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PubMed1999

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.

Atrial Appendage↗
PubMed2001

Conduction left-to-right and right-to-left across the crista terminalis.

A line of block between the vena cava and the crista terminalis (CT) region is important for atrial flutter (AFL), but whether it is fixed or functional is controversial. To test the hypothesis that conduction across the CT normally occurs, but when block occurs in this region it is functional, we analyzed atrial activation during right and left atrial pacing (cycle lengths of 500--130 ms), AFL, and atrial fibrillation in 15 dogs with sterile pericarditis and 7 normal dogs. Electrograms from 396 right, left, and septal atrial sites were simultaneously recorded. Activation across the CT occurred during atrial pacing, AFL, and atrial fibrillation. Activation wave fronts from the right to the left atrium and vice versa traveled over several routes, including Bachmann's bundle and inferior to the inferior vena cava, as well as across the CT. In these models, there is no fixed conduction block across the CT, and when block in the CT region occurs, as during AFL, it is functional.

Animals↗
PubMed2000

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).

Aged↗
PubMed2006

Relationship between left atrial and left ventricular function in hypertrophic cardiomyopathy: a real-time 3-dimensional echocardiographic study.

BACKGROUND: Left atrium (LA) in patients with hypertrophic cardiomyopathy (HC) has been known to have an increased size and decreased contractile function. The purpose of this study was to investigate LA and left ventricular (LV) volume change and function with real-time 3-dimensional (3D) echocardiography and to investigate association between LA and LV function in HC. METHODS: We performed real-time 3D echocardiography on 26 patients with HC and on 15 control subjects. LA and LV time-volume curves were obtained from real-time 3D echocardiography and the maximal slope of the time-volume curve was expressed as dV/dt. LA active emptying fraction was calculated as: [(precontraction LA volume - minimal LA volume)/precontraction LA volume] x 100. RESULTS: The maximal LA volume index was larger, and LA active emptying fraction was lower, in those with HC than control subjects (50.1 +/- 15.9 vs 30.1 +/- 6.8 mL/m(2) and 33.3 +/- 13.7 vs 40.4 +/- 8.6%, both P< .05). LA active emptying fraction showed a negative correlation with precontraction LA volume (r = -0.64, P < .01) in HC. Patients with HC showed decreased LV early diastolic dV/dt compared with control subjects (0.10 +/- 0.05 vs 0.14 +/- 0.04 mL/ms, P < .05). LA passive and active emptying dV/dt were correlated with LV early and late diastolic dV/dt, respectively (r = 0.47 and r = 0.48, both P < .05). CONCLUSION: Our 3D echocardiographic study showed that increased LA volume was related to decreased LA contraction in HC. LA passive emptying was related to LV relaxation whereas LA active contraction was related to LV stiffness.

Adult↗
PubMed2002

High plasma brain natriuretic polypeptide level as a marker of risk for thromboembolism in patients with nonvalvular atrial fibrillation.

BACKGROUND AND PURPOSE: Assessment of left atrial appendage (LAA) function with transesophageal echocardiography is useful for detecting patients at high risk for thromboembolism as a result of atrial fibrillation (AF). A recent study reported that the atrium is the main source of brain natriuretic polypeptide (BNP) in AF patients without overt heart failure. The purpose of this study was to assess a possible relationship between LAA function and plasma BNP levels in nonvalvular AF. METHODS: Thirty-four consecutive patients with chronic nonvalvular AF (age, 69+/-9 years) underwent transesophageal echocardiography and plasma BNP measurement. Thirteen patients with a history of thromboembolism or echocardiographic evidence of thrombus (E + group) were compared with 21 AF patients without complications (E- group). RESULTS: The E+ group patients demonstrated greater impairment of LAA velocity and higher plasma BNP levels than the E- group patients (LAA velocity: 12+/-6 versus 31+/-17 cm/s, P<0.05; plasma BNP: 126+/-53 versus 86+/-45 ng/L, P<0.05). Overall analysis of the continuous variables with multiple logistic regression analysis revealed that BNP was a significant predictor of thromboembolism. There was a weak but significant negative correlation between plasma BNP levels and LAA flow velocity (r=0.38, P<0.05). No intergroup difference in plasma atrial natriuretic polypeptide levels was found. CONCLUSIONS: The present data suggest the usefulness of measuring plasma BNP levels, which may reflect augmented atrial secretion of BNP from the impaired atrial myocardium, in detecting patients at high risk for thromboembolic complications in nonvalvular AF.

