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At least 235 records · Page 13Linked to original sources

Left atrial appendage function during DDD and VVI pacing.

OBJECTIVE: To examine, using transoesophageal echocardiography, the possible disturbances of left atrial appendage function during VVI and DDD pacing in patients with a normal atrium paced with a dual chamber system. DESIGN: Randomised controlled trial. SETTING: Tertiary care centre. PATIENTS: 22 patients (mean age 68 (SD 6) years) who had been paced with dual chamber pacemakers for at least six months. Exclusion criteria were valvar disease, cardiomyopathy, hypertension, and diabetes mellitus. INTERVENTIONS: All patients underwent a transoesophageal echocardiographic evaluation of left atrial appendage function under DDD and VVI modes in random order. Measurements were made after at least two months' pacing in each mode. MAIN OUTCOME MEASURES: Echocardiographic indices of left atrial appendage flow under both pacing modes. RESULTS: All 22 patients had higher emptying and filling flow velocities under DDD than under VVI mode. The filling and emptying flow velocity integrals were also significantly higher under DDD mode (P < 0.001, P = 0.019). CONCLUSIONS: Left atrial appendage function, as reflected in indices of emptying and filling assessed by transoesophageal echocardiography, is significantly different with DDD than with VVI pacing. This may explain the higher incidence of thromboembolic episodes in patients paced under VVI mode.

Aged↗

Left atrial mechanical function in patients with essential hypertension.

OBJECTIVE: This study was carried out to assess the left atrial (LA) mechanical function in patients with essential hypertension with two-dimensional echocardiography by means of left atrial volume measurements. METHODS: LA volumes were measured echocardiographically in 36 untreated hypertensive patients and 20 age-sex-matched healthy controls according to biplane area-length method. LA volume measurements were done at the time of mitral valve opening (Vmax), at the onset of atrial systole (p wave at the electrocardiography = Vp) and at closure (Vmin). All volumes were indexed for body surface area, and the following left atrial emptying functions were calculated: LA passive emptying volume = Vmax -Vp, LA passive emptying fraction = LA passive emptying volume /Vmax, conduit volume = left ventricular stroke volume-(Vmax-Vmin), LA active emptying volume = Vp-Vmin, LA active emptying fraction = LA active emptying volume /Vp, LA total emptying volume = (Vmax-Vmin), LA total emptying fraction = LA total emptying volume /Vmax. RESULTS: Vmax (p < 0.01),Vmin (p < 0.005) and Vp (p < 0.001) were significantly greater in hypertensives than in controls. Although LA passive emptying volume (p < 0.001), LA passive emptying fraction (p < 0.001), conduit volume (p < 0.005) and LA total emptying fraction (p < 0.05) were found to be significantly lower in hypertensives than in controls, LA active emptying volume (p < 0.001) and LA active emptying fraction (p < 0.01) were found to be significantly greater in hypertensives than in controls. LA total emptying volume (p > 0.05) was similar in both groups. CONCLUSION: The results of the present study indicate that chronic hypertension is associated with an increased in left atrial volumes, a decrease in left atrial passive emptying function, and an increase systolic pump function. Increased left atrial pump function represents a compensatory mechanism in hypertensive patients with left ventricular hypertrophy.

Adult↗

Left atrial size after cardioversion for atrial fibrillation: effect of external direct current shock.

OBJECTIVE: The aim of this study was to evaluate the effect of external direct current (DC) shock on left atrial (LA) dimension and volumes after cardioversion for atrial fibrillation, and the relation between LA size and atrial function. METHODS: We evaluated 180 patients who were randomly cardioverted with DC shock (90 patients) or drugs (90 patients). Echocardiographic evaluations included LA size and volumes. LA passive and active emptying volumes were calculated, and LA function was measured as atrial ejection force. Changes in LA diameters and volumes were correlate with atrial systolic function. RESULTS: The LA was dilated in all patients during arrhythmia and decreased after the restoration of sinus rhythm. The entity of reduction was different in the 2 groups of patients. LA maximal and minimal volumes were increased after DC shock as compared with patients treated with drugs (LA maximal volume 34 +/- 4 vs 31 +/- 5; P <.01; LA minimal volume 18 +/- 2.6 vs 15 +/- 3.6; P <.01). The atrial function was also depressed after DC shock and the delay in the recovery of atrial contractility was related to LA dilation. Patients treated with drugs had a higher atrial ejection force that was associated with a more marked reduction in LA maximal volume after the restoration of in sinus rhythm. A relationship between LA volumes and atrial ejection force was observed in the group of patients with depressed atrial mechanic function (r = -0.78; P <.001). The active emptying fraction was lower, although not significantly, in this group, whereas the conduit volume was increased. CONCLUSION: External DC shock induced a depressed atrial mechanic function in many patients and this was associated with a persistence of LA dilation.

