Electrical cardioversion of atrial fibrillation

The Impact of Personal Thoracic Impedance on Electrical Cardioversion in Patients with Atrial Arrhythmias

Background and Objectives: Direct current cardioversion (DCCV) is a safe and useful treatment for atrial tachyarrhythmias. In the past, the energy delivered in DCCV was decided upon empirically, based only on the type of tachyarrhythmia. This conventional method does not consider individual factors and may lead to unnecessary electrical damage. Materials and Methods: We performed DCCV in patients with atrial tachyarrhythmias. The impedance and electrical current at the moment of shock were measured. The human thoracic impedance between both defibrillator patches and the electric current that was used were measured. Results: A total of 683 DCCVs were performed on 466 atrial tachyarrhythmia patients. The average impedance was 64 ± 11 Ω and the average successful current was 23 ± 6 mA. The magnitude of the electrical current that was successful depended upon the human impedance (linear regression, B = −0.266, p < 0.001) and the left atrial diameter (B = 0.092, p < 0.001). Impedance was directly proportional to body mass index (BMI) (B = 1.598, p < 0.001) and was higher in females than in males (77 ± 15 Ω vs. 63 ± 11 Ω, p < 0.001). Notably, the high-impedance (>70 Ω) group had a higher BMI (27 ± 4 kg/m² vs. 25 ± 3 kg/m², p < 0.001) and a higher proportion of females (37% vs. 9%, p < 0.001) than the low-impedance group (<70 Ω). However, thoracic impedance was not an independent predictor for successful DCCV. Conclusions: Human thoracic impedance was one of the factors that impacted the level of electrical current required for successful DCCV in patients with atrial arrhythmias. In the future, it will be helpful to consider individual predictors, such as BMI and gender, to minimize electrical damage during DCCV.

A shock-free approach for ambulatory cardioversion in atrial fibrillation

Atrial fibrillation (AF), the most common persistent arrhythmia, is terminated most effectively by electrical cardioversion. This therapy requires in-hospital sedation to relieve the pain caused by electric shocks. Recently, our research group showed how the heart itself could be enabled to detect and terminate arrhythmias, including AF, thereby revealing the discovery of fully biological, shock-free cardioversion. Because of its biological nature, neither electric shocks nor hardware/software is required for sinus rhythm (SR) restoration, which creates a new perspective for ambulatory AF termination. Increasing evidence suggests that patients may indeed benefit from such continuous real-time rhythm control.

Is there any Link Between Vitamin D and Recurrence of Atrial Fibrillation after Cardioversion?

Introduction

Atrial fibrillation (AF) is the most common chronic arrhythmia in the elderly population. In symptomatic patients, restoration and maintenance of sinus rhythm improve quality of life. Unfortunately, AF recurrence still occurs in a considerable number of patients after cardioversion (CV). In this study, we aimed to evaluate the association between vitamin D (VitD) and AF recurrence after electrical or medical CV.

Method

A total of 51 patients who underwent CV for symptomatic AF were included in the study. AF recurrence was defined as an AF pattern in 12-lead electrocardiography (ECG) recording after CV within 6 months or ECG Holter recording of AF lasting more than 30 seconds at 6-month follow-up.

Results

Mean vitD level was 21.4 ng/ml in our study population. VitD level was lower in the AF recurrence group than in the non-recurrence group (18 ng/ml vs. 26.3 ng/ml, respectively; P=0.001). Additionally, left atrial diameter was larger in the AF recurrence group compared to the non-recurrence group (4.4 vs. 4.1, P=0.025). Patients with AF recurrence were older than patients without AF recurrence, and, although the prevalence of hypertension is higher in the AF recurrence group, there was no statistically significant difference (P=0.107, P=0.867).

Conclusion

In our study, there is a strong association between vitD level and AF recurrence after CV. VitD deficiency might be a predictor of high risk of AF recurrence after CV and vitD supplementation during the follow-up might help the maintenance of sinus rhythm.

