Mechanical dysfunction of the left atrium and the left atrial appendage following cardioversion of atrial fibrillation and its relation to total electrical energy used for cardioversion

In 39 patients undergoing electrical cardioversion for atrial fibrillation (AF), we examined the effect of total electrical energy used for cardioversion on postcardioversion peak left atrial (LA) rapid filling velocity (A) and the atrial emptying fraction, and recovery of LA effective mechanical atrial function (defined as peak A velocity > or = 0.50 m/s), as assessed by transthoracic echocardiography. In a subset of 27 patients who underwent pre- and postcardioversion transesophageal echocardiography, we assessed the relation between total electrical energy and LA appendage filling and emptying velocities and spontaneous echo contrast. Patients were randomized to receive an initial shock of 1.5 J/kg based on body weight, or 2.5, 3.5, 5 J/kg, or 360 J, followed sequentially by higher shock intensities until sinus rhythm was achieved. Patients were classified into 4 groups based on quartiles of total energy delivered for cardioversion. Conversion to sinus rhythm was associated with a significant decrease in the LA appendage filling velocities (0.42 +/- 0.20 m/s vs 0.29 +/- 0.14 m/s; p = 0.002) and LA appendage emptying velocities (0.40 +/- 0.22 m/s vs 0.29 +/- 0.18 m/s; p = 0.03), but no change in the incidence of spontaneous echo contrast (61% vs 70%, p = 0.08). The 4 groups of patients did not differ with respect to postcardioversion LA appendage filling velocities, LA appendage emptying velocities, incidence of spontaneous echo contrast, or worsening of spontaneous echo contrast. Similarly, the change in LA appendage filling and emptying velocities associated with cardioversion was not different between the groups. Furthermore, postcardioversion peak A velocity and atrial emptying fraction and recovery of effective mechanical atrial function were similar between the 4 groups. These results suggest that in patients undergoing electrical cardioversion for AF, the total electrical energy used for cardioversion has no effect on the mechanical function of the left atrium or LA appendage following cardioversion.     

Left atrial appendage flow velocity and spontaneous echo contrast in patients with rheumatic mitral stenosis: a multiplane transesophageal echocardiographic study

BACKGROUND: Left atrial spontaneous echo contrast (LASEC), a putative marker of thrombo-embolic risk, is commonly located in the left atrial appendage (LAA). The aims of this work were to evaluate, using multiplane transesophageal echography, the echocardiographic determinants, specifically LAA outflow Doppler velocity, in the presence of SEC in patients with rheumatic MS. METHODS: Transthoracic and transesophageal echocardiographic tests were performed on 61 patients. The patients were divided into 3 groups based on the presence and type of valvular disease. Patients in group I (n = 28) presented with rheumatic mitral stenosis (MS). Patients in group II (n = 18) presented with valvular heart disease other than MS, and patients in group III (n = 15) had no history of valvular heart disease. The left atrium and appendage were examined for the presence of spontaneous echocontrast and thrombus, using multiplane echo scopy with transducer rotation. Minimal and maximal appendage areas were measured, on a computer-assisted bablet, by tracing a line from the top of the limbus of the left upper pulmonary vein to the appendage endocardial border. The LAA ejection fraction was calculated according to the formula: (maximal area-minimal area)/maximal area. Mitral valvular condition was evaluated with transthoracic and transesophageal echocardiography. Left atrial appendage blood flow velocity profiles were obtained with pulsed-wave Doppler at the orifice of the LAA. RESULTS: LASEC was present in 18 of 28 patients with mitral stenosis (64.3%). Patients with LASEC showed a greater incidence of atrial fibrillation (14/18 vs 12/43, p < 0.005), larger LAD (53.67 +/- 8.74 vs 40.54 +/- 14.85, p < 0.005), smaller LAAEF (38.7 +/- 1.53 vs 69.5 +/- 24.0, p < 0.05), smaller LAAMEV (20.28 +/- 10.07 vs 2.95 +/- 25.11, p < 0.005) and smaller LAAMFV (24.6 +/- 12.23 vs 36.00 +/- 11.01, p < 0.01), when compared with patients without LASEC. For group I, LAAEF, LAAMEV and LAAFV were smaller in patients with SEC than in patients without SEC (p < 0.005, p < 0.05, p < 0.01). However LAD values were similar for patients with and without SEC (53.67 +/- 8.75 vs 54.20 +/- 18.81, p = NS). Both LAAMEV and LAAMFV were related to SEC in patients with atrial fibrillation. However, LAD did not show the same trend. CONCLUSIONS: LASEC is more commonly observed in patients with rheumatic mitral stenosis or atrial fibrillation. Both LAAMEV and LAAMFV are associated with SEC in these patients.     

