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Atrioventricular (AV) nodal conduction is decremental and very prone to alterations in autonomic tone. Conduction through the His-Purkinje system (HPS) is via fast channel tissue and typically not that dependent on autonomic perturbations. Applying these principles, when the sinus rate is stable and then heart block suddenly occurs preceded by even a subtle slowing of heart rate, it typically is caused by increased vagal tone, and block occurs in the AV node. Heart block with activity strongly suggests block in the HPS. Enhanced sympathetic tone and reduced vagal tone can facilitate induction of both AV and atrioventricular node reentry.

Delayed atrioventricular (AV) conduction most commonly occurs in the AV node, resulting from AH prolongation on an intracardiac electrocardiogram and PR prolongation on a surface electrocardiogram. AV conduction may be blocked in a 2:1 manner, with a normal PR interval and wide QRS suggesting infranodal disease, whereas a prolonged PR interval and narrow QRS are more suggestive of AV nodal disease. Block within the His is suspected when there is 2:1 AV block with normal PR and QRS intervals. Complete heart block occurs when the atrial rhythm is totally independent of a junctional or lower escape rhythm.

BACKGROUND: Atrial fibrillation (AF) is a common comorbidity in patients with left ventricular assist devices (LVAD) with no defined guideline treatment strategy of rate versus rhythm control. The purpose of this study is to determine the effects of rate versus rhythm control for AF on the outcomes of patients with LVAD at our institution. METHODS: Consecutive patients who underwent LVAD implantation at St Vincent Hospital from January 1, 2015 to December 31, 2017 were retrospectively evaluated. Patients with AF were identified and divided into rate control or rhythm control groups. The primary outcome evaluated was a composite of death, heart failure admission, gastrointestinal bleed, ventricular tachycardia, cerebrovascular accident, hemolysis, and pump thrombosis. Secondary outcomes included the individual variables from the primary outcome. RESULTS: Out of 201 patients that underwent LVAD implantation, 81 had AF after implantation and were included with a median follow-up period of 384 days. The rate control group (n = 31; 38%) and the rhythm control group (n = 51; 62%) had no difference in composite outcomes (61% vs 59%, p = 0.83). When taken individually there was no difference in outcomes between the two groups. Thirteen patients underwent electrical cardioversion and successful conversion to normal sinus rhythm occurred in 71% of cases with a 60% recurrence rate. CONCLUSIONS: There was no difference in primary outcome between rate and rhythm control groups. These data suggest that maintenance of sinus rhythm may not be necessary in all patients with LVAD.

Background: Current maneuvers for differentiation of atrioventricular node reentry tachycardia (AVNRT) and atrioventricular reentry tachycardia (AVRT) lack sensitivity and specificity for AVRT circuits located away from the site of pacing. We hypothesized that a premature His complex (PHC) will always perturb AVRT because the His bundle is obligatory to the circuit. Further, AVNRT could not be perturbed by a late PHC (≤20 ms ahead of the His) due to the retrograde His conduction time. Earlier PHCs can advance the AVNRT circuit but only by a quantity less than the prematurity of the PHC. Methods: High-output pacing at the distal His location delivered PHCs. AVRT was predicted when late PHCs perturbed tachycardia or when earlier PHCs led to atrial advancement by an amount equal or greater than the degree of PHC prematurity. Results: Among the 73 supraventricular tachycardias, the test accurately predicted AVRT (n=29) and AVNRT (n=44) in all cases. Late PHC advanced the circuit in all 29 AVRTs and none of the AVNRTs (sensitivity and specificity, 100%). With earlier PHCs, the degree of atrial advancement was equal or greater than the PHC prematurity in 26/29 AVRTs and none of the AVNRTs (90% sensitivity and 100% specificity). The mean prematurity of the PHC required to perturb AVNRT was 48 ms (range, 28–70 ms) and the advancement less than the prematurity of the PHC (mean, 32 ms; range, 18–54 ms). Conclusions: The responses to PHCs distinguished AVRT and AVNRT with 100% specificity and sensitivity.