Efficacy and Safety of Outpatient Clinic-based Elective External Electrical Cardioversion in Patients with Atrial Fibrillation

BACKGROUND AND OBJECTIVES

Little is known about the outcomes of outpatient clinic-based elective external cardioversion (OPC-ECV) for persistent atrial fibrillation (PeAF). We investigated the acute, short-term, and long-term elective external cardioversion (ECV) outcomes.

METHODS

We included 1,718 patients who underwent OPC-ECV (74% male, 61.1±11.0 years old, 90.9% long-standing PeAF, 9.1% after atrial fibrillation [AF] ablation) after excluding patients with atrial tachycardia or inappropriate antiarrhythmic drug medication, and in-patient ECV. Biphasic shocks were delivered sequentially until successful cardioversion was achieved (70-100-150-200-250 J). If ECV failed at 150 J, we administered intravenous amiodarone 150 mg and delivered 200 J.

RESULTS

ECV failed in 11.4%, and the complication rate was 0.47%. Within 3 months, AF recurred in 55.5% (44.7% as sustaining AF, 10.8% as paroxysmal AF), and the AF duration was independently associated (odds ratio [OR], 1.01 [1.00-1.02]; p=0.006), but amiodarone was independently protective (OR, 0.46 [0.27-0.76]; p=0.002, Log rank p<0.001) against an early recurrence. Regarding the long-term recurrence, pre-ECV heart failure was protective against an AF recurrence (hazard ratio, 0.63 [0.41-0.96], p=0.033) over 32 (9-66) months of follow-up. ECV energy (p<0.001) and early recurrence rate within 3 months (p=0.007, Log rank p=0.006) were significantly lower in post-ablation patients than in those with long-standing persistent AF.

CONCLUSIONS

The success rate of OPC-ECV was 88.6%, and the complication rate was low. However, AF recurred in 55.5% within 3 months. Amiodarone was protective against short-term AF recurrences, and long-term AF recurrences were less in patients with baseline heart failure.

Study of young patients with myocardial infarction: Design and rationale of the YOUNG-MI Registry

The YOUNG-MI registry is a retrospective study examining a cohort of young adults age ≤ 50 years with a first-time myocardial infarction. The study will use the robust electronic health records of 2 large academic medical centers, as well as detailed chart review of all patients, to generate high-quality longitudinal data regarding the clinical characteristics, management, and outcomes of patients who experience a myocardial infarction at a young age. Our findings will provide important insights regarding prevention, risk stratification, treatment, and outcomes of cardiovascular disease in this understudied population, as well as identify disparities which, if addressed, can lead to further improvement in patient outcomes.

New-onset atrial fibrillation in critically ill patients

New-onset atrial fibrillation is a common problem in critically ill patients, with reported incidence ranging from 5% to 46%. It is associated with significant morbidity and mortality. The present review summarizes studies investigating new-onset atrial fibrillation conducted in the critical care setting, focusing on the etiology, management of the hemodynamically unstable patient, rate versus rhythm control, ischemic stroke risk and anticoagulation. Recommendations for an approach to management in the intensive care unit are drawn from the results of these studies.

Cardioversion in Non-Valvular Atrial Fibrillation

BACKGROUND

Atrial fibrillation is the most common type of cardiac arrhythmia and is associated with elevated rates of stroke, heart failure, hospital admission, and death. Its prevalence in the overall population is 1.5% to 2%. To convert atrial fibrillation to sinus rhythm, cardioversion is needed.

METHODS

This review is based on pertinent articles published from 2004 to December 2014 that were retrieved by a selective PubMed search employing the terms "atrial fibrillation" and "cardioversion."