Cytokines and bioincompatibility

OBJECTIVES: This study explored the mechanisms linking clinical and precordial echocardiographic predictors to thromboembolism in atrial fibrillation (AF) by assessing transesophageal echocardiographic (TEE) correlations. BACKGROUND: Clinical predictors of thromboembolism in patients with nonvalvular AF have been identified, but their mechanistic links remain unclear. TEE provides imaging of the left atrium, its appendage and the proximal thoracic aorta, potentially clarifying stroke mechanisms in patients with AF. METHODS: Cross-sectional analysis of TEE features correlated with low, moderate and high thromboembolic risk during aspirin therapy among 786 participants undergoing TEE on entry into the Stroke Prevention in Atrial Fibrillation III trial. RESULTS: TEE features independently associated with increased thromboembolic risk were appendage thrombi (relative risk [RR] 2.5, p = 0.04), dense spontaneous echo contrast (RR 3.7, p < 0.001), left atrial appendage peak flow velocities < or = 20 cm/s (RR 1.7, p = 0.008) and complex aortic plaque (RR 2.1, p < 0.001). Patients with AF with a history of hypertension (conferring moderate risk) more frequently had atrial appendage thrombi (RR 2.6, p < 0.001) and reduced flow velocity (RR 1.8, p = 0.003) than low risk patients. Among low risk patients, those with intermittent AF had similar TEE features to those with constant AF. CONCLUSIONS: TEE findings indicative of atrial stasis or thrombosis and of aortic atheroma were independently associated with high thromboembolic risk in patients with AF. The increased stroke risk associated with a history of hypertension in AF appears to be mediated primarily through left atrial stasis and thrombi. The presence of complex aortic plaque distinguished patients with AF at high risk from those at moderate risk of thromboembolism.     

Transesophageal echocardiographic predictors for maintenance of sinus rhythm after electrical cardioversion of atrial fibrillation

The aim of this study was to assess the value of transesophageal echocardiography (TEE) in patients with atrial fibrillation in predicting restoration and maintenance of sinus rhythm after electrical cardioversion. TEE was performed in 62 patients with atrial fibrillation before their first elective cardioversion. Clinical variables evaluated were: age, gender, duration, and etiology of atrial fibrillation. TEE variables included: left atrial (LA) length, width, and size, LA annulus size, as well as presence of LA spontaneous contrast, thrombus and mitral regurgitation, LA appendage size and flow, and left ventricular function. Based on initial outcome of cardioversion, patients were grouped into patients who remained in atrial fibrillation and in whom sinus rhythm was restored. The latter group of patients was followed for 1 year, and grouped into patients who reverted to atrial fibrillation and in whom sinus rhythm was maintained. Successful cardioversion was achieved in 50 of 62 patients (81%). None of the clinical or TEE variables were related to initial outcome. At 1-year follow-up, 29 of 50 patients (58%) who underwent successful cardioversion continued to have sinus rhythm. The following variables were related to maintenance of sinus rhythm: duration of atrial fibrillation (6.7 +/- 7.3 vs 2.0 +/- 2.4 months; p < 0.005); LA length (6.2 +/- 0.7 vs. 5.5 +/- 1.0 cm; p < 0.008); width (5.1 +/- 0.5 vs. 4.5 +/- 0.7 cm; p < 0.002); size (26.4 +/- 5.0 vs 19.8 +/- 6.5 cm2; p < 0.0005); annulus size (4.0 +/- 0.2 vs 3.7 +/- 0.3 cm; p < 0.0005); presence of LA spontaneous contrast (13 [62%] vs 4 [14%]; p < 0.002), and LA appendage flow (19 +/- 8 vs 36 +/- 15 cm/s; p < 0.0005). In multivariate logistic regression analysis, LA annulus size, but especially LA appendage flow, were significantly associated with maintenance of sinus rhythm. Thus, in TEE-guided electrical cardioversion of atrial fibrillation, variables often used to assess thromboembolic risk may also be used to predict 1-year outcome of cardioversion.     

Interference of mitral valve stenosis with left ventricular diastole and left atrial appendage flow

Atrial fibrillation (AF) has been reported as an independent risk factor of systemic thromboembolism. Almost half of the left atrial thrombi are located in the left atrial appendage (LAA). LAA function, reflected by LAA flow, thus has an influence on the potential of distal embolic complications. To identify factors other than atrial contraction that influence LAA flow during AF, transthoracic and transesophageal echocardiographic studies were performed on 130 patients. Seventy patients with nonrheumatic AF were divided into two groups with higher peak LAA outflow velocity (group 1) and lower peak LAA outflow velocity (group 2) at the ventricular systolic phase. Sixty patients with rheumatic AF were classified as group 3. Group 1 had a higher peak LAA outflow velocity than group 2 at both the ventricular systolic and diastolic phases. Group 2 had a higher peak LAA outflow at the ventricular diastolic phase than group 3 (18.9 +/- 8.0 vs. 11.8 +/- 7.5 cm/s, p < 0.001), whereas there was no significant difference in the peak LAA outflow at the ventricular systolic phase between the two groups (9.6 +/- 4.0 vs. 10.8 +/- 6.8 cm/s, p = NS). Group 3 was subdivided according to mitral valve area. Patients with severe mitral stenosis (mitral valve area < 1 cm2) had a significantly lower diastolic augmentation of LAA outflow velocity (difference of LAA outflow velocity between ventricle systole and diastole) than patients with mild to moderate stenosis (0.5 +/- 3.2 vs. 2.6 +/- 4.9 cm/s, p < 0.05). In conclusion, patients with rheumatic AF, especially those with severe mitral stenosis, have a lower diastolic augmentation of LAA outflow velocity. The lower diastolic augmentation of the LAA outflow velocity at the ventricular diastolic phase might result from interference with the suction effect of the left ventricular diastole by the stenotic mitral valve.     