Background Electrophysiology study (EPS) is an important part of the diagnosis and workup for supraventricular tachycardia (SVT). Provocative medications are used to induce arrhythmias, when they are not inducible at baseline. The most common medication is the β1-specific agonist, isoproterenol, but recent price increases have resulted in a shift toward the nonspecific agonist, epinephrine. Objective We hypothesize that isoproterenol is a better induction agent for SVT during EPS than epinephrine. Methods We created a retrospective cohort of 131 patients, who underwent EPS and required medication infusion with either isoproterenol or epinephrine for SVT induction. The primary outcome was arrhythmia induction. Results Successful induction was achieved in 71% of isoproterenol cases and 53% of epinephrine cases (P = 0.020). Isoproterenol was significantly better than epinephrine for SVT induction during EPS (odds ratio [OR], 2.35; 95% confidence interval [CI], 1.14-4.85; P = 0.021). There was no difference in baseline variables or complications between the two groups. Other variables associated with successful arrhythmia induction included a longer procedure duration and atrioventricular nodal re-entry tachycardia as the clinical arrhythmia. In a multivariable model, isoproterenol remained significantly associated with successful induction (OR, 2.57; 95% CI, 1.002-6.59; P = 0.05). Conclusions Isoproterenol was significantly better than epinephrine for SVT arrhythmia induction. However, epinephrine was safe and successfully induced arrhythmias in the majority of patients who received it. Furthermore, when atropine was added in epinephrine-refractory cases, in a post hoc analysis there was no difference in arrhythmia induction between medications. Cost savings could thus be significant without compromising safety.

A 25-year-old man with severe nonischemic dilated cardiomyopathy underwent subcutaneous implantable cardioverter defibrillator (S-ICD) implant and subsequently underwent HeartWare ventricular assist device (HVAD) placement. Postoperative interrogation revealed both primary and secondary S-ICD vectors inappropriately regarded sinus rhythm as "noise," and the alternate vector significantly undersensed sinus rhythm. The S-ICD was reinterrogated using high-resolution capture to visually confirm EMI with a dominant frequency in both the primary and secondary vectors of 46.67 Hz that fell within the S-ICD operational range of 9-60 Hz. The 46.67 Hz frequency correlated with the HVAD operational speed of 2,800 RPM. The HVAD pump speed was increased from 2,800 to 3,000 RPM, resulting in a dominant frequency of 50 Hz. The notch filter is nonprogrammable in S-ICDs. However, the built-in filter is 50 Hz for countries in European time zones as opposed to 60 Hz in US time zones due to differences in the anticipated noise from electrical sources within each continent. Thus, the S-ICD time zone was reprogrammed from EST to GMT, which reduced the notch filter from 60 to 50 Hz, resulting in S-ICD successfully eliminating EMI when the patient was in a supine position. The EMI interference was still intermittently present in the upright patient position. This case demonstrates the utility of high-resolution electrogram capture to identify the source and frequency of EMI in S-ICD and offers a potential avenue to troubleshoot dominant frequency oversensing by changing the device time zone.

A 55-year-old woman presented with severe dyspnea during acceleration-dependent left bundle branch block (LBBB). Metoprolol initially ameliorated symptoms by preventing the heart rate at which LBBB occurred. Over time LBBB presented at slower heart rates and the patient developed recurrent dyspnea during an activity that correlated with the development of LBBB on event monitors and exercise stress testing. A biventricular pacemaker was implanted, and the patient's symptoms remain resolved after a follow-up of over 4 years. More research is needed to define the use of cardiac resynchronization therapy in patients with normal heart function.

Introduction Focal impulse and rotor modulation (FIRM)-guided ablation has had mixed results of published success, and most studies have had a follow-up for a year or less. We aimed to study a consecutive group of patients followed for at least 1.5 years, subgrouped into those with an initial FIRM ablation and those with a previous, failed ablation who now received a FIRM guided one, to evaluate for success in each group and factors that might affect success. Methods Of 181 patients, 167 were available for analysis. Group 1 (n = 122) had a first or primary ablation (paroxysmal atrial fibrillation [PAF] 51; persistent atrial fibrillation [PeAF] 71) and group 2 (n = 45) had a redo ablation (PAF 18; PeAF 27). All patients were done under general anesthesia. FIRM mapping was done in the right atrium first and then the left, and only rotors consistently seen on multiple epochs were ablated, using 15 to 30 W. Rotor ablation was discontinued when remapping showed elimination of rotational activity at the site. Wide area catheter ablation was done for pulmonary vein isolation (PVI). Routine follow-up was at 3, 6, and 12 months of the first year, with a Holter monitor at 6 months, and then every 6 months thereafter. Event recorders were given to patients with potential arrhythmic symptoms. Results Mean follow-up was 16 months. Nearly 40% of patients had obstructive sleep apnea; mean body mass index was 32; and average left atrial size was 39.7 mm and 46.2 mm for PAF and PeAF patients, respectively. Freedom from atrial arrhythmia recurrence was: in group 1 patients, 82.4% for PAF and 67.6% for PeAF patients; in group 2 patients, 83.3% for PAF, but only 40.7% for PeAF patients. Comparing outcomes for the first 10 patients studied to the next 20 or more done by three operators showed no difference, suggesting no learning curve affecting the ablation results. Furthermore, the univariate analysis did not show any demographic factor to have an independent significance for ablation success or failure. Spontaneous termination during rotor ablation occurred in 76.8% of PAF and 27.6% of PeAF patients but did not affect the long-term outcomes for maintenance of sinus rhythm. Conclusions FIRM-guided atrial ablation plus PVI in our patient population resulted in good success from a recurrence of atrial arrhythmias in patients undergoing an initial ablation procedure. For those with persistent AF undergoing a second procedure now using FIRM guidance plus PVI, the results are lower. Further research is needed to define better the appropriate population for FIRM-guided ablation and the degree of ablation needed for success in these patients.

