State of the Art: Catheter Ablation of Atrial Fibrillation

Computer Aided Diagnosis for atrial fibrillation based on new artificial adaptive systems

BACKGROUND AND OBJECTIVE

Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice, having been recognized as a true cardiovascular epidemic. In this paper, a new methodology for Computer Aided Diagnosis of AF based on a special kind of artificial adaptive systems has been developed.

METHODS

Following the extraction of data from the PhysioNet repository, a new dataset composed of the R/R distances of 73 patients was created. To avoid redundancy, the training set was created by randomly selecting 50% of the subjects from the entire sample, thus making a choice by patient and not by record. The remaining 50% of subjects were randomly split by records in testing and prediction sets. The original ECG data has been transformed according to the following four orders of abstraction: a) sequence of R/R intervals; b) composition of ECG data into a moving window; c) training of different machine learning systems to abstract the function governing the AF; d) fuzzy transformation of Machine learning estimations. In this paper, in parallel with the classic method of windowing, we propose a variant based on a system of progressive moving averages.

RESULTS

The best performing machine learning, Supervised Contractive Map (SVCm), reached an overall mean accuracy of 95%. SVCm is a new deep neural network based on a different principle than the usual descending gradient. The minimization of the error occurs by means of decomposition into contracted sine functions.

CONCLUSIONS

In this research, atrial fibrillation is considered from a completely different point of view than classical methods. It is seen as the stable process, i.e. the function, that manages the irregularity of the irregularities of the R/R intervals. The idea, therefore, is to abstract from mere physiology to investigate fibrillation as a mathematical object that handles irregularities. The attained results seem to open new perspectives for the use of potent artificial adaptive systems for the automatic detection of atrial fibrillation, with accuracy rates extremely promising for real world applications.

Use of statins and recurrence of atrial fibrillation after catheter ablation or electrical cardioversion

Statins have important pleiotropic effects and have been shown to reduce vascular inflammation. Some evidence suggests that statins may have a role in the primary prevention of atrial fibrillation (AF), whereas little is know on the role of statins in patients with existing AF. We performed a meta-analysis of the literature to assess the effect of statins on the recurrence of AF after electrical cardioversion or ablation. MEDLINE and EMBASE databases were searched up to January 2010. Relative risks (RR) and 95% confidence intervals (CIs) were then calculated and pooled using a random-effects model. Statistical heterogeneity was evaluated through the use of I2 statistics. Sixteen studies were included in our systematic review. Statins did not reduce the risk of AF recurrence after ablation (four studies including 750 patients; RR, 1.04; 95% CI, 0.85–1.28, p=0.71; I2 = 34%). Conversely, the use of statins was associated with a significantly reduced risk of AF recurrence after electrical cardioversion (12 studies including 1790 patients; RR, 0.78; 95% CI, 0.67–0.90, p=0.0003; I2 = 34%). This reduction was not statistically significant when the analysis was restricted to randomised controlled trials (RCTs) only (five studies, 458 patients, RR, 0.76; 95% CI, 0.48–1.20). In conclusion, statins may lower the risk of AF recurrence after electrical cardioversion, but not ablation. However, this finding should be considered with caution, and larger RCTs are warranted to confirm our preliminary results.

Atrial Fibrillation Ablation Strategy: "Ready Made" or "Tailored"?

Atrial fibrillation (AF) is the most common arrhythmia leading to hospital admissions. Catheter ablation has evolved as an effective treatment strategy; however, ablation strategies continue to evolve due to the complex and multifactorial nature of atrial fibrillation. A standardized and primarily anatomical approach may not be sufficient to eliminate all mechanisms of atrial fibrillation. A tailored ablation strategy can target specific triggers and drivers of atrial fibrillation; however, it is limited by the accuracy and sensitivity of the methods used in identifying specific mechanisms of atrial fibrillation.

Five-Year Follow-Up After Catheter Ablation of Persistent Atrial Fibrillation Using the Stepwise Approach and Prognostic Factors for Success

Background—

In the meantime, catheter ablation is widely used for the treatment of persistent atrial fibrillation (AF). There is a paucity of data about long-term outcomes. This study evaluates (1) 5-year single and multiple procedure success and (2) prognostic factors for arrhythmia recurrences after catheter ablation of persistent AF using the stepwise approach aiming at AF termination.