Adult↗

Assessment of left atrial appendage function and its relationship to pulmonary venous flow pattern by transesophageal echocardiography.

We evaluated left atrial appendage function and its relationship to pulmonary venous flow in 53 patients divided into four groups. Group 1 consisted of 10 normal subjects. Group 2 included 15 patients with significant pure mitral stenosis in sinus rhythm. In group 3, there were 13 patients with pure significant mitral stenosis and atrial fibrillation. Group 4 consisted of 15 patients with normal mitral valve and atrial fibrilltion. We found significant decrease in left atrial appendage ejection fraction and maximum emptying flow velocity, velocity time integral of systolic pulmonary venous flow in Groups 2, 3 and 4 in comparison with normal subjects. Systolic pulmonary venous flow velocity was significantly decreased in Groups 3 and 4. There was significant correlation between left atrial appendage ejection fraction and peak emptying flow velocity (r = 0.62, P < 0,001). Systolic peak pulmonary venous flow velocity was significantly correlated with left atrial appendage ejection fraction and maximum emptying flow velocity (r = 0.67, P = 0,01; r = 0.58, P < 0,001, respectively). There was also significant correlation between systolic pulmonary venous flow velocity time integral and left atrial appendage ejection fraction (r = 0.66, P = 0.001). When normals were excluded from analysis, all the correlations were still significant. We concluded that left atrial appendage is a contractile structure, and that systolic pulmonary venous flow velocity is influenced by left atrial appendage dysfunction. Therefore left atrial appendage function needs to be considered when interpreting Doppler transmitral and systolic pulmonary venous flow patterns.

Adult↗

Effects of different atrioventricular intervals during dual-site right atrial pacing on left atrial mechanical function.

Recent studies have suggested that dual-site right atrial (RA) pacing via the high RA and coronary sinus ostium (CSos) prevents atrial fibrillation (AF). However, the programming of the atrioventricular (AV) interval associated with optimal left atrial (LA) mechanical function during high RA and dual-site RA pacing has not been defined. LA mechanical function was studied by measuring transmitral pulsed Doppler echocardiographic peak A wave velocity and percent A wave filling, in six women and three men, 67 +/- 8 years of age, who had received dual-site RA pacemakers in a randomized study. Serial echocardiographic measurements were performed during high RA or dual-site RA pacing at 80 beats/min with AV intervals of 50, 100, 150, or 200 ms tested in random order. High RA and dual-site RA pacing at an AV interval of 50 ms were associated with significantly lower peak A wave velocity and percent A wave filling, compared to the other AV intervals (all P < 0.05). Compared with high RA pacing, dual-site RA pacing was associated with significantly higher peak A wave velocity (85 +/- 12 vs 72 +/- 17 cm/s, P = 0.04) and percent A wave filling (24 +/- 3 vs 20 +/- 4%, P = 0.02) at an AV interval of 100 ms, but a lower peak A wave velocity at an AV interval of 200 ms (77 +/- 10 vs 84 +/- 8 cm/s, P = 0.004). In conclusion, variations in the AV interval during atrial pacing have significant effects on LA function. As a consequence of altered atrial activation, the AV interval associated with optimal LA mechanical function during dual-site RA pacing was significantly shorter than that during RA pacing. This observation has important implications with respect to the programming of dual-site RA pacemakers implanted to prevent AF for hemodynamic purpose.

Aged↗

[Restoration of the left atrial mechanical function after successful electrical cardioversion].

