Catheter ablation for atrial fibrillation

Causal Effect of Atrial Fibrillation on Heart Failure Risk in East Asian Ancestry: A Bidirectional Mendelian Randomization Study Using Genome-wide Association Data

BACKGROUND

Atrial fibrillation (AF) and heart failure (HF) are prevalent cardiovascular conditions in East Asia, with a complex interrelationship. The directionality of the causal impact of AF on HF risk remains uncertain. This study employs Mendelian randomization (MR) to investigate the potential causal effect of AF on HF.

METHODS

Utilizing summary data from genome-wide association studies (GWAS) within the Medical Research Council Integrative Epidemiology Unit open GWAS database, we analyzed 8180 AF cases and 28 612 controls, alongside 9413 HF cases and 203 040 controls, all of East Asian descent. We conducted MR analysis using the inverse variance weighted (IVW) method, complemented by various sensitivity analyses, including bidirectional MR to assess causality in the reverse direction.

RESULTS

Genetically predicted AF was found to be causally associated with an increased risk of HF in East Asian populations (odds ratio = 1.14, 95% CI: 1.10-1.19, P <.001) as per the IVW method. These findings were consistent across multiple MR methods. Sensitivity analyses revealed no significant heterogeneity or pleiotropy. Notably, bidirectional MR analysis showed no causal effect of HF on the risk of developing AF.

CONCLUSIONS

The MR analysis supports a unidirectional causal relationship between AF and increased HF risk in East Asian individuals. The absence of a reverse causal effect reinforces the importance of maintaining sinus rhythm to mitigate HF risk. Further research is warranted to corroborate these findings and to explore their clinical implications in depth.

Electrocardiographic Imaging for Atrial Fibrillation: A Perspective From Computer Models and Animal Experiments to Clinical Value

Electrocardiographic imaging (ECGI) is a technique to reconstruct non-invasively the electrical activity on the heart surface from body-surface potential recordings and geometric information of the torso and the heart. ECGI has shown scientific and clinical value when used to characterize and treat both atrial and ventricular arrhythmias. Regarding atrial fibrillation (AF), the characterization of the electrical propagation and the underlying substrate favoring AF is inherently more challenging than for ventricular arrhythmias, due to the progressive and heterogeneous nature of the disease and its manifestation, the small volume and wall thickness of the atria, and the relatively large role of microstructural abnormalities in AF. At the same time, ECGI has the advantage over other mapping technologies of allowing a global characterization of atrial electrical activity at every atrial beat and non-invasively. However, since ECGI is time-consuming and costly and the use of electrical mapping to guide AF ablation is still not fully established, the clinical value of ECGI for AF is still under assessment. Nonetheless, AF is known to be the manifestation of a complex interaction between electrical and structural abnormalities and therefore, true electro-anatomical-structural imaging may elucidate important key factors of AF development, progression, and treatment. Therefore, it is paramount to identify which clinical questions could be successfully addressed by ECGI when it comes to AF characterization and treatment, and which questions may be beyond its technical limitations. In this manuscript we review the questions that researchers have tried to address on the use of ECGI for AF characterization and treatment guidance (for example, localization of AF triggers and sustaining mechanisms), and we discuss the technological requirements and validation. We address experimental and clinical results, limitations, and future challenges for fruitful application of ECGI for AF understanding and management. We pay attention to existing techniques and clinical application, to computer models and (animal or human) experiments, to challenges of methodological and clinical validation. The overall objective of the study is to provide a consensus on valuable directions that ECGI research may take to provide future improvements in AF characterization and treatment guidance.

Randomised clinical trial of cryoballoon versus irrigated radio frequency catheter ablation for atrial fibrillation-the effect of double short versus standard exposure cryoablation duration during pulmonary vein isolation (CIRCA-DOSE): methods and rationale

INTRODUCTION

Pulmonary vein isolation (PVI) is an effective therapy for paroxysmal atrial fibrillation (AF), but it has limitations. The two most significant recent advances have centred on the integration of real-time quantitative assessment of catheter contact force into focal radio frequency (RF) ablation catheters and the development of dedicated ablation tools capable of achieving PVI with a single ablation lesion (Arctic Front cryoballoon, Medtronic, Minneapolis, MN, USA). Although each of these holds promise for improving the clinical success of catheter ablation of AF, there has not been a rigorous comparison of these advanced ablation technologies. Moreover, the optimal duration of cryoablation (freezing time) has not been determined.