Methods and Results—

A total of 549 patients with persistent AF underwent de novo catheter ablation using the stepwise approach (2007–2009). A total of 493 patients were included (Holter ECGs ≥every 6 months). Mean follow-up was 59±16 months with 2.1±1.1 procedures per patient. Single and multiple procedure success rates were 20.1% and 55.9%, respectively (80% off antiarrhythmic drug). Antiarrhythmic drug–free multiple procedure success was 46%. Long-term recurrences (n=171) were paroxysmal AF in 48 patients (28%) and persistent AF/atrial tachycardia in 123 patients (72%). Multivariable recurrent event analysis revealed the following factors favoring arrhythmia recurrence: failure to terminate AF during index procedure (hazard ratio [HR], 1.279; 95% confidence interval [CI], 1.093–1.497; P =0.002), number of procedures (HR, 1.154; 95% CI, 1.051–1.267; P =0.003), female sex (HR, 1.263; 95% CI, 1.027–1.553; P =0.027), and the presence of structural heart disease (HR, 1.236; 95% CI, 1.003–1.524; P =0.047). AF termination was correlated with a higher rate of consecutive procedures because of atrial tachycardia recurrences ( P =0.003; HR, 1.71; 95% CI, 1.20–2.43).

Conclusions—

Catheter ablation of persistent AF using the stepwise approach provides limited long-term freedom of arrhythmias often requiring multiple procedures. AF termination, the number of procedures, sex, and the presence of structural heart disease correlate with outcome success. AF termination is associated with consecutive atrial tachycardia procedures.

Prospectively quantifying the propensity for atrial fibrillation: a mechanistic formulation

The goal of this study was to determine quantitative relationships between electrophysiologic parameters and the propensity of cardiac tissue to undergo atrial fibrillation. We used a computational model to simulate episodes of fibrillation, which we then characterized in terms of both their duration and the population dynamics of the electrical waves which drove them. Monte Carlo sampling revealed that episode durations followed an exponential decay distribution and wave population sizes followed a normal distribution. Half-lives of reentrant episodes increased exponentially with either increasing tissue area to boundary length ratio (A/BL) or decreasing action potential duration (APD), resistance (R) or capacitance (C). We found that the qualitative form of fibrillatory activity (e.g., multi-wavelet reentry (MWR) vs. rotors) was dependent on the ratio of resistance and capacitance to APD; MWR was reliably produced below a ratio of 0.18. We found that a composite of these electrophysiologic parameters, which we term the fibrillogenicity index (Fb = A/(BL*APD*R*C)), reliably predicted the duration of MWR episodes (r² = 0.93). Given that some of the quantities comprising Fb are amenable to manipulation (via either pharmacologic treatment or catheter ablation), these findings provide a theoretical basis for the development of titrated therapies of atrial fibrillation.

Diagnosis and management of atrial fibrillation: an overview

Atrial fibrillation (AF) has been defined as the new cardiovascular "epidemic". Its prevalence is rising in developed countries, and the associated social and economic costs are high. In the last few years, there has been an increasing interest in understanding the mechanisms of AF and its management. New pharmacotherapies together with novel techniques for surgical and catheter treatment of AF have been developed, allowing the maintenance of sinus rhythm and the alleviation of symptoms in a large number of patients with AF. However, there are still some challenges that need to be addressed. This article gives an overview of the current state of the art on novel techniques for diagnosis and management of AF.

The impact of catheter ablation in the interpulmonary isthmus on atrial fibrillation ablation outcomes: a randomized study

INTRODUCTION

Previous studies have underscored the importance of the interpulmonary isthmus in the initiation and maintenance of atrial fibrillation (AF). The efficacy of additional radiofrequency energy delivery in the interpulmonary isthmus following pulmonary vein antral isolation (PVAI) was investigated.

METHODS AND RESULTS

A total of 76 patients (49 males, mean age 56.8 ± 10.3) with drug-resistant paroxysmal (n = 64) and short-lasting persistent AF (n = 12) underwent PVAI. Patients were then randomly assigned to receive either "no further ablation" (group I, n = 38) or additional lesions in the interpulmonary isthmus of both ipsilateral pulmonary veins (group II, n = 38). There were no significant differences between study groups regarding the clinical and echocardiographic data. A trend towards a longer fluoroscopy time was observed in group II (P = 0.076). After a mean follow-up period of 11.1 ± 2.6 months, 22 patients in group I (57.9%) and 25 patients in group II (65.8%) were free from arrhythmia recurrence without any antiarrhythmic drug treatment after a single ablation procedure. The Kaplan-Meier arrhythmia-free survival curves showed no significant differences between study groups (P = 0.460).

CONCLUSIONS

Additional lesions in the interpulmonary isthmus following PVAI do not have incremental value in preventing AF recurrence.

Impact of atrial fibrillation termination site and termination mode in catheter ablation on arrhythmia recurrence

BACKGROUND

Although atrial fibrillation (AF) termination has been reported as a predictor of clinical outcome after persistent AF (PsAF) ablation, the relationship between AF termination site and mode and clinical outcome has not been fully evaluated.