Transesophageal echocardiography study with dynamic spontaneous contrast of the left atrial appendage, its relationship with the anatomy and thrombus formation

OBJECTIVE: Transesophageal two-dimensional echocardiographic study of anatomical characteristics of the left atrial appendage and its relation to spontaneous dynamic echocardiographic contrast. DESIGN: Outpatients undergoing a prospective two-dimensional transesophageal echocardiographic study. SETTING: Consecutive outpatients studied at the Echocardiographic Laboratory of Gregorio Mara?on General Hospital, Madrid. MATERIAL AND METHODS: In each patient at the level of the left atrial appendage we calculated the following transesophageal echocardiographic parameters: end-systolic and end-diastolic maximal longitudinal and transversal diameters, total systolic and diastolic areas, percentage of systolic fractional shortening, presence of left atrial appendage thrombus and spontaneous dynamic echo-contrast. MAIN RESULTS: Left atrial appendage spontaneous dynamic contrast was observed in 48% of the total population. In the group of patients with left atrial spontaneous echo-contrast we observed larger longitudinal systolic (44 +/- 14 mm vs 28 +/- 13 mm, p = 0.01) and diastolic (52 +/- 16 mm vs 38 +/- 12 mm, p = 0.005) diameters, larger transversal systolic (25 +/- 10 mm vs 19 +/- 6 mm, p = 0.03) and diastolic (28 +/- 8 mm vs 25 +/- 9 mm, p = NS) diameters and also larger systolic (601 +/- 204 mm2 vs 337 +/- 110 mm2, p < 0.0001) and diastolic (715 +/- 230 mm2 vs 507 +/- 184 mm2, p = 0.001) areas, compared to the group without this dynamic echocardiographic phenomena. Left atrial appendage percentage of fractional shortening was considerably reduced in patients with spontaneous dynamic echo-contrast (15 +/- 14% vs 39 +/- 18%, p = 0.001) and related to local thrombus formation (13% vs 1%, p < 0.001). CONCLUSIONS: Left atrial spontaneous dynamic echo-contrast is more common in patients with enlarged left atrial appendage systo-diastolic diameters and areas. In this group of patients the presence of left atrial spontaneous echo-contrast is related to a significant reduction in left atrial appendage contractile function and thrombus formation. Parameter analysis of left atrial appendage anatomy by two-dimensional transesophageal echocardiography may have clinical relevance in the assessment of patients with high risk for left atria thromboembolic phenomena.     

Hypercoagulability and chronic atrial fibrillation: the role of markers of thrombin generation

BACKGROUND: We have studied 64 patients with congestive heart failure, half of them also with chronic nonvalvular atrial fibrillation (AF). Patients were also stratified according to a history of prior stroke. METHODS: The generation of thrombin was investigated by means of the molecular markers prothrombin fragment 1 + 2 (F1 + 2) and thrombin-antithrombin III complex (TAT), because AF patients may have a hypercoagulable state. There was only a trend toward higher values of TAT and F1 + 2 for AF patients, while subjects with previous stroke (irrespective of AF) had increased levels of the markers of thrombin generation (TAT stroke+ 18.95 +/- 5.15 vs TAT stroke- 8.34 +/- 2.41; F1 + 2 stroke+ 2.22 +/- 0.29 vs F1 + 2 stroke- 1.32 +/- 0.12). The presence of spontaneous echo contrast (SEC) within left atrium was also investigated in 32 AF patients by transesophageal echocardiography. RESULTS: TAT were significantly higher in subjects (n = 11) with SEC (TAT sec+ 37.5 +/- 13.41 vs TAT sec- 8.7 +/- 2.51, p = 0.008). CONCLUSIONS: Finally, when we grouped into 1) those with both AF and stroke, 2) AF alone, 3) stroke alone and 4) sinus rhythm without stroke, levels of F1 + 2 were higher (and marginally higher TAT) in patients with AF and stroke than in those without stroke, revealing that there is a true clotting activation state in these subjects.     