A 15-year-old girl with a history of paroxysmal supraventricular tachycardia underwent an electrophysiology study (EPS) for diagnosis and ablation. Her baseline electrocardiogram and echocardiogram were normal. At EPS, she had dual atrioventricular nodal (AVN) conduction, but isoproterenol was needed to initiate the slow-fast form of AVN reentry. Before ablation without any isoproterenol, she began to have a spontaneous block in the fast pathway with continuous conduction over the slow pathway. After ablation of the slow pathway, all complexes conducted over the fast pathway during a 25-year follow-up. Possible electrotonic interaction between the slow and fast pathways is proposed as the mechanism for this phenomenon.

A report of the American College of Cardiology, American Heart Association Task Force on practice guidelines and the European Society of Cardiology Committee for practice guidelines.

A 57-year-old man with a structurally normal heart and normal baseline ECG (Figure 1) underwent pulmonary vein isolation for atrial fibrillation. An electrophysiology study was then undertaken with an octapolar catheter positioned at the His bundle and an ablation catheter at the mid-right atrium. Figure 1. Baseline 12 lead ECG. See Editor’s Perspective p 985 At baseline, the sinus cycle length was 890 ms, the AH interval 48 ms, the HV interval 80 ms, and the QRS duration 80 ms. During extrastimulus atrial pacing, the HV interval shortened and the QRS complex widened with a left bundle branch block morphology (Figure 2). Atrial burst pacing at cycle length 330 ms demonstrates progressive shortening of the HV interval and widening of the QRS complex with left bundle branch block morphology (Figure 3A and 3B). On the final 3 beats in the figure, a His bundle electrogram seems after the QRS complex. On termination of pacing, a wide QRS complex tachycardia of identical morphology is noted (Figure 4). The atrial (A), His (H), and ventricular (V) electrograms are labeled. What is the mechanism of the tachycardia? Figure 2. Atrial extrastimulus pacing. Following S2, the QRS widens, the HV interval shortens and the His and right bundle activation sequence reverses. Dotted line and arrows provide reference for the anterograde to retrograde activation change. Preexcitation with a long AV interval, left bundle branch block morphology, and right bundle activation preceding ventricular activation suggest an atriofascicular accessory pathway. His 7 to 8 through 1 to 2 His bundle catheter recordings are proximal to distal; pacing intervals in milliseconds are marked. H indicates His; RA, right atrium; S1, drive train stimulus; and S2, extrastimulus. Legends …

A 65-year-old man, with no significant past medical history, presented with an episode of sudden onset palpitations and lightheadedness. He was hemodynamically stable and the ECG revealed a left bundle branch block (LBBB) morphology tachycardia at 214 beats per minute (Figure 1A). The tachycardia terminated spontaneously with conversion to normal sinus rhythm and LBBB (Figure 1B). Further evaluation included a 2-dimensional echocardiogram showing a left ventricular ejection fraction of 40% to 45%, left heart catheterization showing angiographically normal coronaries, and cardiac magnetic resonance imaging revealing atypical septal motion with left ventricular ejection fraction of 60% to 65% and no scar or ischemia. The patient underwent an electrophysiology study. At baseline, the sinus cycle length was 890 ms, atrial-His interval was 64 ms, His-ventricular interval was 108 ms, and QRS duration was 120 ms. Spontaneous onset of the LBBB morphology tachycardia after a sinus beat is shown in Figure 2. The tachycardia cycle length is 306 ms, and the His-ventricular interval is 120 ms. The QRS while similar to the LBBB seen during sinus rhythm shows change in axis and the morphology in aVR is predominantly positive. There is no ventriculo-atrial conduction during the tachycardia. Attempts at entrainment from right ventricle (RV) led to termination of the tachycardia. His refractory premature ventricular complexes (PVCs) delivered from RV apex during tachycardia after the His depolarization advances the next H and V (Figure 3). What is the mechanism of the tachycardia? See Editor's Perspective by Asirvatham and Stevenson Figure 1. A , ECG showing wide complex tachycardia with left bundle branch block (LBBB) morphology. B , ECG showing sinus rhythm and LBBB. Figure 2. Spontaneous initiation of tachycardia during sinus rhythm. The first sinus complex does not conduct because of a premature ventricular complexes. The second sinus complex conducts with a His-ventricular (HV) interval of 108 …

