Slow conduction through an arc of block: A basis for arrhythmia formation postmyocardial infarction.

Introduction: The electrophysiologic basis for characteristic rate-dependent, constant-late-coupled (390 + 54 milliseconds) premature ventricular beats (PVBs) present 4-5 days following coronary artery occlusion were examined in 108 anesthetized dogs.

Methods And Results: Fractionated/double potentials were observed in injured zone bipolar and composite electrograms at prolonged sinus cycle lengths (1,296 ± 396 milliseconds). At shorter cycle lengths, conduction of the delayed potential decremented, separating from the initial electrogram by a progressively prolonged isoelectric interval.

Intermittent vs. Continuous Anticoagulation theRapy in patiEnts with Atrial Fibrillation (iCARE-AF): a randomized pilot study.

Purpose: We hypothesized that intermittent anticoagulation based on daily rhythm monitoring using the novel oral anticoagulants (NOACs) is feasible and safe among patients with paroxysmal atrial fibrillation (AF).

Methods: Patients with paroxysmal AF and ≥1 risk factors for stroke were randomized to either intermittent or continuous anticoagulation. Those in the intermittent group were instructed to transmit a daily ECG using an iPhone-based rhythm monitoring device.

Functional aspects of His bundle physiology and pathophysiology: Clinical implications.

In this review we present evidence from many experimental studies which challenge the concept of predestination of His bundle fibers. Using both intra- and extracellular His bundle pacing in the context of atrio-ventricular block and the development of bundle branch blocks these experimental studies provide the underlying mechanisms for the recent clinical findings showing the benefits of permanent His bundle pacing.

Spectral Analysis of Baseline Electrocardiogram During Atrial Fibrillation Predicts Response to Antiarrhythmic Drug Therapy in Patients With Persistent Atrial Fibrillation.

Background: We evaluated the ability of spectral analysis of the baseline ECG during atrial fibrillation (AF) to predict the response of persistent AF to antiarrhythmic drug therapy.

Methods: Patients with persistent AF who were admitted for dofetilide loading were prospectively enrolled in the study. Atrial activity was extracted from the ECG using an Independent Component Analysis method and then subjected to a Modified Periodogram.

Current concepts of anatomy and electrophysiology of the sinus node.

The sinoatrial node, or sinus node, of humans is the principal pacemaker of the heart. Over the last century, studies have unraveled the complex molecular architecture of the sinus node and the expression of unique ion channels within its specialized myocytes. Aim of this review is to describe the embriology, the anatomy, the histology and the electrophisiology of the sinus node.

The role of the autonomic ganglia in atrial fibrillation.

Recent experimental and clinical studies have shown that the epicardial autonomic ganglia play an important role in the initiation and maintenance of atrial fibrillation (AF). In this review, we present the current data on the role of the autonomic ganglia in the pathogenesis of AF and discuss potential therapeutic implications. Experimental studies have demonstrated that acute autonomic remodeling may play a crucial role in AF maintenance in the very early stages.

Low-level transcutaneous electrical vagus nerve stimulation suppresses atrial fibrillation.

Background: Transcutaneous low-level tragus electrical stimulation (LLTS) suppresses atrial fibrillation (AF) in canines.

Objectives: This study examined the antiarrhythmic and anti-inflammatory effects of LLTS in humans.

Methods: Patients with paroxysmal AF who presented for AF ablation were randomized to either 1 h of LLTS (n = 20) or sham control (n = 20).

Relationship between catheter contact force and radiofrequency lesion size and incidence of steam pop in the beating canine heart: electrogram amplitude, impedance, and electrode temperature are poor predictors of electrode-tissue contact force and lesion size.

Background: Electrode-tissue contact force (CF) is believed to be a major factor in radiofrequency lesion size. The purpose of this study was to determine, in the beating canine heart, the relationship between CF and radiofrequency lesion size and the accuracy of predicting CF and lesion size by measuring electrogram amplitude, impedance, and electrode temperature.

