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

Systolic Tissue Velocity Is a Useful Echocardiographic Parameter in Assessment of Left Atrial Appendage Function in Patients with Mitral Stenosis

BACKGROUND

The incidence of thromboembolism remains high in patients with mitral stenosis (MS). The left atrial appendage (LAA) is a potential site for development of thrombus and LAA dysfunction is an independent predictor of thromboembolism. The LAA dysfunction is represented by reduced LAA late emptying velocity. But the magnitude of LAA flow velocities is dependent on acute changes in loading conditions.

AIM

To investigate the value of the LAA tissue velocities obtained by tissue Doppler imaging (TDI) in assessment of LAA function in MS patients with and without thromboembolic events.

METHODS

The study population consisted of 98 isolated MS patients of 32 age and sex-matched healthy controls. All subjects underwent transesophageal echocardiography (TEE). LAA late peak emptying (LAAEV) and filling (LAAFV) flow velocities were recorded. LAA peak late tissue systolic (LSV) and diastolic (LDV) tissue velocities by TDI were measured. The patients were divided into three groups as Group I (n = 38, sinus rhythm and LAAEV > or = 25 cm/s), Group II (n = 26, sinus rhythm and LAAEV < 25 cm/s), and Group III (n = 34, atrial fibrillation).

RESULTS

Twenty-one patients had thromboembolic events. LAAEV, LAAFV, LSV, and LDV were significantly reduced in patients with embolic events. Spontaneous echo contrast (SEC) density was strongly negative correlated with LSV, whereas weakly negative correlated with LAAEV. Multivariate regression analysis showed that LSV and the presence of SEC were independently associated with embolic events.

CONCLUSION

LSV seems more reliable and useful parameter in evaluating LAA function. LAA function is more depressed among patients with embolic events.

Serious Complications from Dislocation of a Watchman Left Atrial Appendage Occluder

Left atrial appendage (LAA) elimination is regarded to protect patients with atrial fibrillation (AF) from stroke or embolism. The Watchman occluder is a device for percutaneous LAA occlusion and is at present investigated in the PROTECT AF trial. In a 78-year-old man, embolization of the Watchman device occurred 10 minutes after implantation. At emergency cardiac surgery, the device was removed from the aortic valve and an aortic bioprosthesis and a pacemaker had to be implanted. One year postoperatively, he still suffers from heart failure. This case shows that percutaneous LAA occlusion may result in serious complications.

[New developments for surgical ablation of atrial fibrillation]

The Cox-Maze procedure and less complex modifications have gained widespread use as a treatment modality for patients with concomitant atrial fibrillation. Hypothermic or hyperthermic energy sources play a significant role in rapidly creating linear lesions. Endocardial ablation is easy to perform and effective with different energy sources. Epicardial techniques may simplify the procedure by allowing surgery on a beating heart. But epicardial fat and the heat sink effect of the flowing endocardial blood are obstacles to effective ablation. New devices using bipolar (irrigated) radiofrequency, microwave or laser energy, cryoablation or focused ultrasound are in clinical or pre-clinical stages and permit lesions to be created on a beating heart without cardiopulmonary bypass. Minimally invasive or video-assisted surgical techniques and effective devices for epicardial ablation will enable the treatment of patients suffering from lone atrial fibrillation. To facilitate the comparison between different techniques and devices, guidelines for reporting clinical results are necessary.

Left atrial appendage exclusion for stroke prevention in patients with nonrheumatic atrial fibrillation

The efficacy of oral anticoagulation (OAC) for stroke prevention in patients with nonrheumatic atrial fibrillation (AF) has clearly been established. However, a substantial number of patients with AF who are at high risk for thromboembolic events are not candidates for long-term OAC. The left atrial appendix (LAA) is the most common place of thrombosis in patients with AF, and it can easily be excluded from the systemic circulation at the time of cardiac surgery by excision, ligation, suturing, or stapling. Currently, removal of the LAA at the time of mitral valve surgery is recommended to reduce future stroke risk. The ongoing LAA Occlusion Study (LAAOS) is evaluating the efficacy of the routine LAA occlusion in patients undergoing elective coronary artery bypass graft surgery. Recently, two devices specifically designed for percutaneous transcatheter LAA occlusion have been introduced: the Percutaneous LAA Transcatheter Occlusion (PLAATO; Appriva Medical Inc) and WATCHMAN LAA system (Atritech, Inc). More than 200 PLAATO devices were implanted worldwide in patients with nonrheumatic AF who were at high risk for ischemic stroke and not candidates for long-term OAC. In a follow-up time of 258 patient-years, an estimated 61% reduction in stroke risk was achieved with PLAATO procedure. The WATCHMAN Left Atrial Appendage System for Embolic PROTECTion in Patients With Atrial Fibrillation (PROTECT AF) study was designed to demonstrate the safety and efficacy of the WATCHMAN device in patients with nonvalvular AF who are eligible for long-term OAC. The trial is assessing whether the treatment arm (WATCHMAN device) is noninferior to the control arm (warfarin). Although present results suggest that LAA occlusion may reduce the long-term stroke risk, available data are still very limited. At present, percutaneous LAA occlusion may be an acceptable option in selected high-risk patients with AF who are not candidates for OAC. The current understanding of LAA exclusion for the prevention of stroke in patients with nonrheumatic AF is the major focus of this review.