Background— Definitive diagnosis of bilateral bundle-branch delay/block may be made when catheter-induced right bundle-branch block (RBBB) develops in patients with baseline left bundle-branch (LBB) block. We hypothesized that a RBBB pattern with absent S waves in leads I and aVL will identify bilateral bundle-branch delay/block. Methods and Results— Fifty patients developing transient RBBB pattern in lead V1 during right heart catheterization were studied. Patients were grouped according to whether the baseline ECG demonstrated a normal QRS, left fascicular blocks, or LBB block pattern. The RBBB morphologies in each group were compared. The prevalence of bilateral bundle-branch delay/block pattern was examined in our hospital ECG database. All patients with baseline normal QRS complexes (n=30) or left fascicular blocks (4 anterior, 5 posterior) developed a typical RBBB pattern. Among the 11 patients with a baseline LBB block pattern, 7 developed an atypical RBBB pattern with absent S waves in leads I and aVL and the remaining 4 demonstrated a typical RBBB. The absence of S waves in leads I and aVL during RBBB was 100% specific and 64% sensitive for the presence of pre-existing LBB block. Among the consecutive 2253 hospitalized patients with RBBB, 34 (1.5%) had the bilateral bundle-branch delay/block pattern. Conclusions— An ECG pattern of RBBB in lead V1 with absent S wave in leads I and aVL indicates concomitant LBB delay. Pure RBBB and bifascicular blocks are associated with S waves in leads I and aVL.

The incidence and prevalence of atrial fibrillation (AF) are increasing globally, and the arrhythmia has profound impact on patient outcomes [(1)][1]. The precise reasons for the rising AF epidemic are unclear, and proposed causes include the aging population and increased incidence of risk factors

Studies have established the superiority of atrial fibrillation ablation in controlling the rhythm compared with medical therapy. The procedure, however, has significant associated risks. Whether ablation therapy would improve the major outcomes of survival and stroke is not yet established. Until this information becomes available, ablation should continue to be used as a second-line option for most patient subgroups when one or more antiarrhythmic medications are ineffective.

Introduction Paroxysmal atrial fibrillation (AF) may progress to persistent AF. We studied the clinical correlates and the effect of rhythm-control strategy on AF progression. Methods RecordAF was a worldwide prospective survey of AF management. Consecutive eligible patients with recent-onset AF were included and allocated to rate or rhythm control according to patient/physician choice. A total of 2,137 patients were followed up for 12 months. Atrial fibrillation progression was defined as a change from paroxysmal to persistent/permanent AF. Results Progression of AF occurred in 318 patients (15%) after 1 year. Patients with AF progression were older; had a higher diastolic blood pressure; and more often had a history of coronary artery disease, stroke or transient ischemic attack, hypertension, or heart failure. Patients treated with rhythm control were less likely to show progression than those treated only with rate control (164/1542 [11%] vs 154/595 [26%], P

