Atrial fibrillation: epidemiologic considerations and rationale for conversion and maintenance of sinus rhythm

Epicardial Atrial Ablation Using a Novel Articulated Robotic Medical Probe via a Percutaneous Subxiphoid Approach

Objective

Minimally invasive epicardial atrial ablation to cure atrial fibrillation through the use of a percutaneous subxiphoid approach currently has a lack of dedicated technology for intrapericardial navigation around the beating heart. We have developed a novel articulated robotic medical probe and performed preliminary experiments in a porcine preparation.

Methods

In five large, healthy pigs, the teleoperated robotic system was introduced inside the pericardial space through a percutaneous subxiphoid approach. Secondary visualization of the left atrium and left atrial appendage was achieved with the use of a 5-mm scope inserted through a left thoracic port. The operator actively controlled the path of the robot by using a master manipulator. The catheter, with an irrigated radiofrequency tip, was guided through the working port of the robot to achieve epicardial ablation of the left atrium.

Results

Access to the pericardial space and progression around the left atrium was successful in all cases, with no interference with the beating heart such as a fatal arrhythmia, unexpected bleeding, and hypotension. Epicardial ablation was successfully performed in all five cases. No adverse hemodynamic or electrophysiological events were noted during the trials. When the animals were killed, there was no visually detected injury on the surrounding mediastinal structures caused by ablation. Transmural ablation was confirmed by histopathology of the left atrium.

Conclusions

We have developed a dedicated articulated robotic medical probe and successfully performed epicardial left atrial radiofrequency ablation. Based on the feedback from these preliminary experiments, the radius of curvature and proper visualization of the device are being improved in the next generation prototype.

Electrocardiogram PR Interval Is a Surrogate Marker to Predict New Occurrence of Atrial Fibrillation in Patients with Frequent Premature Atrial Contractions

The clinical significance of prolonged PR interval has not been evaluated in patients with frequent premature atrial contractions (PACs). We investigated whether prolonged PR interval could predict new occurrence of atrial fibrillation (AF) in patients with frequent PACs. We retrospectively analyzed 684 patients with frequent PACs (> 100 PACs/day) who performed repeated 24-hour Holter monitoring. Prolonged PR interval was defined as longer than 200 msec. Among 684 patients, 626 patients had normal PR intervals (group A) and 58 patients had prolonged PR intervals (group B). After a mean follow-up of 59.3 months, 14 patients (24.1%) in group B developed AF compared to 50 patients (8.0%) in group A (P < 0.001). Cox regression analysis showed that prolonged PR interval (hazard ratio [HR], 1.950; 95% CI, 1.029-3.698; P = 0.041), age (HR, 1.033; 95% CI, 1.006-1.060; P = 0.015), and left atrial (LA) dimension (HR, 1.061; 95% CI, 1.012-1.112; P = 0.015) were associated with AF occurrence. Prolonged PR interval, advanced age, and enlarged LA dimension are independent risk factors of AF occurrence in patients with frequent PACs.

Renal Denervation And Pulmonary Vein Isolation In Patients With Drug Resistant Hypertension And Symptomatic Atrial Fibrillation

Systemic hypertension is the most consistent modifiable risk factor for atrial fibrillation (AF) in adults with consistent data from both animal models and human studies suggesting a consistent pattern of autonomic imbalance underlying both conditions. Relative sympathetic nervous system activation is a demonstrably common attendant to the local mechanisms in pulmonary veins that sustain persistent or recurrent AF and may represent a new objective for adjunctive treatment. Established management of AF aims to achieve durable control through either pharmacologic or catheter-based interventions. The introduction of catheter-based renal denervation as a safe, alternate approach to target the sympathetic nervous system therapeutically represents a potential opportunity to treat the shared pathophysiological mechanisms with minimal additional treatment burden when added in this context. Preliminary investigations have demonstrated both proof-of-concept and the technical feasibility of combined renal denervation and AF ablation procedures with the suggestion of benefit in terms of freedom from AF recurrence. The available data is promising but absolute confirmation of efficacy remains unconfirmed in the absence of more definitive evidence. This paper reviews the role of autonomic imbalance in the initiation and maintenance of AF by summarizing the observations from both experimental models and clinical studies from the perspective of potential therapeutic overlap between catheter-based treatments.

Efficacy of dronedarone versus propafenone in the maintenance of sinus rhythm in patients with atrial fibrillation after electrical cardioversion

PURPOSE

Our objective was to compare the efficacy of dronedarone and propafenone in maintaining sinus rhythm in patients with atrial fibrillation (AF) after electrical cardioversion.