Transesophageal echocardiography to assess embolic risk in patients with atrial fibrillation. ELAT Study Group. Embolism in Left Atrial Thrombi

BACKGROUND: Transesophageal echocardiography visualizes the left atrium and its appendage, thrombi, and spontaneous echocardiographic contrast. OBJECTIVE: To assess the association of transesophageal echocardiographic characteristics with stroke or embolism in atrial fibrillation. DESIGN: Multicenter observational follow-up study. SETTING: Hospitals in Austria and Slovakia. PATIENTS: 409 outpatients with nonrheumatic atrial fibrillation and without recent stroke. INTERVENTION: Patients with thrombi received anticoagulation, and patients without thrombi received aspirin. MEASUREMENTS: Primary events were stroke or embolism. Secondary events were death not caused by stroke or embolism and need for anticoagulation. RESULTS: In the left atrium or left atrial appendage, 10 patients (2.5%) had thrombi and 47 (12%) had spontaneous echocardiographic contrast. The appendage had a mean (+/- SD) length of 44+/-10 mm, a mean width of 23+/-6 mm, and a mean area of 5.8+/-2.5 cm2. Follow-up ranged from 1 to 74 months (mean, 58 months). Fifty patients had stroke or embolism, 53 died of a cause other than stroke or embolism, and 38 required anticoagulation. On univariate analysis, thrombi (risk ratio, 3.9 [95% CI, 1.4 to 10.1]; P = 0.009), length of the left atrial appendage (risk ratio, 1.6 [CI, 1.05 to 2.5]; P = 0.03), and width of the left atrial appendage (risk ratio, 2.4 [CI, 1.2 to 4.81; P = 0.01) were associated with stroke or embolism. Multivariate analysis identified hypertension (risk ratio, 3.6 [CI, 1.8 to 8.4]; P = 0.001), previous stroke (risk ratio, 3.7 [CI, 1.5 to 7.5]; P = 0.002), and age (risk ratio, 1.1 [CI, 1.0 to 1.11; P < 0.001) as risk factors for stroke or embolism and provided evidence of an association between thrombi and stroke or embolism (risk ratio, 2.4 [CI, 0.9 to 6.9]; P = 0.09). CONCLUSIONS: In outpatients with atrial fibrillation and without recent stroke, thrombi of the left atrium or left atrial appendage and length and width of the left atrial appendage were associated with stroke or embolism in univariate analysis. In a multivariate analysis, age, hypertension, and previous stroke were risk factors for stroke or embolism, and thrombi of the left atrium or left atrial appendage were possible risk factors. In these patients, history may be more useful than transesophageal echocardiography for the assessment of embolic risk.     

Short deceleration time of mitral inflow E velocity: prognostic implication with atrial fibrillation versus sinus rhythm

The present study retrospectively identified 367 patients who had restrictive physiology as defined by deceleration time < or = 130 msec; 293 were in sinus rhythm (SR) (194 men and 99 women; mean age 64 +/- 14 years) and 74 were in atrial fibrillation (AF) (51 men and 23 women; mean age 72 +/- 11 years; p < 0.001). Both groups had similar underlying diagnoses and no significant difference in Doppler indices (E wave, 96 +/- 23 vs 99 +/- 22 cm/sec in SR and AF, respectively; deceleration time, 116 +/- 12 vs 116 +/- 13 msec; and left ventricular outflow tract time velocity integral, 14.8 +/- 4.8 vs 14.5 +/- 4.4 cm). Left ventricular ejection fraction was significantly lower in SR patients (29% +/- 16% vs 39% +/- 20%; p = 0.0003). There were 120 deaths (41%) in the SR group and 35 (47%) in the AF group (median follow-up for both groups, 2.2 years). Restrictive physiology as defined by Doppler echocardiography (deceleration time < or = 130 msec) appears to predict a similar poor prognosis with AF as with SR.     

Vertebral artery injury in C1-2 transarticular screw fixation: results of a survey of the AANS/CNS section on disorders of the spine and peripheral nerves. American Association of Neurological Surgeons/Congress of Neurological Surgeons

OBJECTIVES: The goal of this study was to investigate the possible role of transesophageal echocardiography in the evaluation of patients with clinical pacemaker syndrome. BACKGROUND: Several reports on transthoracic echocardiographic features of ventricular pacing were described; however, no previous study of transesophageal echocardiography has been undertaken in patients at the severe end of pacemaker syndrome who need reprogramming of dual-chamber pacing for symptom relief. METHODS: Twelve patients with ventricular-inhibited pacemakers (VVI) with clinical symptomatic pacemaker syndrome (group I) and 10 patients with VVI without pacemaker syndrome (group II) were prospectively studied. The two groups were pacemaker dependent and had persistent ventriculoatrial conduction. Transesophageal echocardiographic parameters were assessed in group II and within 6 hours before reprogramming to the DDD mode in group I. Follow-up transesophageal echocardiographic study was performed 28+/-5 days after reprogramming in group I. RESULTS: All patients in group I had subjective improvements of symptoms after DDD reprogramming. The atrial reverse flow velocities of pulmonary veins in group I before reprogramming were significantly higher in group II (39.3+/-11.4 versus 15.7+/-13.5 cm/sec, p < 0.0001). Spontaneous echo contrast in the descending aorta was detected in all patients from group I before reprogramming. The prevalence of significant mitral regurgitation (> or = moderate) was significantly higher in group I before reprogramming than in group II (67% versus 8%, p = 0.01). Significant mitral regurgitation and spontaneous echo contrast in the descending aorta in group I disappeared after reprogramming to the DDD mode. CONCLUSIONS: Transesophageal echocardiography provides physiologic, pacemaker-related hemodynamic changes in paced patients. Significantly higher atrial reverse flow velocities of pulmonary veins, increased frequency of spontaneous echo contrast in the descending aorta, and significant mitral regurgitation are peculiar echocardiographic findings in patients with VVI with clinical pacemaker syndrome.     