METHODS AND RESULTS

A total of 135 patients (62±9 years) underwent their first ablation procedure for PsAF (76 longstanding PsAF). With an endpoint of AF termination, the ablation procedure was performed sequentially in the following order: pulmonary vein (PV) antrum isolation, and left atrial and right atrial substrate modification. AF termination was achieved in 69 patients (51%; 24 at the PV antrum, and 45 in the atrium; direct conversion to sinus rhythm in 21, and atrial tachycardia [AT] in 48). With a mean of 1.7±0.7 procedures/patient, 100 patients (74%) were free from atrial tachyarrhythmia (ATa) during a median of 15.0 months of follow-up. During the initial procedure, the AF termination site (atrium vs. PV antrum, hazard ratio [HR], 1.38; 95% confidence interval [CI]: 0.72-3.77; no termination vs. PV antrum, HR, 2.32; 95% CI: 1.26-6.30; P=0.023) and mode (AT vs. sinus rhythm, HR, 1.47; 95% CI: 0.77-4.01; no termination vs. sinus rhythm, HR, 2.38; 95% CI: 1.26-6.46; P=0.017) were independent predictors of ATa recurrence after the last ablation procedure.

CONCLUSIONS

The site and mode of AF termination during the index ablation procedure predict ATa recurrence following multiple catheter ablation procedures for PsAF.

Management of atrial fibrillation in chronic kidney disease: double trouble

Chronic kidney disease (CKD) has a very well-established link with cardiovascular disease. Below stage 3 CKD (glomerular filtration rate <60 mL/min), there is a progressive increase in both total mortality and cardiovascular-specific mortality as kidney function declines; indeed, it is more likely for a patient with CKD stage 3 to die of cardiovascular disease than to progress to CKD stage 4 and beyond. Arrhythmia is particularly common in patients with CKD. Depending on the study and measurement used, the prevalence of patients with CKD with chronic atrial fibrillation (AF) is quoted at 7% to 18%, rising to 12% to 25% for those older than 70 years. These rates are up to 2 to 3 times higher than in the general population. Of all patients with AF, 10% to 15% will have CKD. However, not all standard rate and rhythm methods are suitable for this population and those that are tend to be less effective. Meanwhile, anticoagulation has long been a thorny subject, with much conflicting evidence around the balance between bleeding and stroke risk. To help clarify this, we first highlight the challenges of performing evidence-based medicine in the patient with renal disease, and then review recent and emerging research to suggest an approach to the management of patients with renal disease who have AF. We also review the potential role of the different new oral anticoagulant drugs in CKD.

Pulmonary vein isolation in 2012: is it necessary to perform a time consuming electrophysical mapping or should we focus on rapid and safe therapies? A retrospective analysis of different ablation tools

BACKGROUND

Pulmonary Vein Isolation (PVI) is evolving as an established treatment option in atrial fibrillation (AF). Different fluoroscopy-guided ablation devices exist either on the basis of expandable circumferential and mesh designs with mapping and ablation of pulmonary vein potentials, or of a balloon technology, a "single shot" device with a purely anatomical approach. Systematic comparisons between procedure duration (PD), fluoroscopy time (FT) and clinical outcome in using different ablation tools are lacking in the literature.

METHODS

In a single center retrospective analysis, 119 PVI procedures were performed between August 2008 and March 2011 in paroxysmal AF (PAF, 59.7%) and persistent AF (persAF, 40.3%) patients with mean age of 59.4±10.3 years and history of AF since 8.1±9.7 months. The PVI procedures were evaluated by comparing PD and FT using I) the High Density Mesh Mapper (HDMM), II) the High Density Mesh Ablator (HDMA), and III) the Arctic Front® Cryoballoon. The primary endpoints were FT and PD, the secondary endpoint was procedural safety and efficacy in short- and longterm follow-up.

RESULTS

The procedures performed for 119 patients (63.0 % male) included 42 PVIs with the HDMM (35.3 %), 47 with the HDMA (39.5 %) and 30 with the cryoballoon (25.2 %). Comparing the 30 first procedures in groups of 10 in the HDMM and HDMA group, PD and FT fell in the HDMM group (PD from 257.5 to 220.9 min and FT from 80.5 to 67.3 min, both p < 0.05) as well as in the HDMA group (PD from 182.9 to 147.2 min and FT from 41.02 to 29.1 min, both p < 0.05). In the cryoballoon group, there was a steep learning curve with a steady state after the first 10 procedures (PD and FT decreased significantly from 189.5 to 138.1 min and 36.9 to 27.3 min, p values 0.005 and 0.05 respectively). With respect to recurrence of AF in a 24 months follow up, the HDMM and cryoballoon group showed comparable results with ~72% of patients free of arrhythmias. None of the patients died due to severe complications, or suffered a hemodynamic relevant pericardial effusion and/or stroke. Impairment of the phrenic nerve was observed in three patients.