Adult↗
PubMed1996

Left atrial enlargement in healthy obese: prevalence and relation to left ventricular mass and diastolic function.

BACKGROUND: Left atrial (LA) enlargement has been reported in the obese. However, its prevalence in the healthy obese, clinical correlates and relation to left ventricular (LV) mass and diastolic function have been little investigated. METHODS: Thirty-five consecutive, healthy, normotensive obese (body mass index greater than 28, mean +/- SD 34.2 +/- 2.3 kg/m2) and 35 nonobese subjects (body mass index 24.6 +/- 2.3 kg/m2) comparable in age and sex underwent echocardiographic measurements of LA posteroanterior (parasternal view), mediolateral and superoinferior (apical views) dimensions, aortic root diameter, LV mass and Doppler assessment of LV diastolic function. LA enlargement was defined as a posteroanterior dimension greater than 40 mm. A ratio of LA posteroanterior dimension to aortic root diameter greater than 1.4 was used as an index for disproportionate LA enlargement. RESULTS: LA enlargement was more frequent in the obese than in the nonobese (37% versus 6%, P<0.0001). Similarity, disproportionate LA enlargement was more frequent in the obese (34% versus 6%, P<0.0001). LA posteroanterior dimension correlated well with body mass index (r=0.52, P<0.0001) and LV mass (r=0.56, P<0.0001), and weakly with blood pressure (r=0.28, P<0.02). There was no significant correlation with LV diastolic function, age or sex. In multivariate analysis (multiple r=0.61, P<0.0001), LA posteroanterior dimension correlated significantly only with mass (P<0.005), and the association with body mass index and blood pressure became nonsignificant. Similar results were obtained when LA posteroanterior dimension was replaced with mediolateral or superoinferior dimensions. CONCLUSIONS: LA enlargement is frequent in the normotensive, otherwise healthy obese and correlates well with LV mass. It is not mediated through impairment of LV diastolic function, and likely reflects a physiological adaptation of the heart to the obese state. Further studies are needed to determine whether LA enlargement in the obese is associated with adverse long term outcome.

Adult↗
PubMed1993

On-line assessment of left atrial area and function by echocardiographic automatic boundary detection.

BACKGROUND: Direct assessment of left atrial (LA) function has not been previously performed by noninvasive techniques; rather, LA function has been evaluated only indirectly via the analysis of transmitral flow velocity by Doppler. The recent development of real-time two-dimensional echocardiographic automatic boundary detection suggests that LA dimensions can be measured instantaneously to provide on-line assessment of its systolic and diastolic functions. METHODS AND RESULTS: We performed echocardiographic assessment of LA dimensions and function with automatic boundary detection in 45 patients by using the apical four-chamber view. Thirty-seven patients had structural or functional cardiac abnormalities, 35 patients were in sinus rhythm, and 10 patients had atrial fibrillation. Moderate to severe mitral regurgitation (MR) was noted in 16 patients. We also studied 10 control subjects to assess normal values of LA cavity area and indexes of function. From the instantaneously derived LA area, we derived indexes of systolic atrial expansion and diastolic atrial emptying. There were excellent correlations between the on-line-derived LA areas and those measured off line from videotaped images of conventional echocardiography (r = .91 for end-diastolic and .93 for end-systolic areas; SEE, 4.0 and 3.8 cm2, respectively). Patients in atrial fibrillation had depressed diastolic emptying index (0.17 +/- 0.05) compared with those in sinus rhythm (0.28 +/- 0.12; P < .02). Furthermore, patients with chronic MR exhibited larger LA cavity areas and depressed systolic and diastolic LA function as compared with those without MR. In addition, the Doppler-determined mitral E/A ratio was related to the ratio of early diastolic-to-late diastolic change in LA cavity area (r = .79; SEE 0.6; n = 35). CONCLUSIONS: Instantaneous LA cavity area measurement by echocardiographic automatic boundary detection is accurate and feasible in patients with diverse cardiac disorders. Patients with atrial fibrillation had a depressed diastolic emptying index and those with significant mitral regurgitation had depressed systolic expansion index as well. LA functional indexes in both systole and diastole can be derived providing an approach for quantitative evaluations of left atrial-left ventricular interactions based on geometric assessment noninvasively.