Predictors of left atrial thrombus and spontaneous echo contrast in rheumatic valve disease before and after mitral valve replacement

In this study we aimed to analyze, with reference to mitral regurgitation (MR), the incidence and predictors of left atrial (LA) thrombus and spontaneous echo contrast in patients with rheumatic valve disease before and after mitral valve replacement. The incidence of LA thrombus is known to be less in patients with MR. The impact of mitral valve replacement on this beneficial effect has not been studied in detail. The study included 169 consecutive patients (59 men and 110 women, average age 40 +/- 13 years) with rheumatic mitral valve disease who underwent transesophageal echocardiographic examination 1 to 3 days before and within 7 days (mean 4.0 +/- 1.3) after mitral valve replacement using mechanical prostheses in a single institution. The preoperative incidence of echocardiographic LA spontaneous echo contrast (SEC) was 1.1%, 30%, and 54%, and the incidence of thrombus was 1.1%, 13%, and 17% in the groups with MR, combined mitral stenosis + MR, and isolated mitral stenosis, respectively. In the MR group, SEC and thrombus incidence increased significantly after surgery. The independent predictors for postoperative thrombus development were atrial fibrillation, postoperative SEC, and preoperative thrombus. Thrombus recurred after surgery in 64% of 14 patients who had surgical thrombectomy. The presence of postoperative MR was associated with decreased risk of postoperative SEC and thrombus development. The interaction between MR and SEC and thrombus both before and after surgery provides further support for the protective effect of MR against LA thrombus formation.     

Clinical shock tolerability and effect of different right atrial electrode locations on efficacy of low energy human transvenous atrial defibrillation using an implantable lead system

OBJECTIVES: The objectives of this study were 1) to evaluate the effect of different right atrial electrode locations on the efficacy of low energy transvenous defibrillation with an implantable lead system; and 2) to qualitate and quantify the discomfort from atrial defibrillation shocks delivered by a clinically relevant method. BACKGROUND: Biatrial shocks result in the lowest thresholds for transvenous atrial defibrillation, but the optimal right atrial and coronary sinus electrode locations for defibrillation efficacy in humans have not been defined. METHODS: Twenty-eight patients (17 men, 11 women) with chronic atrial fibrillation (AF) (lasting > or = 1 month) were studied. Transvenous atrial defibrillation was performed by delivering R wave-synchronized biphasic shocks with incremental shock levels (from 180 to 400 V in steps of 40 V). Different electrode location combinations were used and tested randomly: the anterolateral, inferomedial right atrium or high right atrial appendage to the distal coronary sinus. Defibrillation thresholds were defined in duplicate by using the step-up protocol. Pain perception of shock delivery was assessed by using a purpose-designed questionnaire; sedation was given when the shock level was unacceptable (tolerability threshold). RESULTS: Sinus rhythm was restored in 26 of 28 patients by using at least one of the right atrial electrode locations tested. The conversion rate with the anterolateral right atrial location (21 [81%] of 26) was higher than that with the inferomedial right atrial location (8 [50%] of 16, p < 0.05) but similar to that with the high right atrial appendage location (16 [89%] of 18, p > 0.05). The mean defibrillation thresholds for the high right atrial appendage, anterolateral right atrium and inferomedial right atrium were all significantly different with respect to energy (3.9 +/- 1.8 J vs. 4.6 +/- 1.8 J vs. 6.0 +/- 1.7 J, respectively, p < 0.05) and voltage (317 +/- 77 V vs. 348 +/- 70 V vs. 396 +/- 66 V, respectively, p < 0.05). Patients tolerated a mean of 3.4 +/- 2 shocks with a tolerability threshold of 255 +/- 60 V, 2.5 +/- 1.3 J. CONCLUSIONS: Low energy transvenous defibrillation with an implantable defibrillation lead system is an effective treatment for AF. Most patients can tolerate two to three shocks, and, when the starting shock level (180 V) is close to the defibrillation threshold, they can tolerate on average a shock level of 260 V without sedation. Electrodes should be positioned in the distal coronary sinus and in the high right atrial appendage to achieve the lowest defibrillation threshold, although other locations may be suitable for certain patients.     