Impact of left atrial appendage exclusion on left atrial function

OBJECTIVES

We sought to investigate the short-term and midterm effects of left atrial appendage exclusion on left atrial function. Left atrial appendage exclusion is considered a possible therapeutic option for stroke prevention in patients with atrial fibrillation. Favorable outcomes have encouraged widespread use of left atrial appendage exclusion for cardiac surgical patients-even for patients in sinus rhythm who have stroke risk factors; however, the chronic effects on left atrial function of left atrial appendage exclusion are unclear.

METHODS

Nineteen mongrel dogs (29.7 +/- 5.2 kg) in sinus rhythm were studied. The Doppler signals from the pulmonary venous flow, transmitral flow, and tissue Doppler imaging of mitral annular motion were obtained before and after left atrial appendage exclusion. Dogs were evaluated in the same manner at 7 days (n = 2), 30 days (n = 7), or 90 days (n = 10) after left atrial appendage exclusion.

RESULTS

Except for a significant increase in early diastolic transmitral flow velocity after left atrial appendage exclusion (P = .01), no significant differences were found in any parameters related to the transmitral flow and tissue Doppler imaging measurements throughout follow-up. The systolic components of pulmonary venous flow at follow-up revealed a significant reduction relative to baseline (peak systolic velocity P < .0001, systolic velocity-time integral P < .0001), despite the lack of significant changes in left atrial pressure, left ventricular volume, and stroke volume.

CONCLUSION

Left atrial appendage exclusion may affect left atrial reservoir function in the short-term and midterm periods. Further long-term studies with more clinically relevant models are needed.

Antithrombotic and interventional treatment options in cardioembolic transient ischaemic attack and ischaemic stroke

Peer-reviewed data pertaining to anti-thrombotic and interventional therapy for transient ischaemic attack (TIA) or ischaemic stroke patients with non-valvular atrial fibrillation, atrial flutter, interatrial septal abnormalities, or left ventricular thrombus were reviewed. Long-term oral anticoagulant therapy with warfarin is the treatment of choice for secondary stroke prevention following TIA or minor ischaemic stroke in association with persistent or paroxysmal non-valvular atrial fibrillation or atrial flutter. If warfarin is contraindicated, long-term aspirin is a safe, but much less effective alternative treatment option in this subgroup of patients with cerebrovascular disease. Management of young patients with TIA or stroke in association with an interatrial septal defect is controversial. Various treatment options are outlined, but readers are encouraged to include these patients in one of the ongoing randomised clinical trials in this area. It is reasonable to consider empirical anticoagulation in patients with TIA or ischaemic stroke in association with left ventricular thrombus formation following myocardial infarction or in association with idiopathic dilated cardiomyopathy. If warfarin is prescribed, one should aim for a target international normalised ratio of 2.5 (range 2-3) to achieve the best balance between adequate secondary prevention of cardioembolic events and the risk of major haemorrhagic complications.

Evaluation of a novel device for left atrial appendage exclusion: The second-generation atrial exclusion device

BACKGROUND

The left atrial appendage is a frequent source of thromboemboli in patients with atrial fibrillation. Exclusion of the left atrial appendage may reduce the risk of stroke in patients with atrial fibrillation. The atrial exclusion device, previously developed to perform left atrial appendage exclusion on a beating heart, was modified to accommodate different anatomic patterns of the human left atrial appendage and to ensure uniform pressure and occlusion. The purpose of this study was to evaluate this second-generation atrial exclusion device during a midterm period in a canine model.

METHODS

Ten mongrel dogs (mean weight 28.9 +/- 4.6 kg) were used in this study. The atrial exclusion device, constructed from two parallel and rigid titanium tubes and two nitinol springs with a knit-braided polyester fabric, was implanted at the base of the left atrial appendage through a left thoracotomy on a beating heart using a specially designed delivery tool. Dogs were evaluated at 30 days (n = 4) and 90 days (n = 6) by epicardial echocardiography, left atrial and coronary angiography, gross pathology, and histologic inspection.

RESULTS

Device implantation was performed without complications in all dogs. Complete left atrial appendage exclusion without device migration or hemodynamic instability was confirmed, and there was no damage to the left circumflex artery or pulmonary artery. Macroscopic and microscopic assessments revealed favorable biocompatibility during midterm follow-up.

CONCLUSION

The atrial exclusion device enabled rapid, reliable, and safe exclusion of the left atrial appendage. Clinical application may provide a new therapeutic option for reducing the risk of stroke in patients with atrial fibrillation.