CONCLUSION

Use of the cryoballoon technology was associated with a steep learning curve and a reduced PD and FT; the long-term outcome was similar compared with the HDMM group. The efficacy and safety of the devices but also PD and FT should be respected as the strongest indicators of the quality of ablation. Further studies with long time follow-ups will show if the time for correct mapping of the PV potentials is a price we should be willing to pay or if we should adopt a "wait-and-see" attitude referring the AF recurrence.

Ablation of atrial tachycardia occurring after catheter ablation of atrial fibrillation in patients with corrected rheumatic valve disease

OBJECTIVE

The purpose of this study is to investigate the mechanism and the effectiveness of ablation of atrial tachycardia (AT) recurring after atrial fibrillation (AF) ablation in patients with rheumatic valvular disease (RVD) and mitral valve prosthesis.

METHODS

Twenty-eight consecutive patients with RVD and mitral valve prosthesis and a 1:2 matched control group (n = 56) without RVD underwent reablation for recurrent AT after catheter ablation of long-standing persistent AF.

RESULTS

Macro- or localized reentrant ATs were identified in 47 (87 %) of 54 ATs from RVD group and in 65 (78.3 %) of 83 ATs from control. There were more average ATs per patient in the RVD group than in the control (1.9 ± 0.6 vs.1.5 ± 0.6, P = 0.002). The proportion of patients having ≥2 ATs was significantly higher in the RVD group than in the control (78.6 vs.41.1 %, P = 0.001). In the RVD group, ATs were successfully ablated in 44 (81.5 %) of 54 ATs and terminated in 18 (64.3 %) of 28 patients. In the control, ATs were successfully ablated in 72 (86.7 %) of 83 ATs and terminated in 45 (80.4 %) of 56 patients, P = 0.54 and 0.10, respectively. After a mean follow-up of 13 months, 16 patients (57.1 %) from the RVD group and 45 patients (80.4 %) from the control were free of further recurrence, P = 0.02.

CONCLUSIONS

Macro- or localized reentries were the predominant type of recurrent AT after long-standing persistent AF ablation in both the RVD and the control groups. Compared with patients without RVD, patients with RVD had more average number of ATs and had higher probability of further recurrence despite the similar acute effectiveness of reablation.

Impact of adenosine-provoked acute dormant pulmonary vein conduction on recurrence of atrial fibrillation

INTRODUCTION

Adenosine can be associated with acute recovery of conduction to the pulmonary veins (PVs) immediately after isolation. The objective of this study was to evaluate whether the response to adenosine predicts atrial fibrillation (AF) recurrence after a single ablation procedure in patients with paroxysmal AF.

METHODS AND RESULTS

A total of 109 consecutive patients (61 ± 10 years; 91 males) with drug-refractory paroxysmal AF who underwent AF ablation were analyzed. After PV antrum isolation (PVAI), dormant PV conduction was evaluated by an administration of adenosine in all patients. No acute reconnections were provoked by the adenosine in 70 (64.2%) patients (Group-1), but they were provoked in at least one side of the ipsilateral PVs in 39 (35.8%) patients (Group-2). All adenosine-provoked dormant conductions were successfully eliminated by additional ablation applications. By 12 months after the initial procedure, 72 (66.1%) patients were free of AF recurrences without any antiarrhythmic drugs. A Cox regression multivariate analysis of the variables including the adenosine-provoked reconductions, age, gender, duration of AF, presence of hypertension or structural heart disease, left atrial size, left ventricular ejection fraction, and body mass index demonstrated that adenosine-provoked reconductions were an independent predictor of AF recurrence after a single ablation procedure (hazard ratio: 1.387; 95% confidence interval: 1.018-1.889, P = 0.038). At the repeat session for recurrent AF, conduction recovery was observed similarly in both groups (P = 0.27).

CONCLUSION

Even after the elimination of any adenosine-provoked dormant PV conduction, the appearance of acute adenosine-provoked reconduction after the PVAI was an independent predictor of AF recurrence after a single AF ablation procedure.

Two-year clinical follow-up after pulmonary vein isolation using high-intensity focused ultrasound (HIFU) and an esophageal temperature-guided safety algorithm

BACKGROUND AND OBJECTIVE

High-intensity frequency ultrasound (HIFU) can achieve pulmonary vein isolation (PVI), but severe complications have happened. An esophageal temperature (ET)-guided safety algorithm was implemented. We investigated medium-term outcome.

METHODS

After left atrial access, HIFU was applied until complete PVI. The safety algorithm was as follows: ≤3 complete ablations per pulmonary vein, early abortion when ET ≥40.0°C, use of Power Modulation at ET >39.0°C or when after 20 to 30 seconds no change in PV electrograms: to reduce the ablation temperature in the surrounding tissue, acoustic power is switched on and off with a frequency of 1 Hz; in all first ablations, use of Power Modulation after 50% of programmed time. Touch-up radiofrequency ablation when PVI failed. Follow-up included interviews and Holter electrocardiograms. Recurrence was defined as atrial fibrillation (AF) >30 seconds without a blanking period.