METHODS AND ANALYSIS

Patients undergoing an initial PVI procedure for paroxysmal AF will be recruited. Patients will be randomised 1:1:1 between contact-force irrigated RF ablation, short duration cryoballoon ablation (2 min applications) and standard duration cryoballoon ablation (4 min applications). The primary outcome is time to first documented AF recurrence on implantable loop recorder. With a sample size of 111 per group and a two-sided 0.025 significance level (to account for the two main comparisons), the study will have 80% power (using a log-rank test) to detect a difference of 20% between contact force RF catheter ablation and either of the two cryoballoon ablation groups. Factoring in a 4% loss to follow-up, 116 patients per group should be randomised and followed for a year (total study population of 348).

ETHICS AND DISSEMINATION

The study was approved by the University of British Columbia Office of Research (Services) Ethics Clinical Research Ethics Board. Results of the study will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT01913522; Pre-results.

Atrial fibrillation: cure or treat?

Controversies exist with regard to the optimal management of atrial fibrillation (AF). Restoration and maintenance of sinus rhythm is a desirable goal in AF patients because the prevention of recurrences may improve cardiac function, relieve symptoms and should reduce the likelihood of adverse events. Pharmacological therapy for AF has been disappointing with unacceptable rates of AF recurrence and other proarrhythmic sequelae. Recent studies suggested that potential benefit of sinus-rhythm maintenance with respect to mortality may have been neutralized by harmful effects of currently available antiarrhythmic therapies. Because of the inefficacy and dangers with nonablative therapies currently available for maintaining sinus rhythm, alternative treatments are certainly desirable. Curative treatment of atrial fibrillation with catheter ablation is now a legitimate option for a large number of patients. In several studies AF ablation has consistently been demonstrated to be superior to antiarrhythmic medications for the maintenance of sinus rhythm. Nevertheless, many aspects of the therapy are still controversial and large-scale prospective studies are needed to confirm the efficacy and safety of this approach.

Thoracoscopic microwave ablation of atrial fibrillation

The aim of the study was to assess the safety and efficacy of thoracoscopic microwave ablation in treating atrial fibrillation (AF). AF predisposes to embolic complications and may cause heart failure. The treatment of AF is still challenging in spite of the promising results of endocardial radiofrequency approach. The present study is a follow-up study of 22 patients (mean age 45 years, range 21-59) with disabling paroxysmal (n=10) or persistent (n=12) AF who underwent a thoracoscopic microwave isolation of pulmonary veins. The patients had a lone AF. All the patients had suffered from severely disabling AF for >1 year (range 1-16 years) without any response to antiarrhythmic medication. The patients have been followed-up on an average of 11 months (range 3-22 months). During the follow-up, 13 (60%) patients have become asymptomatic without any documentation of AF since at least two months, six (27%) patients with anti-arrhythmic medication have clinically improved. Because of major intrathoracic bleeding and because of liver damage the thoracoscopy wound had to be expanded to open thoracotomy in two patients. Thoracoscopic AF microwave ablation seems to be a promising alternative to endocardial ablation in the treatment of highly symptomatic paroxysmal and persistent AF.

Early complications of pulmonary vein catheter ablation for atrial fibrillation: A multicenter prospective registry on procedural safety

BACKGROUND

Data on the procedural safety of pulmonary vein radiofrequency catheter ablation for atrial fibrillation (AF) are as yet scant.

OBJECTIVE

The aims of the present study were to prospectively evaluate the incidence of early complications of pulmonary vein ablation for AF in an unselected population of consecutive patients, and to identify possible predictors.

METHODS

From April 2005 to October 2006, data from 1,011 consecutive patients who were undergoing radiofrequency catheter ablation for every type of AF in 10 Italian centers were collected. All complications occurring from the admission of the patient up to the 30th day were considered.

RESULTS

No procedure-related death was observed. Complications occurred in 40 patients (3.9%): 12 (1.2%) had peripheral vascular complications, 8 (0.8%) had conservatively treated pericardial effusion, 6 (0.6%) had cardiac tamponade (successfully drained), 5 (0.5%) had cerebral embolisms, 4 (0.4%) presented pulmonary vein stenosis >50%, and 5 (0.5%) presented other isolated adverse events. History of coronary artery disease (odds ratio 5,603, 95% confidence interval 1,559 to 20,139, P < .008) characterized patients who presented with hemorrhagic complications.

CONCLUSION

Early complications of pulmonary vein catheter ablation seem to be fewer than in the early years of AF ablation, but still occur in 3.9% of procedures.

Current strategies in the surgical treatment of atrial fibrillation: review of the literature and Onze Lieve Vrouw Clinic's strategy

Atrial fibrillation is the most common rhythm disturbance in clinical practice. It is a major source of stroke and morbidity. Although the Cox maze procedure effectively eliminates atrial fibrillation in most patients, the procedure has not found widespread application. As a consequence, new operations that use alternative sources of energy, such as radiofrequency, microwave, cryothermy, laser, and ultrasound have emerged to surgically create lesion sets to treat atrial fibrillation. This article reviews the fundamentals and current strategies in the surgical treatment of atrial fibrillation.