RESULTS

In electrical cardioversion, a defibrillator is used to pass a pulse of current between two electrodes. In pharmacological cardioversion, antiarrhythmic drugs are given intravenously or orally. Electrical cardioversion results in sinus rhythm in more than 85% of patients; pharmacological cardioversion results in sinus rhythm in about 70% of patients with recent-onset atrial fibrillation. As a rule, cardioversion should be carried out only under effective therapeutic anticoagulation with heparin, a vitamin K antagonist, or a new oral anticoagulant drug. If atrial fibrillation has been present for more than 48 hours, cardioversion must be preceded by transesophageal echocardiography to rule out blood clot in the left atrium, or else the patient is pretreated with an anticoagulant drug for at least 3 weeks. As cardioversion can transiently impair left atrial pumping function, anticoagulation is usually maintained for 4 weeks after the procedure. The decision whether to continue anticoagulation beyond this point is based on the risk of stroke, as assessed with the CHA2DS2-VASc score.

CONCLUSION

The main risks of cardioversion-thrombo--embolism and clinically significant hemorrhage--occur in 1% of cases or less (in the first 30 days after treatment) if the procedure is carried out as recommended in therapeutic guidelines. Serious complications still occur, but they are rare.

Sinus rhythm restoration and treatment success: insight from recent clinical trials

Atrial fibrillation (AF) is a common supraventricular tachyarrhythmia with substantial morbidity and mortality. This review briefly describes the mechanisms of AF development and progression, including electrical, structural, and contractile remodeling. In addition, the potential benefits of achieving and maintaining sinus rhythm are discussed. For example, rhythm control has been associated with improvements in left ventricular function, AF symptoms, exercise tolerance, the ability to perform activities of daily living, and quality of life. More recently, dronedarone, a noniodinated benzofuran derivative approved for use in the treatment of AF, was shown to significantly improve clinical outcomes including cardiovascular hospitalizations and death from any cause in A Placebo-Controlled, Double-Blind, Parallel Arm Trial to Assess the Efficacy of Dronedarone 400 mg bid for the Prevention of Cardiovascular Hospitalization or Death From Any Cause in Patients With Atrial Fibrillation/Atrial Flutter (ATHENA). The review concludes with an examination of AF treatment options and expectations. Evidence suggests that the complete absence of AF recurrence is not always achievable; however, complete restoration of sinus rhythm may not be necessary for patients to achieve clinically meaningful benefits. Copyright © 2011 Wiley Periodicals, Inc. The editorial assistance provided for this manuscript was funded by Sanofi-Aventis. The authors were fully responsible for all content and editorial decision, and received no financial support or other form of compensation related to the development of the paper. The authors have no other funding, financial relationships, or conflicts of interest to disclose.

Antiarrhythmic drugs for atrial fibrillation

INTRODUCTION

Atrial fibrillation (AF) is associated with increased mortality and morbidity. Although stroke prevention is the only way to improve prognosis, antiarrhythmic drugs (AADs) are of primary importance both in the conversion to sinus rhythm and in the long-term control of rhythm and rate.

AREAS COVERED

We searched the Cochrane Library and Medline Database for articles published in English concerning efficacy and safety of AADs in AF. Particular attention was paid to the recently published European Society of Cardiology guidelines. This review provides an overview of the currently available drugs used in AF, with a particular emphasis on their comparative efficacy and safety in different kind of patients. Recent important findings, and advantages and disadvantages of recently approved drugs such as vernakalant and dronedarone, are also discussed.

EXPERT OPINION

AADs remain fundamental in the acute and long-term management of AF, to control symptoms and to reduce the negative impact of the arrhythmia on QoL. The choice of a rate- over rhythm-control strategy should be individualized and based on accurate evaluation of patient medical history and symptoms. New agents will contribute to improve treatment efficacy together with the guarantee of better safety profiles.

