Clinical value of left atrial appendage flow velocity for predicting of cardioversion success in patients with non-valvular atrial fibrillation

BACKGROUND

Echocardiographic parameters for predicting cardioversion outcome in patients with non-valvular atrial fibrillation are not accurately defined.

OBJECTIVE

To evaluate the role of left atrial appendage flow velocity detected by transoesophageal echocardiography for prediction of cardioversion outcome in patients with non-valvular atrial fibrillation enrolled in a prospective. multicentre, international study.

METHODS

Four hundred and eight patients (257 males, mean age: 66 +/- 10 years) with non-valvular atrial fibrillation lasting more than 48 h but less than 1 year underwent transthoracic echocardiography and transoesophageal echocardiography before either electrical (n=324) or pharmacological (n=84) cardioversion.

RESULTS

Cardioversion was successful in restoring sinus rhythm in 328 (80%) and unsuccessful in 80 patients (20%). Mean left atrial appendage peak emptying flow velocity was significantly higher in patients with successful than in those with unsuccessful cardioversion (32.4 +/- 17.7 vs 23.5 +/- 13.6 cm x s(-1); P<0.0001). At multivariate logistic regression analysis, three parameters proved to be independent predictors of cardioversion success: the atrial fibrillation duration <2 weeks (P=0.011, OR=4.9, CI 95%=1.9-12.7), the mean left atrial appendage flow velocity >31 cm x s(-1) (P=0.0013, OR=2.8, CI 95%=1.5-5.4) and the left atrial diameter <47 mm (P=0.093, OR=2.0, CI 95%=1.2-3.4). These independent predictors of cardioversion success outperformed other univariate predictors such as left ventricular end-diastolic diameter <58 mm, ejection fraction >56% and the absence of left atrial spontaneous echo contrast.

CONCLUSION

In patients with non-valvular atrial fibrillation, measurement of the left atrial appendage flow velocity profile by transoesophageal echocardiography before cardioversion provides valuable information for prediction of cardioversion outcome.

Location, size and morphological characteristics of left atrial thrombi as assessed by echocardiography in patients with rheumatic mitral valve disease

AIMS

This study aimed to assess the use of transthoracic and transoesophageal echocardiography in diagnosing the thrombi located in the left atrium and/or left atrial appendage in patients with rheumatic mitral valve disease, and to investigate the characteristics of thrombi in comparison to intraoperative findings.

METHODS AND RESULTS

The study group was comprised of 474 patients who underwent transthoracic and transoesophageal echocardiography prior to mitral valve surgery. Location, thickness and morphological characteristics of thrombi were determined by transoesophageal echocardiography. Intraoperative assessment disclosed left atrial thrombi in 105 patients. Thickness of thrombi < or = 1cm, and thrombi confined to left atrial appendage were associated with false-negative results by transthoracic echocardiography. However, diameter and morphological characteristics of thrombi, left atrial and left atrial appendage size, and the presence of the spontaneous echo contrast were not associated with the diagnosis of thrombi by transthoracic echocardiography. For overall left atrial thrombi, sensitivity and specificity of transthoracic echocardiography were 32%, and 94%, respectively. Sensitivity and specificity of transoesophageal echocardiography for thrombi in the left atrial appendage were 98%, and 98%, for thrombi in the main left atrial cavity were 81%, and 99%, and for thrombi located in both left atrium and appendage cavities were 100%, and 100%, respectively.

CONCLUSION

In patients with rheumatic mitral valve disease, detection of left atrial thrombi by transthoracic echocardiography seems to be determined by thickness and location of thrombi. The multilobed structure of the left atrial appendage and artifacts over posterior wall of the left atrium may still prevent precise diagnosis even with transoesophageal echocardiography.

Assessment of left atrial appendage filling pattern by using intravenous administration of microbubbles: comparison between mitral stenosis and mitral regurgitation

Mitral stenosis (MS) and mitral regurgitation (MR) are the most frequent conditions that cause a dilation and dysfunction of the left atrial appendage (LAA). Despite similarly dilated LAA in patients with MS and MR, the incidence of LAA thrombi and the risk of thromboembolism is different between these patients. The purpose of this study was to characterize the filling pattern of LAA by using intravenous administration of perfluorocarbon-exposed dextrose albumin (PESDA) during transesophageal echocardiographic examination in patients with MS and MR. Twenty-four patients with moderate to severe MS, 12 patients with severe MR, and a control group including 30 patients with conditions other than mitral valve disease underwent transesophageal echocardiographic examination with an intravenous bolus injection of PESDA. LAA emptying and filling velocities and maximal and minimal areas of LAA and LAA ejection fraction were measured. Digital gray-scale intensity (GSI) of the left atrial (LA) and LAA cavity after PESDA injection was measured by off-line analysis. Compared with control patients, patients with MS or MR had larger maximal and minimal areas of LAA and reduced LAA ejection fraction. LAA peak emptying flow velocity was significantly lower in patients with MS compared with those of MR or control patients. LAA peak filling velocity was significantly lower in patients with MS compared with that of control patients. However, there was no significant difference of LAA peak filling velocity between the patients with MS and MR. There was no significant difference of GSI ratio of LAA and LA between patients with MR and control patients; however, GSI ratio of LAA and LA was significantly lower in patients with MS compared with that of MR. The incidence of LAA spontaneous echo contrast and LAA thrombi in patients with MS was significantly higher than that of the patients with MR and control subjects (P <.005). Despite similarly dilated LAA area and depressed contractile function of LAA in patients with MS and MR compared with control patients, profoundly impaired LAA filling with resultant flow stasis was demonstrated by contrast echocardiography in patients with MS. These findings may explain the higher incidence of LAA spontaneous echo contrast and thrombus in patients with MS.