RESULTS

A total of 28 symptomatic patients (18 males, age 63 years), with paroxysmal AF (n = 19) and persistent AF (n = 9) were included. After a median follow-up of 738 days, 22 of the 28 patients (79%) were free of AF without antiarrhythmic drugs. After 1 repeat procedure with radiofrequency ablation, 5 patients remained free of AF. The complications were as follows: 1 lethal atrial-to-esophageal fistula at day 31, 1 pericardial effusion at day 48, 1 unexplained death at day 49, and 2 persistent phrenic nerve palsies with full recovery within 12 months.

CONCLUSIONS

Two-year follow-up after PVI using HIFU and an ET-guided safety algorithm shows success rates similar to those of radiofrequency-based procedures but with higher complication rates. Importantly, the ET-guided safety algorithm failed to prevent severe complications. HIFU does not meet safety standards required for the treatment of AF, and this led to a halt of its clinical use.

Spatiotemporal electrophysiological changes in a murine ablation model

AIMS

High recurrence rates after complex radiofrequency ablation procedures, such as for atrial fibrillation, remain a major clinical problem. Local electrophysiological changes that occur following cardiac ablation therapy are incompletely described in the literature. The purpose of this study was to determine whether alterations in conduction velocity, action potential duration (APD), and effective refractory period resolve dynamically following cardiac ablation.

METHODS AND RESULTS

Lesions were delivered to the right ventricle of mice using a subxiphoid approach. The sham-operated control group (SHAM) received the same procedure without energy delivery. Hearts were isolated at 0, 1, 7, 30, and 60 days following the procedure and electrophysiological parameters were obtained using high-resolution optical mapping with a voltage-sensitive dye. Conduction velocity was significantly decreased at the lesion border in the 0, 7, and 30 day groups compared to SHAM. APD(70) at the lesion border was significantly increased at all time points compared to SHAM. Effective refractory period was significantly increased at the lesion border at 0, 1, 7, and 30 days but not at 60 days post-ablation. This study demonstrated that post-ablation electrophysiological changes take place immediately following energy delivery and resolve within 60 days.

CONCLUSIONS

Cardiac ablation causes significant electrophysiological changes both within the lesion and beyond the border zone. Late recovery of electrical conduction in individual lesions is consistent with clinical data demonstrating that arrhythmia recurrence is associated with failure to maintain bi-directional conduction block.

Electrophysiological features of atrial tachyarrhythmias after the creation of a left atrial roof line during catheter ablation of atrial fibrillation

Left atrial roof line (LARL) can prevent the perpetuation of atrial fibrillation (AF) by delineation of the arrhythmogenic substrate, but it may be associated with an increased incidence of atrial tachycardia (AT). This study was performed to evaluate the characteristics and clinical implications of inducible AT after LARL.A total of 139 consecutive patients with AF who underwent catheter ablation were prospectively enrolled in this study. LARL was required to prevent the perpetuation of AF in 98 of 139 patients (71%). LARL significantly reduced the incidence of inducible AF (before versus after: 100% versus 44%, respectively, P < 0.01), whereas it significantly increased the incidence of AT (18% versus 63%, P < 0.01). ATs were observed after LARL in 62 of 98 patients (63%), and these circuits were determined in 99 of 112 stable ATs (88%), including tricuspid isthmus-dependent (n = 35), mitral annulus (n = 22), septal (n = 15), surrounding right pulmonary veins (PVs) (n = 12), coronary sinus (CS) ostium (n = 4), upper loop (n = 4), surrounding left PVs (n = 4), and LA anterior wall (n = 3). Catheter ablation (CA) successfully terminated 111 of 122 stable ATs (91%) during CA. The occurrence of AT after CA was significantly higher in patients with than in those without residual AT (26% versus 2%, P < 0.05).Induced AT with a stable circuit after LARL creation could be mapped, and delineation of the induced AT may lead to a favorable outcome.

Autonomic remodeling in the left atrium and pulmonary veins in heart failure: creation of a dynamic substrate for atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is commonly associated with congestive heart failure (CHF). The autonomic nervous system is involved in the pathogenesis of both AF and CHF. We examined the role of autonomic remodeling in contributing to AF substrate in CHF.

