Assessment of left atrial appendage function by biplane transesophageal echocardiography in patients with nonrheumatic atrial fibrillation: identification of a subgroup of patients at increased embolic risk

Influence of age on left atrial appendage function in patients with nonvalvular atrial fibrillation

BACKGROUND

Age is an independent risk factor for thromboembolism in nonvalvular atrial fibrillation (NVAF). An association between low left atrial appendage (LAA) Doppler velocities and thromboembolic risk in NVAF has been reported.

HYPOTHESIS

The study was undertaken to identify age-related differences in LAA function that may explain the higher thromboembolic rates in older patients with NVAF.

METHODS

Forty-two consecutive patients (age 69+/-2 years [range 42-92], 24 [57%] men) with NVAF underwent transthoracic and transesophageal echocardiography. The following were compared in 22 patients younger and 20 older than 70 years: left ventricular (LV) diameter, mass and ejection fraction, left atrial (LA) diameter and volume, LAA area and volume, LAA peak emptying (PE) and peak filling (PF) velocities, presence and severity of spontaneous echo contrast (SEC) and mitral regurgitation (MR).

RESULTS

Left atrial diameter (4.6+/-0.1 vs. 4.5+/-0.2 cm), LA volume (105+/-10 vs. 92+/-8 ml), LAA area (6.8+/-0.6 vs. 5.2+/-0.8 cm2), and LAA volume (5.6+/-0.9 vs. 3.9+/-1.0 ml) were similar (p>0.05) in both groups. Older patients had lower LAA PE (26+/-2 vs. 34+/-3 cm/s, p = 0.02) and PF (32+/-2 vs. 41+/-4 cm/s, p = 0.04) velocities, lower LV mass (175+/-13 vs. 234+/-21 gm, p = 0.02), higher relative wall thickness (0.52+/-0.02 vs. 0.43+/-0.03, p = 0.02), smaller LV diastolic diameter (4.3+/-0.1 vs. 5.2+/-0.2 cm, p < 0.001), and higher LV ejection fraction (62+/-2 vs. 55+/-2%, p = 0.025). Frequency and severity of SEC and MR were similar in both groups. Multivariate analysis identified older age as the only significant predictor of reduced LAA velocities.

CONCLUSION

Compared with younger patients, older patients with NVAF have lower LAA velocities despite higher LV ejection fraction, smaller LV size, and similar LA and LAA volumes. These findings may explain the higher thromboembolic rates in older patients with NVAF.

Strain and Strain Rate Imaging in Evaluating Left Atrial Appendage Function by Transesophageal Echocardiography

BACKGROUND

This study was planned to assess whether strain rate (Sr) and strain (S) echocardiography is a useful method for functional assessment of the left atrial appendage (LAA).

MATERIAL AND METHODS

Fifty-seven consecutive patients underwent a clinically indicated study. LAA late empty velocity (LAAEV) was calculated as a gold standard for left atrial appendage function. Real-time 2-dimensional color Doppler myocardial imaging data were recorded from the LAA at a high frame rate. Analysis was performed for LAA longitudinal strain rate and strain from midsegment of lateral wall of LAA. LAA strain determines regional lengthening expressed as a positive value or shortening expressed as a negative value. Peak systolic values were calculated from the extracted curve.

RESULTS

Spearman correlation test results showed a statistically significant positive correlation was between the S, Sr variables and LAAEV (LAAEV vs S; r = 0.886, P < 0.001; LAAEV vs Sr: r = 0.897, P < 0.001, respectively). Strain and strain rate values were also significantly lower in patients with spontaneous echocardiographic contrast when compared with those without (strain; 2.42 +/- 0.98 vs 13.1 +/- 5.9, P < 0.001 and strain rate: 0.97 +/- 0.54 vs 3.34 +/- 1.15, P < 0.001, respectively). In addition, LAA strain and strain rate values were significantly lower in the patients with LAA thrombus (strain; 2.15 +/- 0.96 vs 8.35 +/- 6.9, P < 0.001, strain rate; 0.79 +/- 0.46 vs 2.30 +/- 1.48, P < 0.001, respectively).

CONCLUSION

S and Sr imaging can be considered a robust technique for the assessment of the LAA systolic deformation.

Atrial fibrillatory rate and risk of left atrial thrombus in atrial fibrillation

AIMS

In atrial fibrillation (AF), a relation between electrocardiogram (ECG) fibrillatory wave amplitude and thrombus formation has been sought for long with conflicting results. In contrast, the possible relation between atrial fibrillatory rate obtained from the surface ECG and left atrial thrombus formation in patients with AF is unknown and was consequently evaluated in this study.

METHODS AND RESULTS

One-hundred and twenty-five patients (mean age 64 +/- 12 years, 72% male) with persistent non-valvular AF (mean duration 28 +/- 80 days) undergoing transesophageal echocardiography were studied. In all patients, standard 12-lead ECG recordings were acquired before the examination. Atrial fibrillatory rate was determined using spatiotemporal QRST cancellation and time-frequency analysis of lead V1. Atrial fibrillatory rate measured 401 +/- 63 fibrillations per minute (fpm, range 235-566 fpm) and was related with age (R = -0.326, P < 0.001), ventricular rate (R = -0.202, P = 0.024), gender (407 +/- 62 in males vs. 387 +/- 64 fpm in females, P = 0.038) but not AF duration (R = 0.088, P = 0.374), presence of lone AF (408 +/- 66 vs. 394 +/- 58 fpm, P = 0.228), or beta-blocker or calcium channel blocker treatment (398 +/- 63 vs. 405 +/- 62 fpm, P = 0.556). Age was the only independent predictor of fibrillatory rate (B = -1.714, P < 0.001). In patients with left atrial thrombus (n = 10), spontaneous echo contrast (SEC) was more frequently present (70 vs. 29 %, p = 0.007) and left atrial appendage (LAA) outflow velocity was lower (26 +/- 20 vs. 37 +/- 15 cm/s, P = 0.012) than in patients without thrombus (n = 115). In contrast, mean fibrillatory rate, which showed a weak inverse correlation with LAA velocity (R = -0.118, P = 0.048) was not different between both groups (380 +/- 56 vs. 403 +/- 63 fpm, P = 0.226). Similarly, presence of thrombus and SEC combined was not related with fibrillatory rate.