Left atrial appendage dysfunction in chronic nonvalvular atrial fibrillation is significantly associated with an elevated level of brain natriuretic peptide and a prothrombotic state

The study tested the hypothesis that left atrial appendage (LAA) dysfunction in nonvalvular atrial fibrillation (NVAF) correlates with a prothrombotic state, and investigated whether the plasma natriuretic peptides are marker of LAA dysfunction in NVAF. Sixty-seven patients underwent transthoracic and transesophageal echocardiography. The left ventricular fractional shortening, left atrial diameter (LAD), LAA flow velocity and the grade of spontaneous echo contrast (SEC) were determined. The plasma concentrations of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), D-dimer, and thrombin-antithrombin III complex (TAT) were measured. The patients were divided into 2 groups according to LAA flow velocity: group I (LAA velocity <20 cm/s) and group II (LAA velocity > or = 20cm/s). The SEC score, D-dimer, TAT, BNP and LAD were significantly increased in group I. Based on simple linear regression analysis, SEC score (r=-0.638), LAD (r=-0.493), D-dimer (r = -0.485), BNP (r = -0.463), TAT (r = -0.455) and age (r = -0.314) were inversely correlated with LAA flow velocity. Multivariate analysis showed that SEC score (p = 0.0014) and plasma BNP level (p=0.0075) were independent negative predictors for LAA flow velocity. In conclusion, LAA dysfunction is associated with a prothrombotic state, and the plasma BNP concentration may serve as a determinant of LAA function in NVAF.

Effect of blood pressure reduction on abnormal left atrial appendage function in untreated systemic hypertensive patients with sinus rhythm

To investigate whether reduction in blood pressure has a beneficial effect on left atrial appendage (LAA) function, the authors evaluated 24 untreated systemic hypertensive patients with normal left ventricular systolic function in sinus rhythm at baseline and at 3 months after initiation of antihypertensive therapy. They performed transthoracic and transesophageal echocardiographic examinations in hypertensive patients before and after treatment of hypertension. Three of the 24 patients had blood pressure that failed to respond to the regimen of antihypertensive therapy and were removed from the analysis. Of the remaining 21 patients, mean systolic and diastolic blood pressures at baseline were 170 +/- 18 and 104 +/- 6 mm Hg, respectively, and fell significantly at 3 months to 141 +/- 10 and 90 +/- 5 mm Hg, respectively, (p<0.001) after initiation of antihypertensive therapy. There was no significant change in heart rate with treatment (baseline 81 +/- 8 and at 3 months 84 +/- 9 beats/min). There was no significant change in left ventricular end-diastolic diameter, left ventricular ejection fraction, left ventricular wall thickness, or left atrial diameter from baseline (49 +/- 4 mm, 58 +/- 5%, 12 +/- 1 mm, and 41 +/- 4 mm, respectively) at 3 months (48 +/- 5 mm, 59 +/- 4%, 12 +/- 1 mm, and 40 +/- 3 mm). The treatment caused a significant reduction in maximal LAA areas (6.3 +/- 1.3 cm2 at baseline, 4.6 +/- 0.7 cm2 at 3 months, p<0.001), with a concomitant increase in LAA emptying velocity (44 +/- 7 cm/sec at baseline, 60 +/- 9 cm/sec at 3 months, p<0.001). In conclusion, these findings suggest that reduction in blood pressure with antihypertensive therapy could improve LAA function in hypertensive patients with normal left ventricular systolic function in sinus rhythm.

Evolving role of echocardiography in the management of atrial fibrillation

The most common cardiovascular arrhythmia is atrial fibrillation (AF), with an estimated prevalence of 2.5 million in 1994. The extent of this public health problem is enormous, particularly in its stroke sequelae. Routine management of this public health problem includes anticoagulation as the primary stroke-preventive measure. Echocardiography has been an important adjunctive tool in the evaluation of AF. More innovative and controversial is the putative role of transesophageal echocardiography in the treatment strategy of AF cardioversion to sinus rhythm. The standard of care for AF of less than 1-year duration is to attempt cardioversion to sinus rhythm. An alternative strategy is to utilize the assets of transesophageal echocardiography to visually screen the left atrium for thrombus, thereby playing an active role in the treatment strategy of AF. This review will discuss the role of echocardiography in AF as it was initially used as a diagnostic tool with weak prognostic features, and, more recently, as it can be used today as an adjunctive tool to guide therapy with excellent stroke risk-stratification features.