Echocardiographic factors predicting the maintenance of sinus rhythm one year after cardioversion for non-valvular atrial arrhythmias]

Echocardiographic factors predictive of the maintenance of sinus rhythm after successful cardioversion were investigated in 94 patients with non-valvular atrial arrhythmias of recent onset. Seventy-five patients with atrial fibrillation and 19 with atrial flutter admitted for reduction of their arrhythmias underwent transthoracic and transoesophageal echocardiography. After excluding a thrombus in the left atrial appendage or checking that it had disappeared (5 patients), and electrical (n = 74) or pharmacological (n = 20) cardioversion was successfully performed. The maintenance of sinus rhythm (n = 44) or recurrence of arrhythmia (n = 50) were controlled every 3 months for one year. The mean value of the peak positive blood flow in the left atrial appendage was 38 +/- 20 cm/s for the whole group. It was not possible to identify an echocardiographic parameter predictive of maintenance of sinus rhythm at one year either in the whole group or in the subgroups with atrial flutter or atrial fibrillation. In the group in atrial flutter, the mean value of the peak positive blood flow in the left atrial appendage was significantly greater than in the group with atrial fibrillation: 49 +/- 22 cm/s vs 35 +/- 18 cm/s, respectively; p < 0.05. The peak of positive flow in the left atrial appendage was statistically related to indirect parameters of left atrial function and of left ventricular function in the group with atrial fibrillation but only with parameters of left ventricular function in the smaller group with atrial flutter.     

Atrial vulnerability in patients with paroxysmal "lone" atrial fibrillation

Little is known about the electrophysiological properties of the atrium predisposing to paroxysmal atrial fibrillation (AF), especially in patients without structural heart disease. This study was conducted to analyze intraatrial conduction, atrial refractoriness, and arrhythmia inducibility in patients with lone paroxysmal AF. An electrophysiological study was performed in 24 patients with a documented history of lone paroxysmal AF but in sinus rhythm at the time of the electrophysiological study. Twelve patients without any history of atrial arrhythmias served as controls. The patients with lone paroxysmal AF showed a significant prolonged local conduction time S1A1 (70 +/- 21 ms vs 36 +/- 12 ms, P < 0.0001), a lack of rate adaptation of the functional refractory period (FRP changes/cycle length changes < 10% in 15 of 24 patients with lone paroxysmal AF vs 1/12 controls, P = 0.002) and a higher incidence of inducible AF with only one extrastimulus (13/24 vs 0/12, P = 0.0014). The total P wave duration in the surface ECG (89 +/- 14 ms vs 83 +/- 8 ms, P = 0.15), the intraatrial conduction time (36 +/- 14 ms vs 28 +/- 8 ms, P = 0.07), the presence of a fragmented atrial electrogram (16/24 vs 7/12, P = 0.62), the absolute value of the effective refractory period (204 +/- 28 ms vs 212 +/- 23 ms, P = 0.42), and the vulnerability index (3.0 +/- 1.5 vs 3.6 +/- 1.5, P = 0.26) were not statistically different between the two groups. The presence of a prolonged (> 50 ms) S1A1 and/or the presence of a lack of rate adaptation of the FRP and/or the presence of inducible AF identified patients with spontaneous lone paroxysmal AF with a sensitivity of 96%, a specificity of 67%, a positive predictive value of 85%, and a negative predictive value of 89%. In patients with lone paroxysmal AF, the electrophysiological study using conventional techniques allows not only to detect AF inducibility using a nonaggressive protocol, but also to reveal several electrophysiological abnormalities related to the atrial substrate itself. This atrial vulnerability may explain the high incidence of recurrences in patients with lone paroxysmal AF.     

Effects of left atrial dilatation on the endocardial atrial defibrillation threshold: a study in an ovine model of pacing induced dilated cardiomyopathy

Left atrial (LA) dilation is a common finding in patients with chronic atrial fibrillation (AF). Progressive dilatation may alter the atrial defibrillation threshold (ADFT). In our study, epicardial electrodes were implanted on the LA free wall and right ventricular apex of eight adult sheep. Large surface area, coiled endocardial electrodes were positioned in the coronary sinus and right atrium (RA). LA dilatation was induced by rapid ventricular pacing (190 beats/min) for 6 weeks and echocardiographically assessed weekly along with the ADFT (under propofol anesthesia). LA effective refractory period (ERP) was measured every 2-3 days using a standard extra stimulus technique and 400 ms drive. The AF cycle length (AFCL) was assessed from LA electrograms. During the 6 weeks of pacing the mean LA area increased from 6.1 +/- 1.5 to 21.3 +/- 2.4 cm2. There were no significant changes in the mean ADFT (122 +/- 15 V), circuit impedance (46 +/- 5 omega), or LA AFCL (136 +/- 23 ms). There was a significant increase in the mean LA ERP (106 +/- 10 ms at day 0, and 120 +/- 13 ms at day 42 of pacing). In this study, using chronically implanted defibrillation leads, the minimal energy requirements for successful AF were not significantly altered by ongoing left atrial dilatation. This finding is a further endorsement of the efficiency of the coronary sinus/RA shock vector. Furthermore, the apparent stability of the AF present may be a further indication of a link between the type of AF and the ADFT.     

