Left atrial dimension and atrial fibrillation in surgical heart disease patients

Objective The effect of left atrial (LA) dimension on the occurrence of atrial fibrillation (AF) has been examined in some small studies.Less is known about the relationship of LA dimension,hemodynamic with AF during echocardiographic evaluation,especially,the flow dynamics in LA poorly described.The objective of this study was to investigate the relationship between LA dimension and the occurrence of AE Methods Two hundred and forty-five consecutive patients with heart disease scheduled to undergo open heart surgery were prospectively enrolled in the study.Patients were divided into 2 groups according to atrial fibrillation:AF group (n=148,99 men and 49 women,with a mean age 59.3+8.4 years),and no-AF group (n= 97,60 men and 37 womem).Echocardiography was performed before surgery.All measurements were performed following the American Society of Echocardiography recommendations.Results There were more patients with congestive heart failure in AF group than in no-AF group (45.9% vs 39.1%,P ＜0.05).The mean LA volume was 49.2±12.2 ml/m2 in AF group and 33.1±10.8 ml/m2 in no-AF group.There were also significant differences between two groups in left atrial end systolic dimension (LAESD) (50±13mm vs 27±14mm),left atrial end diastolic dimension (LAEDD) (79±17mm vs 53±13mm),PA pressure ( 41.3+11.6 mmHg vs 37.5±10.4 mmHg),and ratio of mitral E velocity and septal mitral annulus motion velocity (E/E') .The percentage of abnormal diastolic function grades (DGF) was also higher in AF than in no-AF group (89.9% versus 59.8% );.Conclusion Atrial fibrillation is associated more frequently with an increased LA dimension and more severe atrial hemodynamics disorder.(J Geriatr Cardiol 2008;5:11-4)     

Statin for atrial fibrillation

In the long term effects of simvastatin on protectingagainst atrial fibrillation in patients with acute myocardialinfarction, in this issue of the Journal of GeriatricCardiology, Chi et al. presented interesting data regard-ing the positive beneficial effects of simvastatin in the re-duction of the frequency of atrial fibrillation in a selectedgroup of patients. There have been occasional reports sug-gestive of mild antiarrhythmic properties of simvastatin,but these were more observational in nature. What isthought provoking about this report is that the group re-ceiving simvastatin actually received less beta blockertherapy than the control group. It remains unclear as tohow simvastatin actually reduces dispersion of tissuerefractoriness, the basis of most arrhythmias. It also re-     

Left atrial “stunning” following radiofrequency catheter ablation of chronic atrial flutter

Objectives. This study examined the effect of radiofrequency ablation (RFA) on left atrial (LA) and left atrial appendage (LAA) function in humans with chronic atrial flutter (AFL).Background. Atrial stunning and the development of spontaneous echocardiographic contrast (SEC) is a consequence of electrical cardioversion of AFL to sinus rhythm. This phenomenon has been termed “stunning” and is associated with thrombus formation and embolic stroke. Radiofrequency ablation is now considered to be definitive treatment for chronic AFL, but whether this procedure is complicated by LA stunning is unknown.Methods. Fifteen patients with chronic AFL undergoing curative RFA underwent transesophageal echocardiography to evaluate LA and LAA function and SEC before and immediately, 30 minutes and 3 weeks after RFA. To control for possible direct effects of RFA on atrial function, seven patients undergoing RFA for paroxysmal AFL were also studied. In this group, RF energy was delivered in sinus rhythm and echocardiographic parameters were assessed before and immediately and 30 minutes following RFA.Results. Chronic AFL: Mean arrhythmia duration was 17.2 ± 13.3 months. Twelve patients (80%) developed SEC following RF energy application and reversion to sinus rhythm. LAA velocities decreased significantly from 54.0 ± 14.2 cm/s in AFL to 18.0 ± 7.1 cm/s in sinus rhythm after arrhythmia termination (p < 0.01). These changes persisted for 30 minutes. Following 3 weeks of sustained sinus rhythm, significant improvements in LAA velocities (68.9 ± 23.6 vs. 18.0 ± 7.1 cm/s, p < 0.01) and mitral A-wave velocities (49.8 ± 10.3 vs. 13.4 ± 11.2 cm/s, p < 0.01) were evident and SEC had resolved in all patients. Paroxysmal AFL: Radiofrequency energy delivered in sinus rhythm had no significant effect on any of the above indexes of LA or LAA function and no patient developed SEC following RFA.Conclusions. Radiofrequency ablation of chronic AFL is associated with significant LA stunning and the development of SEC. Left atrial stunning is not secondary to the RF energy application itself. Sustained sinus rhythm for 3 weeks leads to resolution of these acute phenomena. Left atrial stunning occurs in the absence of direct current shock or antiarrhythmic drugs, suggesting that its mechanism may be a function of the preceding arrhythmia rather than the mode of reversion.     