CONCLUSION

Atrial fibrillatory rate obtained from surface ECG lead V1 is not a risk marker for left atrial thrombus formation in AF.

Assessment of Atrial Function

This article discusses the traditional and more recent echocardiographic measures that have been employed to evaluate atrial function. Conventional parameters commonly used and reported in the literature include the study of the various phases of atrial activity using atrial volume measurements, the peak A wave velocity, its velocity time integral (VTI) and the fraction of atrial contribution (all obtained from transmitral flow), as also the atrial ejection force. Newer parameters for atrial function assessment include Doppler tissue imaging (DTI) including segmental atrial contractility using colour Doppler tissue imaging (CDTI) and estimates of atrial strain and strain rate.

Clinical and Echocardiographic Risk Factors for Embolization in the Presence of Left Atrial Thrombus

AIMS

The aim of our study was to evaluate the factors leading to embolization in patients with left atrial thrombi (LAT). With this purpose, we retrospectively analyzed clinical, transthoracic, transesophageal echocardiographic data of patients with LAT in the transesophageal echocardiographic evaluation.

METHODS AND RESULTS

One hundred ninety-two patients with LAT not on anticoagulant therapy were divided into two groups according to the presence of prior ischemic stroke. The group with ischemic stroke included more patients with sinus rhythm and less patients with mitral stenosis. They had smaller left atrial diameter, more left atrial appendage spontaneous echo-contrast, higher appendage ejection fraction, and emptying velocity.

CONCLUSION

Once the thrombus has been formed, cerebral embolization seems to be higher in patients with relatively preserved appendage ejection fraction and emptying velocity. Presence of atrial appendage spontaneous echo-contrast also favor embolization. Factors leading to embolization seem to differ in some respects from the causes of thrombus formation.

Plasma Brain Natriuretic Peptide Levels Indicating Thromboembolism in Very Elderly Patients With Non-Valvular Atrial Fibrillation

BACKGROUND

Assessment of left atrial (LA) function by transesophageal echocardiography is useful for detecting patients with a high risk thromboembolism secondary to atrial fibrillation (AF). A recent study showed that the atrium is the main source of brain natriuretic peptide (BNP) in AF patients without overt heart failure. The purpose of this study was to assess the possible relationship between LA function and plasma BNP levels in very elderly patients with non-valvular AF.

METHODS AND RESULTS

Seventy-four consecutive patients with chronic non-valvular AF (aged, 82+/-6 years) underwent transthoracic and transesophageal echocardiography and measurement of plasma BNP. Thirteen AF patients who had a history of cerebral embolism or echocardiographic evidence of thrombus (TE+ group) were compared with 61 AF patients who had no such complications (TE- group). The TE+ group demonstrated a lower LA appendage (LAA) velocity and higher plasma BNP level than the TE- group. Assessment of variables by multiple logistic regression analysis revealed that BNP was a significant predictor of thromboembolism. There was a significant negative correlation between the plasma BNP level and the LAA peak flow velocity.

CONCLUSIONS

The present findings would suggest the usefulness of measuring plasma BNP to detect very elderly non-valvular AF patients at high risk for thromboembolism.

Cardiovascular Imaging in the Management of Atrial Fibrillation

Atrial fibrillation (AF) is he most commonly encountered arrhythmia in clinical practice, with an overall prevalence of 0.4% in the general population. Recent advances in technology and in the understanding of the pathophysiology of AF have led to more definitive and potentially curative therapeutic approaches. Echocardiography has a well-established role in the assessment of cardiac structure and function and risk stratification, and has become an essential part of the guidelines for management of AF. The development of intracardiac echocardiography has led to real-time guidance of percutaneous interventions, including radiofrequency ablation and left atrial appendage closure procedures for patients with AF. Other imaging modalities, including computed tomography and magnetic resonance angiography, have allowed for more accurate measurement and better understanding of the cardiac anatomy. We review the impact of various imaging modalities in the evaluation and management of AF.

AVE0118, Blocker of the Transient Outward Current ( I to ) and Ultrarapid Delayed Rectifier Current ( I Kur ), Fully Restores Atrial Contractility After Cardioversion of Atrial Fibrillation in the Goat

Background— The loss of atrial contractile function after cardioversion of atrial fibrillation (AF) contributes to the thromboembolic risk associated with AF. The newly developed blocker of the transient outward current ( I to ) and ultrarapid delayed rectifier current ( I Kur ) AVE0118 prolongs atrial action potential duration and might therefore enhance atrial contractility. We compared the ability of AVE0118 to restore atrial contraction after cardioversion of AF with the efficacy of conventional positive inotropic compounds in the goat model of AF.