Objectives RECORDAF is the first worldwide, prospective, observational survey of management of atrial fibrillation (AF) in unselected, community-based patients. Background Primary outcomes were therapeutic success and clinical outcomes associated with rhythm-control and rate-control strategies. Methods Patients with recent-onset AF were included (n = 5,604). Treatment strategy (rhythm control or rate control) was noted at baseline. Follow-up was 12 months. Therapeutic success required that strategy was unchanged without clinical events. Further maintenance of sinus rhythm was required in the rhythm-control group, and heart rate ≤80 beats/min in the rate-control group. Results Data from 5,171 patients were assessable. Therapeutic success was 54% overall (rhythm control 60% vs. rate control 47%), a result driven by control of AF: rhythm control, 81% vs. rate control, 74%. After adjustment for propensity score quintiles, the rhythm-control strategy was significantly related to superior therapeutic success (odds ratio: 1.34, 95% confidence interval: 1.15 to 1.55; p = 0.0002). Clinical events occurred in 18% of patients. The arrhythmia management strategy was not predictive of clinical events. The type (persistent), presence at baseline visit, and duration (>3 months) of AF, together with age older than 75 years and the presence of heart failure, predicted progression to permanent AF. The choice of rhythm control reduced the likelihood of AF progression (odds ratio: 0.20, 95% confidence interval: 0.17 to 0.25; p Conclusions Clinical outcomes in AF patients were driven mainly by hospitalizations for arrhythmia/proarrhythmia and other cardiovascular causes, but not by the choice of rate or rhythm strategy. Rhythm-control patients progressed less rapidly to permanent AF.

Developed in partnership with the Heart Rhythm Society L. Samuel Wann, MD, MACC, FAHA, Chair[‡][1]; Anne B. Curtis, MD, FACC, FAHA[‡][1],[§][2]; Kenneth A. Ellenbogen, MD, FACC, FHRS[†][3],[§][2]; N.A. Mark Estes III, MD, FACC, FHRS[∥][4]; Michael D. Ezekowitz, MB, ChB, FACC[‡][1]

The REgistry on Cardiac rhythm disORDers assessing the control of Atrial Fibrillation (RecordAF) is the first worldwide, 1-year observational, longitudinal study of the management of paroxysmal/persistent atrial fibrillation (AF) in recently diagnosed patients. The study was conducted at 532 sites in 21 countries across Europe, America, and Asia; recruitment was completed in April 2008. The primary objectives were to prospectively assess the therapeutic success and clinical outcomes in rhythm- and rate-control strategies. The study design and patient baseline data are reported. A total of 5,814 patients with AF were registered, and 5,604 were eligible for evaluation. Rhythm- and rate-control strategies were applied to 55% and 45% of patients, respectively, at study inclusion. Rhythm-control patients mainly received class III agents (45%) or beta blockers (51%), except for sotalol, and rate-control patients mainly received beta blockers (72%), except for sotalol, or cardiac glycosides (34%). Patients receiving a rhythm-control strategy were younger, had a lower resting heart rate, were more frequently symptomatic, and were more likely to have recently diagnosed AF or paroxysmal AF compared to patients receiving a rate-control strategy. A rate-control strategy was more common in patients with a history of heart failure or valvular heart disease and persistent AF. Rate-control patients more often had previous electrocardiographic evidence of AF and were not in sinus rhythm at inclusion (p0.01 for both end points). Patients were followed at 6 and 12 months, and changes in therapeutic strategy and clinical outcomes were recorded. In conclusion, the RecordAF study results will provide a global perspective on current AF treatment strategies.

Background: The Registry on Cardiac Rhythm Disorders Assessing the Control of Atrial Fibrillation (RecordAF) study is the first worldwide, prospective, survey of real-life management of atrial fibrillation (AF) in recently diagnosed patients (n = 5604) with a 1-year follow-up. Hypothesis: Surveys of AF management have identified a divergence between guidelines and clinical practice, and an overinterpretation of guidelines in low-risk patients. Methods: Physicians' theoretical approaches to rhythm and rate control were investigated using a pre-study questionnaire. Results: One cardiologist, from each of the 583 sites in 6 regions, completed a questionnaire on their practice and management of AF patients. In AF patients with structural heart disease (SHD), amiodarone was the most frequent choice of first-line rhythm control agents in all regions. Amiodarone or sotalol tended to be the preferred second-line rhythm control agents, 1 exception being Central/South America. β-Blockers were the first-line rate control agents for patients with AF and SHD in all regions, and calcium channel blockers and cardiac glycosides were the most common second-line rate control treatments in all regions, except Asia. In lone AF patients, propafenone (30.6%), flecainide (24.1%), and amiodarone (21.7%) were the most common global choices of first-line rhythm control, and amiodarone or sotalol were the preferred second-line rhythm control agents, 1 exception being Central/South America. Conclusions: These results highlight points of divergence from the American College of Cardiology (ACC)/ American Heart Association (AHA)/European Society of Cardiology (ESC) guidelines for the management of AF in terms of first-line drug selection in patients with associated SHD or coronary artery disease. Copyright © 2010 Wiley Periodicals, Inc.

