Abstract
Background
Systemic embolization threatens patients with atrial fibrillation (AF). The risk is enhanced at the time of cardioversion. Transesophageal echocardiography (TEE) prior to cardioversion to screen for left atrial thrombus (LAT), a marker of high risk for embolization, is recommended for many patients with AF.
Objective
To determine clinical and echocardiographic factors associated with LAT formation in AF.
Methods
Data from 600 consecutive patients with AF undergoing TEE prior to cardioversion for the detection of LAT were analyzed. Clinical, laboratory, and echocardiographic parameters were abstracted from the clinical record.
Results
TEE identified LAT in 70 (11.6%) and dense (LA) spontaneous echo contrast (SEC) in 156 (26%). Baseline characteristics and echocardiographic parameters of patients with or without LAT are compared. A prior myocardial infarction, 21 (29.4 %) vs. 31 (5.8), (p < 0.001); hypertension, 60 (85.7%) vs. 386 (72.8), (p 0.02); CHADS 2 ≥ 2, 56 (80%) vs. 308 (58.1%), (p < 0.001) prevalence was higher in patients with LAT. Patients with LAT had lower ejection fraction 38.2 ± 15.6 vs. 46.2 ± 14.5, (p < 0.001); higher LA diameter 4.98 ± 0.7 vs. 4.52 ± 0.7, (p < 0.001); dense LA SEC 44 (62.8) vs. 112 (21.1), (p < 0.001); and low LA appendage emptying velocity 21.7 ± 12.9 vs. 37.5 ± 19.4, (p < 0.001). Multivariate analysis was done, and it revealed that low LA emptying velocity had the strongest independent association with LAT (HR 0.89 [CI 0.83–0.96], p value < 0.001.
Conclusion
LAT is not an uncommon finding of AF patients prior to cardioversion. The current practice of TEE examination may be justified since neither clinical nor routine 2D echo examinations reliably identify LAT.
1
Introduction
Atrial fibrillation is one of the most common arrhythmias encountered in clinical practice. AF is associated with increased risk of thrombo-embolic stroke with thrombi most frequently located in the left atrial appendage (LAA). Transesophageal echocardiography (TEE) is considered the gold standard in detecting the left atrial thrombus with 97% sensitivity and 100% specificity . TEE has been used in clinical practice to exclude the presence of left atrial thrombus in patients with recent onset AF that has persisted more than 48 hours or in the setting of subtherapeutic anticoagulation before cardioversion . The present study aimed to determine the incidence of LAA thrombus in patients with AF and the clinical and echocardiographic parameters associated with left atrial thrombus formation.
2
Methods
The study was approved by the MedStar Health Research Institute Institutional Review Board and is compliant with the Health Insurance Portability and Accountability Act.
2.1
Study population
This single-center retrospective study included 600 consecutive patients with AF undergoing TEE from 2008 to 2013 for the detection of LAA thrombus before cardioversion. The patients were referred for TEE because of new onset AF more than 48 hours or with subtherapeutic international normalized ratios (goal range, 2.0–3.0) despite being on anticoagulation. Pertinent clinical features, echocardiographic parameters, laboratory parameters, and comorbidities were abstracted from the clinical records and recorded in the database.
2.2
Transesophageal echocardiography
TEE was performed using commercially available equipment (Sonos 5500 or iE33; Philips Medical Systems, Andover, MA) and interpreted by very experienced echocardiographers.
Multiplane TEE was performed in a standard manner. Special attention was given to ensuring that the entire left atrium and the left atrial appendage (LAA) were recorded from the midesophageal view. LAA emptying velocity was recorded by placing the pulse-wave Doppler cursor within 1 cm of the LAA orifice. Cine loops of the left atrium and the LAA were stored.
LAA thrombus was identified as independently mobile round, oval, or irregularly shaped echodensities. Dense spontaneous contrast was defined as dynamic swirling smoke, such as echo signals imaged with optimal gain settings.