Impact of pulmonary vein isolation on atrial vagal activity and atrial electrical remodeling

Objective Mechanisms of pulmonary vein isolation (PVI) for atrial fibrillation remain controversy.This study aimed to investigate the impact of PVI on vagal modulation to atria.Methods Eighteen adult mongrel dogs under general anesthesia were randomly divided into two groups.Bilateral cervical sympathovagal trunks were decentralized and sympathetic effects was blocked by metoprolol administration.Atrial electrical remodeling (AER) was established by rapid right atrial pacing at the rate of 600 bpm for 30 minutes.PVI was performed in group A.Atrial effective refractory period (ERP),vulnerability window (VW) of atrial fibrillation,and sinus rhythm cycle length (SCL) were measured at baseline and during vagal stimulation before and after atrial rapid pacing with and without PVI at fight atrial appendage (RAA),left atrial appendage (LAA),distal coronary sinus (CSd) and proximal coronary sinus (CSp).Results (1) Effects of PVI on vagal modulation:Shortening of SCL during vagal stimulation decreased significantly after PVI compared with that before PVI in group A (P＜0.001).Shortening of ERP during vagal stimulation decreaseed significantly after PVI compared with that before PVI (P＜0.05).VW of atrial fibrillation during vagal stimulation decreased significantly after PVI compared with that before PVI (P＜0.05).(2) Effects of PVI on AER:shortening of ERP before and after atrial rapid pacing increased significantly at baseline and vagal stimulation in group B compared with that in group A (P＜0.05).VW during vagal stimulation increased significantly after atrial rapid pacing in group B (P＜0.05).Conclusion PVI attenuates the vagal modulation to the atria,thereby decreases the susceptibility to atrial fibrillation mediated by vagal activity.PVI releases AER,which maybe contributes to the vagal denervation.Our study indicates that PVI not only can eradicate triggered foci but also modify substrates for AF.(J Geriatr Cardiol 2008;5:28-32)     

Is time to first recurrence of atrial fibrillation correlated with atrial fibrillation burden?

The time to the first recurrence of atrial fibrillation (AF) and the AF burden have commonly been used as end points for AF therapy. We conducted a retrospective analysis of data from a large pacemaker registry to assess the relation between the time to the first recurrence and the AF burden. Although a statistical association exists, the small correlation coefficients limit the clinical value of the time to first recurrence as an indicator of AF burden.     

Is left atrial fibrosis an independent determinant of atrial fibrillation in mitral stenosis?

We prospectively studied whether left atrial (LA) fibrosis is a determinant of atrial fibrillation (AF) in mitral stenosis in patients who underwent balloon mitral valvotomy. There were 2 groups: Group A (n = 16), with AF and Group B (n = 27), without AF. Fibrosis was assessed by MRI. Patients underwent cardioversion before MRI. There were 27 females and 16 males, aged 29 ± 6 years. The LA areas in Groups A and B were 54.3 ± 4.4 mm² and 39.4 ± 2.3 mm² (p < 0.05) and the LA volume index was 46.2 ± 2.9 ml/m² vs 33 ± 3 ml/m² respectively (p < 0.0001). The presence of LA scarring was not statistically different in the two groups.     

Compensatory changes in atrial volumes with normal aging: is atrial enlargement inevitable?

OBJECTIVES: The aim of this study was to evaluate left atrial volume and its changes with the phases (active and passive) of atrial filling, and to examine the effect of normal aging on these parameters and pulmonary vein (PV) flow patterns. BACKGROUND: Atrial volume change with normal aging has not been adequately described. Pulmonary vein flow patterns have not been volumetrically evaluated in normal aging. Combining atrial volumes and PV flow patterns obtained using transthoracic echocardiography could estimate shifts in left atrial mechanical function with normal aging. METHODS: A total of 92 healthy subjects, divided into two groups: Group Y (young <50 years) and Group O (old > or =50 years), were prospectively studied. Maximal (Vol(max)) and minimal (Vol(min)) left atrial volumes were measured using the biplane method of discs and by three-dimensional echocardiographic reconstruction using the cubic spline interpolation algorithm. The passive filling, conduit, and active emptying volumes were also estimated. Traditional measures of atrial function, mitral peak A-wave velocity, velocity time integral (VTI), atrial emptying fraction, and atrial ejection force were measured. RESULTS: As age increased, Vol(max), Vol(min), and total atrial contribution to left ventricle (LV) stroke volume were not significantly altered. However, the passive emptying volume was significantly higher (14.2 +/- 6.4 ml vs. 11.6 +/- 5.7 ml; p = 0.03) whereas the active emptying volume was lower (8.6 +/- 3.7 ml vs. 10.2 +/- 3.8 ml; p = 0.04) in Group Y versus Group O. Pulmonary vein flow demonstrated an increase in peak diastolic velocity (Group Y vs. Group O) with no corresponding change in diastolic VTI or systolic fraction. CONCLUSIONS: Normal aging does not increase maximum (end-systolic) atrial size. The atrium compensates for changes in LV diastolic properties by augmenting active atrial contraction. Pulmonary vein flow patterns, although diastolic dominant using peak velocity, demonstrated no volumetric change with aging.     

Pulmonary vein dilatation: another possible crosslink between left atrial enlargement and atrial fibrillation?

The interplay between left atrial (LA) dilatation and atrial fibrillation (AF) has been well established, but the underlying mechanisms of this vicious circle are not fully understood. Recent studies indicated that pulmonary vein (PV) dilatation is implicated in the development of AF. On the other hand, PV dilatation has been associated with LA dilatation. It is therefore reasonable to assume that PV dilatation represents a common pathophysiologic pathway between LA enlargement and AF.