Left atrial appendage outflow velocity index is superior to conventional criteria for prediction of maintenance of sinus rhythm after cardioversion. An echocardiographic study in patients with atrial fibrillation of a few months' duration

OBJECTIVE

To investigate whether left atrial appendage outflow velocity alone or in relation to left atrial diameter is a superior predictor of sinus rhythm maintenance after cardioversion compared with traditional clinical or echocardiography parameters.

DESIGN

Sixty-two patients with their first episode of atrial fibrillation were examined using echocardiography before DC-cardioversion. At one month's follow-up, 42 patients had maintained sinus rhythm (group A), and 20 had relapsed into atrial fibrillation (group B). There were no differences in arrhythmia duration or antiarrhythmic therapy between the groups.

RESULTS

Left atrial diameter measured by echocardiography was smaller in group A (42 mm, 95% CI 40.9-44.1 mm) compared with group B (46 mm, 95% CI 43.4-48.2, p < 0.05). Patients in group A had a higher left atrial appendage outflow velocity at 0.44 m/s (95% CI 0.39-0.49) compared with 0.34 m/s (95% CI 0.30-0.37) in group B (p < 0.01). The ratio of left atrial appendage flow to left atrial diameter was 0.011 (95% CI 0.009-0.012) in group A compared with 0.008 (95% CI 0.007-0.009) in group B, and 63% (95% CI 33-78) of the patients in group A had velocity ratio >0.009 compared with 20% (95% CI 2-38) in group B, (p < 0.01). Stepwise multiple logistic regression analysis showed that a velocity ratio >0.009 was the only predictor for maintenance of sinus rhythm one month after cardioversion with an odds ratio of 6.4 (95% CI 1.9-23.8), (p = 0.004).

CONCLUSION

The ratio of left atrial appendage outflow velocity to left atrial diameter is superior to the traditionally used criteria for prediction of maintenance of sinus rhythm following DC-conversion of first-episode atrial fibrillation.

Does acute-phase beta blockade reduce left atrial appendage function in patients with chronic nonvalvular atrial fibrillation?

To investigate whether acute-phase beta-blocker therapy has a harmful effect on left atrial appendage (LAA) function in patients with chronic nonvalvular atrial fibrillation by transesophageal echocardiography (TEE), we evaluated 21 patients with normal left ventricular systolic function and a poorly controlled ventricular rate, despite the use of digoxin. Baseline parameters that were obtained included heart rate, blood pressure, LAA emptying velocities, and left atrial spontaneous echo contrast intensity. Then, each patient was given a bolus dose of 5 mg metoprolol. Ten minutes later, a second set of assessments was performed. After the first TEE studies, each patient began treatment with metoprolol (50 mg orally twice daily for 1 week). A second TEE study was performed after 1 week of continuous oral metoprolol therapy at maintenance dose, and values were again determined. The average resting apical heart rate was 91 +/- 7 bpm. As expected, beta-blocker therapy showed a marked decrease in heart rate at 10 minutes (79 +/- 6 bpm, P <.001) and at 1 week (71 +/- 4 bpm, P <.001). Beta-blocker therapy caused a significant reduction in systolic and diastolic blood pressures (144 +/- 16 / 93 +/- 6 mm Hg at baseline, 137 +/- 16 / 87 +/- 9 mm Hg at 10 minutes, and 135 +/- 12 / 86 +/- 8 mm Hg at 1 week, P <.001). With the beta-blocker therapy, the baseline transesophageal Doppler parameter of LAA emptying velocities (at baseline 24 +/- 7 cm/s) fell significantly at 10 minutes (19 +/- 7 cm/s, P <.001) and at 1 week (17 +/- 6 cm/s, P <.001) after initiation of beta-blocker therapy. After a bolus of metoprolol, spontaneous echo contrast intensity did not change in any patients, but 1 week later, it increased in 1 patient. In 2 patients who had not been found to have an LAA thrombus at baseline TEE study, the second TEE examination demonstrated new thrombi in the LAA. In conclusion, our findings suggest that in patients with chronic nonvalvular atrial fibrillation who have normal left ventricular systolic function and a poorly controlled ventricular rate despite the use of digoxin, acute-phase beta blockade may have a harmful effect on LAA function.

[Function of the left atrial appendage after electrical cardioversion of atrial fibrillation to sinus rhythm]

INTRODUCTION

It is widely believed that atrial fibrillation appears in a secondly manner to atrial enlargement. Morfological alteration might be the source of disturbance of electrical activation and mechanical function to fibres that facilitate arrhythmia preservation as well as life threatening complications.