Methods and Results— Eighteen goats were chronically instrumented with epicardial electrodes, a pressure transducer in the right atrium, and piezoelectric crystals to measure right atrial diameter. Atrial contractility and refractoriness and QT duration were measured before and after 1 week (3 to 8 days) of AF induced by repetitive burst pacing. The measurements were repeated after administration of digoxin (0.02 mg/kg), dobutamine (5 μg · kg −1 · min −1 ), the Ca 2+ sensitizer EMD57033 (1 mg · kg −1 · min −1 ), the L-type Ca 2+ channel agonist BayY5959 (0.1 mg · kg −1 · min −1 ), and AVE0118 (0.01 to 0.2 mg · kg −1 · min −1 ). The effect of AVE0118 on the configuration of atrial monophasic action potentials was determined for comparison. After 1 week of AF, atrial contractility during sinus rhythm or slow atrial pacing was reduced to <10%. Digoxin and dobutamine failed to increase atrial contractility. EMD57033 restored 41% and BayY5959 restored 48% of atrial contractility at baseline. BayY5959 significantly prolonged QT duration by 24.7%. AVE0118 enhanced atrial contraction to 156% of the baseline value. The positive inotropic effect was accompanied by a pronounced prolongation of atrial action potential duration and refractoriness, whereas QT duration remained unchanged.

Conclusions— Conventional positive inotropic drugs showed limited effect on atrial contractility after cardioversion of AF or produced QT prolongation. In contrast, the I to / I Kur blocker AVE0118 fully restored atrial contraction without proarrhythmic effects on the ventricle.

[TEE-guided cardioversion in patients with atrial fibrillation without previous anticoagulation]

A total of 332 patients (mean age 65+/-10 years, 86 female) with nonvalvular atrial fibrillation (AF) of more than 48 hours duration and lack of a sufficient anticoagulation were included. After exclusion of thrombotic material in the left atrium using transesophageal echocardiography (TEE) cardioversion (CV) was performed within 24 hours. At the same time oral anticoagulation (AC) (overlapping with PTT-affecting heparinisation) was started. If thrombi were found by TEE, the examination was repeated after at least four weeks of anticoagulation. If thrombi were absent at this time, CV was performed. Periprocedural embolism was defined as primary endpoint, whereas the detection of atrial thrombi before CV was defined as secondary endpoint. In 33 of the 332 Patients (9.9%) the TEE showed a thrombus in the left atrium respectively the left atrial appendage (n=22) or thrombi could not be excluded (n=11). 383 TEEs were performed without complications in an overall of 332 patients.A total of 305 CV were performed (electrical n=300, pharmacological n=5) and during periprocedural monitoring and in the time of four weeks after CV no thromboembolic complications were observed.TEE-guided CV in patients with AF persisting for more than 48 hours and without previous AC can be considered as a method that is both safe and effective.

Left atrial appendage flow velocity as a quantitative surrogate parameter for thromboembolic risk: determinants and relationship to spontaneous echocontrast and thrombus formation--a transesophageal echocardiographic study in 500 patients with cerebral ischemia

BACKGROUND

Hemostasis in the left atrial (LA) appendage (LAA) is an important cause in the formation of thrombi. Determination of the LAA flow velocity (LAAV) could be a quantitative parameter for estimating thromboembolic risk. The objective of this study was to: (1) determine the relationship between LAAV and qualitative parameters with elevated thromboembolic risk (thrombus/spontaneous echocontrast [SEC]); and (2) define factors that influence LAAV.

METHODS

In all, 500 patients with stroke were examined consecutively by transesophageal echocardiography. In addition to measurement of the LAAV, the atrial appendage was examined for the presence of thrombi or SEC.

RESULTS

LAAV differed significantly among patients with sinus rhythm (71 +/- 16 cm/s), paroxysmal atrial fibrillation (AF) and in sinus rhythm during transesophageal echocardiography (46 +/- 13 cm/s), paroxysmal AF and AF during transesophageal echocardiography (32 +/- 12 cm/s), and chronic AF (27 +/- 9 cm/s, P < .001). Independent of the rhythm, the risk of thrombus/SEC increased significantly at an LAAV less than 55 cm/s. At an LAAV 55 cm/s or more there is only a minimal risk of thrombus/SEC (negative predictive value 100% and 99%, respectively). Multivariate analysis showed that LAAV is the strongest predictor for the occurrence of thrombus/SEC (P < .0001). Further multivariate analysis showed that left ventricular ejection fraction, LA size, (paroxysmal) AF, age, and sex are independent parameters influencing LAAV.

CONCLUSION

Independent of the basic rhythm, there is a close relationship between LAAV and qualitative parameters of elevated thromboembolic risk. LAAV could, therefore, be a quantitative surrogate parameter for risk stratification. It is influenced by both cardiac and extracardiac factors.

