recurrent stroke when receiving aspirin therapy alone. Empiric therapy with systemic anticoagulation may be indicated in patients with stroke unexplained by carotid atherosclerotic disease.     

Transesophageal echocardiography for detection of cardiac diseases in patients with retinal artery occlusion.

OBJECTIVE: We analyzed the usefulness of transesophageal echocardiography (TEE) for detection of cardiac diseases in patients with retinal artery occlusion (RAO). PATIENTS AND METHODS: We retrospectively reviewed the charts of 22 consecutive patients with acute RAO. The patients had been evaluated by conventional studies, including transthoracic echocardiography (TTE) and TEE. RESULTS: TEE findings were abnormal in 13 (59%) of the 22 patients. The findings revealed a decrease of flow velocity in the left atrial appendage (n=7), atrial septal aneurysm (n=4), patent foramen ovale (n=2), spontaneous echo contrast (n=1), ascending aortic plaque (n=1) and left atrial thrombus (n=1). Evaluations, including TEE, disclosed cardiac abnormalities in 16 (73%) of these 22 patients. However, excluding the analysis by TEE, cardiac abnormalities were revealed in only 6 (27%) patients. CONCLUSION: In patients with RAO, TEE may be a useful examination for detecting potential cardiac diseases.     

Cardiological diagnosis in arterial embolism]

Potential cardiac sources of arterial embolism are in particular thrombi within the left atrium or ventricle, or attached to a prosthetic valve, intracardiac tumors, and vegetations due to endocarditis. Patent foramen ovale and atrial septal defect may lead to paradoxical embolism, and spontaneous echo contrast within the heart has to be considered as a parameter of increased thromboembolic risk. In rare cases, atrial septal aneurysm, mitral valve prolapse or annulus calcification and calcified aortic stenosis has to be taken into consideration. Current method of choice for diagnosis of these abnormalities is echocardiography. When the transthoracic approach fails, transesophageal echocardiography (TEE) leads to a definite diagnosis in most cases. Precordial echocardiography allows the detection of left ventricular thrombi with a sensitivity ranging between 72 and 95%, and monoplane TEE does usually not increase these numbers. In contrast, thrombi within the left atrium and particularly in the left atrial appendage can be detected with a significantly higher detection rate when TEE is used. The same is true for spontaneous echo contrast in the left atrium, a phenomenon which is almost exclusively diagnosed by TEE, as well as for endocarditis associated vegetations that can be identified by TEE with a sensitivity higher than 90%. Patient foramen ovale is usually diagnosed by precordial contrast echocardiography combined with a Valsalva maneuver; color Doppler or contrast TEE allows to increase the detection rate. In the diagnosis of prosthetic valve attached thrombi and vegetations, TEE is clearly superior compared to the precordial examination, at least concerning prosthetic devices in mitral position. If echocardiography fails to identify a potential cardiac source of embolism, other techniques don't add significant information in most cases. Detection of a potential source of embolism, however, does not necessarily prove that the particular finding represents the true etiology of an embolic event; results of all clinical and technical examinations have to be evaluated in a critical synopsis. In addition, proper therapeutic consequences in quite a number of abnormalities considered as potential cardiac sources of embolism are not yet defined.     

The role of the 12-lead ECG as a screening test for cardiac source of embolus

BACKGROUND: Investigation for cardiac source of embolus (CSE) is one of the commonest referrals for transthoracic echocardiography (TTE) of hospital inpatients, but has a relatively low-diagnostic yield. We sort to investigate whether 12-lead ECG might be useful in screening patients to obviate the need for TTE, in a subset of patients referred for echocardiographic investigation of cardiac source of embolus. METHODS: We collected ECG and echo data for 400 consecutively referred inpatients for TTE investigation of possible cardiac source of embolus. We analysed this data for evidence of cardiac source of embolism on TTE in patients with a normal or abnormal ECG. RESULTS: 41/400 (10%) subjects had possible CSE identified on TTE. Diagnostic yield for CSE was higher for those with abnormal compared with normal ECG (17% versus 6%, p<0.001). Of 232/400 (58%) patients with a normal ECG, 200 had a normal TTE (86%). Of the 32 with normal ECG and abnormal TTE, echo found a possible embolic source in 13. Of those 168 (42%) with an abnormal ECG, TTE was normal in 73 and abnormal in 95, of whom 28 patients had an echo that identified a possible cardio-embolic source. ECG, therefore, had a sensitivity of 68%, specificity of 61%, positive predictive value of 0.17 and negative predictive value of 0.94 for detecting possible cardiac sources of embolus. CONCLUSIONS: Although TTE is a relatively low-yield investigation for the detection of cardiac source of embolus, 12-lead ECG is not sufficiently sensitive to identify the approximately 10% of patients in whom echo will demonstrate a diagnostic abnormality.     

Superiority of transesophageal echocardiography in detecting cardiac source of embolism in patients with cerebral ischemia of uncertain etiology

The diagnostic yield of transesophageal and transthoracic echocardiography for identifying a cardiac source of embolism was compared in 79 patients presenting with unexplained stroke or transient ischemic attack. There were 35 men and 44 women with a mean age of 59 years (range 17 to 84); 52% had clinical cardiac disease. Both transthoracic and transesophageal echocardiograms were performed using Doppler color flow and contrast imaging. Transesophageal echocardiography identified a potential cardiac source of embolism in 57% of the overall study group compared with only 15% by transthoracic echocardiography (p less than 0.0005). Compared with transthoracic echocardiography, transesophageal echocardiography more frequently identified atrial septal aneurysm associated with a patent foramen ovale (9 versus 1 of 79 patients, p less than 0.005), left atrial thrombus or tumor (6 versus 0 of 79 patients, p less than 0.05) and left atrial spontaneous contrast (13 versus 0 of 79 patients, p less than 0.0005). All cases of left atrial thrombus or spontaneous contrast were identified in patients with clinically identified cardiac disease. In the 38 patients with no cardiac disease, transesophageal echocardiography identified isolated atrial septal aneurysm and atrial septal aneurysm with a patent foramen ovale more frequently than transthoracic echocardiography (8 versus 2 of 38 patients, p less than 0.05). The two techniques had a similar rate of identifying apical thrombus and mitral valve prolapse. Overall, transesophageal echocardiography identified abnormalities in 39% of patients with no cardiac disease versus 19% for transthoracic echocardiography (p less than 0.005). Thus, transesophageal echocardiography identifies potential cardiac sources of embolism in the majority of patients presenting with unexplained stroke.(ABSTRACT TRUNCATED AT 250 WORDS)