Methods And Results: Eight dogs were studied closed chest.

Atrial tachyarrhythmias induced by the combined effects of β1/2-adrenergic autoantibodies and thyroid hormone in the rabbit.

Activating autoantibodies (AAb) to β-adrenergic receptors (βAR) are associated with atrial fibrillation in patients with Graves' disease. In the present study, we examined the interaction of thyroid hormone with β1/2AR-AAb in inducing atrial tachyarrhythmias in the rabbit. Immunization of rabbits with a β1AR or β2AR second extracellular loop peptide produced high titers of β1AR-AAb or β2AR-AAb.

The Propensity for Inducing Atrial Fibrillation: A Comparative Study on Old versus Young Rabbits.

It is well established that atrial fibrillation (AF) is far more common in elderly humans. Autonomic activation is thought to be an operative mechanism for AF propensity. The aim of the study was to investigate the impact of age on atrial tachyarrhythmia induction in a rabbit model.

Risk of coronary artery injury with radiofrequency ablation and cryoablation of epicardial posteroseptal accessory pathways within the coronary venous system.

Background: Ablation of epicardial posteroseptal accessory pathways requires ablation within the coronary venous system. We assessed the risk of coronary artery (CA) injury with radiofrequency ablation (RFA) within the coronary venous system as a function of the distance between the CA and ablation site. We also examined the efficacy and safety of cryoablation close to a CA.

Inducible cardiac arrhythmias caused by enhanced β1-adrenergic autoantibody expression in the rabbit.

Previous studies demonstrated burst pacing and intravenous infusion of ACh induced sustained atrial tachycardia when rabbits were immunized to produce β2-adrenergic receptor (β2AR)-activating autoantibodies. The objective of this study was to examine the arrhythmogenic effect of β1-adrenergic receptor (β1AR)-activating autoantibodies in the rabbit. Eight New Zealand white rabbits were immunized with a β1AR second extracellular loop peptide to raise β1AR antibody titers.

Wide complex tachycardia in the presence of class I antiarrhythmic agents: a diagnostic challenge.

We present two patients with paroxysmal atrial fibrillation on class 1C antiarrhythmic drugs without concomitant atrioventricular (AV) nodal blocking agents who developed atrial flutter with 1:1 AV conduction. Their electrocardiogram revealed wide complex tachycardia with rates >200/minute. Atrial flutter with 1:1 conduction in the presence of class IC antiarrhythmic drugs may present a diagnostic challenge.

Inhibition of atrial fibrillation by low-level vagus nerve stimulation: the role of the nitric oxide signaling pathway.

Purpose: We examined the role of the phosphatidylinositol-3 kinase (PI3K)/nitric oxide (NO) signaling pathway in low-level vagus nerve stimulation (LLVNS)-mediated inhibition of atrial fibrillation (AF).

Methods: In 17 pentobarbital anesthetized dogs, bilateral thoracotomies allowed the attachment of electrode catheters to the superior and inferior pulmonary veins and atrial appendages. Rapid atrial pacing (RAP) was maintained for 6 h.

Atrial tachycardia provoked in the presence of activating autoantibodies to β2-adrenergic receptor in the rabbit.

Background: A recent clinical study of patients with inappropriate sinus tachycardia reported that autoantibodies to β-adrenergic receptors (β2ARs) could act as agonists to induce atrial arrhythmias.

Objective: To test the hypothesis that activating autoantibodies to the β2AR in the rabbit atrium are arrhythmogenic.

Methods: Five New Zealand white rabbits were immunized with a β2AR second extracellular loop peptide to raise β2AR antibody titers.

Development and validation of a prognostic index for risk stratification of patients with early repolarization.

Background: Early repolarization (ER) is associated with increased mortality in the general population. We sought to develop and validate a prognostic index (PI) of mortality in patients with ER.