Transthoracic Echocardiographic Predictors of the Left Atrial Appendage Contraction Velocity in Stroke Patients with Sinus Rhythm

Systemic embolization is a potential complication in patients with thrombi situated in the left atrium and particularly, in the left atrial appendage (LAA). Reduced LAA contraction velocities, determined by the transesophageal echocardiography (TEE), are associated with increased risk of LAA spontaneous echocontrast and thrombus formation, and a history of systemic embolism. However, TEE remains a semi-invasive procedure, limiting its serial application as a screening tool. Therefore, it is desirable to obtain information regarding LAA function by transthoracic echocardiography in patients having cardioembolic stroke. The present study was designed to investigate various echocardiographic variables for patients with stroke to predict LAA dysfunction, reflected as reduced LAA contraction velocity. We studied a total of 61 patients with newly diagnosed acute embolic stroke (42 patients) and transient ischemic attack (19 patients). Computerized tomographic scanning was performed for the diagnosis of embolic stroke. Left atrial functional parameters determined by transthoracic echocardiography, such as left atrial active emptying fraction and acceleration slope of mitral inflow A wave, had significant correlations with the LAA contraction velocity (r = 0.57, p < 0.001; r = 0.54, p < 0.001, respectively). Left atrial volume index, left atrial active emptying volume and left atrial fractional shortening were also correlated with LAA contraction velocity (r = -0.44, p < 0.001; r = 0.38, p = 0.003; r = 0.37, p = 0.004, respectively). In conclusion, transthoracic echocardiography can provide valuable and reliable information about the LAA contraction velocity in stroke patients with sinus rhythm. This finding gives new insights for the appropriate strategy in the evaluation of an acute ischemic stroke.

Higher Levels of Serum Fibrin-Monomer Reflect Hypercoagulable State and Thrombus Formation in the Left Atrial Appendage in Patients With Acute Ischemic Stroke

BACKGROUND

It is sometimes difficult to make a diagnosis of cardioembolic stroke in the stroke care unit, because of the splashing and vanishing of the intracardiac source of the emboli on transesophageal echocardiography. Serum fibrin-monomer (FM) is a new marker for coagulation activity that is useful for identifying older individuals at increased risk of ischemic stroke.

METHODS AND RESULTS

Two hundred and four patients with acute ischemic stroke were examined for serum coagulation and fibrinolytic activity on admission, and underwent transesophageal echocardiography within 7 days of onset. Serum levels of FM was significantly higher in patients with left atrial appendage (LAA) thrombus formation (n=24) than in those with no thrombus (88+/-52 vs 14+/-9 microg/ml, p<0.0001). On multivariate logistic regression analysis, FM was an independent predictor for LAA thrombus (RR 2.975, 95% confidence interval 1.114 to 4.820, p=0.0214). In patients with LAA thrombus negative group, cases with LAA emptying flow velocity at atrial systole that was absent or smaller than at early diastole had significantly higher FM levels as compared to cases with larger velocity (42+/-12 vs 8+/-5 microg/ml, p<0.0001).

CONCLUSION

Higher levels of serum FM reflect LAA flow pattern alterations and thrombus formation in patients with acute ischemic stroke.

Echocardiographic Predictors of Left Atrial Appendage Spontaneous Echocontrast in Patients with Stroke and Atrial Fibrillation

OBJECTIVE

The presence of spontaneous echocontrast (SEC) in the left atrium (LA) or LA appendage (LAA) has been associated with a higher risk of thromboembolism and cerebrovascular accidents. The purpose of this study was to define the new transesophageal echocardiographic predictors of SEC for patients with stroke and atrial fibrillation.

METHODS

We studied 47 patients with stroke and atrial fibrillation who were undergoing transesophageal echocardiography for the evaluation of source of cardiac emboli. Patients were divided into two groups based on the absence (group 1) or presence (group 2) of SEC in the LAA.

RESULTS

Compared with group 1, group 2 had larger LA, larger LAA minimum and maximum areas, and decreased LAA flow velocity, LAA wall velocity, LAA tissue intensity, and intensity ratio. In the stepwise discriminate analysis tissue intensity of LAA, minimum LAA area, LAA flow velocity, and LAA wall velocity were found as independent predictors of LAA SEC. LAA wall velocity had the greatest area under the receiver operating characteristic curve, indicating that the most powerful parameter for SEC is LAA wall velocity.

CONCLUSION

Decreased LAA flow velocity and LA wall velocity, increased LAA size, and less negative LAA tissue intensity are associated with SEC in patients with nonvalvular atrial fibrillation. Strain and strain measurements of LAA give no more benefit.

The Left Atrial Appendage, a Small, Blind-Ended Structure

The increasing prevalence of stroke and atrial fibrillation is a stimulus for new therapeutic strategies and also warrants a review of imaging modalities of the most important source of cardiac systemic embolic events: the left atrial appendage (LAA). This blind-ended, complex structure is embryologically distinct from the body of the left atrium and is sometimes regarded as just a minor extension of the atrium. However, it should routinely be analyzed as part of a transesophageal echocardiographic (TEE) examination. A pulsed Doppler TEE analysis of LAA emptying flow should supplement a two-dimensional (2-D) analysis; these examinations have proven to be highly reproducible and to help assess thromboembolic risk. In 2-D imaging, potential thrombus and spontaneous echo contrast should be sought. In addition, LAA plays a hemodynamic role that participates in atrial function and is influenced by various hemodynamic conditions. In view of the embolic risks from a dysfunctional appendage, the LAA is often ligated during cardiac valve surgery. New devices are under evaluation for percutaneous closure of the LAA, and further studies should improve the definition, understanding, and treatment of LAA dysfunction.