Comparison of antero-lateral versus antero-posterior electrode position for biphasic external cardioversion of atrial flutter

External cardioversion is an established and very important tool to terminate symptomatic atrial flutter. The superiority of the biphasic waveform has been demonstrated for atrial flutter, but whether electrode position affects the efficacy of cardioversion in this population is not known. The aim of this trial was to evaluate whether anterior-lateral (A-L) compared with anterior-posterior (A-P) electrode position improves cardioversion results. Of 130 screened patients, 96 (72 men, mean age 62 +/- 12 years) were included and randomly assigned to a cardioversion protocol with either A-L or A-P electrode position. In each group, 48 patients received sequential biphasic waveform shocks using a step-up protocol consisting of 50, 75, 100, 150, or 200 J. The mean energy (65 +/- 13 J for A-L vs 77 +/- 13 J for A-P, p = 0.001) and mean number of shocks (1.48 +/- 1.01 for A-L vs 1.96 +/- 1.00 for A-P, p = 0.001) required for successful cardioversion were significantly lower in the A-L group. The efficacy of the first shock with 50 J in the A-L electrode position (35 of 48 patients [73%]) was also highly significantly greater than the first shock with 50 J in the A-P electrode position (18 of 48 patients [36%]) (p = 0.001). In conclusion, the A-L electrode position increases efficacy and requires fewer energy and shocks in external electrical cardioversion of common atrial flutter. Therefore, A-L electrode positioning should be recommended for the external cardioversion of common atrial flutter.

Cardioversion for atrial fibrillation: treatment options and advances

Atrial fibrillation (AF) is associated with significant morbidity and mortality. There are two basic approaches to managing AF: slowing the ventricular rate, while allowing the arrhythmia to continue (the rate-control approach), and restoring and maintaining sinus rhythm (the rhythm-control approach) with antiarrhythmic drugs (AADs) and/or ablation, electrical cardioversion (CV), if needed, or both. Strategy trials comparing rate and rhythm control have found no survival advantage of one approach over the other, but other considerations, such as symptom reduction, often necessitate pursuit of rhythm control. Electrical, or direct current, CV is a widely used and effective method for termination of nonparoxysmal AF, although its success can be affected by patient- and technique-related variables. Pharmacological CV options also exist and are preferable in specific circumstances. Both pharmacological and electrical CV are associated with the risk of proarrhythmia. Many AADs are under development for both CV and maintenance of sinus rhythm. Some are atrioselective, such as vernakalant, and target ion channels in the atria, with little or no effects in the ventricle. Vernakalant, currently under Food and Drug Administration review, appears to offer a safer profile than current CV agents and is likely to expand the role of pharmacological CV. Other new AADs that provide increased efficacy or safety while maintaining normal sinus rhythm may also be better than current drugs; if so, rate-rhythm comparisons will differ from those of previous studies. In conclusion, further trials should clarify the long-term safety profiles of new atrioselective agents and other investigational drugs and define their role in the treatment of AF.

Increases of cardiac troponin in conditions other than acute coronary syndrome and heart failure

BACKGROUND

Although cardiac troponin (cTn) is a cornerstone marker in the assessment and management of patients with acute coronary syndrome (ACS) and heart failure (HF), cTn is not diagnostically specific for any single myocardial disease process. This narrative review discusses increases in cTn that result from acute and chronic diseases, iatrogenic causes, and myocardial injury other than ACS and HF.

CONTENT

Increased cTn concentrations have been reported in cardiac, vascular, and respiratory disease and in association with infectious processes. In cases involving acute aortic dissection, cerebrovascular accident, treatment in an intensive care unit, and upper gastrointestinal bleeding, increased cTn predicts a longer time to diagnosis and treatment, increased length of hospital stay, and increased mortality. cTn increases are diagnostically and prognostically useful in patients with cardiac inflammatory diseases and in patients with respiratory disease; in respiratory disease cTn can help identify patients who would benefit from aggressive management. In chronic renal failure patients the diagnostic sensitivity of cTn for ACS is decreased, but cTn is prognostic for the development of cardiovascular disease. cTn also provides useful information when increases are attributable to various iatrogenic causes and blunt chest trauma.