METHODS

In this single-center, open-label, randomized trial, we randomly assigned patients with AF after electrical cardioversion to receive dronedarone 400 mg BID or propafenone 150 mg TID. Follow-up clinical evaluations were conducted at 1, 2, 3, and 6 months of treatment. The primary end point was the time to the first recurrence of AF.

FINDINGS

A total of 98 patients were enrolled (79 men; mean age, 59.2 years; n = 49 per group). The median times to first recurrence of AF were 31 days in the dronedarone group and 32 days in the propafenone group (P = 0.715). The median (interquartile range) ventricular rates at first recurrence of AF were 76.5 (67.3-86.5) beats/min in the dronedarone group and 83.0 (71.0-96.0) beats/min in the propafenone group (P = 0.059).

IMPLICATIONS

Dronedarone and propafenone had similar efficacies in maintaining sinus rhythm in patients with AF after electrical cardioversion. The ventricular rate at the first recurrence of AF was numerically but not statistically significantly lower in the dronedarone group than in the propafenone group. ClinicalTrials.gov identifier: NCT01991119.

Safety considerations in the pharmacological management of atrial fibrillation

The pharmacological management of atrial fibrillation (AF) requires careful consideration from a safety perspective. This article focuses primarily on maintenance therapy using antiarrhythmic drugs (AADs). The foremost safety issue for AADs is the propensity of class IA and III agents to cause torsade de pointes arrhythmias. Class IA drugs, particularly quinidine, can induce torsade de pointes at low or subtherapeutic doses, but higher doses are not necessarily associated with an increased incidence. 'Pure' class III drugs such as dofetilide induce torsade de pointes in a dose-related manner, but some class III agents with more complex actions such as amiodarone have a markedly lower potential to cause this arrhythmia. The risk of torsade de pointes precludes the use of class IA and 'pure' class III agents in patients with left ventricular hypertrophy and bradycardia. Class IC agents may cause sustained monomorphic ventricular tachycardias and are generally precluded in ischaemic and structural heart disease. Advanced heart failure patients may be treated with amiodarone or dofetilide, but most other AADs are unsuitable. The most important extracardiac toxicities occurring with AADs are those of amiodarone. Drug interactions are a significant safety issue in the management of AF, including pharmacokinetic interactions in which plasma levels of the AAD are raised - increasing the risk of proarrhythmia - and concomitant use of drugs that prolong the QT interval. Notwithstanding these considerations, most patients with AF can be considered for rhythm control, provided there is adequate pre-treatment assessment and protocols for initiation, dosing and monitoring are followed with care.

Dronedarone for maintenance of sinus rhythm in atrial fibrillation or flutter

BACKGROUND

Amiodarone is effective in maintaining sinus rhythm in atrial fibrillation but is associated with potentially serious toxic effects. Dronedarone is a new antiarrhythmic agent pharmacologically related to amiodarone but developed to reduce the risk of side effects.

METHODS

In two identical multicenter, double-blind, randomized trials, one conducted in Europe (ClinicalTrials.gov number, NCT00259428 [ClinicalTrials.gov] ) and one conducted in the United States, Canada, Australia, South Africa, and Argentina (termed the non-European trial, NCT00259376 [ClinicalTrials.gov] ), we evaluated the efficacy of dronedarone, with 828 patients receiving 400 mg of the drug twice daily and 409 patients receiving placebo. Rhythm was monitored transtelephonically on days 2, 3, and 5; at 3, 5, 7, and 10 months; during recurrence of arrhythmia; and at nine scheduled visits during a 12-month period. The primary end point was the time to the first recurrence of atrial fibrillation or flutter.

RESULTS

In the European trial, the median times to the recurrence of arrhythmia were 41 days in the placebo group and 96 days in the dronedarone group (P=0.01). The corresponding durations in the non-European trial were 59 and 158 days (P=0.002). At the recurrence of arrhythmia in the European trial, the mean (+/-SD) ventricular rate was 117.5+/-29.1 beats per minute in the placebo group and 102.3+/-24.7 beats per minute in the dronedarone group (P<0.001); the corresponding rates in the non-European trial were 116.6+/-31.9 and 104.6+/-27.1 beats per minute (P<0.001). Rates of pulmonary toxic effects and of thyroid and liver dysfunction were not significantly increased in the dronedarone group.

CONCLUSIONS

Dronedarone was significantly more effective than placebo in maintaining sinus rhythm and in reducing the ventricular rate during recurrence of arrhythmia.