METHODS AND RESULTS

Electrophysiological mapping was performed in the pulmonary veins and left atrium in 38 rapid ventricular-paced dogs (CHF group) and 39 control dogs under the following conditions: vagal stimulation, isoproterenol infusion, β-adrenergic blockade, acetylcholinesterase (AChE) inhibition (physostigmine), parasympathetic blockade, and double autonomic blockade. Explanted atria were examined for nerve density/distribution, muscarinic receptor and β-adrenergic receptor densities, and AChE activity. In CHF dogs, there was an increase in nerve bundle size, parasympathetic fibers/bundle, and density of sympathetic fibrils and cardiac ganglia, all preferentially in the posterior left atrium/pulmonary veins. Sympathetic hyperinnervation was accompanied by increases in β(1)-adrenergic receptor R density and in sympathetic effect on effective refractory periods and activation direction. β-Adrenergic blockade slowed AF dominant frequency. Parasympathetic remodeling was more complex, resulting in increased AChE activity, unchanged muscarinic receptor density, unchanged parasympathetic effect on activation direction and decreased effect of vagal stimulation on effective refractory period (restored by AChE inhibition). Parasympathetic blockade markedly decreased AF duration.

CONCLUSIONS

In this heart failure model, autonomic and electrophysiological remodeling occurs, involving the posterior left atrium and pulmonary veins. Despite synaptic compensation, parasympathetic hyperinnervation contributes significantly to AF maintenance. Parasympathetic and/or sympathetic signaling may be possible therapeutic targets for AF in CHF.

Persistence of pulmonary vein isolation after robotic remote-navigated ablation for atrial fibrillation and its relation to clinical outcome

AIMS

A robotic navigation system (RNS, Hansen™) has been developed as an alternative method of performing ablation for atrial fibrillation (AF). Despite the growing application of RNS-guided pulmonary vein isolation (PVI), its consequences and mechanisms of subsequent AF recurrences are unknown. We investigated the acute procedural success and persistence of PVI over time after robotic PVI and its relation to clinical outcome.

METHODS AND RESULTS

Sixty-four patients (60.7 ± 9.8 years, 53 male) with paroxysmal AF underwent robotic circumferential PVI with 3-dimensional left atrial reconstruction (NavX™). A voluntary repeat invasive electrophysiological study was performed 3 months after ablation irrespective of clinical course. Robotic PVI was successful in all patients without complication (fluoroscopy time: 23.5 [12-34], procedure time: 180 [150-225] minutes). Fluoroscopy time demonstrated a gradual decline but was significantly reduced after the 30th patient following the introduction of additional navigation software (34 [29-45] vs 12 [9-17] minutes; P < 0.001). A repeat study at 3 months was performed in 63% of patients and revealed electrical conduction recovery in 43% of all PVs. Restudied patients without AF recurrence (n = 28) showed a significantly lower number of recovered PVs (1 (0-2) vs 2 (2-3); P = 0.006) and a longer LA-PV conduction delay than patients with AF recurrences (n = 12). Persistent block of all PVs was associated with freedom from AF in all patients. At 3 months, 67% of patients were free of AF, while reablation of recovered PVs led to an overall freedom from AF in 81% of patients after 1 year.

CONCLUSION

Robotic PVI for PAF is safe, effective, and requires limited fluoroscopy while yielding comparable success rates to conventional ablation approaches with PV reconduction as a common phenomenon associated with AF recurrences.

Current ablation strategies for persistent and long-standing persistent atrial fibrillation

Atrial fibrillation (AF) is associated with an increased risk of cardiac and overall mortality. Restoration and maintenance of sinus rhythm is of paramount importance if it can be accomplished without the use of antiarrhythmic drugs. Catheter ablation has evolved into a well-established treatment option for patients with symptomatic, drug-refractory AF. Ablation strategies which target the pulmonary veins are the cornerstone of AF ablation procedures, irrespective of the AF type. Ablation strategies in the setting of persistent and long-standing persistent AF are more complex. Many centers follow a stepwise ablation approach including pulmonary vein antral isolation as the initial step, electrogram-based ablation at sites exhibiting complex fractionated atrial electrograms, and linear lesions. Up to now, no single strategy is uniformly effective in patients with persistent and long-standing persistent AF. The present study reviewed the efficacy of the current ablation strategies for persistent and long-standing persistent AF.