Comparison of transesophageal echocardiographic identification of embolic risk markers in patients with lone versus non-lone atrial fibrillation

Although transesophageal echocardiographically derived parameters, notably spontaneous echocardiographic contrast (SEC) in the left atrium or left atrial appendage (LAA), are known predictors of embolism in atrial fibrillation, their value is less well known in patients who have lone atrial fibrillation (LAF). This study describes transesophageal echocardiographic findings and identifies clinical predictors of SEC in the left atrium or LAA in a cohort of patients who had LAF. Eighty-two patients who had LAF and 289 patients who had non-LAF and underwent transesophageal echocardiography were enrolled from July 1998 to March 2002. LAA abnormality was defined as the presence of an LAA area >5 cm(2), emptying or filling LAA velocities <25 cm/s, or the presence of SEC or thrombus in the left atrium or LAA; LAA abnormalities were significantly less frequent in patients who had LAF than in those who had non-LAF. SEC in the left atrium or LAA was significantly less frequent in patients who had LAF than in those who had non-LAF (29.3% vs 49.8%, respectively, p <0.001). In patients who had LAF, SEC in the left atrium or LAA was significantly (p <0.05) less frequent in patients who were </=60 years old (17.9%) than in patients who were >60 years old (39.5%) and in patients who had paroxysmal LAF (5.9%) than in those who had persistent LAF (45.8%). On multivariate analysis, age and persistent LAF were the only clinical variables independently associated with SEC. Thus, transesophageal echocardiography detects thromboembolism risk markers in patients who have LAF. These abnormalities are less frequent in patients who have LAF than in those who are at low risk and have non-LAF; however, in patients who have LAF, older age and persistent atrial fibrillation are associated with these risk markers.

Left atrial appendage assessment by second harmonic transthoracic echocardiography after an acute ischemic neurologic event

Although second harmonic (sh) imaging is widely available in most contemporary ultrasound systems, its accuracy to evaluate left atrial appendage (LAA) morphology and function remains poorly characterized. We conducted a cross-sectional survey of patients with acute ischemic neurologic conditions (n = 51) who underwent both transesophageal and transthoracic echocardiography (TTE) to explore the performance of sh in LAA assessment. Doppler and LAA area evaluation by sh TTE were feasible in most patients (98%). We observed positive and significant associations between sh TTE and transesophageal echocardiography assessment of LAA peak emptying velocities (r = 0.63, P < .001) and LAA maximum area (r = 0.73, P < .001). In addition, all patients (n = 7) with LAA thrombus or spontaneous contrast had peak emptying velocities less than 50 cm/s on sh TTE (negative predictive value of 100%). In multivariate analysis, LAA peak emptying velocity remained independently associated with LAA thrombus or contrast. In conclusion, sh TTE can provide valuable and clinically relevant information of LAA morphology and dynamics.

Evaluation of left atrial appendage functions in patients with thrombus and spontaneous echo contrast in left atrial appendage by using color Doppler tissue imaging

OBJECTIVE

Thrombus and spontaneous echo contrast (SEC) develops in the left atrial appendage (LAA) when LAA function is disturbed. Decrease of left atrial appendage emptying velocity shows LAA dysfunction. The purpose of this study is to examine the incidence of SEC and/or thrombus in LAA in patients with acute myocardial infarction and to assess the LAA function using color Doppler tissue imaging (CDTI) of the patients with detected SEC and/or thrombus.

METHOD AND RESULTS

Eighty-four patients with acute myocardial infarction were included in the study. Spontaneous echo contrast and/or thrombus were observed in 24 (29%) of the 84 patients who were categorized as group 1 (mean age 59 +/- 12 years). Sixty patients (71%) without thrombus and/or SEC in LAA were categorized as group 2 (mean age 58 +/- 8 years). Left atrial diameters and left ventricular ejection fraction were measured by using transthoracic echocardiography. Left atrial appendage emptying and LAA filling velocity were measured by transesophageal Doppler echocardiography. Systolic appendage tissue velocities (SaV cm/s) were measured at the basal, mid, and tip of medial wall of LAA by transesophageal CDTI. Group 1 had significantly decreased LAA emptying velocities, mid SaVs, and left ventricular ejection fractions compared to group 2 (37 +/- 9 cm/s vs 55 +/- 22 cm/s, 3.1 +/- 1.6 cm/s vs 3.7 +/- 1.2 cm/s, and 47 +/- 13% vs 58 +/- 10%, respectively, P = 0.002, P = 0.04, P = 0.03). Group 1 had significantly increased left atrial diameters compared to group 2 (40 +/- 5 mm vs 36 +/- 6 mm P = 0.001). Left atrial appendage-filling velocities, basal SaVs and tip SaVs in group 1 were lower than those in group 2 but not significantly.

CONCLUSIONS

Mid-SaV of LAA medial wall and LAA emptying velocity decrease in patients with thrombus and/or SEC were an indication of functional disorder of LAA. Color Doppler tissue imaging appears to be a clinically applicable and reliable imaging technique that allows quantitative assessment of regional LAA systolic function.

Assessment of cardiac structure and left atrial appendage functions in primary antiphospholipid syndrome: a transesophageal echocardiographic study

BACKGROUND AND PURPOSE

Although thromboembolic events are the major complication of primary antiphospholipid syndrome (PAPS), cardiac involvement is commonly present. Left atrial appendage (LAA) is recognized as an important source for thrombus formation and thromboembolism. The purpose of the study was to assess the structure and function of LAA with transesophageal echocardiography (TEE) in PAPS patients.

METHODS

Thirty-one PAPS patients (22 women, mean age 36+/-9 years) in sinus rhythm and 31 (17 women, mean age 37+/-7 years) controls with normal TEE examination were investigated.