THE OBJECTIVE

It is crucial to establish whether reversion of atrial fibrillation to sinus rhythm causes size diminishment and function improvement of the left atrial appendage, which creates hope to avoid dangerous complications, particularly systemic embolisation. DATA AND METHODOLOGY: 30 patients were qualified including 18 males and 12 females aged between 52 and 86 (average age was 63.81 +/- 9.22). All the patients suffered from nonrheumatic atrial fibrillation. The echocardiographic examination was conducted before reversion of atrial fibrillation, right after reaching sinus rhythm and after 6 months observation at sustained sinus rhythm. During the transesophageal echocardiographic examination the following parameters were investigated: LAApodł, LAApoprz, LAAobw, LAApole, LAAF, LAAB, LAAF intg, LAAB intg, spontaneous echocardiographic contrast, thrombus.

RESULTS

Left atrial appendage size right after reversion of atrial fibrillation did not considerably differ from the values registered at the time of arrhythmia. It significantly diminished in the case of sustained stabilisation of sinus rhythm. The diminishment of the left atrial appendage size was connected with its function improvement expressed by increased maximum filling and emptying velocities as well as their integrals. SEC appearance frequency considerably increased right after reaching sinus rhythm. SEC appeared very rarely in the examination after 6 months. No single case of THR in LAA was noted. At the same time several cases of THR were disclosed both before and directly after restoration of sinus rhythm.

CONCLUSIONS

Sinus rhythm restoration and its sustaining for a longer period of time results in size diminishing and function improvement of left atrial appendage. The stability of sinus rhythm is closely tied with thromboembolism risk factors.

Differences in pacing from the atrial appendage and the lateral atrial free wall on left ventricular filling and haemodynamics during DDD pacing

INTRODUCTION

Atrioventricular sequential pacing involves stimulation from electrodes in the right atrium, generally the atrial appendage (RAA) and the right ventricular apex. The appendage, however, may be unsuitable if a stable position cannot be achieved. The aim of this study was to assess the haemodynamic consequences of different atrial stimulation sites during DDD pacing.

METHODS

In 12 consecutive patients (mean age 67 +/- 7 years) who underwent DDD pacemaker implantation, an additional temporary bipolar pacing electrode was positioned on the right atrial free wall. Pacing was performed alternating from the two locations at 85, 100 and 120 beats per minute (bpm). Paced atrioventricular delay was set at 180 ms. Cardiac output and mitral inflow measurements were performed using Doppler echocardiography.

RESULTS

Pacing at 85 and 100 bpm resulted in a significantly higher A-peak velocity from the RAA compared with the right atrial free wall. Cardiac index was consistently higher from the RAA location (2.4 +/- 1.2 vs 2.1 +/- 0.91. min-1 m-2 at 85 bpm, 2.71 +/- 1.4 vs 2.35 +/- 1.11. min-1 m-2 at 100 bpm and 2.94 +/- 1.5 vs 2.61 +/- 1.41. min-1 m-2 at 120 bpm, P < 0.05).

CONCLUSION

Stimulation from the RAA was superior to stimulation from the right atrial free wall with respect to left ventricular filling and cardiac output. Compared with stimulation from the right atrial free wall, RAA pacing resulted in an increase of 10-15% in cardiac output.

Incidence of left atrial thrombi in patients in sinus rhythm and with a recent neurologic deficit

OBJECTIVES

We sought to determine the incidence of left atrial (LA) thrombi in patients in sinus rhythm (SR) and with a recent neurologic deficit and to analyze the relation between LA thrombi and LA chamber and appendage function in patients in SR.

METHODS

A prospective study was conducted in 869 consecutive patients. The study group consisted of 583 patients in SR (67%). The remaining 286 patients had atrial fibrillation (AF) and served as controls (33%).

RESULTS

The incidence of LA thrombi was significantly higher in patients with AF (n = 39 [14%]) compared with patients in SR (n = 6 [1%]; P <.001). Three of 6 patients with thrombi in SR had mitral stenosis, 1 patient had aortic stenosis, 1 patient had coronary artery disease, and another patient had a cardiomyopathy. Of the patients with detected thrombi, those in SR did not receive anticoagulation, whereas those with AF did in 18 cases. Patients with thrombi in SR and with AF did not significantly differ in LA diameter (5.1 +/- 0.8 cm vs 4.8 +/- 0.7 cm; 95% confidence interval [CI], -0.78 to 0.45), left ventricular ejection fraction (46% +/- 13% vs 42% +/- 15%; 95% CI, -18.7 to 7.4), LA appendage area (5.8 +/- 2.7 cm(2) vs 6.7 +/- 3.2 cm(2); 95% CI, -1.9 to 3.6), peak emptying velocity of the LA appendage (0.19 +/- 0.08 m/s vs 0.17 +/- 0.07 m/s; 95% CI, -0.08 to 0.04), or LA spontaneous echo contrast (3. 5 +/- 0.6 vs 3.9 +/- 0.5; 95% CI, -0.06 to 0.45).

CONCLUSIONS

LA appendage thrombi are an infrequent cause of thromboembolism in patients in SR and are associated either with mitral valve disease or LA chamber and appendage dysfunction. Routine transesophageal echocardiography for the exclusion of LA thrombi is not recommended in patients in SR without underlying heart disease and normal LA function as assessed by transthoracic echocardiography.