Pathophysiological mechanisms of atrial fibrillation: a translational appraisal

Atrial fibrillation (AF) is an arrhythmia that can occur as the result of numerous different pathophysiological processes in the atria. Some aspects of the morphological and electrophysiological alterations promoting AF have been studied extensively in animal models. Atrial tachycardia or AF itself shortens atrial refractoriness and causes loss of atrial contractility. Aging, neurohumoral activation, and chronic atrial stretch due to structural heart disease activate a variety of signaling pathways leading to histological changes in the atria including myocyte hypertrophy, fibroblast proliferation, and complex alterations of the extracellular matrix including tissue fibrosis. These changes in electrical, contractile, and structural properties of the atria have been called "atrial remodeling." The resulting electrophysiological substrate is characterized by shortening of atrial refractoriness and reentrant wavelength or by local conduction heterogeneities caused by disruption of electrical interconnections between muscle bundles. Under these conditions, ectopic activity originating from the pulmonary veins or other sites is more likely to occur and to trigger longer episodes of AF. Many of these alterations also occur in patients with or at risk for AF, although the direct demonstration of these mechanisms is sometimes challenging. The diversity of etiological factors and electrophysiological mechanisms promoting AF in humans hampers the development of more effective therapy of AF. This review aims to give a translational overview on the biological basis of atrial remodeling and the proarrhythmic mechanisms involved in the fibrillation process. We pay attention to translation of pathophysiological insights gained from in vitro experiments and animal models to patients. Also, suggestions for future research objectives and therapeutical implications are discussed.

Surgical Maze procedure as a treatment for atrial fibrillation: a meta-analysis of randomized controlled trials

Surgical or modified Maze procedures have been promoted to treat atrial fibrillation (AF); however, few randomized controlled clinical trials (RCTs) examine their outcomes. The purpose of this meta-analysis is to compare the efficacy of surgical Maze procedures performed concomitantly with referral cardiac surgery versus pharmacologic therapy for the treatment of AF. We searched MEDLINE, Cochrane database, FDA web-portal, and clinicaltrials.gov for all RCTs comparing surgical Maze procedures with medical therapy for sinus rhythm maintenance. Primary outcomes were either freedom from AF within 12 months postprocedure off antiarrhythmic drug (AAD), or freedom from AF while taking an AAD. Secondary outcomes included operative mortality, all-cause mortality, hospital length of stay, and postoperative complications. Both fixed- and random-effects models were used for a meta-analysis of 9 randomized controlled trials (n = 472, of which 249 underwent a Maze procedure and 213 underwent referral surgery alone). The surgical Maze procedure significantly increased the odds of freedom from AF within 12 months compared with cardiac surgery alone (OR 5.22, 95% CI 1.71-15.88). There was significant heterogeneity among the trials for freedom from AF (chi-square = 15.98 for 4 degrees of freedom, P= 0.003). Among the two studies that fully reported AAD use, there was no evidence of improved survival free from AF and AAD therapy (OR 1.78, 95% CI 0.73-4.34). Among patients with valvular AF, surgical Maze procedures are associated with a decrease in AF one year postprocedure without significant increase in mean length of hospital stay, perioperative complications, operative, or all-cause mortality. Large RCTs defining rates of freedom from AF without AADs postprocedure, are still needed to evaluate outcomes and determine the appropriate role for surgical Maze procedures in the management of AF.

Advances in imaging for atrial fibrillation ablation

Over the last fifteen years, our understanding of the pathophysiology of atrial fibrillation (AF) has paved the way for ablation to be utilized as an effective treatment option. With the aim of gaining more detailed anatomical representation, advances have been made using various imaging modalities, both before and during the ablation procedure, in planning and execution. Options have flourished from procedural fluoroscopy, electroanatomic mapping systems, preprocedural computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and combinations of these technologies. Exciting work is underway in an effort to allow the electrophysiologist to assess scar formation in real time. One advantage would be to lessen the learning curve for what are very complex procedures. The hope of these developments is to improve the likelihood of a successful ablation procedure and to allow more patients access to this treatment.

Combined effects of up- and downstream therapies on atrial fibrillation in a canine rapid stimulation model

BACKGROUND

Recent reports suggest angiotensin receptor blockers (ARBs) and some antiarrhythmic agents affect atrial remodeling in atrial fibrillation (AF). We evaluated the effect of combination therapy with olmesartan (Olm) and bepridil (Bep) in a canine model of AF.

METHODS AND RESULTS

An atrial stimulation device was implanted in 10 dogs undergoing 6-week pacing at 400 bpm. They were divided into Olm (2 mg/kg/day) (n=5) and Olm+Bep (Olm, 2 mg/kg/day; Bep, 10 mg/kg/day) groups (n=5). Atrial effective refractory period (AERP), conduction velocity (CV), and AF inducibility were evaluated weekly, and hemodynamics, atrial histology, and mRNA expression and protein expression of ion-channel and gap junction-related molecules at 6 weeks. Data were compared between groups and with non-pacing control and pacing-control groups from our previous report. The pacing-control group exhibited shortened AERP, decreased CV, increased AF inducibility and tissue fibrosis, and down-regulated L-type Ca(2+) channel (LCC), SCN5A, Kv4.3 and connexin43 (Cx43). By comparison, the Olm group exhibited suppression of the decrease in CV and of the increase in AF inducibility, but no change in AERP shortening. The Olm+Bep group exhibited suppression of AERP shortening as well as the greatest decrease in AF inducibility. Histologically, tissue fibrosis was suppressed in Olm and Olm+Bep groups. Down-regulation of Cx43 was partly suppressed in the Olm group while that of LCC, SCN5A, and Cx43 was suppressed in the Olm+Bep group.