Methods: We identified 852 consecutive patients (mean age 49 ± 12 years) with ER (J-point elevation ≥0.

The intrinsic autonomic nervous system in atrial fibrillation: a review.

The procedure of catheter ablation for the treatment of drug resistant atrial fibrillation (AF) has evolved but still relies on lesion sets intended to isolate areas of focal firing, mainly the myocardial sleeves of the pulmonary veins (PVs), from the rest of the atria. However the success rates for this procedure have varied inversely with the type of AF. At best success rates have been 20 to 30% below that of other catheter ablation procedures for Wolff-Parkinson-White syndrome, atrioventricular junctional re-entrant tachycardia and atrial flutter.

Diverse spectrum of presentation of coronary slow flow phenomenon: a concise review of the literature.

The coronary slow flow phenomenon (CSFP) is a disease entity characterized by slow progression of angiographic contrast in the coronary arteries in the absence of stenosis in the epicardial vessels. CSFP has a diverse presentation from mild chest discomfort to ST-segment elevation myocardial infarction. It can also have severe morbidity and mortality implications and can significantly hamper the quality of life of those affected.

Extra- and intracellular recordings from the avjunction: discerning the mechanisms for irregular ventricular responses during supraventricular arrhythmias.

Introduction: There has been a long-standing controversy regarding the mechanism(s) to explain the irregular ventricular response during atrial tachycardia (AT) or atrial fibrillation (AF) and where the site of block, if any, resides in the atrioventricular (AV) junction.

Methods: We studied 12 Langendorff preparations perfused with modified Tyrode's solution containing 5-10 mM diacetyl monoxime which suppressed contractility but allowed the use of intracellular action potential (AP) recordings. Octapolar catheters (2-mm rings, 2-mm spacing) were secured along the tricuspid annulus from the apex to the base of the triangle of Koch and along the anterior limbus of the fossa ovalis to record extracellular, slow pathway, fast pathway, His bundle (Hb) and AV nodal (AVN) extracellular potentials as well as intracellular action potentials.

Antiarrhythmic effects of vasostatin-1 in a canine model of atrial fibrillation.

Background: We examined the antiarrhythmic effects of vasostatin-1, a recently identified cardioregulatory peptide, in canine models of atrial fibrillation (AF).

Methods And Results: In 13 pentobarbital-anesthetized dogs bilateral thoracotomies allowed the attachment of multielectrode catheters to superior and inferior pulmonary veins and atrial appendages (AA). Rapid atrial pacing (RAP) was maintained for 6 hours.

Rapid high resolution electroanatomical mapping: evaluation of a new system in a canine atrial linear lesion model.

Background: A canine right atrial (RA) linear lesion model was used to produce a complex pattern of RA activation to evaluate a novel mapping system for rapid, high resolution (HR) electroanatomical mapping.

Methods And Results: The mapping system (Rhythmia Medical, Incorporated) uses an 8F deflectable catheter with a minibasket (1.8 cm diameter), containing 8 splines of 8 electrodes (total 64 electrodes, 2.

Interactions between atrial electrical remodeling and autonomic remodeling: how to break the vicious cycle.

Background: The mechanism(s) underlying the maintenance of atrial fibrillation (AF) during the first few hours after AF was initiated remains poorly understood.

Objective: To investigate the roles of the intrinsic cardiac autonomic nervous system in the maintenance of AF at the early stage.

Methods: In 10 anesthetized dogs, we attached multielectrode catheters on atria and pulmonary veins.

Pharmacological prevention and termination of focal atrial fibrillation.

Aims: Patients undergo ablation for focal atrial fibrillation (AF) as a result of failure of anti-arrhythmic drugs. Our basic studies have implicated cholinergic and adrenergic neurotransmitter release as the underlying mechanism for focal AF. Therefore, we tested the efficacy of a combination of sodium channel-blocking agents with additional vagolytic properties and a β-blocker to terminate and prevent focal AF.