Right atrial appendage function in patients with chronic nonvalvular atrial fibrillation

To assess right atrial appendage (RAA) flow and its possible relationship to left atrial appendage (LAA) flow in chronic nonvalvular atrial fibrillation (AF), transesophageal echocardiography (TEE) was performed in 26 patients with chronic nonvalvular AF (group I). For the purpose of comparison, an additional group of 27 patients with chronic valvular AF due to mitral stenosis (group II) was analyzed. The clinically estimated duration of AF in group I was significantly longer than that of group II (8.7+/-3.4 versus 2.7+/-1.1 years). Although right atrial size and RAA maximal area were larger in group I than those in group II, left atrial size was larger in group II than that in group I. Group II had larger LAA maximal areas than group I, but this difference did not reach statistical significance. The two groups were not different with respect to the RAA or LAA emptying velocities. Significant correlations were observed between echocardiographic parameters of the two atria in patients with nonvalvular AF (r range, 0.4 to 0.7). In contrast, in patients with valvular AF, no correlation was observed between the echocardiographic parameters of the two atria (appendage emptying velocity, r = 0.38, p = 0.051; atrial size, r = -0.03, p = 0.89; maximal appendage area, r = 0.07, p = 0.75, respectively). There were no significant differences in the presence of right and left atrial spontaneous echo contrast and thrombus between the groups. All of the right and left atrial thrombi were confined to their respective appendages and were found in the atria with spontaneous echo contrast. Both RAA and LAA thrombi were present in one patient. In conclusion, our findings suggest that AF could affect both atria equally in nonvalvular AF, in contrast to valvular AF. Therefore, the assessment of RAA function as well as LAA may be important in patients with chronic nonvalvular AF.

Relation of transesophageal echocardiographic findings to subtypes of cerebral infarction in patients with atrial fibrillation

BACKGROUND

Transesophageal echocardiography (TEE) has been used to identify the potential risk for cardiogenic embolism in patients with atrial fibrillation (AF). However, ischemic stroke in patients with AF is not always attributable to embolism. Identification of the risk of embolic versus atherothrombotic stroke should lead to the optimal individualized management of patients with AF.

HYPOTHESIS

The goal of the study was to determine the relation between cortical infarction and perforating infarction and TEE findings in patients with AF.

METHODS

We investigated the clinical usefulness of TEE in the risk stratification of clinical subtyping of the cerebral infarctions which were divided into two territories of the cortical branch (cortical infarction due to embolism) and deep perforators (perforating infarction due to atherothrombosis). Left atrial spontaneous echo contrast, peak flow velocity in the left atrial appendage, and generalized atherosclerosis as estimated by the intima-media wall thickness of the thoracic aorta were assessed by TEE in 118 consecutive patients with either paroxysmal (n = 44) or chronic (n = 74) AF. All patients underwent either brain computed tomography or magnetic resonance imaging.

RESULTS

Cortical and perforating infarction was found in 39 and 18% of patients, respectively. The grade of spontaneous echo contrast was higher in patients with than in those without cortical infarction (p < 0.05). In contrast, patients with perforating infarction showed significant increase in the aortic wall thickness when compared with patients without perforating infarction (p < 0.05). In addition, multivariate logistic analysis revealed that spontaneous echo contrast was an independent predictor of cortical infarction, while intima-media wall thickness of the aorta, hypertension, and age were useful in predicting the risk of perforating infarction.

CONCLUSIONS

Transesophageal echocardiography has a potential role in the risk stratification for cortical and perforating infarction in patients with AF.

Hemodynamic abnormalities in the left atrial appendage in patients with paroxysmal atrial fibrillation, with special reference to albumin-contrast echocardiographic aspects

AIM

We assessed the prolonged dysfunction of the left atrial appendage caused by paroxysmal atrial fibrillation.

METHODS AND RESULTS

Transesophageal echocardiography with intravenous albumin-microspheres (Albunex, 0.2 ml/kg) was performed in 100 consecutive patients (44 patients in sinus rhythm without previous paroxysmal atrial fibrillation: 13 patients in sinus rhythm who had had previous episodes of paroxysmal atrial fibrillation; and 43 patients with sustained atrial fibrillation). We compared the left atrial appendage ejection fraction and degree of opacification in the left atrial appendage with Albunex in the groups. Patients with previous paroxysmal atrial fibrillation had lower left atrial appendage ejection fractions than patients in sinus rhythm without paroxysmal atrial fibrillation (33 +/- 14 vs. 47 +/- 14%, p < 0.001). More than half of the patients (7/13 [54%]) with previous paroxysmal atrial fibrillation showed delayed and incomplete opacification of the left atrial appendage with Albunex.

CONCLUSION

We conclude that paroxysmal atrial fibrillation causes left atrial appendage stunning, at least in some patients.