CONCLUSION

Olm and Bep in combination suppressed AF inducibility more strongly than Olm alone, and may be more useful in the suppression of AF.

Biological therapies for cardiac arrhythmias: can genes and cells replace drugs and devices?

Cardiac rhythm disorders reflect failures of impulse generation and/or conduction. With the exception of ablation methods that yield selective endocardial destruction, present therapies are nonspecific and/or palliative. Progress in understanding the underlying biology opens up prospects for new alternatives. This article reviews the present state of the art in gene- and cell-based therapies to correct cardiac rhythm disturbances. We begin with the rationale for such approaches, briefly discuss efforts to address aspects of tachyarrhythmia, and review advances in creating a biological pacemaker to cure bradyarrhythmia. Insights gained bring the field closer to a paradigm shift away from devices and drugs, and toward biologics, in the treatment of rhythm disorders.

The permanency of pulmonary vein isolation using a balloon cryoablation catheter

BACKGROUND

Because of its technical feasibility and presumed safety benefits, balloon cryoablation is being increasingly employed for pulmonary vein (PV) isolation. While acute isolation has been demonstrated in most patients, little data are available on the chronic durability of cryoballoon lesions.

METHODS AND RESULTS

Twelve atrial fibrillation patients underwent PV isolation using either a 23-mm or 28-mm cryoballoon. For each vein, after electrical isolation was verified with the use of a circular mapping cathether, 2 bonus balloon ablation lesions were placed. Gaps in balloon occlusion were overcome using either a spot cryocatheter or a "pull-down" technique. A prespecified second procedure was performed at 8-12 weeks to assess for long-term PV isolation. Acute PV isolation was achieved in all PVs in the patient cohort (n = 48 PVs), using the cryoballoon alone in 47/48 PVs (98%); a "pull-down" technique was employed for 5 PVs (1 right superior pulmonary vein, 2 right inferior pulmonary veins, and 2 left inferior pulmonary veins). The gap in the remaining vein was ablated with a spot cryocatheter. During the second mapping procedure, 42 of 48 PVs (88%) remained isolated. One vein had reconnected in 2 patients, while 2 veins had reconnected in another 2 patients. All PVs initially isolated with the "pull-down" technique remained isolated at the second procedure.

CONCLUSIONS

Cryoballoon ablation allows for durable PV isolation with the use of a single balloon. With maintained chronic isolation in most PVs, it may represent a significant step toward consistent and lasting ablation procedures.

Electrophysiological remodeling in heart failure

Heart failure affects nearly 6 million Americans, with a half-million new cases emerging each year. Whereas up to 50% of heart failure patients die of arrhythmia, the diverse mechanisms underlying heart failure-associated arrhythmia are poorly understood. As a consequence, effectiveness of antiarrhythmic pharmacotherapy remains elusive. Here, we review recent advances in our understanding of heart failure-associated molecular events impacting the electrical function of the myocardium. We approach this from an anatomical standpoint, summarizing recent insights gleaned from pre-clinical models and discussing their relevance to human heart failure.

Ablation strategies for atrial fibrillation

Atrial fibrillation remains the most common arrhythmia in the USA and is associated with an increased risk for stroke, congestive heart failure and overall mortality. There has been a tremendous advance in the field of catheter ablation of atrial fibrillation that has resulted in better outcomes for patients. The approach for ablation of atrial fibrillation can be different depending on patients' presentation of paroxysmal or persistent atrial fibrillation. Pulmonary vein isolation remains the cornerstone of any ablation strategy for atrial fibrillation; however, further ablation, end points of the procedure, clinical end points for successful ablation and appropriate follow-up remain controversial. We aim to discuss these different approaches and the major controversies in catheter ablation of atrial fibrillation.

Persistent atrial fibrillation converts to common type atrial flutter during CFAE ablation

BACKGROUND

Catheter ablation of persistent and long-standing persistent atrial fibrillation (AF) is still challenging. So far different ablation techniques have been reported, including pulmonary vein isolation, additional linear lesions, ablation of complex fractionated atrial electrograms (CFAE), and combinations of these techniques. During ablation of CFAE, the occurrence of left atrial (LA) tachycardia is well known. The occurrence of right atrial flutter on the other hand is less well described.

METHODS

Here, we report three patients who had been ablated because of symptomatic persistent atrial fibrillation.

SUMMARY

In all patients, AF changed into a cavotricuspid isthmus = dependent right atrial flutter during ablation of CFAE in the LA.