Atrial Fibrillation↗
PubMed1998

Clinical and echocardiographic features influencing recovery of atrial function after cardioversion of atrial fibrillation.

Atrial mechanical dysfunction after cardioversion for atrial fibrillation has been widely evaluated in recent years. Nevertheless, the influence of many clinical and echocardiographic parameters is not yet understood. The aim of the present study was to evaluate the influence of clinical and echocardiographic parameters on the return of effective atrial contraction. A total of 109 patients were evaluated: 41 patients had spontaneous recovery of sinus rhythm and 68 patients were randomly treated using either direct-current (DC) shock or intravenous procainamide. Elective cardioversion was accomplished pharmacologically in 23 patients (67%) and with DC shock in 29 patients (85%). Patients underwent a complete echocardiographic examination 1 hour after the restoration of sinus rhythm and after 1 and 7 days and 1 month. The following parameters were evaluated: patient age, cardiac disease, duration and etiology of atrial fibrillation, mode of cardioversion, left ventricular diameters and function, and left atrial diameter and function assessed as atrial ejection force. The relation between these variables and atrial ejection force was tested. Atrial ejection force was greater immediately and 24 hours after cardioversion in patients who had spontaneous recovery of sinus rhythm and in patients treated with drugs than in patients treated with DC shock. The mode of cardioversion was significantly associated with the recovery of atrial mechanical function by day 1 in univariate and multivariate analyses (odds ratio 0.14; 95% confidence interval 0.02 to 1.2). The other variable associated with the recovery of function was normal left atrial size (odds ratio 0.16; 95% confidence interval 0.12 to 1.6). In conclusion, atrial ejection force is a noninvasive parameter that can be easily measured and can provide accurate information about the recovery of left atrial mechanical function. The recovery of atrial function was influenced by the mode of cardioversion and the size of the left atrium.

Aged↗
PubMed2003

Concomitant recovery of atrial mechanical and endocrine function after cardioversion in patients with persistent atrial fibrillation.

OBJECTIVES: The purpose of this study was to evaluate left atrial mechanical function recovery and plasma atrial natriuretic peptide (ANP) release following successful cardioversion of persistent atrial fibrillation (AF). BACKGROUND: Atrial fibrillation is characterized by functional deterioration, loss of atrial contraction, and elevation of plasma ANP levels. The response of ANP release toward atrial mechanical function after cardioversion of AF has not been fully examined. METHODS: We examined 29 patients with successfully cardioverted persistent AF in whom sinus rhythm was maintained for at least 30 days after cardioversion. We assessed mechanical function of the left atrium at 24 h and 7 and 30 days after cardioversion and evaluated plasma ANP level at the same time. Atrial mechanical function was assessed during echocardiographic examination by means of the peak velocity of the transmitral A-wave, early transmitral to atrial flow velocity ratio, and atrial filling fraction (AFF). The plasma ANP level was determined by the radioimmunoassay method. RESULTS: Plasma ANP levels were significantly reduced from 59.4 +/- 16.6 pg/ml to 31.1 +/- 9.2 pg/ml at 24 h after successful cardioversion. Within 30 days, we noted progressive improvement of atrial systolic function (increase in AFF from 21% to 31%, p < 0.05). At the same time, plasma ANP levels gradually increased from 31.1 +/- 9.2 pg/ml at 24 h to 36.9 +/- 12.8 pg/ml on day 30 following cardioversion (p < 0.05). CONCLUSIONS: Plasma ANP levels significantly decreased in patients with persistent AF after successful cardioversion. In the 30 days after cardioversion, gradual elevation of plasma ANP concentration was observed concomitantly with an increase of AFF. Plasma ANP release after successful cardioversion of persistent AF might be due to recovery of atrial mechanical function.

Atrial Fibrillation↗
PubMed2001

Restoration of atrial mechanical function after successful radio-frequency catheter ablation of atrial flutter.

BACKGROUND: Atrial mechanical dysfunction and its recovery time course after successful radiofrequency ablation of chronic atrial flutter (AFL) has been largely unknown. We serially evaluated left atrial function by echocardiography after successful ablation of chronic atrial flutter. METHODS: In 13 patients with chronic AFL, mitral E wave A wave, and the ratio of A/E velocity were measured at 1 day, 1 month, 3 months and 6-12 months after successful radiofrequency (RF) ablation. Doppler tissue imaging (DTI) technique was also used to avoid load-dependent variation in the flow velocity pattern. RESULTS: Left atrial mechanical function, assessed by A wave velocity and the annular motion, was depressed at 1 day, but improved significantly at 1 month and maintained through 6-12 months after the ablation. Left atrial size did not change significantly. CONCLUSION: Left atrial mechanical function was depressed immediately after successful RF ablation of chronic AFL, but it improved significantly after 1 month and was maintained over one year.