The effect of transient balloon occlusion of the mitral valve on left atrial appendage blood flow velocity and spontaneous echo contrast: a comparison in sinus rhythm and atrial fibrillation patients

OBJECTIVE

To investigate the relationship between spontaneous echo contrast (SEC) and left atrial appendage (LAA) blood flow velocity using transesophageal echocardiography (TEE) during percutaneous balloon mitral valvotomy (PBMV) in patients with atrial fibrillation and sinus rhythm.

METHODS

Thirty-five patients (21 in sinus rhythm and 14 in atrial fibrillation) with rheumatic mitral stenosis underwent PBMV with intraoperative transesophageal echocardiography monitoring. We measured LAA blood flow velocities and observed the left atrium for various grades of SEC (from 0 = none to 4 = severe), before and after each balloon inflation.

RESULTS

Left atrial appendage maximal emptying velocity (LAA MEV) was reduced from 35 +/- 14 cm/s to 6 +/- 2 cm/s at peak balloon inflation and increased to 40 +/- 16 cm/s after balloon deflation. Comparison of the values before balloon inflation and after balloon deflation showed that LAA velocities were significantly lower (P < 0.001). During balloon inflation, both maximal emptying velocity (MEV) and maximal filling velocity (MFV) were significantly decreased, compared to those before inflation and after balloon deflation (P < 0.01). And both MEV and MFV were significantly higher after balloon deflation relative to those before balloon inflation. Patients with atrial fibrillation had significantly lower MEV and MFV before and during balloon inflation and after balloon deflation than patients with sinus rhythm. At peak balloon inflation, new or increased SEC grades were observed during 54 of 61 (88%) inflations and unchanged during 7 (12%) inflations. SEC grades were reduced after 55 balloon deflations (90%), completely disappeared after 18 deflations (30%) and remained unchanged after 6 deflations (10%). At peak balloon inflation, left atrium spontaneous echo contrast (LASEC) grade 4 was observed during 14 of 27 (93%) inflations in the atrial fibrillation patients, significantly higher than in patients with sinus rhythm (8 of 34, 24%; P < 0.05). LASEC completely disappeared after 16 of 34 deflations (47%) in the patients with sinus rhythm, significantly higher than in the atrial fibrillation patients (2 of 27 deflations; P < 0.01). The mean time to achieve maximal SEC grade (2.5 +/- 1.2 s) correlated with the mean time to trough LAA velocities (2.3 +/- 1.1 s) after balloon inflation. Both the time to lowest LAA velocity and the time to highest LASEC were significantly longer in the patients with sinus rhythm than in the atrial fibrillation patients (2.6 +/- 1.1 s vs 1.7 +/- 1.0 s, P < 0.05 and 2.8 +/- 1.4 s vs 1.9 +/- 1.3 s, P < 0.05, respectively). Upon deflation, the mean time to lowest SEC grade (2.9 +/- 1.8 s) correlated with the mean time to achieve maximal LAA velocities (2.7 +/- 1.6 s). Both intervals are significantly shorter in the patients with sinus rhythm than in the atrial fibrillation patients (2.0 +/- 1.6 s vs 3.5 +/- 1.5 s, P < 0.01 and 2.2 +/- 1.7 s vs 3.6 +/- 1.6 s, P < 0.05).

CONCLUSION

Reducing the blood flow velocity in the human left atrium by balloon occlusion of the mitral valve may enhance SEC, whereas restoring blood flow after balloon deflation would cause enhanced echogenic blood to disappear or decrease in both groups of patients. Patients with atrial fibrillation demonstrate more severe blood stagnation of the left atrial body and appendage during transient balloon inflation at mitral valve orifice and slower recovery from the stagnation, decreasing to a lesser extent after balloon deflation, when compared to patients with sinus rhythm.

Effect of inotropic stimulation on left atrial appendage function in atrial myopathy of chronic atrial fibrillation

Atrial fibrillation (AF) leads to remodeling of the left atrium (LA) and left atrial appendage (LAA), resulting in atrial myopathy. Reduced LA and LAA function in chronic AF leads to thrombus formation and spontaneous echo contrast (SEC). The effect of inotropic stimulation on LAA function in patients with chronic AF is unknown. LAA emptying velocity (LAAEV) and maximal LAA area at baseline and after dobutamine were measured by transesophageal echocardiography in 14 subjects in normal sinus rhythm (NSR) and 6 subjects in AF. SEC in the LA was assessed before and after dobutamine. LAAEV increased significantly in both groups. However, the LAAEV at peak dobutamine in patients with AF remained significantly lower than the baseline LAAEV in patients who were in NSR (P = 0.009). Maximal LAA area decreased significantly with dobutamine in both groups, but LAA area at peak dose of dobutamine in patients with AF remained greater than baseline area in those in NSR (P = 0.01). Despite the increase in LAAEV, SEC improved in only two of five patients. We conclude that during AF, the LAA responds to inotropic stimulation with only a modest improvement in function.