MR guidance of laser disc decompression: preliminary in vivo experience

BACKGROUND: The mechanism of atrial natriuretic peptide (ANP) release has been difficult to demonstrate in patient studies because of inaccuracies in measuring atrial volumes using conventional techniques. METHODS: Magnetic resonance imaging was performed in 28 clinically stable patients (New York Heart Association class 3) with chronic heart failure to determine right atrial (RA), left atrial (LA), and ventricular volumes. In addition, right heart catheterization was serially performed and plasma ANP levels (in picograms per milliliter) were drawn from the right atrium. RESULTS: Five patients had to be excluded from data analysis for technical reasons. The remaining 23 patients had the following hemodynamic measurements (mean +/- SD): RA mean pressure 7+/-5 mm Hg, pulmonary artery mean pressure 28+/-10, pulmonary capillary wedge pressure 21+/-8 mm Hg, and cardiac index 2.9+/-1.4 (L/min/m2), respectively. Plasma ANP levels were significantly elevated at 162+/-117 (normal range 20 to 65 pg/ml, p < 0.05), as were LA and RA volumes compared with healthy controls (RA volume 128+/-64 ml vs 82+/-25 ml, p < 0.05; LA volume 157+/-54 ml vs 71+/-24 ml, p < 0.01, respectively). ANP showed a stronger relation with atrial volumes (RA volume, r = 0.91, p = 0.0001; LA volume, r = 0.80, p = 0.001) than with atrial pressures (RA mean pressure, r = 0.45, p = 0.03; pulmonary capillary wedge pressure, r = 0.67, p = 0.001). A subgroup analysis of patients with increased RA or LA volumes (>1 SD of mean of controls) revealed a stronger relation between ANP and RA volumes than between ANP and LA volumes. CONCLUSIONS: These data suggest that increased right heart volume with subsequent increased atrial stretch is the major determinant for ANP release in patients with stable CHF.     

Prevention of recurrent atrial fibrillation with chronic dual-site right atrial pacing

OBJECTIVES: We investigated 1) the feasibility, safety and efficacy of multisite right atrial pacing for prevention of atrial fibrillation (AF); and 2) the ability of atrial pacing in single- and dual-site modes to increase arrhythmia-free intervals in patients with drug-refractory AF. BACKGROUND: We recently developed and applied a novel technique of dual-site right atrial pacing in an unselected group of consecutive patients with AF requiring demand pacing. A prospective crossover study design was used to evaluate single- and dual-site right atrial pacing modes. METHODS: The frequency of AF during the 3 months before pacemaker implantation was analyzed. Consecutive consenting patients underwent insertion of two atrial leads and one ventricular lead with a DDDR pulse generator. Patients were placed in a dual-site pacing mode for the first 3 months and subsequently mode switched to single site pacing for 3 months. Mode switching was repeated at 6-month intervals thereafter. RESULTS: Atrial pacing resulted in a marked decline in AF recurrences (p < 0.001). During dual-site pacing with an optimal drug regimen, there was no AF recurrence in any patient compared with five recurrences in 12 patients during single-site pacing (p = 0.03). The mean (+/-SD) arrhythmia-free interval before pacing (14 +/- 14 days) was prolonged with dual- (89 +/- 7 days, p < 0.0001) and single-site pacing (76 +/- 27 days, p < 0.0001). Symptomatic AF episodes showed a declining trend during dual- and single-site pacing compared with those during the preimplantation period (p = 0.10). Mean antiarrhythmic drug use for all classes declined from 4 +/- 1.9 drugs before implantation to 1.5 +/- 0.5 (p < 0.01) drugs after implantation. Twelve (80%) of 15 patients remained in atrial paced rhythm at 13 +/- 3 months. CONCLUSIONS: We conclude that multisite right atrial pacing is feasible, effective and safe for long-term application. Atrial pacing significantly prolongs arrhythmia-free intervals in patients with drug-refractory paroxysmal AF. Dual-site right atrial pacing may offer additional benefits and should be considered either as the primary mode or in patients unresponsive to single-site pacing.     

Spontaneous reinitiation of atrial fibrillation following transvenous atrial defibrillation

Spontaneous reinitiation of atrial fibrillation (AF) has not been systematically looked at in patients undergoing transvenous AF. This study involved 11 patients, the mean age 60 +/- 8 years, 3 male and 8 female, in whom transvenous atrial defibrillation successfully converted AF to sinus rhythm. Eight patients had paroxysmal AF and three patients had chronic persistent AF for 4 weeks or more. Four patients were taking antiarrhythmic medications at the time of testing. Multipolar transvenous catheters were positioned inside the coronary sinus, right atrium, and the right ventricle. Atrial defibrillation testing was performed using the METRIX atrial defibrillation system in nine patients and the Ventritex HVSO2 in the remaining two patients. A total of 64 therapeutic shocks (range 3-11) were delivered in the 11 patients, and 31 of these successfully converted AF to sinus rhythm. In four patients spontaneous AF was reinitiated following 12 successful transvenous atrial defibrillation episodes. The mean time to reinitiation of AF following shock delivery and restoration of sinus rhythm was 8.26 +/- 5.25 seconds, range 1.8-19.9 seconds. All 12 episodes of spontaneous AF were preceded by a spontaneous premature atrial complex. The coupling interval of the premature atrial complexes was 443 +/- 43 ms, range 390-510 ms. None of the patients taking antiarrhythmic medications or those demonstrating no premature atrial complexes had spontaneous reinitiation of AF. In conclusion, spontaneous reinitiation of AF can occur in a significant proportion of patients with AF undergoing transvenous atrial defibrillation. This phenomenon is preceded by the occurrence of atrial premature complex. Findings of this study may have significant clinical implications.     