Adult↗
PubMed1989

[Relationship between left atrial diameter and cardiac function in myocardial infarction--assessment of left ventricular end-diastolic pressure by the left atrial index].

To study the assessment of cardiac function in acute myocardial infarction (AMI), we measured left atrial diameter, left ventricular end-diastolic pressure (LVEDP), pulmonary capillary wedge pressure (PCWP), ejection fraction (EF) in 20 patients with acute myocardial infarction. Left atrial diameter was measured using echocardiography and was expressed as left atrial index (LAI, mm/m2) dividing by body surface area. LAI in AMI was 21.3 +/- 2.7 mm/m2 and significantly larger than LAI in normal subject (19.9 +/- 2.0 mm/m2) (p less than 0.05), In AMI, LVEDP was 13.3 +/- 3.4 mmHg, PCWP was 9.0 +/- 2.8 mmHg and EF was 52.3 +/- 14.8%, Relationship (r value) between LAI and LVEDP (r = 0.70, p less than 0.001, y = 0.87 x-5.4 x; LAI, y; LVEDP) was greater than PCWP and LVEDP (r = 0.60, p less than 0.01). LVEDP calculated from LAI using this method was directly measured LVEDP directly measured +/- 2.4 mmHg. In 9 patients, LAI was larger than 20.9 mm/m2, in 8 patients of them LVEDP was higher than 13 mmHg. In 11 patients LAI was smaller than 20.9 mmHg, only in 2 of them LVEDP was lower than 13 mmHg. It concluded that sensitivity was 88.9%, specificity was 81.8%, accuracy was 85.0%. Relationship between LAI and PCWP (r = 0.30), LAI and EF (r = -0.36) were not significant. We can measure LAI repeatedly in AMI non-invasively, and predict LVEDP. Thus, the measurement of LAI is useful in treatment of AMI.

Adult↗
PubMed2000

Mini-maze suffices as adjunct to mitral valve surgery in patients with preoperative atrial fibrillation.

INTRODUCTION: After mitral valve (MV) surgery, preoperative atrial fibrillation (AF) often recurs while cardioversion therapy generally fails. Additional Cox maze surgery improves postoperative arrhythmia outcome, but the extensive nature of such an approach limits general appliance. We investigated the clinical outcome of a simplified, less extensive Cox maze procedure ("mini-maze") as adjunct to MV surgery. METHODS AND RESULTS: Thirteen patients with MV disease and preoperative AF were treated with combined surgery (group 1). Nine control patients without previous AF underwent isolated MV surgery (group 2). We retrospectively compared the results to findings in 23 patients with preoperative AF who had undergone isolated MV surgery (group 3). In group 1, mini-maze took an additional 46 minutes of perfusion time. One 75-year-old patient died of postoperative multiple organ failure. Seven patients showed spontaneously converting (within 2 months) postoperative AF. After 1 year, 82% were in sinus rhythm (SR). No sinus node dysfunction was observed. In group 2, all patients were in SR after 1 year. In group 3, only 53% were in SR after 1 year, despite serial cardioversion and antiarrhythmic drug therapy. Exercise tolerance and heart rate were comparable for groups 1 and 2. Left atrial function was present in all but one patient in group 1 and in all patients in group 2 (after MV reconstruction). CONCLUSION: Adding a relatively simple mini-maze to MV surgery improves arrhythmia outcome in patients with preoperative AF without introducing sinus node dysfunction or persistent absence of left atrial function. The results of this type of combined surgery are encouraging and deserve further attention.

Aged↗
PubMed1999

Pulmonary venous flow in hypertrophic cardiomyopathy as assessed by the transoesophageal approach. The additive value of pulmonary venous flow and left atrial size variables in estimating the mitral inflow pattern in hypertrophic cardiomyopathy.