Structural remodeling of the left atrial appendage in patients with chronic non-valvular atrial fibrillation: Implications for thrombus formation, systemic embolism, and assessment by transesophageal echocardiography

Left atrial appendage (LAA) is frequently the site of thrombus formation in patients with chronic atrial fibrillation (AF). Transesophageal echocardiography and hematologic studies have identified blood flow stasis (spontaneous echogenic contrast) and abnormal coagulation (increased serum fibrinogen) as important predisposing factors to formation of LAA thrombi. However, the third component of the Virchow's triad, i.e., endothelial abnormalities, has not been adequately studied. Accordingly, we studied, at necropsy, the LAA morphology in 46 hearts of patients with (n = 22) and without (n = 24) chronic AF. Compared to patients without AF, those with AF had significantly larger LAA volumes (1.7% 1.1 vs. 5. 4% 3.7 mL, p = 0.0002), and larger luminal surface area of the bisected LAA (4.4% 1.8 vs. 7.1% 4.5 cm(2), p = 0.01). However, both the absolute and relative surface area of the transected pectinate muscles were reduced in patients with AF (2.6% 1.1 vs. 1.8% 1.0 cm(2), p = 0.02 and 38% 15 vs. 21% 14%, p = 0.0003). In addition, in most patients (73%) with chronic AF, the LAA showed significant endocardial thickening with fibrous and elastic tissue (endocardial fibroelastosis) compared to those without AF (13%, p < 0.0001). Endocardial fibroelastosis resulted in a smooth LAA luminal surface and encased the pectinate muscles. These findings suggest that LAA remodeling (dilation, stretching, and reduction in pectinate muscle volume, as well as endocardial fibroelastosis) occurs frequently in chronic AF and may contribute to the increased risk of thrombus formation and systemic embolism. Additionally, the information may have relevance in interpreting transesophageal echocardiographic images of the LAA in patients with chronic AF.

Atrial tachycardia as the presenting sign of a left atrial appendage aneurysm

A patient presented with atrial tachycardia. The work-up, guided by the tachycardia morphology, led to the diagnosis of left atrial appendage aneurysm. Surgical removal of the atrial appendage resulted in cure of the tachycardia and associated symptoms.

Left atrial and appendage mechanical function after pharmacological or electrical cardioversion in patients with chronic atrial fibrillation: a multicenter, randomized study

BACKGROUND

Transient atrial and appendage dysfunction occurs after cardioversion of atrial fibrillation. It has been suggested that one component of early dysfunction is related to the method of restoration of sinus rhythm and it is less severe in patients undergoing pharmacological than electrical cardioversion. The aim of this study was to compare left atrial chamber and left atrial appendage mechanical function before and after 48 hours from electrical or pharmacological cardioversion in patients with chronic atrial fibrillation.

METHODS

We studied the effects of the mode of cardioversion on Doppler left atrial and appendage function in 19 patients with persistent atrial fibrillation (> or = 4 weeks), who were randomized to pharmacological (quinidine) or electrical cardioversion (protocol: 200, 300, 360 J) after pre-treatment with verapamil. Transthoracic and transesophageal echocardiography were performed before and 48 hours after the restoration of sinus rhythm. To determine left atrial and appendage mechanical dysfunction, the peak A wave velocities were obtained from transmitral flow velocity profiles recorded in the apical 4-chamber view, and peak emptying and filling appendage velocities were measured by the transesophageal approach with the sample volume placed at the orifice of the left atrial appendage. All the patients were pre-treated with verapamil before cardioversion in order to achieve a satisfactory control of heart rate.

RESULTS

Mean peak A wave velocities were 0.52 +/- 0.12 m/s in the patients treated electrically and 0.54 +/- 0.08 m/s in those treated pharmacologically (p = NS). Before and after electrical cardioversion, the peak filling velocities of the left atrial appendage were 0.42 +/- 0.17 and 0.43 +/- 0.17 m/s respectively, and the peak emptying velocities 0.30 +/- 0.14 and 0.36 +/- 0.17 m/s respectively; before and after pharmacological treatment, the peak filling velocities were 0.38 +/- 0.1 and 0.43 +/- 0.1 m/s respectively, and the peak emptying velocities were 0.30 +/- 0.13 and 0.43 +/- 0.24 m/s respectively (p = 0.08).

CONCLUSIONS

Even a long period of atrial fibrillation does not lead to a marked depression of global left atrial and left atrial appendage function 48 hours after the restoration of sinus rhythm by means of electrical or pharmacological cardioversion. There is no evidence that electrical cardioversion causes greater post-cardioversion atrial and/or appendage dysfunction than pharmacological treatment after 48 hours. Pre-treatment with verapamil may have reduced the dysfunction (probably because of a reduction in mechanical remodeling during atrial fibrillation).

Echocardiographic assessment of the left atrial appendage

The left atrial (LA) appendage is a common source of cardiac thrombus formation associated with systemic embolism. Transesophageal echocardiography allows a detailed evaluation of the structure and function of the appendage by two-dimensional imaging and Doppler interrogation of appendage flow. Specific flow patterns, reflecting appendage function, have been characterized for normal sinus rhythm and various abnormal cardiac rhythms. Appendage dysfunction has been associated with LA appendage spontaneous echocardiographic contrast, thrombus formation and thromboembolism. These associations have been studied extensively in patients with atrial fibrillation or atrial flutter, in patients undergoing cardioversion of atrial arrhythmias and in patients with mitral valve disease. The present review summarizes the literature on the echocardiographic assessment of LA appendage structure, function and dysfunction, which has become an integral part of the routine clinical transesophageal echocardiographic examination.