SUMMARY

Information on the diagnostic and prognostic uses of cTn in conditions other than ACS and heart failure is accumulating. Although increased cTn in settings other than ACS or heart failure is frequently considered a clinical confounder, the astute physician must be able to interpret cTn as a dynamic marker of myocardial damage, using clinical acumen to determine the source and significance of any reported cTn increase.

Treatment of new-onset atrial fibrillation in noncardiac intensive care unit patients: a systematic review of randomized controlled trials

OBJECTIVE

Atrial fibrillation is a common problem associated with morbidity and mortality in critically ill patients; however, evidence-based treatment recommendations are lacking. The objective of this systematic review was to evaluate the efficacy of pharmacologic rhythm control of new-onset atrial fibrillation in noncardiac, critically ill adults.

DATA SOURCE

Citations identified from an electronic search of Medline, the Cochrane register of controlled trials, and Embase databases (1966 to August 2006) were independently reviewed by two investigators.

STUDY SELECTION

All prospective randomized controlled trials evaluating pharmacologic rhythm conversion regimens for new-onset atrial fibrillation in (noncardiac surgery) critically ill adult patients were included. The primary end point was atrial fibrillation resolution.

DATA EXTRACTION

Using a standardized data extraction form, data related to study design, population characteristics, pharmacologic intervention, and outcome measures were collected.

DATA SYNTHESIS

Four trials met inclusion criteria from 1995 citations screened. Of the 143 evaluable patients in these trials 89 (76%) had atrial fibrillation while the remaining ones had other atrial tachyarrhythmias. Drugs evaluated for rhythm conversion included amiodarone (n = 26), procainamide (n = 14), magnesium (n = 18), flecainide (n = 15), esmolol (n = 28), verapamil (n = 15), and diltiazem (n = 27). The definition of treatment success ranged from conversion within 1 hr to conversion within 24 hrs. No study evaluated maintenance of conversion, and one study included hemodynamically unstable patients. Lack of methodologic homogeneity prevented any pooled analysis.

CONCLUSIONS

Using the current published literature, we cannot recommend a standard treatment for atrial fibrillation in noncardiac critically ill adult patients. Clinical trials evaluating rhythm conversion in critically ill populations outside of cardiac surgery are lacking. Further trials that address goals of care in hemodynamically stable and unstable patients and utilize standardized definitions of successful cardioversion are required.

Transvenous electrical cardioversion of atrial fibrillation in six horses using custom made cardioversion catheters

Pharmacological conversion of atrial fibrillation (AF) to sinus rhythm in horses can be difficult. The objective of this study was to investigate the feasibility of transvenous electrical cardioversion with custom made catheters in eight horses, of which three had failed cardioversion using quinidine sulfate. Two cardioversion catheters and one pacing/sensing electrode were inserted via the right jugular vein and placed using ultrasound guidance into the left pulmonary artery, the right atrium and the right ventricle, respectively. Because immediate recurrence of AF was encountered in the second horse treated, pre-treatment with amiodarone was given to each of the remaining six horses. Induction of general anaesthesia was associated with dislocation of the cardioversion catheter in three horses, requiring a second catheterisation procedure. During general anaesthesia, biphasic R wave synchronised shocks of up to 360 J were delivered between both cardioversion electrodes. In six horses (75%), including two which had failed quinidine sulfate treatment, sinus rhythm was restored with a mean energy level of 295+/-62 J. No side effects were observed. Blood analysis 3 h after cardioversion revealed normal parameters, including cardiac troponin I values. Transvenous electrical cardioversion of atrial fibrillation with custom made cardioversion catheters can be considered as a treatment option for atrial fibrillation in horses, especially when conventional drugs fail.