Some papers indicate that restoration of the left atrial mechanical function (LAMF) can be delayed to even 7 days after successful electrical cardioversion. The goals of the paper include the estimation of delay in restoration of LAMF and factors that influence it. 75 patients (53 males and 22 females, av. age 56.5 +/- 10.8) after elective electrical cardioversion underwent daily echocardiography to determine LAMF, taking A/E ratio > 1/3 as a criterion. The patients were divided into 2 subgroups: G1--with restoration of LAMF < 24 h after cardioversion and G2: the remaining ones. The analysed parameters were: left atrium diameter, rheumatic valvular disease, duration of atrial fibrillation, global and segmental contractility disorders. The data were analysed with ANOVA. The restoration of LAMF < 24 h was found in 53 patients; on the 2nd day in 6 patients, on the 3rd-8th day in 14 patients. In 2 patients no LAMF could be found on the 14th day after cardioversion. Failure to restore LAMF on the cardioversion day was related to: left atrium enlargement, rheumatic valvular disease, duration of atrial fibrillation > 14 days and contractility disorders.

Atrial Fibrillation↗

Mechanical hyperventilation: effect on specialized atrioventricular conduction, supraventricular refractoriness, and experimental atrial arrhythmias in dogs anesthetized with pentobarbital or pentobarbital-halothane.

The effect of hypocapnia (PCO2ET 25 vs 40 torr) on specialized atrioventricular (AV) conduction, supraventricular refractory periods, and experimental atrial arrhythmias provoked by premature atrial stimulation (atrial echoes-echoes, repetitive atrial firing (RAF)) was assessed in dogs anesthetized with pentobarbital or pentobarbital-halothane (1.0% end-tidal). Catheter His bundle electrocardiography was used. Both hypocapnia and halothane prolonged AV nodal conduction, but the effect of halothane was more pronounced. Halothane prolonged the atrial functional (AtFRP), atrial effective (AtERP), and AV nodal functional refractory (AVFRP) periods. These effects of halothane were linked to an increased incidence of RAF but not to echoes. Hypocapnia prolonged the AVFRP (less than halothane), had no effect on the AtFRP and shortened the AtERP. These effects of hypocapnia were associated with an increased incidence of echoes, but not with RAF. Echoes and RAF are thought to be caused by reentry within the sinus node, atria, and AV node. The differing effects of halothane and hypocapnia on the incidence of these arrhythmias may be due to differning effects on supraventricular refractoriness.

Anesthesia↗

Stroke in paced patients with sick sinus syndrome: relevance of atrial mechanical function, pacing mode and clinical characteristics.

Patients with sick sinus syndrome have a high prevalence of cerebral ischemia and emboli of the viscera and extremities. The present study was designed to establish the prevalence of stroke in patients with sick sinus syndrome, with specific attention to pacing mode, atrial function (evaluated using Doppler echocardiography) and the clinical condition of the patients. The prospective study analyzed 80 consecutive patients with sick sinus syndrome who received either atrial, dual chamber or ventricular pacemakers. Patients underwent a cranial CT scan at the time of enrollment and again at the end of the study 24 months later. End points of the study were cerebral ischemia or emboli of the viscera or extremities. Clinical and echocardiographic features were assessed at the beginning of the study. A multivariate regression analysis was applied to all variables that had at least a marginal univariate predictive value. Cerebral ischemia occurred in 13 patients and emboli of the viscera or extremities were observed in 2 patients. Univariate predictors for embolism consisted of a prior history of cerebrovascular disease (p < 0.001), low atrial ejection force (p < 0.01) and a dilated left atrium with spontaneous echo contrast (p < 0.05). Independent risk factors for stroke included a history of previous cerebral ischemia, age > 65 years, left atrial echo contrast on an echocardiogram and a depressed atrial ejection force. These findings identified patients at high risk for the development of peripheral embolism among the group of patients paced for sick sinus syndrome.

Adolescent↗

Intracellular pH regulatory mechanism in human atrial myocardium: functional evidence for Na(+)/H(+) exchanger and Na(+)/HCO(3)(-) symporter.