Mitral Annular Systolic Velocity Reflects the Left Atrial Appendage Function in Mitral Stenosis

BACKGROUND

Left atrial appendage (LAA) dysfunction is an independent predictor of thromboembolism in mitral stenosis (MS).

OBJECTIVES

To investigate whether there is a relation between annular velocities obtained by tissue Doppler imaging and LAA function and to determine if the annular velocities can predict the presence of the inactive LAA in MS.

METHODS

Eighty-five MS patients and 80 healthy controls were evaluated by transthoracic echocardiography and all patients underwent transesophageal echocardiography. The annular systolic (S-wave) and diastolic (E- and A-waves) velocities were recorded. Inactive LAA was defined as LAA emptying velocity <25 cm/sec. Patients were divided into three groups; group I (n = 43): sinus rhythm (SR) and LAA emptying velocity > or =25 cm/sec, group II (n = 15): SR and LAA emptying velocity <25 cm/sec and group III (n = 27): atrial fibrillation.

RESULTS

Thrombus was detected in 12 patients and spontaneous echo contrast (SEC) was detected in 48 patients. Both S-wave and peak LAA emptying velocities were decreasing, while SEC frequency and density were increasing from group I to group III. There was a positive correlation between LAA emptying and S-wave velocities (P < 0.001, r = 0.682). Multivariate regression analysis showed that only S-wave is the independent predictor of inactive LAA (P = 0.001, odds ratio = 0.143, 95% CI = 0.047-0.434). In patients with SR, the cutoff value of S-wave was 13.5 cm/sec for the prediction of the presence of inactive LAA (sensitivity: 95.3%, specificity: 93.3%).

CONCLUSIONS

S-wave is an independent predictor of inactive LAA and a useful parameter in estimating inactive LAA in MS with SR.

Innovative Monolateral Approach for Closed-Chest Atrial Fibrillation Surgery

Surgical treatment of atrial fibrillation recently gained new popularity since the introduction of different energy sources as an alternative to the original cut-and-sew technique. Recently an innovative approach for closed-chest thoracoscopic epicardial pulmonary veins isolation has been described for patients suffering from lone atrial fibrillation. Nevertheless in an effort to further reduce the invasiveness of closed-chest atrial fibrillation surgery, we developed a novel monolateral approach for thoracoscopic arrhythmia surgery.

Surgical Closure of the Left Atrial Appendage – A Beneficial Procedure?

BACKGROUND

Closure of the fibrillating left atrial appendage (LAA) has been recommended during valve surgery to decrease the risk of arterial embolism. However, patients undergoing surgical LAA closure have not systematically been reevaluated for complete LAA obliteration.

METHODS AND RESULTS

During a 12-month period, we studied 6 consecutive patients with paroxysmal (n = 3) or permanent (n = 3) atrial fibrillation who underwent surgical LAA closure at the time of valve surgery. Transesophageal echocardiography (TEE) performed 23-159 days (mean 51) postoperatively demonstrated complete LAA closure in only 1 patient. In 5 patients, incomplete LAA closure was found due to disruption of the closure line. The size of the residual LAA orifice ranged from 3 to 20 mm. There was a high flow velocity at the LAA orifice (0.33-2.2 m/s), whereas flow in the LAA body was low (<0.2 m/s). Spontaneous echocardiographic contrast (SEC) in the LAA had newly developed (n = 3) or was much more intense than preoperatively (n = 2). Despite therapeutic anticoagulation 2 patients showed a LAA thrombus which had not been present on the preoperative TEE, and 1 patient with SEC suffered a stroke 4 weeks after attempted LAA closure.

CONCLUSION

Surgical LAA closure was incomplete in most patients, resulting in blood stagnation and an increased likelihood of clot formation. Incomplete surgical LAA closure, therefore, may promote rather than reduce the risk of stroke. Intraoperative TEE is mandatory to verify complete LAA obliteration.

Surgical Treatment of Lone Atrial Fibrillation in an Awake Patient

Surgical treatment of atrial fibrillation recently gained new popularity since the introduction of different energy sources and the development of minimally invasive techniques as an alternative to the original "cut-and-sew" technique. However, closed-chest ablation procedures are not feasible in presence of pericardial or pleural adhesions. To our knowledge, this is the first report of surgical treatment of atrial fibrillation in a conscious patient by means of a high epidural anesthesia. Since evidence of fibrothorax was found, a conscious patient suffering from lone atrial fibrillation underwent a beating-heart pulmonary veins isolation with a microwave device through a standard sternotomic approach. At 6 months follow-up, the patient is in stable sinus rhythm, without any palpitation nor electrocardiographic evidence (Holter monitoring) of recurrent atrial fibrillation.

Mitral valve replacement with mechanical or bioprosthetic valve

A presentation on the technique of mitral valve replacement is shown: exposure and excision of the diseased mitral valve is demonstrated along with the use of sub-annular and supra-annular interrupted suture techniques for securing biological and mechanical mitral prostheses. A brief overview of the literature is presented.