2.3
Statistical analysis
Statistical analysis was performed using SAS 8.2 (SAS Institute, Cary, North Carolina). Continuous variables are expressed as mean ± SD and as percentages for categorical variables. Differences between continuous variables were assessed by using Student’s t-test. Categorical variables were compared using the χ 2 -test or Fisher’s exact test. Significance was set at p < 0.05. Multivariate logistic regression analysis was performed to identify variables with a significant correlate with LAA thrombus. To determine independent predictors of LAA thrombus, we initially performed a logistic regression model univariate analysis using all variables recorded in the categories of baseline clinical and echocardiographic characteristics. All univariate predictors of LAA thrombus with p value ≤ 0.2 were then used in a stepwise multivariate logistic regression model. P values of < 0.05 were considered statistically significant for all analyses.
2
Methods
The study was approved by the MedStar Health Research Institute Institutional Review Board and is compliant with the Health Insurance Portability and Accountability Act.
2.1
Study population
This single-center retrospective study included 600 consecutive patients with AF undergoing TEE from 2008 to 2013 for the detection of LAA thrombus before cardioversion. The patients were referred for TEE because of new onset AF more than 48 hours or with subtherapeutic international normalized ratios (goal range, 2.0–3.0) despite being on anticoagulation. Pertinent clinical features, echocardiographic parameters, laboratory parameters, and comorbidities were abstracted from the clinical records and recorded in the database.
2.2
Transesophageal echocardiography
TEE was performed using commercially available equipment (Sonos 5500 or iE33; Philips Medical Systems, Andover, MA) and interpreted by very experienced echocardiographers.
Multiplane TEE was performed in a standard manner. Special attention was given to ensuring that the entire left atrium and the left atrial appendage (LAA) were recorded from the midesophageal view. LAA emptying velocity was recorded by placing the pulse-wave Doppler cursor within 1 cm of the LAA orifice. Cine loops of the left atrium and the LAA were stored.
LAA thrombus was identified as independently mobile round, oval, or irregularly shaped echodensities. Dense spontaneous contrast was defined as dynamic swirling smoke, such as echo signals imaged with optimal gain settings.
2.3
Statistical analysis
Statistical analysis was performed using SAS 8.2 (SAS Institute, Cary, North Carolina). Continuous variables are expressed as mean ± SD and as percentages for categorical variables. Differences between continuous variables were assessed by using Student’s t-test. Categorical variables were compared using the χ 2 -test or Fisher’s exact test. Significance was set at p < 0.05. Multivariate logistic regression analysis was performed to identify variables with a significant correlate with LAA thrombus. To determine independent predictors of LAA thrombus, we initially performed a logistic regression model univariate analysis using all variables recorded in the categories of baseline clinical and echocardiographic characteristics. All univariate predictors of LAA thrombus with p value ≤ 0.2 were then used in a stepwise multivariate logistic regression model. P values of < 0.05 were considered statistically significant for all analyses.
3
Results
Left atrial thrombus is not an uncommon finding as was seen in 11.6% of our patients presenting with atrial fibrillation. The incidence of LAA thrombus based on the CHADS 2 score is presented in Fig. 1 .
The clinical characteristics of patients with LAA thrombus compared to patients without LAA thrombus are shown in Table 1 . Prior myocardial infarction 21 (29.4 %) vs. 31 (5.8), (p < 0.001); hypertension, 60 (85.7%) vs. 386 (72.8), (p 0.02); CHADS 2 ≥ 2, 56 (80%) vs. 308 (58.1), (p < 0.001) prevalence was higher in patients with LAT. The echocardiographic factors in both groups with and without LAA thrombus are shown in Table 2 . Patients with LAT had lower ejection fraction 38.2 ± 15.6 vs. 46.2 ± 14.5, (p < 0.001); higher LA diameter 4.98 ± 0.7 vs. 4.52 ± 0.7, (p < 0.001); dense LA SEC 44 (62.8) vs. 112 (21.1), (p < 0.001); and low LA appendage emptying velocity 21.7 ± 12.9 vs. 37.5 ± 19.4, (p < 0.001).