Intracellular pH (pH(i)) exerts considerable influence on cardiac contractility and rhythm. Over the last few years, extensive progress has been made in understanding the system that controls pH(i) in animal cardiomyocytes. In addition to the housekeeping Na(+)-H(+) exchanger (NHE), the Na(+)-HCO(3)(-) symporter (NHS) has been demonstrated in animal cardiomyocytes as another acid extruder. However, whether the NHE and NHS functions exist in human atrial cardiomyocytes remains unclear. We therefore investigated the mechanism of pH(i) recovery from intracellular acidosis (induced by NH(4)Cl prepulse) using intracellular 2',7'-bis(2-carboxethyl)-5(6)-carboxy-fluorescein fluorescence in human atrial myocardium. In HEPES (nominally HCO(3)(-)-free) Tyrode solution, pH(i) recovery from induced intracellular acidosis could be blocked completely by 30 microM 3-methylsulfonyl-4-piperidinobenzoyl, guanidine hydrochloride (HOE 694), a specific NHE inhibitor, or by removing extracellular Na(+). In 3% CO(2)-HCO(3)(-) Tyrode solution, HOE 694 only slowed the pH(i) recovery, while addition of HOE 694 together with 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (an NHS inhibitor) or removal of extracellular Na(+) inhibited the acid extrusion entirely. Therefore, in the present study, we provided evidence that two acid extruders involved in acid extrusion in human atrial myocytes, one which is HCO(3)(-) independent and one which is HCO(3)(-) dependent, are mostly likely NHE and NHS, respectively. When we checked the percentage of contribution of these two carriers to pH(i) recovery following induced acidosis, we found that the activity of NHE increased steeply in the acid direction, while that of NHS did not change. Our present data indicate for the first time that two acid extruders, NHE and NHS, exist functionally and pH(i) dependently in human atrial cardiomyocytes.

Fluoresceins↗

Discrimination between ventricular and supraventricular tachycardia by dual chamber cardioverter defibrillators: importance of the atrial sensing function.

Although the addition of atrial sensing in dual chamber ICDs may improve the ability of the device to discriminate between supraventricular (SVT) and ventricular tachycardia (VT), atrial sensing errors may also negatively affect tachycardia classification. This prospective study evaluated the incidence of atrial sensing errors in a dual chamber ICD and their impact on VT/SVT discrimination. In 145 patients, a dual chamber ICD (Defender) was implanted. Analysis of 1,241 tachycardia episodes stored during a mean follow-up of 14+/-8 months revealed atrial sensing errors in 817 (66%) episodes. Upon expert review, device-based classification was confirmed in 509 (98%) of 522 SVT episodes. No false device-based SVT classification was related to atrial sensing errors. Of 719 episodes classified as VT by the device, 645 (90%) were confirmed. There were 74 episodes of false-positive VT detection. Of these, 63 were related to atrial sensing errors: atrial undersensing in 58 (92%) and atrial oversensing in 5 (8%) episodes. Atrial sensing errors led to incorrect VT/SVT discrimination in 51 (4%) of 1,241 episodes. Only the occurrence of paroxysmal atrial fibrillation and abdominal site of device implantation showed a significant influence on false VT/SVT discrimination. Atrial sensing errors are frequently encountered in dual chamber ICDs. Due to the VT/SVT discrimination algorithm, atrial sensing errors only led to misclassification in 4 % of all episodes, mainly due to atrial undersensing. No VT underdetection due to atrial oversensing occurred.

Algorithms↗

Fast algorithms for the analysis of sino-atrial node function.

The calculations of parameters of the sino-atrial node function have previously required the application of a non-linear least squares curve-fitting algorithm. We have compared five algorithms, three of which eliminate the need for direct non-linear least squares routines. The fast algorithms can provide greater accuracy while using less than 10% of the computing time. They make it feasible to provide real-time analysis during clinical electrophysiological studies.

Arrhythmias, Cardiac↗

Evaluation of left atrial appendage function by measurement of changes in flow velocity patterns after electrical cardioversion in patients with isolated atrial fibrillation.