RESULTS

Eighty-four percent of the PAPS patients had functional and structural valvular defect predominantly in the mitral valve. Valvular lesions were especially frequent in PAPS patients with a history of cerebrovascular events, patients with history of arterial thrombosis (91.6%), and patients with high titers of IgG anticardiolipin antibodies (100%). Intracardiac thrombus was present in 5 patients and in 1 of them it was located in LAA. The structure of LAA was similar between groups. Left atrial appendix ejection fraction (51.8+/-4 versus 48.6+/-5.5%; P<0.05) and LAA peak outflow velocity (87+/-10.9 versus 80.6+/-10.3 cm/s; P=0.02) was significantly higher in PAPS group compared with controls. In PAPS patients with mitral regurgitation (MR), LAA outflow peak velocity (84.3+/-10 versus 98.6+/-6.5 cm/s; P=0.002) and LAA inflow peak velocity (67.8+/-10.5 versus 80.8+/-8.6 cm/s; P=0.009) were significantly lower compared with PAPS patients without MR.

CONCLUSIONS

It was concluded that disease process in PAPS frequently involved cardiac valves especially mitral valve but spared LAA function. LAA function was normal, but intracardiac thrombus was present in 5 patients and 1 of them was located in LAA. MR in PAPS patients seems to impair LAA function.

Usefulness of intracardiac Doppler assessment of left atrial function immediately post-pulmonary vein antrum isolation to predict short-term recurrence of atrial fibrillation

Doppler assessments of pulmonary venous (PV) and left atrial appendage flows are useful surrogates of left atrial (LA) function, but it is unknown if these can predict atrial fibrillation (AF) recurrence after pulmonary vein antrum isolation. We compared Doppler surrogates of LA function immediately after pulmonary vein antrum isolation in patients with AF recurrence versus matched patients without recurrence. Patients with a 6-month recurrence had significantly lower LA appendage peak emptying velocity (19 +/- 10 vs 29 +/- 11 cm/s) and lower peak PV systolic wave velocity (36 +/- 17 vs 46 +/- 22 cm/s) compared with those without, suggesting that intracardiac Doppler assessment of LA function after AF ablation predicts AF recurrence.

REDUCED HIGH SERUM HEPATOCYTE GROWTH FACTOR LEVELS AFTER SUCCESSFUL CARDIOVERSION IN PATIENTS WITH ATRIAL FIBRILLATION

1. Serum hepatocyte growth factor (HGF) is considered to be a potent marker of vascular endothelial injury. The present study was designed to examine serum HGF levels in atrial fibrillation and after successful direct current (DC) cardioversion. 2. We measured serum HGF levels before and 7 days and 1 month after DC cardioversion in 39 patients with atrial fibrillation in whom sinus rhythm was maintained for at least 7 days after DC cardioversion and in 30 age- and sex-matched normal control subjects with sinus rhythm. We also measured acetylcholine-induced changes in forearm blood flow (FBF) using venous occlusive plethysmography in 10 patients. 3. Serum HGF levels were significantly higher in the atrial fibrillation patients (both lone atrial fibrillation and with underlying heart disease) than in the controls (0.16 +/- 0.07 vs 0.10 +/- 0.04 ng/mL; P < 0.001). Seven days after successful DC cardioversion, the patients' serum HGF levels had decreased significantly (0.16 +/- 0.07 vs 0.12 +/- 0.06 ng/mL; P < 0.05) and in the 24 patients maintaining sinus rhythm 1 month after DC cardioversion, serum HGF levels decreased to control values (0.10 +/- 0.08 ng/mL at 1 month). Serum HGF levels of the 15 patients who had relapsed into atrial fibrillation 1 month after DC cardioversion tended to decrease 7 days after DC cardioversion, but increased again 1 month after DC cardioversion. Percentage changes in FBF between baseline and the highest dose of acetylcholine before and after DC cardioversion were 180 +/- 98 and 323 +/- 196%, respectively (P = 0.0051). The rate of increase in FBF at the highest dose of acetylcholine between before and after DC cardioversion correlated negatively with the rate of decrease in serum HGF levels between before and after DC cardioversion (r = -0.837; P = 0.0025). 4. This study is the first to demonstrate that serum HGF levels increase in atrial fibrillation and decrease after successful DC cardioversion. This may reflect the fact that atrial fibrillation induces vascular endothelial injury.

Prognostic differences between atrial fibrillation and atrial flutter

This report presents the outcome of a cohort of 94 patients with atrial fibrillation from the Canadian Registry of Atrial Fibrillation, in which we paid particular attention to the probability of stroke and death. We also evaluated warfarin use over time and compared left atrial dimensions in patients with atrial flutter with those with atrial fibrillation.

Expression of the von Willebrand Factor in Atrial Endocardium is Increased in Atrial Fibrillation Depending on the Extent of Structural Remodeling

BACKGROUND

The incidence of stroke in patients suffering atrial fibrillation (AF) is increased when left atrial enlargement occurs. Recently, the platelet adhesive molecule, von Willebrand factor (vWF), located in the atrial endocardium, has been shown to be increased in patients with a variety of heart diseases compared with patients who have no cardiac problems.

METHODS AND RESULTS

We investigated the expression of vWF mRNA and protein in the endocardium as a possible prothrombotic alteration of AF in association with atrial structural remodeling. Atrial appendage specimens were obtained during either heart surgery or at an autopsy from AF patients with and without underlying heart disease. The immunohistochemical and in situ hybridization signals for vWF in the endocardium were well correlated and varied widely among the individual atrial appendages examined. The increased expression of vWF in the endocardium was associated with enlarged left atrial dimensions in mitral valvular disease or increased myocyte diameters in the underlying myocardium. Platelet adhesion/aggregation on the endocardium was always found under the fresh thrombi and was colocalized with strong vWF staining, but not necessarily with fibrinogen and/or fibrin staining.