A review of the investigational antiarrhythmic agent dronedarone

Arrhythmias are a major cause of morbidity and mortality, and atrial fibrillation is the most widespread disorder of cardiac rhythm. Amiodarone is an effective antiarrhythmic agent that has been in clinical use for about 20 years. It is effective for multiple types of arrhythmias, including atrial fibrillation, and has a low incidence of cardiac adverse events, including Torsade de Pointes. It has many noncardiac adverse effects that are serious and limit its long-term use. Dronedarone is an investigational antiarrhythmic agent that is designed to have similar cardiac effects to amiodarone but with fewer adverse effects. This review presents some of the animal and human studies that evaluate the effects of dronedarone.

The progressive nature of atrial fibrillation: a rationale for early restoration and maintenance of sinus rhythm

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, affecting young as well as elderly patients and presenting a major therapeutic challenge for clinical cardiologists. Recent research has elucidated the progressive nature of AF, including the structural and electrical remodelling that may become manifest if normal sinus rhythm is not restored, and the serious morbidities associated with long-term disease. The controversy over the merits of ventricular rate control vs. the restoration and maintenance of normal sinus rhythm in the treatment of AF has been explored in a number of large-scale, randomized clinical trials. The results of these trials suggest that whereas the two strategies may be equivalent for some patient populations, with both approaches requiring accompanying anticoagulation therapy, the restoration and maintenance of sinus rhythm provide important haemodynamic as well as subjective benefits not afforded by rate control. Although early intervention to limit the progression of this arrhythmia is hindered by the limitations of existing anti-arrhythmic therapies, it is nevertheless a critical goal.

Amiodarone: A multifaceted antiarrhythmic drug

Synthesized as an antianginal compound 40 years ago, amiodarone has emerged as a uniquely effective antiarrhythmic compound in recent years. It has numerous properties, the most prominent being the ability to lengthen repolarization in the atria and ventricles associated with bradycardia without the significant potential for torsades de pointes. Amiodarone effectively controls a wide spectrum of atrial and ventricular antiarrhythmic disorders, but its limiting side effects, such as thyroid dysfunction, pulmonary fibrosis, and dermatologic changes, may limit its long-term use in some patients. What aspects of the multiplicity of the properties of amiodarone are relevant to its unusual efficacy is not known. Deiodination and other structural changes in the amiodarone molecule have has led to a the loss of thyroid and pulmonary effects in the resulting derivative, dronedarone, which is in advanced clinical development.

Relation of atrial arrhythmia-related symptoms to health-related quality of life in patients with newly diagnosed atrial fibrillation: A community hospital-based cohort

BACKGROUND

Atrial fibrillation is the most common sustained cardiac rhythm disturbance encountered in clinical practice. Despite its high prevalence and associated hospital admissions, few studies document the actual perceived symptoms of atrial fibrillation and its relationship to health-related quality of life.

OBJECTIVES

The purposes of this study were to explore the patients' symptoms of atrial fibrillation and to examine the relationship between specific symptoms and self-reported health-related quality of life in patients newly diagnosed with atrial fibrillation.

METHODS

This study used a descriptive correlational and cross-sectional survey design using a face-to-face interview method. Arrhythmia-related symptoms and health-related quality of life were measured by Version 3 of the Symptom Checklists: Frequency and Severity and the Short Form-36 Health Survey of the Medical Outcomes Study questionnaire, respectively. The data collected were statistically analyzed by t tests and partial correlation analyses to examine the group differences in symptoms and the relationship between arrhythmia-related symptoms and health-related quality of life, respectively.

RESULTS

A total of 81 subjects newly diagnosed with atrial fibrillation within 6 months before data collection were interviewed from two community hospitals in Cleveland, Ohio. Among 16 atrial arrhythmia-related symptoms, tiredness was the most frequently reported. Furthermore, reported symptoms were significantly different between the two groups divided only by age. Symptom frequency had a significant correlation with both physical health and mental health. Specifically, the relationships between "shortness of breath" and physical health, and "tiredness" and mental health were shown to be the strongest in each dimension of health-related quality of life.

CONCLUSION

This study demonstrates that patients with more frequent symptoms perceived poorer physical health and mental health compared with those with less frequent symptoms. Thus, the general conception that "atrial fibrillation is asymptomatic" should be reconsidered. In clinical situations, as a health care provider caring for patients with atrial fibrillation, the assessment of the nature and severity of symptoms should be performed to promote patients' quality of life.