We investigated temporary changes in left atrial appendage (LAA) flow velocity patterns in patients undergoing electrical cardioversion for chronic isolated atrial fibrillation, and evaluated the role of active LAA contraction in directing blood flow to the left atrial main chamber and left ventricle. The study consisted of 26 patients with chronic isolated atrial fibrillation treated with electrical cardioversion and 20 normal controls in sinus rhythm. Using transthoracic and transesophageal Doppler echocardiography, we recorded transmitral, pulmonary venous, and LAA flow velocity patterns before, 24 hours, and 1 week after cardioversion in all subjects. In the 15 patients who underwent successful cardioversion, the maximal LAA area 24 hours after cardioversion was smaller than the area before cardioversion, whereas LAA ejection fraction during atrial systole and peak atrial systolic emptying velocity of the LAA flow were lower 24 hours after cardioversion than those in the control group. One week after cardioversion, maximal LAA area and LAA peak atrial systolic emptying velocity were restored to levels approximately equivalent to those in the control group, although LAA ejection fraction was lower than in the control group. Maximal LAA area and LAA peak atrial systolic emptying velocity correlated negatively and positively with LAA ejection fraction, respectively, 24 hours and 1 week after cardioversion. These results suggest that LAA and the left atrial main chamber show stunning 24 hours after cardioversion, and the atrial systolic emptying wave of LAA flow is generated by active LAA contraction.

Adult↗

Imaging of thrombi and assessment of left atrial appendage function: a prospective study comparing transthoracic and transoesophageal echocardiography.

OBJECTIVE: To compare the value of current transthoracic echocardiographic systems and transoesophageal echocardiography for assessing left atrial appendage function and imaging thrombi. DESIGN: Single blind prospective study. Patients were first investigated by transthoracic echocardiography and thereafter by a second investigator using transoesophageal echocardiography. The feasibility of imaging the left atrial appendage, recording its velocities, and identifying thrombi within the appendage were determined by both methods. PATIENTS: 117 consecutive patients with a stroke or transient neurological deficit. SETTING: Tertiary cardiac and neurological care centre. RESULTS: Imaging of the complete appendage was feasible in 75% of the patients by transthoracic echocardiography and in 95% by transoesophageal echocardiography. Both methods were concordant for the detection of thrombi in 10 cases. Transoesophageal echocardiography revealed two additional thrombi. In one of these patients, transthoracic echocardiography was not feasible and in the other the thrombus had been missed by transthoracic examination. In patients with adequate transthoracic echogenicity, the specificity and sensitivity of detecting left atrial appendage thrombi were 100% and 91%, respectively. Recording of left atrial appendage velocities by transthoracic echocardiography was feasible in 69% of cases. None of the patients with a velocity > 0.3 m/s had left atrial appendage thrombi. In the one patient in whom transthoracic echocardiographic evaluation missed a left atrial appendage thrombus, the peak emptying velocity of the left atrial appendage was 0.25 m/s. CONCLUSIONS: A new generation echocardiographic system allows for the transthoracic detection of left atrial appendage thrombi and accurate determination of left atrial appendage function in most patients with a neurological deficit.

Adult↗

Surgery for supraventricular tachycardia.

1995 is the fifth anniversary of the advent of catheter ablation for the treatment of supraventricular tachycardia. Surgery has established the principles of the interventional approaches: 1) identification of the mechanism; 2) localization of the site of the mechanism; 3) identification of the anatomical arrhythmogenic substrate and its localization using preoperative and intraoperative electrophysiological cardiac mapping; 4) ablation of the arrhythmogenic substrate using "surgical" dissection or excision or various forms of energy to neutralize the substrate: cryoablation, laser, etc. Surgical approaches also established the EP interventions as the first line of therapy because they are curative. Currently, surgery for supraventricular tachycardia is essentially confined to atrial fibrillation, and after attempted catheter ablation for the Wolff-Parkinson-White syndrome. Atrial fibrillation is a complex arrhythmia, commonly associated with structural heart disease. To understand atrial fibrillation, a number of premises should be reviewed: atrial functional anatomy, atrial pathology, atrial fibrillation mechanism (s) and clinical presentation. The role of atrial fibrillation in terms of symptoms, morbidity and mortality is not clear because it is difficult to determine if atrial fibrillation is a symptom, a marker, an autonomous disease albeit it is in most cases an aggravating factor. Surgical rationales for atrial fibrillation are based on three concepts: exclusion, fragmentation and channelling. The Corridor operation was the first used direct surgical approach. The Maze operation and other techniques (fragmentation, spiral) have been reported. All surgical techniques have been reported with good results in terms of sinus node function and exercise tolerance, and to various degrees, in terms of atrial contraction. Currently, there is a trend to combine direct atrial fibrillation surgery with surgery for mitral valve albeit beneficial effects are not documented.