AIMS: This study was conducted to assess the characteristics of the pattern of pulmonary venous flow and to document the interaction of this flow and left atrial function with the pattern of mitral inflow in hypertrophic cardiomyopathy. METHODS AND RESULTS: Pulmonary venous and mitral flows were evaluated by the transoesophageal approach in 80 patients with hypertrophic cardiomyopathy. Left atrial size and function were measured by the transthoracic approach. Their values were compared with those obtained from 35 normal controls. Twelve patients showed significant (> 2+) mitral regurgitation. As a group, hypertrophic cardiomyopathy patients showed increased atrial reversal flow and longer deceleration time of the diastolic wave, but a wide variability of pulmonary venous flow patterns were observed. Thirty patients (37.5%) had pseudonormal mitral flow patterns. Stepwise multilinear regression analysis identified the ratio of systolic to diastolic pulmonary venous flow velocity, the ratio of velocity-time integrals of both flow waves at atrial contraction, the left atrial minimal volume and the systolic fraction as independent predictive variables of the mitral E/A wave velocity ratio (r = 0.82). By logistic regression, the former three variables were selected as independent predictive covariates of a pseudonormal mitral flow pattern (sensitivity: 83%, specificity: 90%). The ratio of velocity-time integrals of both atrial waves was the most important predictive variable in both analyses. CONCLUSIONS: The observed variability in the configuration of pulmonary venous flow velocity waveform is related to what occurs in transmitral flow in patients with hypertrophic cardiomyopathy. Significant mitral regurgitation is not an independent correlate of pseudonormal mitral inflow patterns in these patients. Our results further emphasize the complementary, additive value of the pulmonary venous flow velocity pattern and left atrial size in the interpretation of the mitral flow velocity pattern, and indirectly suggest the underlying increased left ventricular filling pressures of patients with hypertrophic cardiomyopathy and pseudonormal mitral flow patterns.

Adult↗
PubMed1997

Left atrial appendage "stunning" after electrical cardioversion of atrial flutter: an attenuated response compared with atrial fibrillation as the mechanism for lower susceptibility to thromboembolic events.

OBJECTIVES: This study sought to determine whether left atrial appendage stunning occurs in patients with atrial flutter and to compare left atrial appendage function in the pericardioversion period with that in patients with atrial fibrillation. BACKGROUND: Left atrial appendage stunning has recently been proposed as a key mechanistic phenomenon in the etiology of postcardioversion thromboembolic events in atrial fibrillation. Atrial flutter is thought to be associated with a negligible risk of thromboembolic events; therefore, anticoagulation is commonly withheld before and after cardioversion in these patients. METHODS: Sixty-three patients with atrial flutter (n = 19) or atrial fibrillation (n = 44) underwent transesophageal echocardiography immediately before and after electrical cardioversion. In addition to assessing the presence of thrombus and spontaneous echo contrast, we measured left atrial appendage emptying velocity and calculated shear rates by pulsed wave Doppler and two-dimensional echocardiography. RESULTS: Patients with atrial flutter exhibited greater left atrial appendage flow velocities before cardioversion than those with atrial fibrillation (42 +/- 19 vs. 28 +/- 15 cm/s [mean +/- SD], p < 0.001). Left atrial appendage shear rates were also higher in patients with atrial flutter (103 +/- 82 vs. 59 +/- 37 s-1, p < 0.001). After cardioversion, left atrial appendage flow velocities decreased compared with precardioversion values in patients with atrial fibrillation (28 +/- 15 before to 15 +/- 14 cm/s after cardioversion, p < 0.001) and atrial flutter (42 +/- 19 to 27 +/- 18 cm/s, respectively, p < 0.001). Shear rates decreased from 59 +/- 37 before cardioversion to 30 +/- 31 s-1 after cardioversion in atrial fibrillation (p < 0.001), and from 103 +/- 82 s to 65 +/- 52 s-1, respectively (p < 0.001), in atrial flutter. This decrease in flow velocity from before to after cardioversion occurred in 36 (82%) of 44 patients with atrial fibrillation and 14 (74%) of 19 with atrial flutter. The impaired left atrial appendage function after cardioversion was less pronounced in the group with atrial flutter (27 +/- 18 cm/s for atrial flutter vs. 15 +/- 14 cm/s for atrial fibrillation, p < 0.001). New or increased spontaneous echo contrast occurred in 22 (50%) of 44 patients with atrial fibrillation versus 4 (21%) of 19 with atrial flutter (p < 0.05). CONCLUSIONS: Left atrial appendage stunning also occurs in patients with atrial flutter, although to a lesser degree than in those with atrial fibrillation. These data suggest that patients with atrial flutter are at risk for thromboembolic events after cardioversion, although this risk is most likely lower than that in patients with atrial fibrillation because of better preserved left atrial appendage function.