CONCLUSIONS

Endocardial overexpression of vWF may occur during the process of atrial structural remodeling contributing to the thrombotic predilection of AF in association with underlying heart disease.

Atrial stunning: basics and clinical considerations

Conversion of atrial fibrillation and flutter to sinus rhythm results in a transient mechanical dysfunction of atrium and atrial appendage, termed atrial stunning. Atrial stunning has been reported with all modes of conversion of atrial fibrillation and flutter to sinus rhythm including both transthoracic and low energy internal electrical, pharmacological, and spontaneous cardioversion, and conversion by overdrive pacing and by radiofrequency ablation. Atrial stunning is a function of the underlying arrhythmia becoming apparent at the restoration of sinus rhythm, not the function of the mode of conversion, and does not develop after the unsuccessful attempts of cardioversion or the delivery of electric current to the heart during rhythms other than atrial fibrillation or flutter. Tachycardia-induced atrial cardiomyopathy, cytosolic calcium accumulation, and atrial hibernation are the suggested mechanisms of atrial stunning. Atrial stunning is at maximum immediately after cardioversion and improves progressively with a complete resolution within a few minutes to 4-6 weeks depending on the duration of the preceding atrial fibrillation, atrial size, and structural heart disease. Atrial stunning causes postcardioversion thromboembolism despite restoration of sinus rhythm. Duration of anticoagulation therapy after successful cardioversion should depend on the duration of atrial stunning. Lack of improvement in cardiac output and functional recovery of patients immediately after cardioversion is attributed to the atrial stunning. Verapamil, acetylstrophenathidine, isoproterenol, and dofetilide have been reported to protect from atrial stunning in animal and small human studies. Right atrium stunning is less marked and improves earlier than that of left atrium, resulting in a differential atrial stunning explaining the rare occurrence of pulmonary edema after cardioversion.

Elimination of the Left Atrial Appendage To Prevent Stroke or Embolism?

The "elimination" of the left atrial appendage (LAA) seems to be an attractive alternative to oral anticoagulation in the treatment of atrial fibrillation, especially in patients with contraindications to oral anticoagulation therapy. The LAA, however, plays an important role in the maintenance and regulation of the cardiac function, in arterial hypertension, atrial fibrillation, coronary heart disease, valvular heart disease, and heart failure. Data, mainly from animal studies, indicate that elimination of the LAA may impede thirst in patients with hypovolemia, may impair hemodynamic response to volume or pressure overload, may decrease cardiac output, and may promote heart failure. It may have adverse effects in humans as well. Further studies on the hemodynamic and neurohumoral consequences of left atrial appendage elimination are required to advance our understanding of LAA physiology and pathophysiology.

Role of left atrial appendage obliteration in stroke reduction in patients with mitral valve prosthesis: a transesophageal echocardiographic study

OBJECTIVES

The aim of our study was to assess whether left atrial appendage (LAA) ligation in patients undergoing mitral valve replacement is associated with the risk of future embolisms.

BACKGROUND

Previous studies show that the LAA plays an important role in the development of intracardiac thrombus. According to this decisive role, LAA surgical closure in patients undergoing cardiac surgery may be an attractive choice for reducing stroke.

METHODS

We retrospectively studied 205 patients with previous mitral valve replacement and referred for echocardiography study. Patients were excluded if other causes of systemic embolism were found. The main outcome measure was the occurrence of an embolic event.

RESULTS

Ligation of LAA was performed in 58 patients. However, an incomplete ligation was verified in six patients. During a median time from valve replacement to echocardiography study of 69.4 months (1 to 329), 27 patients had an embolism. Multivariate analysis identified the absence of LAA ligation (odds ratio [OR] 6.7 [95% confidence interval [CI] 1.5 to 31.0]; p = 0.02) and the presence of left atrial thrombus as the only independent predictors of occurrence of an embolic event. Moreover, when the identification of an incomplete LAA ligation was considered together with the absence of LAA ligation, risk of embolism increased up to 11.9 x (OR 11.9 [95% CI 1.5 to 93.6]; p = 0.02).

CONCLUSIONS

Our study shows that LAA ligation during surgery of mitral valve replacement, performed in a high-risk population, is consistent with a reduction of the risk of late embolism and supports this technique if a mitral valve replacement is indicated.

Mechanical occlusion of the left atrial appendage

INTRODUCTION

Oral anticoagulation therapy reduces significantly the risk of thromboembolism in patients with atrial fibrillation. However, effective oral anticoagulation therapy is not feasible in all patients. The interventional occlusion of the left atrial appendage may reduce the risk of thromboembolism in the latter patients. The aim of this prospective study was to assess the feasibility, safety, and technical aspects of interventionally occluding the left atrial appendage.

METHODS AND RESULTS

The left atrial appendage was interventionally occluded with the new PLAATO device in nine patients. Serial transthoracic and transesophageal echocardiographic studies and neurologic assessment were performed prior to and during the procedure, and <48 hours, 3 months, 6 months, and 1 year after the procedure. Contraindications to oral anticoagulation were bleeding complications in 6 of 9 cases, cerebral aneurysm in 1, and allergies to warfarin therapy in 2 of 9. Baseline echocardiographic studies demonstrated spontaneous echo contrast grade 3 +/- 1, peak emptying velocities of 0.26 +/- 0.12 m/sec, and excluded atrial thrombi in all cases. Interventional occlusion was feasible in all cases. One patient had a minor plexus paresis that resolved within 4 weeks after the procedure. Neurologic assessment during a mean follow-up of 5 +/- 4.4 months did not demonstrate any new neurologic complications. Serial echocardiographic assessment excluded the formation of thrombi on the implanted device and demonstrated its complete thrombosis after 6 months. One patient developed a minimal pericardial effusion 48 hours after the procedure that resolved within 3 months.