Atrial Fibrillation↗

[Study of spontaneous echo contrast in patients with rheumatic mitral stenosis by transesophageal echocardiography].

Spontaneous echo contrast (SEC) is common in the areas of slow blood flow. This study was conducted to examine the correlation of SEC and left atrial appendage function, atrial fibrillation (Af) and thrombus in patients with rheumatic mitral stenosis. The transthoracic and multiplane transesophageal echocardiograms were performed on 117 patients(mean age 42.22 +/- 10.79 years). Left atrial size, left atrial appendage area, mitral valve area, left atrial appendage flow peak emphatic velocity and full velocity were measured. The presence of SEC and thrombus in the left atrium and appendage was noted. The results showed that among the patients, 57 had normal sinus rhythm, 60 had Af; 19 had thrombus, 98 had no thrombus; 71 had SEC and 46 had no SEC. Compared with the patients without SEC, the patients with SEC showed greater incidence of thrombus (28.76% vs 0, P < 0.05), higher rate of Af (69.01% vs 23.91%, P < 0.05), larger LAD (46.93 +/- 0.85 mm vs. 41.76 +/- 1.05 mm, P < 0.05), larger LAA area (8.06 +/- 0.32 cm2 vs 6.92 +/- 0.31 cm2, P < 0.05), smaller MVA area (1.07 +/- 0.23 cm2 vs 1.32 +/- 0.35 cm2, P < 0.05), lower LAA flow peak emphatic velocity (0.17 +/- 0.01 m/s vs 0.32 +/- 0.02 m/s, P < 0.05), and lower LAA full velocity (0.18 +/- 0.01 m/s vs 0.31 +/- 0.03 m/s, P < 0.05). These findings indicate that the presence of SEC is associated with significantly greater incidence of thrombus, higher rate of Af, larger LAD and LAA area, smaller MVA area, lower LAA flow peak emphatic velocity and full velocity. Atrial fibrillation, the diameter of left atrium and the area of mitral valve are independent predictors of SEC. SEC is significantly associated with LAA function and thrombus formation.

Adolescent↗

Left atrial appendage function in patients with mitral stenosis in sinus rhythm.

AIMS: Left atrial appendage thrombi are believed to be the source of embolism in patients with rheumatic mitral stenosis in atrial fibrillation. There are a few studies which search the effects of left atrial appendage dysfunction in patients with mitral stenosis in sinus rhythm. METHODS AND RESULTS: Left atrial appendage function and flow patterns in 41 patients with rheumatic mitral stenosis in sinus rhythm and 11 healthy subjects were studied by transoesophageal echocardiography. Left atrial appendage flow profiles were recorded within the proximal third of the appendage. The left atrial appendage ejection fraction was expressed as (maximal area of appendage minimal area of appendage)/maximal area of appendage. In addition, two-dimensional imaging was used to determine the presence of spontaneous echocardiographic contrast and thrombus formation. Patients with mitral stenosis in sinus rhythm had significantly decreased left atrial appendage emptying and filling velocities compared to controls (0.40+/-0.15m/s vs 0.82+/-0.19 m/s and 0.42+/-0.21 m/s vs 0.68+/-0.28, respectively, P<0.001 and P<0.05). Compared with the control subjects, patients with mitral stenosis had significantly greater maximal area of the appendage and had reduced left atrial appendage ejection fraction (5.3+/-2.2 cm(2) vs 2.4+/-0.5 cm(2) and 50+/-16% vs 70+/-7%, respectively, P<0.001 and P<0.05). Of the patients with mitral stenosis in sinus rhythm, seven patients had spontaneous echocardiographic contrast and one of these had left atrial appendage thrombus. Compared with patients without spontaneous echocardiographic contrast, patients with spontaneous echocardiographic contrast had decreased left atrial appendage ejection fraction (33+/-21% vs 54+/-13%,P <0.01). One of the patients with mitral stenosis had central retinal artery occlusion, but thrombus was not observed in left atrial appendage. CONCLUSION: The study found that left atrial appendage dysfunction may occur in patients with mitral stenosis in sinus rhythm.

Adult↗