Totally Endoscopic Ablation of Lone Atrial Fibrillation: Initial Clinical Experience

BACKGROUND

Atrial fibrillation is the most common form of arrhythmia leading to hospital admission. Over 2.2 million Americans are affected by atrial fibrillation and approximately 160,000 new cases are identified annually. As the population continues to age, the number of patients will increase. AF is an incremental risk factor for death and stroke, and consumes billions of dollars in health care expenditures.

METHODS

Between August 2003 and October 2004, 50 drug-resistant, symptomatic atrial fibrillation patients underwent thoracoscopic or robotic-assisted off-pump epicardial microwave ablation with the FLEX 10 device (Guidant, Indianapolis, IN). There were 35 men (70.0%) and 15 women (30.0%), mean age 59.1 years +/- 10.0 (range, 37-75 years). Mean duration of atrial fibrillation was 73.5 months +/- 82.3 (range, 5-480 months). Thirty-three patients (66.0%) had intermittent atrial fibrillation and 17 (34.0%) continuous. Intermittent patients had pulmonary vein isolation whereas continuous patients had additional right and left atrial lesions performed. Forty-six patients (92.0%) had endoscopic stapling of the left atrial appendage.

RESULTS

There were no hospital deaths. Postoperative in-hospital complications were minimal with 2 patients (4.0%) experiencing diaphragmatic dysfunction. No patient required a permanent pacemaker implant. Mean postoperative length of stay was 3.7 +/- 2.2 days. Cumulative follow-up was 335.8 patient months, mean 7.6 months (range, 2.0-15.9 months). There was 1 late death (2.0%). In 5 patients (10.0%) the MicroMaze operation and subsequent electrophysiology intervention failed and a Cox-Maze III operation was performed. Follow-up was 100% complete with 79.5% (35 of 44) patients in normal sinus rhythm.

CONCLUSIONS

Totally endoscopic closed-chest microwave ablation for treatment of intermittent and continuous atrial fibrillation is technically feasible and presents minimal risk to the patient. Initial results are impressive and demonstrate an enhanced quality of life and freedom from atrial fibrillation in drug-resistant symptomatic patients.

Economic impact of the reduced incidence of atrial fibrillation in patients with heart failure treated with enalapril

BACKGROUND

Atrial fibrillation (AF) in the setting of heart failure (HF) is linked to embolic stroke and exacerbation of HF. The rate of new-onset AF in patients with left ventricular dysfunction and mild to moderate HF enrolled in the SoLVD trials was significantly lower with enalapril than with placebo (5.4% vs 24% over 2.9 years, P < .0001). The objective of this study was to predict economic benefits over 5 and 10 years of reduced AF incidence in patients receiving enalapril for the treatment of HF from a Canadian third-party payer perspective.

METHODS

Consequences of reduced incidence of AF in enalapril-treated patients were modeled using a Markov model. Patients were assigned to 1 health state: no AF, AF, poststroke, or death, and moved from one state to the other according to published incidence rates. It was assumed that most patients with AF would receive warfarin for stroke prevention. Resource use and costs were mostly retrieved from published Canadian studies.

RESULTS

Reduced incidence of AF resulted in savings of 382 dollars and 525 dollars per patient treated with enalapril over 5 and 10 years, respectively, which stemmed mainly from reduced AF hospitalization and less need for warfarin and amiodarone. Sensitivity analyses demonstrated that enalapril becomes more cost saving as the baseline risk for embolic stroke in patients with AF increases and the use of warfarin prophylaxis decreases.

CONCLUSIONS

Reduced incidence of AF with enalapril leads to significant clinical and economic advantages on top of the already well-established benefits of enalapril for patients with HF.

Amiodarone versus sotalol for atrial fibrillation

BACKGROUND

The optimal pharmacologic means to restore and maintain sinus rhythm in patients with atrial fibrillation remains controversial.

METHODS

In this double-blind, placebo-controlled trial, we randomly assigned 665 patients who were receiving anticoagulants and had persistent atrial fibrillation to receive amiodarone (267 patients), sotalol (261 patients), or placebo (137 patients) and monitored them for 1 to 4.5 years. The primary end point was the time to recurrence of atrial fibrillation beginning on day 28, determined by means of weekly transtelephonic monitoring.