Pathophysiology and treatment of cardioembolic stroke

To elucidate the pathophysiologic mechanism of cardioembolic stroke in elderly people and to devise therapeutic strategies for it, was analyzed 120 consecutive patients (77 men and 43 women aged 65 +/- 13 years) with acute cardioembolic stroke who were admitted within 7 days of the stroke onset. We compared underlying heart diseases. NIH stroke scale on admission, lesion size on computed tomography (CT), the relation between anticoagulant therapy and recurrence, complications during admission. ADL at discharge, recurrence, and death during the follow up period in three groups: patients aged less than 65 years (the young group), those aged from 65 to 74 years (the "non-old" group), and those aged more than 75 years (the "old old" group). In the "old old" group, non valvular atrial fibrillation (75.8%) was the most common underlying heart disease and so was rheumatic heart disease (33.3%) in the "non-old" group. NIH stroke scale score (median, 11) and the proportion of patients with a large lesion (> 3 cm) of CT were higher in the "old old" group than in the other two groups. Immediate anticoagulation (A/C) within 14 days of onset was performed in more than 70% of the "non-old" and the "young old" groups but in only 57.6% of the "old old" group. Stroke recurred more often in 34 patients who did not receive immediate A/C than in the 86 who did (11.8% v.s. 2.3%. Chi square test, p = 0.053). Hemorrhage during immediate A/C and other complications (infection and pulmonary embolism) were seen in 2 and 14 patients, respectively, in both the "young old" groups, but not in the "non-old" group. Good outcomes (able to walk with or without cane) were more common in the "non-old" group (78.9%) than the other groups (57.1%, Chi square test, p < (0.01). A/C after the acute stage was done in more than 80% of those in the "non-old" and the "young old" groups, but in less than 30% of those in the "old old" group (Chi square test, p = 0.0514). Survival without recurrence during the observation period (605 +/- 550 days) was significantly lower in the "old old" group than in the other two groups (log-rank test, p = 0.0091). Cardioembolic stroke in the elderly may be characterized as follows: (1) non valvular atrial fibrillation is the most common, (2) severe neurologic deficits on admission and large lesions on CT are noted, (3) complications (infection and pulmonary embolism) often occur, (4) A/C in both acute and chronic stages are done infrequently. Therefore, the indication and intensity of A/C for primary and secondary prevention and prevention of complications are important in management of cardioembolic stroke in the elderly.     

Exclusion of atrial thrombus by transesophageal echocardiography does not preclude embolism after cardioversion of atrial fibrillation. A multicenter study

BACKGROUND: Transesophageal echocardiography (TEE) has been used recently to detect atrial thrombi before cardioversion of atrial arrhythmias. It has been assumed that embolic events after cardioversion result from embolism of preexisting atrial thrombi that are accurately detected by TEE. This study examined the clinical and echocardiographic findings in patients with embolism after cardioversion of atrial fibrillation despite exclusion of atrial thrombi by TEE. METHODS AND RESULTS: Clinical and echocardiographic data in 17 patients with embolic events after TEE-guided electrical (n = 16) or pharmacological (n = 1) cardioversion were analyzed. All 17 patients had nonvalvular atrial fibrillation, including four patients with lone atrial fibrillation. TEE before cardioversion showed left atrial spontaneous echo contrast in five patients and did not show atrial thrombus in any patient. Cardioversion resulted in return to sinus rhythm without immediate complication in all patients. Thirteen patients had cerebral embolic events and four patients had peripheral embolism occurring 2 hours to 7 days after cardioversion. None of the patients were therapeutically anticoagulated at the time of embolism. New or increased left atrial spontaneous echo contrast was detected in four of the five patients undergoing repeat TEE after cardioversion including one patient with a new left atrial appendage thrombus. CONCLUSIONS: Embolism may occur after cardioversion of atrial fibrillation in inadequately anticoagulated patients despite apparent exclusion of preexisting atrial thrombus by TEE. These findings suggest de novo atrial thrombosis after cardioversion or imperfect sensitivity of TEE for atrial thrombi and suggest that screening by TEE does not obviate the requirement for anticoagulant therapy at the time of and after cardioversion. A randomized clinical trial is needed to compare conventional anticoagulant management with a TEE-guided strategy including anticoagulation after cardioversion.