CONCLUSION

Interventional occlusion of the left atrial appendage is feasible and safe in patients with atrial fibrillation and contraindications to oral anticoagulation therapy. Furthermore, no neurologic complications, development of atrial thrombi, or thrombus formation on the device were observed during follow-up. Future prospective studies are needed to clarify the long-term treatment effect of this new technique.

Factor V Leiden mutation and its relation to left atrial thrombus in chronic nonrheumatic atrial fibrillation

The genetic defect of coagulation factor V, known as factor V Leiden, produces a resistance to degradation by activated protein C and increased venous thrombosis. However, the role of factor V Leiden in the formation of left atrial thrombus with nonrheumatic atrial fibrillation has not been studied. We investigated whether factor V Leiden is a risk factor for left atrial thrombus in patients with nonrheumatic atrial fibrillation. We analyzed clinical, echocardiographic, and biochemical data in 105 consecutive patients with nonrheumatic atrial fibrillation. These patients were divided into two groups: group A (n = 37) with left atrial thrombus and group B (n = 68) without left atrial thrombus. The study also included 42 control subjects. Left atrial thrombus was investigated by using both transthoracic echocardiography and transesophageal echocardiography. Blood samples from the patients and controls were analyzed for the factor V Leiden mutation by DNA analysis, using the polymerase chain reaction. There was no significant difference in the prevalence of factor V Leiden between the patients and control subjects. The prevalence of factor V Leiden mutation was 8.1% (3/37) in patients with left atrial thrombus, and 8.8% (6/68) in patients without left atrial thrombus. The prevalence of factor V Leiden was 7.1% (3/42) in control subjects. The prevalance of factor V Leiden was 10% (2/20) in patients with spontaneous echo contrast and 8% (7/85) in patients without spontaneous echo contrast. Multivariate analyses showed that left ventricular ejection fraction was an independent predictor of left atrial thrombus. Factor V Leiden mutation is not a risk factor for left atrial thrombus formation and spontaneous echo contrast in patients with nonrheumatic atrial fibrillation.

Atrial fibrillation: relation between clinical risk factors and transoesophageal echocardiographic risk factors for thromboembolism

OBJECTIVE

To correlate clinical risk factors for thromboembolism with transoesophageal echocardiography (TOE) markers of a thrombogenic milieu.

DESIGN

Clinical risk factors for thromboembolism and TOE markers of a thrombogenic milieu were assessed in consecutive patients with non-rheumatic atrial fibrillation. The following TOE parameters were assessed: presence of spontaneous echo contrast, thrombi, and left atrial appendage blood flow velocities. A history of hypertension, diabetes mellitus, or thromboembolic events, patient age > 65 years, and chronic heart failure were considered to be clinical risk factors for thromboembolism.

SETTING

Tertiary cardiac care centre.

PATIENTS

301 consecutive patients with non-rheumatic atrial fibrillation scheduled for TOE.

RESULTS

255 patients presented with clinical risk factors. 158 patients had reduced left atrial blood flow velocities, dense spontaneous echo contrast, or both. Logistic regression analysis showed that a reduced left ventricular ejection fraction and age > 65 years were the only independent predictors of a thrombogenic milieu (both p < 0.0001). The probability of having a thrombogenic milieu increased with the number of clinical risk factors present (p < 0.0001). 17.4% of the patients without clinical risk factors had a thrombogenic milieu whereas 41.2% of the patients presenting one or more clinical risk factors had none.

CONCLUSION

There is a close relation between clinical risk factors and TOE markers of a thrombogenic milieu. In addition, TOE examination allows for the identification of patients with a thrombogenic milieu without clinical risk factors.

Relationship between left atrial appendage function and left atrial thrombus in patients with nonvalvular chronic atrial fibrillation and atrial flutter

The relationship between the left atrial appendage (LAA) function, as assessed by transesophageal echocardiography, and the incidence of left atrial thrombus was evaluated in 62 patients with nonvalvular chronic atrial fibrillation (AF; n=50) and atrial flutter (AFL; n=12). It was hypothesized that in both AF and AFL not only the LAA flow velocity (LAAFV), but also the frequency of the LAA movement (the LAA flow time, LAAFT) is a major contributing factor to thrombus formation. LAAFT was defined as the average duration of LAA flow with emptying and filling waves. The patients with AF were divided into 2 groups: lone AF (n=14) and non-lone AF (n=36). LAA thrombus was found in 6 patients with none-lone AF. LAAFV was lower and LAAFT was shorter in patients with thrombus as compared with patients without thrombus (12.0+/-2.2 cm/s vs 24.1+/-10.6 cm/s, 68.7+/-1.5 ms vs 72.9+/-3.3 ms, p<0.01, respectively). Patients with AFL had higher LAAFV and longer LAAFT than those with chronic AF. The present data suggest that, in addition to LAAFV, LAAFT characterized LAA function and might serve as a predictor of thrombus formation in chronic AF. With respect to LAA function, patients with lone AF or AFL are at low risk for thrombus formation.