Plasma brain natriuretic peptide concentrations in patients undergoing pulmonary vein isolation

OBJECTIVE

To examine whether raised plasma brain natriuretic peptide (BNP) concentrations decrease after successful pulmonary vein isolation (PVI) in patients with atrial fibrillation (AF).

METHODS

53 patients (mean age 53 years) with drug-refractory, paroxysmal lone AF underwent segmental ostial PVI. Blood samples were collected before and after PVI. BNP concentrations were determined by immunoassays.

RESULTS

Median plasma BNP concentrations were significantly higher in patients with lone AF than in controls (patients with supraventricular tachyarrhythmias, n = 21) (64.6 (71.9) v 13.9 (7.8) pg/ml, p < 0.01). AF recurred in 21 patients after the initial PVI procedure (recurrent AF group), and the others were free from AF without antiarrhythmic drugs (non-recurrent AF group). BNP concentrations were significantly decreased by PVI in the non-recurrent AF group (38.9 (39.1) to 18.3 (16.1) pg/ml, p < 0.01) but not in the recurrent AF group.

CONCLUSIONS

Raised plasma BNP concentrations decreased after successful segmental ostial PVI in patients with AF.

Cost-effectiveness of radiofrequency catheter ablation for atrial fibrillation

OBJECTIVES

We sought to compare the cost-effectiveness of left atrial catheter ablation (LACA), amiodarone, and rate control therapy in the management of atrial fibrillation (AF).

BACKGROUND

Left atrial catheter ablation has been performed to eliminate AF, but its cost-effectiveness is unknown.

METHODS

We developed a decision-analytic model to evaluate the cost-effectiveness of LACA in 55- and 65-year-old cohorts with AF at moderate and low stroke risk. Costs, health utilities, and transition probabilities were derived from published literature and Medicare data. We performed primary threshold analyses to determine the minimum level of LACA efficacy and stroke risk reduction needed to make LACA cost-effective at 50,000 dollars and 100,000 dollars per quality-adjusted life-year (QALY) thresholds.

RESULTS

In 65-year-old subjects with AF at moderate stroke risk, relative reduction in stroke risk with an 80% LACA efficacy rate for sinus rhythm restoration would need to be > or =42% and > or =11% to yield incremental cost-effectiveness ratios (ICERs) <50,000 dollars and 100,000 dollars per QALY, respectively. Higher and lower LACA efficacy rates would require correspondingly lower and higher stroke risk reduction for equivalent ICER thresholds. In the 55-year-old moderate stroke risk cohort, lower LACA efficacy rates or stroke risk reduction would be needed for the same ICER thresholds. In patients at low stroke risk, LACA was unlikely to be cost-effective.

CONCLUSIONS

The use of LACA may be cost-effective in patients with AF at moderate risk for stroke, but it is not cost-effective in low-risk patients. Our threshold analyses may provide a framework for the design of future clinical trials by providing effect size estimates for LACA efficacy needed.

Imaging in percutaneous ablation for atrial fibrillation

Percutaneous ablation for electrical disconnection of the arrhythmogenic foci using various forms of energy has become a well-established technique for treating atrial fibrillation (AF). Success rate in preventing recurrence of AF episodes is high although associated with a significant incidence of pulmonary vein (PV) stenosis and other rare complications. Clinical workup of AF patients includes imaging before and after ablative treatment using different noninvasive and invasive techniques such as conventional angiography, transoesophageal and intracardiac echocardiography, computed tomography (CT) and magnetic resonance imaging (MRI), which offer different information with variable diagnostic accuracy. Evaluation before percutaneous ablation involves assessment of PVs (PV pattern, branching pattern, orientation and ostial size) to facilitate position and size of catheters and reduce procedure time as well as examining the left atrium (presence of thrombi, dimensions and volumes). Imaging after the percutaneous ablation is important for assessment of overall success of the procedure and revealing potential complications. Therefore, imaging methods enable depiction of PVs and the anatomy of surrounding structures essential for preprocedural management and early detection of PV stenosis and other ablation-related procedures, as well as long-term follow-up of these patients.

Rate versus rhythm control strategies for AF

The safest long-term management strategy for elderly patients with persistent or recurrent episodes of atrial fibrillation (AF) is careful rate control with medications in conjunction with appropriate oral warfarin anticoagulation. Atrioventricular junctional ablation, with pacemaker implantation, may be necessary in patients who cannot have their rate controlled adequately, or have marked fluctuations in rate with standard medical therapies. Maintenance of sinus rhythm with repeat cardioversions, antiarrhythmic medications, device therapy, or atrial ablation approaches are appropriate to consider for younger patients and those elderly patients who suffer from substantial symptoms shown to be related directly to AF.