Electrical cardioversion for persistent atrial fibrillation or atrial flutter in clinical practice: predictors of long-term outcome

Despite the results of Atrial Fibrillation Follow-up Investigation of Rhythm Management and Rate Control versus Electrical Cardioversion for Persistent Atrial Fibrillation trials, which favour a general shift in atrial fibrillation (AF) therapeutic approach towards control of ventricular rate, a strategy based on restoration of sinus rhythm could still play a role in selected patients at lower risk of AF recurrence. We explored possible predictors of relapses after external electrical cardioversion among patients with persistent AF or atrial flutter (AFL). We analysed the clinical characteristics and conventional echocardiographic parameters of patients with persistent AF/AFL enrolled in an institutional electrical cardioversion programme. Among 242 patients (AF/AFL, 195/47; mean age 62+/-13 years), sinus rhythm was restored in 215 (89%) and maintained in 73 (34%) at a follow-up of 930 days (median). No baseline clinical/echocardiographic variables predicted acute efficacy of cardioversion at logistic regression analysis. However, two variables predicted long-term AF/AFL recurrence among patients with successful cardioversion at multivariate Cox's proportional hazards analysis: (i) duration of arrhythmia>or=1 year (HR, 2.07; 95% CI, 1.29-3.33) and (ii) presence of previous cardioversion (HR, 1.67; 95% CI, 1.17-2.38). These variables also presented high-positive predictive values (72% and 80% respectively). Whereas the high acute efficacy of electrical cardioversion (approximately 90%) does not appear to be predictable, two simple clinical variables could help identify patients at higher risk of long-term AF/AFL recurrence after successful electrical cardioversion. We think there could be a case for initially attempting external electrical cardioversion to patients who have had AF/AFL for <1 year. In such patients, the chance of long-term success appears to be relatively high.

Intracardiac atrial defibrillation

Intravascular ventricular defibrillation and intravascular atrial defibrillation have many similarities. An important factor influencing the outcome of the shock is the potential gradient field created throughout the ventricles or the atria by the shock. A minimum potential gradient is required throughout the ventricles and probably the atria in order to defibrillate. The value of this minimum potential gradient is affected by several factors, including the duration, tilt, and number of phases of the waveform. For shock strengths near the defibrillation threshold, earliest activation following failed shocks arises in a region in which the potential gradient is low. The defibrillation threshold energy can be decreased by adding a third and even a fourth defibrillation electrode in regions where the shock potential gradient is low for the shock field created by the first two defibrillation electrodes and giving two sequential shocks, each through a different set of electrodes. However, the addition of more electrodes and sequential shocks complicates both the device and its implantation. Because patients are conscious when the atrial defibrillation shock is given, they experience pain during the shock, which is one of the main drawbacks of intravascular atrial defibrillation. Unfortunately, the pain threshold for defibrillation shocks is so low that a shock less than 1 J is uncomfortable and is not much less painful than shocks several times stronger. Therefore, even though electrode configurations exist that have lower atrial defibrillation threshold energy requirements than the atrial defibrillation threshold with standard defibrillation electrode configurations used in implantable cardioverter-defibrillators (ICDs) for ventricular defibrillation, they are not clinically practical because their shocks are almost as painful as with the standard ICD electrode configurations. Such electrode configurations would make the ICD more complicated, leading to greater difficulty and longer time required for implantation.

Is Helicobacter pylori a cause of atrial fibrillation?

Inflammation has been implicated in the pathogenesis of cardiovascular diseases. C-reactive protein, a sensitive marker of systemic inflammation, has recently been reported to be significantly higher in patients with atrial fibrillation (AF) compared with a control group with no history of atrial arrhythmia. Elevated C-reactive protein levels in patients with AF reflects an underlying inflammatory process. Histological anomalies in the atria of patients with AF have also been observed. These anomalies may have an inflammatory basis, although it is not known if any structural changes within the atria are a cause or a consequence of the arrhythmia. Ongoing chronic infection(s) has been suggested as a possible cause of the inflammatory process demonstrated in patients with AF. Helicobacter pylori, a Gram-negative bacterium more commonly known for infecting the gastric mucosa and causing peptic ulcers, is a noncardiac factor that has been controversially reported to be associated with cardiovascular diseases. This article gives a brief overview of AF and specifically explores the recent evidence that suggests that Helicobacter pylori infection causes AF.