Pathophysiologic correlates of thromboembolism in nonvalvular atrial fibrillation: I. Reduced flow velocity in the left atrial appendage (The Stroke Prevention in Atrial Fibrillation [SPAF-III] study)

Stroke associated with atrial fibrillation (AF) is mainly due to embolism of thrombus formed during stasis of blood in the left atrial appendage (LAA). Pathophysiologic correlates of appendage flow velocity as assessed by transesophageal echocardiography (TEE) in patients with AF have not been defined. To evaluate the hypothesis that reduced velocity is associated with spontaneous echocardiographic contrast and thrombus in the LAA and with clinical embolic events, we measured LAA flow velocity by TEE in 721 patients with nonvalvular AF entering the Stroke Prevention in Atrial Fibrillation (SPAF-III) study. Patient features, TEE findings, and subsequent cardioembolic events were correlated with velocity by multivariate analysis. Patients in AF during TEE displayed lower peak antegrade (emptying) flow velocity (Anu(p)) than those with intermittent AF in sinus rhythm during TEE (33 cm/s vs 61 cm/s, respectively, P <.0001). Anu(p) < 20 cm/s was associated with dense spontaneous echocardiographic contrast (P <.001), appendage thrombus (P <.01), and subsequent cardioembolic events (P <.01). Independent predictors of Anu(p) < 20 cm/s included age (P =.009), systolic blood pressure (P <.001), sustained AF (P =.01), ischemic heart disease (P =.01), and left atrial area (P =.04). Multivariate analysis found both Anu(p) <20 cm/s (relative risk 2.6, P =.02) and clinical risk factors (relative risk 3.3, P =.002) independently associated with LAA thrombus. LAA Anu(p) is reduced in AF and associated with spontaneous echocardiographic contrast, appendage thrombus, and cardioembolic stroke. Systolic hypertension and aortic atherosclerosis, independent clinical predictors of stroke in patients with AF, also correlated with LAA Anu(p). Our results support the role of reduced LAA Anu(p) in the generation of stasis, thrombus formation, and embolism in patients with AF, although other mechanisms also contribute to stroke.

Left atrial appendage: structure, function, and role in thromboembolism

The left atrial appendage (LAA) is derived from the left wall of the primary atrium, which forms during the fourth week of embryonic development. It has developmental, ultrastructural, and physiological characteristics distinct from the left atrium proper. The LAA lies within the confines of the pericardium in close relation to the free wall of the left ventricle and thus its emptying and filling may be significantly affected by left ventricular function. The physiological properties and anatomical relations of the LAA render it ideally suited to function as a decompression chamber during left ventricular systole and during other periods when left atrial pressure is high. These properties include the position of the LAA high in the body of the left atrium; the increased distensibility of the LAA compared with the left atrium proper; the high concentration of atrial natriuretic factor (ANF) granules contained within the LAA; and the neuronal configuration of the LAA. Thrombus has a predilection to form in the LAA in patients with atrial fibrillation, mitral valve disease, and other conditions. The pathogenesis has not been fully elucidated; however, relative stasis which occurs in the appendage owing to its shape and the trabeculations within it is thought to play a major role. Obliteration or amputation of the LAA may help to reduce the risk of thromboembolism, but this may result in undesirable physiological sequelae such as reduced atrial compliance and a reduced capacity for ANF secretion in response to pressure and volume overload.

Ionic mechanisms of electrical remodeling in human atrial fibrillation

OBJECTIVES

Atrial fibrillation (AF) is associated with a decrease in atrial ERP and ERP adaptation to rate as well as changes in atrial conduction velocity. The cellular changes in repolarization and the underlying ionic mechanisms in human AF are only poorly understood.

METHODS

Action potentials (AP) and ionic currents were studied with the patch clamp technique in single atrial myocytes from patients in chronic AF and compared to those from patients in stable sinus rhythm (SR).

RESULTS

The presence of AF was associated with a marked shortening of the AP duration and a decreased rate response of atrial repolarization. L-type calcium current (ICa,L) and the transient outward current (Ito) were both reduced about 70% in AF, whereas an increased steady-state outward current was detectable at test potentials between -30 and 0 mV. The inward rectifier potassium current (IKI) and the acetylcholine-activated potassium current (IKACh) were increased in AF at hyperpolarizing potentials. Voltage-dependent inactivation of the fast sodium current (INa) was shifted to more positive voltages in AF.

CONCLUSIONS

AF in humans leads to important changes in atrial potassium and calcium currents that likely contribute to the decrease in APD and APD rate adaptation. These changes contribute to electrical remodeling in AF and are therefore important factors for the perpetuation of the arrhythmia.