RESULTS

Spontaneous conversion occurred in 27.1 percent of the amiodarone group, 24.2 percent of the sotalol group, and 0.8 percent of the placebo group, and direct-current cardioversion failed in 27.7 percent, 26.5 percent, and 32.1 percent, respectively. The median times to a recurrence of atrial fibrillation were 487 days in the amiodarone group, 74 days in the sotalol group, and 6 days in the placebo group according to intention to treat and 809, 209, and 13 days, respectively, according to treatment received. Amiodarone was superior to sotalol (P<0.001) and to placebo (P<0.001), and sotalol was superior to placebo (P<0.001). In patients with ischemic heart disease, the median time to a recurrence of atrial fibrillation was 569 days with amiodarone therapy and 428 days with sotalol therapy (P=0.53). Restoration and maintenance of sinus rhythm significantly improved the quality of life and exercise capacity. There were no significant differences in major adverse events among the three groups.

CONCLUSIONS

Amiodarone and sotalol are equally efficacious in converting atrial fibrillation to sinus rhythm. Amiodarone is superior for maintaining sinus rhythm, but both drugs have similar efficacy in patients with ischemic heart disease. Sustained sinus rhythm is associated with an improved quality of life and improved exercise performance.

Pharmacological cardioversion of atrial fibrillation: current management and treatment options

Atrial fibrillation (AF) is the most common form of arrhythmia, carrying high social costs. It is usually first seen by general practitioners or in emergency departments. Despite the availability of consensus guidelines, considerable variations exist in treatment practice, especially outside specialised cardiological settings. Cardioversion to sinus rhythm aims to: (i) restore the atrial contribution to ventricular filling/output; (ii) regularise ventricular rate; and (iii) interrupt atrial remodelling. Cardioversion always requires careful assessment of potential proarrhythmic and thromboembolic risks, and this translates into the need to personalise treatment decisions. Among the many clinical variables that affect strategy selection, time from onset is crucial. In selected patients, pharmacological cardioversion of recent-onset AF can be a safely used, feasible and effective approach, even in internal medicine and emergency departments. In most cases of recent-onset AF, pharmacological cardioversion provides an important--and probably more cost effective--alternative to electrical cardioversion, which can then be employed as a second-line therapy for nonresponders. Class IC agents (flecainide or propafenone), which can be safely used in hospitalised patients with recent-onset AF without left ventricular dysfunction, can provide rapid conversion to sinus rhythm after either intravenous administration or oral loading. Although intravenous amiodarone requires longer conversion times, it is still the standard treatment for patients with heart failure. Ibutilide also provides good conversion rates and could be used for AF patients with left ventricular dysfunction (were it not for high costs). For long-lasting AF most pharmacological treatments have only limited efficacy and electrical cardioversion remains the gold standard in this setting. However, a widely used strategy involves pretreatment with amiodarone in the weeks before planned electrical cardioversion: this provides optimal prophylaxis and can sometimes even restore sinus rhythm. Dofetilide may also be capable of restoring sinus rhythm in up to 25-30% of patients and can be used in patients with heart failure. The potential risk of proarrhythmia increases the need for careful therapeutic decision making and management of pharmacological cardioversion. The results of recent trials (AFFIRM [Atrial Fibrillation Follow-up Investigation of Rhythm Management] and RACE [Rate Control versus Electrical Cardioversion for Persistent Atrial Fibrillation]) on rate versus rhythm control strategies in the long term have led to a generalised shift in interest towards rate control. Although carefully designed studies are required to better define the role of pharmacological rhythm control in specific AF settings, this alternative option remains a recommendable strategy for many patients, especially those in acute care.

Occipital lobe infarction following cardiac ablation

A 60-year-old man presented with the chief complaint of seeing a blurred area just up and to the left of the center of his vision. The patient noted this visual field defect immediately after he awoke from a cardiac electrophysiologic study with a catheter ablation procedure. On neuro-ophthalmologic testing, a small scotoma was present superior and left of fixation in both eyes. MRI showed a small irregular area of abnormal signal in the right occipital lobe consistent with an ischemic lesion. To the best of our knowledge, this represents the first case report of a homonymous visual field defect secondary to an occipital lobe infarction following a cardiac catheter ablation procedure.

Ablation for atrial fibrillation: are cures really achieved?

During the past 10 years numerous studies on the treatment of paroxysmal atrial fibrillation (AF) by right and left atrial ablation procedures have been published. The results of studies based on follow-up periods of a few months have been repeatedly interpreted as providing evidence for curative therapy. However, insufficient focus on the variability of the natural history of paroxysmal AF, the inadequate detection of silent arrhythmic events, the eclectic post-interventional use of antiarrhythmic drugs, and the lack of appropriate control groups make the reports unconvincing. Randomized controlled trials are needed to confirm postulated long-term cure rates for AF.