New Insights Into the Predictors of Left Atrial Stunning After Successful Direct-Current Cardioversion of Atrial Fibrillation and Flutter

A prediction model based on functional mitral regurgitation for the recurrence of paroxysmal atrial fibrillation (PAF) after post-circular pulmonary vein radiofrequency ablation (CPVA)

AIM

To construct a prediction model based on functional mitral regurgitation (FMR) in patients with paroxysmal atrial fibrillation (PAF) to predict atrial fibrillation recurrence after the post-circular pulmonary vein radiofrequency ablation (CPVA).

METHODS

We retrospectively analyzed 289 patients with PAF who underwent CPVA for the first time. The patients were randomly divided into modeling group and verification group at the ratio of 75:25. In the modeling group, the multivariate logistic regression was used to analyze and construct a prediction model for post-CPVA recurrence in PAF patients, which was then validated in the verification group.

RESULTS

(1) After 3-6 months of follow-up, the patients were divided into sinus rhythm group (252 cases) and recurrence group (24 cases); (2) In the modeling group, the age, left atrial diameter (LAD), and the degree of MR (mild, moderate, severe) were higher in recurrence group than that of the sinus rhythm group, and the left atrial appendage emptying velocity (LAAV) was lower in recurrence group (all p < .05). (3) A model for predicting the recurrence of PAF after radiofrequency ablation was constructed in the modeling group. The equation was: Logit(P) = -3.253 + .092 × age + 1.263 × mild MR + 2.325 × moderate MR + 5.111 × severe MR -.113 × LAAV. The area under the curve (AUC) of the model was .889 in modeling group and .866 in verification group, and the difference was not statistically significant (p > .05).

CONCLUSION

The prediction model of atrial fibrillation (AF) recurrence after CPVA in PAF patients has good predictive efficacy, specificity, and accuracy.

Risk of left atrial appendage thrombus and stroke in patients with atrial fibrillation and mitral regurgitation

OBJECTIVE

To investigate the association of mitral regurgitation (MR) on thromboembolic risk of patients with non-valvular atrial fibrillation (NVAF) undergoing transoesophageal echocardiography (TEE)-guided cardioversion.

METHODS

Data for consecutive patients who underwent TEE-guided cardioversion for NVAF between 2000 and 2012 were analysed. MR severity was assessed by Doppler echocardiography and classified as ≤mild, moderate or severe. Left atrial appendage emptying velocities were averaged for five consecutive cycles. Multivariable regression models were used to identify independent predictors of left atrial appendage thrombus (LAAT) and stroke.

RESULTS

2950 patients (age, 69.3±12.2 years, 67% men) were analysed. 2173 (73.7%) had ≤mild MR; 631 (21.4%), moderate MR; and 146 (4.9%), severe MR. Patients with moderate (age, 72.4±10.7 years) and severe (age, 72.8±12.1 years) MR were older than those with ≤mild MR (age, 68.2±12.5 years). The prevalence of LAAT was 1.5% (n=43). CHA₂DS₂-VASc scores (≤mild MR, 3.0±1.6; moderate MR, 3.5±1.5; severe MR, 3.9±1.5; p<0.001) and heart failure frequency (≤mild MR, 38.4%; moderate MR, 48.0%; severe MR, 69.2%; p<0.001) were increasingly higher with greater MR severity. Multivariable logistic regression analysis showed no association of moderate MR (OR 0.77, 95% CI 0.38 to 1.56) or severe MR (OR 0.55, 95% CI 0.21 to 1.49) with LAAT. During a mean follow-up of 7.3±5.1 years (median 7.5, IQR, 2.7-10.9), 216 patients had an ischaemic stroke. Adjusted Cox regression analysis showed no significant association of moderate MR (HR 1.22, 95% CI 0.88 to 1.68) or severe MR (HR 0.73, 95% CI 0.31 to 1.46) with stroke.

CONCLUSIONS

Among patients with NVAF, the presence or severity of MR was not associated with a decreased risk of LAAT or stroke.