Aged↗
PubMed2006

Epicardial beating heart cryoablation using a novel argon-based cryoclamp and linear probe.

OBJECTIVE: Epicardial, beating heart cryoablation for the treatment of atrial fibrillation may be limited by heat from intracardiac blood flow. We therefore evaluated the ability to create cryolesions using an argon-based cryoclamp device, which temporarily occludes blood flow and facilitates transmurality. METHODS: Six mongrel dogs underwent sternotomy. A clamp employing a 10-cm argon-based linear cryoablation device was used epicardially to isolate the pulmonary veins and left atrial appendage. After clamping of lesions, the probe was removed from the cryoclamp device, and the remaining linear lesions, analogous to the Cox maze III, were performed. Pulmonary vein stenosis was evaluated with the use of magnetic resonance imaging. Left atrial function and pulmonary venous flow velocities were assessed with transesophageal echocardiography. Transmurality was confirmed both electrically and histologically. Animals were then put to death at 30 days. RESULTS: All acute and chronic cryoclamp lesions produced conduction block. There was no change in right (RPV) or left pulmonary vein (LPV) diameter on the basis of magnetic resonance imaging at baseline and at planned death (RPV-1, 19.6 +/- 2.9 mm vs 16.9 +/- 2.8 mm, P = .22; RPV-2, 13.2 +/- 2.0 mm vs 11.8 +/- 1.6 mm, P = .22; and LPV, 12.2 +/- 2.4 mm vs 11.2 +/- 1.9 mm, P = .30). Left atrial function and pulmonary venous flow velocities were unchanged. Tissue sections determined transmurality in 93% of cryoclamp lesions and 84% of linear ablations performed with the 10-cm malleable probe. CONCLUSIONS: Epicardial application of this cryoclamp device on the beating heart produced transmural lesions, which persisted 30 days. Linear epicardial cryoablation was not as effective as the cryoclamp device at producing consistent transmural lesions. This novel, versatile device may be useful in treating patients with atrial fibrillation on the beating heart without cardiopulmonary bypass.

Animals↗
PubMed1991

Prediction of outcome after mitral valve replacement in patients with symptomatic chronic mitral regurgitation. The importance of left atrial size.

BACKGROUND: The ability to predict outcome after mitral valve replacement remains limited in patients with symptomatic chronic mitral regurgitation. The aims of this study were to determine the preoperative predictors of postoperative cardiac-related mortality and to assess the additive prognostic value of tests performed in such patients. METHODS AND RESULTS: Accordingly, 176 patients (mean age, 57 +/- 14 years) who underwent mitral valve replacement were followed up for 3.8 +/- 0.5 years. Four categories of variables were analyzed to predict postoperative cardiac-related mortality: clinical, laboratory, two-dimensional echocardiographic (2DE), and cardiac catheterization. There were 39 cardiac-related deaths (29 due to congestive heart failure and 10 sudden). When the four categories were analyzed separately, two clinical, one laboratory, two 2DE, and one catheterization variable best predicted postoperative death. When these six variables were examined simultaneously, only three (one clinical and two 2DE) remained significant predictors of cardiac-related mortality: presence of pulmonary rales, left atrial size, and the ratio of left ventricular wall thickness to left ventricular cavity dimension in end systole. A model based on these three variables may predict cardiac-related death with considerable accuracy. Laboratory data did not add to clinical information for predicting death. 2DE variables provided significant additional information in this regard (p less than 0.001). Further addition of catheterization variables was not useful. Prognostic value did not change significantly when 50 patients with prior mitral valve surgery or 49 patients undergoing concomitant aortic valve replacement or coronary artery bypass surgery were excluded from analysis. CONCLUSIONS: We conclude that 1) measures of both left ventricular systolic function and left atrial size are equally important in predicting postoperative cardiac-related mortality in patients with symptomatic chronic mitral regurgitation undergoing mitral valve replacement; 2) left atrial size may be important because it reflects the "history" (severity and duration) of mitral regurgitation; 3) 2DE assessment of left atrial size and left ventricular function provides prognostic information that is significantly greater than that obtained from clinical and laboratory parameters alone; the addition of catheterization variables does not increase the prognostic value of the clinical and 2DE data.

Atrial Function, Left↗