Real-Time Pathophysiologic Correlates of Left Atrial Appendage Thrombus in Patients Who Underwent Transesophageal-Guided Electrical Cardioversion for Atrial Fibrillation

Although current guidelines advocate using the CHA₂DS₂-VASc score to assess the risk of stroke in patients with atrial fibrillation (AF), compared with transesophageal echocardiography (TEE), its ability to predict left atrial appendage thrombus (LAAT) is limited. We studied 3,324 consecutive patients with sustained AF from our prospective registry of patients who underwent first-time TEE-guided electrical cardioversion (ECV) from May 2000 through March 2012. The association of CHA₂DS₂-VASc score or TEE risk factors with the occurrence of LAAT was analyzed. The mean (SD) age was 69 (12.5) years and 67% were men. LAAT was identified in 49 (1.5%) during pre-ECV TEE. Compared with patients without LAAT, those with LAAT had lower peak left atrial appendage emptying velocity (LAAEV) (17.2 ± 8.5 vs 36.6 ± 20.8; p <0.001) and left ventricular ejection fraction (LVEF) (39.9 ± 17.6 vs 51.4 ± 13.7; p <0.001); their CHA₂DS₂-VASc score also was higher, but the difference was not statistically significant (3.6 ± 1.4 vs 3.2 ± 1.6; p = 0.06). Multivariate logistic regression analysis identified an LVEF ≤40% (adjusted odds ratio 2.48, 95% confidence interval 1.38 to 4.46), LAAEV 20.3 to 33.9 cm/s (odds ratio 12.19, 95% confidence interval 1.53 to 96.86), and LAAEV ≤20.2 cm/s as independent predictors of LAAT. An LAAEV cut-point of 20 cm/s and an LVEF ≤40% were optimal for detecting LAAT (sensitivity 75% and 62%; specificity 77% and 75%; area under the curve 0.822 and 0.776, respectively). On follow-up, LAAT was an independent risk factor of subsequent ischemic stroke but did not influence survival. In conclusion, reduced LVEF and reduced LAAEV are important pathophysiologic correlates of left atrial appendage thrombogenesis and subsequent ischemic stroke in patients who underwent TEE-guided ECV for AF.

MicroRNAs as Biomarkers for Acute Atrial Remodeling in Marathon Runners (The miRathon Study--A Sub-Study of the Munich Marathon Study)

Introduction

Physical activity is beneficial for individual health, but endurance sport is associated with the development of arrhythmias like atrial fibrillation. The underlying mechanisms leading to this increased risk are still not fully understood. MicroRNAs are important mediators of proarrhythmogenic remodeling and have potential value as biomarkers in cardiovascular diseases. Therefore, the objective of our study was to determine the value of circulating microRNAs as potential biomarkers for atrial remodeling in marathon runners (miRathon study).

Methods

30 marathon runners were recruited into our study and were divided into two age-matched groups depending on the training status: elite (ER, ≥55 km/week, n = 15) and non-elite runners (NER, ≤40 km/week, n = 15). All runners participated in a 10 week training program before the marathon. MiRNA plasma levels were measured at 4 time points: at baseline (V1), after a 10 week training period (V2), immediately after the marathon (V3) and 24h later (V4). Additionally, we obtained clinical data including serum chemistry and echocardiography at each time point.

Results

MiRNA plasma levels were similar in both groups over time with more pronounced changes in ER. After the marathon miR-30a plasma levels increased significantly in both groups. MiR-1 and miR-133a plasma levels also increased but showed significant changes in ER only. 24h after the marathon plasma levels returned to baseline. MiR-26a decreased significantly after the marathon in elite runners only and miR-29b showed a non-significant decrease over time in both groups. In ER miRNA plasma levels showed a significant correlation with LA diameter, in NER miRNA plasma levels did not correlate with echocardiographic parameters.

Conclusion

MiRNAs were differentially expressed in the plasma of marathon runners with more pronounced changes in ER. Plasma levels in ER correlate with left atrial diameter suggesting that circulating miRNAs could potentially serve as biomarkers of atrial remodeling in athletes.

The left atrial appendage: anatomy, function, and noninvasive evaluation

The left atrial appendage (LAA) is a finger-like extension originating from the main body of the left atrium. Atrial fibrillation (AF) is the most common clinically important cardiac arrhythmia, occurring in approximately 0.4% to 1% of the general population and increasing with age to >8% in those >80 years of age. In the presence of AF thrombus, formation often occurs within the LAA because of reduced contractility and stasis; thus, attention should be given to the LAA when evaluating and assessing patients with AF to determine the risk for cardioembolic complications. It is clinically important to understand LAA anatomy and function. It is also critical to choose the optimal imaging techniques to identify or exclude LAA thrombi in the setting of AF, before cardioversion, and with current and emerging transcatheter therapies, which include mitral balloon valvuloplasty, pulmonary vein isolation, MitraClip (Abbott Laboratories, Abbott Park, Illinois) valve repair, and the implantation of LAA occlusion and exclusion devices. In this review, we present the current data regarding LAA anatomy, LAA function, and LAA imaging using the currently available noninvasive imaging modalities.

Techniques To Improve Left Atrial Appendage Imaging

The clinical importance of the left atrial appendage (LAA) is increasingly recognized. The assessment of the unique anatomy and function of the LAA is especially important in the setting of atrial fibrillation (AF). AF is the most commonly occurring cardiac arrhythmia, and the association of LAA thrombi and AF has been well established. Transesophageal echocardiography (TEE) is a widely available imaging tool to exclude the potential presence of LAA thrombus prior to cardioversion in patients with AF. Commercially available products containing microbubbles to enhance ultrasound images, termed "ultrasound contrast agents" (UCA) are indicated for use with transthoracic echocardiography to improve cardiac structure and function assessment, but can also be used with TEE as an adjunctive tool to assess the LAA. Integrative multimodality imaging techniques can be used in evaluation of the LAA as indicated in various clinical scenarios including: stroke risk assessment, decision-making prior to cardioversion in AF, placement and assessment percutaneous transcatheter LAA occlusion procedures, and assessment of results of procedural or surgical exclusion of LAA. In this article, various imaging techniques that are available for non-invasive visualization of the LAA will be reviewed along with the clinical importance of assessment of LAA anatomy and function.

Role of Left Ventricular Diastolic Dysfunction in Predicting Atrial Fibrillation Recurrence after Successful Electrical Cardioversion

The role of left ventricular (LV) diastolic dysfunction in predicting atrial fibrillation (AF) recurrence after successful electrical cardioversion is largely unknown. Studies suggest that there may be a link between abnormal LV compliance and the initial development, and recurrence of AF after electrical cardioversion. Although direct-current cardioversion (DCCV) is a well-established and highly effective method to convert AF to sinus rhythm, it offers little else beyond immediate rate control because it does not address the underlying cause of AF. Preservation of sinus rhythm after successful cardioversion still remains a challenge for clinicians. Despite the use of antiarrhythmic drugs and serial cardioversions, the rate of AF recurrence remains high in the first year. Current evidence suggests that diastolic dysfunction, which is associated with atrial volume and pressure overload, may be a mechanism underlying the perpetuating cycle of AF recurrence following successful electrical cardioversion. Diastolic dysfunction is considered to be a defect in the ability of the myofibrils, which have shortened against a load in systole to eject blood into the high-pressure aorta, to rapidly or completely return to their resting length. Consequently, LV filling is impaired and the non-compliant left ventricle is unable to fill at low pressures. As a result, left atrial and pulmonary vein pressure rises, and electrical and structural remodeling of the atrial myocardium ensues, creating a vulnerable substrate for AF. In this article, we review the current evidence highlighting the association of LV diastolic dysfunction with AF recurrence after successful electrical cardioversion and provide an approach to the management of LV diastolic dysfunction to prevent AF recurrence.

Mitral annular velocity by Doppler tissue imaging for the evaluation of atrial stunning after cardioversion of atrial fibrillation

OBJECTIVE

Atrial and/or appendage stunning (AS) usually occur after successful cardioversion of atrial fibrillation (AF). Several parameters except mitral annular velocity were previously evaluated to determine AS. We investigated whether mitral annular velocity was useful for determining of AS.

METHODS

This study consisted of 52 consecutive patients with AF <3 months who converted to the sinus rhythm. Mitral inflow and annular velocities were measured before and after cardioversion. Left atrial appendage (LAA) size and flow were assessed. The average velocity of septal and lateral segments of mitral annulus was considered as the final annular velocity. Thrombus and/or spontaneous echo contrast (SEC) were also investigated.

RESULTS

Of 52 patients, 29 (56%) had AS but 23 did not. There was no significant difference in age, gender, and cardioversion type between two groups. Hypertension was more prevalent in patients without AS compared to those with AS (P = 0.02). Mitral annular systolic and E-wave velocities were comparable in both groups (P > 0.05). Mitral annular A-wave velocity (3.1 +/- 2.9 vs. 7.1 +/- 2.2 cm/s, P < 0.001), and its velocity-time integral (0.27 +/- 0.22 vs. 0.74 +/- 0.19 cm, P < 0.001) were significantly lower in patients with AS compared with those without AS. The annular A-wave velocity < or =3.3 cm/s predicted AS with a sensitivity of 59% and specificity of 76%. It was correlated with mitral inflow A velocity (r = 0.85, P < 0.001), LAA emptying velocity (r = 0.41, P = 0.003) and presence of SEC (r = -0.52, P < 0.001).

CONCLUSION

After cardioversion of AF, mitral annular A-wave velocity may be a new marker to determine AS.