Venice Chart International Consensus Document on Ventricular Tachycardia/Ventricular Fibrillation Ablation ANDREA NATALE, M.D.,∗ ANTONIO RAVIELE, M.D.,† AMIN AL-AHMAD, M.D.,‡ OTTAVIO ALFIERI, M.D.,¶ ETIENNE ALIOT, M.D.,∗∗ JESUS ALMENDRAL, M.D.,†† GUNTER BREITHARDT, M.D.,‡‡ JOSEP BRUGADA, M.D.,¶¶ HUGH CALKINS, M.D.,∗∗∗ DAVID CALLANS, M.D.,††† RICCARDO CAPPATO, M.D.,‡‡‡ JOHN A. CAMM, M.D.,¶¶¶ PAOLO DELLA BELLA, M.D.,∗∗∗∗ GERARD M. GUIRAUDON, M.D.,†††† MICHEL HAISSAGUERRE, M.D.,‡‡‡‡ GERHARD HINDRICKS, M.D.,¶¶¶¶ SIEW YEN HO, M.D.,∗∗∗∗∗ KARL H. KUCK, M.D.,††††† FRANCIS MARCHLINSKI, M.D.,‡‡‡‡‡ DOUGLAS L. PACKER, M.D.,¶¶¶¶¶ ERIC N. PRYSTOWSKY, M.D.,∗∗∗∗∗∗ VIVEK Y. REDDY, M.D.,†††††† JEREMY N. RUSKIN, M.D.,‡‡‡‡‡‡ MAURICIO SCANAVACCA, M.D.,¶¶¶¶¶¶ KALYANAM SHIVKUMAR, M.D.,∗∗∗∗∗∗∗ KYOKO SOEJIMA, M.D.,††††††† WILLIAM J. STEVENSON, M.D.,‡‡‡‡‡‡‡ SAKIS THEMISTOCLAKIS, M.D.,¶¶¶¶¶¶¶ ATUL VERMA, M.D.,∗∗∗∗∗∗∗∗ and DAVID WILBER, M.D.,†††††††† for the Venice Chart members From the ∗Texas Cardiac Arrhythmia Institute, St. David’s Medical Center, Austin, TX, USA; †Cardiovascular Department, Ospedale dell’Angelo, Mestre-Venice, Italy; ‡Cardiac Arrhythmia Service, Stanford University Medical School, Stanford, USA; ¶Department of Cardiac Surgery, Ospedale San Raffaele, Milan, Italy; ∗∗Department of Cardio-Vascular Diseases, CHU de Nancy, Hopital de Brabois, Vandoeuvre-les-Nancy, France; ††Division of Cardiology, Hospital General Gregorio Maranon, Madrid, Spain; ‡‡Department of Cardiology and Angiology, University Hospital of Munster, Munster, Germany; ¶¶Thorax Institute-Cardiology, Hospital Clinic, University of Barcelona, Barcelona, Spain; ∗∗∗Department of Cardiology, The Johns Hopkins Hospital, Baltimore, MD, USA; †††Department of Medicine, Section of Cardiovascular Disease, Hospital of the University of Pennsylvania, Philadelphia, PA, USA; ‡‡‡Department of Electrophysiology, Policlinico San Donato, San Donato Milanese, Italy; ¶¶¶Cardiac and Vascular Sciences, St. George’s Hospital Medical School, London, UK; ∗∗∗∗Cardiology Division, Centro Cardiologico Monzino, Milan, Italy; ††††Cardiac Surgery, University of Western Ontario, London, Canada; ‡‡‡‡Hopital Cardiologique du Haut Leveque, Bordeaux, France; ¶¶¶¶Heart Center, Department of Cardiology, University of Leipzig, Leipzig, Germany; ∗∗∗∗∗Cardiac Morphology Unit, Royal Brompton Hospital, London and Imperial College, London, UK; †††††Department of Cardiology, Asklepios Klinik St. Georg, Hamburg, Germany; ‡‡‡‡‡Department of Medicine, Section of Cardiovascular Disease, University of Pennsylvania, Philadelphia, PA, USA; ¶¶¶¶¶Cardiac Translational and Electrophysiology Laboratory, Saint Mary’s Hospital Complex, Mayo Clinic Foundation, Rochester, NY, USA; ∗∗∗∗∗∗The Care Group, Indianapolis, IN, USA; ††††††Cardiac Arrhythmia Service, Miller School of Medicine, University of Miami, Miami, USA; ‡‡‡‡‡‡Arrhythmia Service, Massachusetts General Hospital, Boston, MA, USA; ¶¶¶¶¶¶Heart Institute, University of San Paulo Medical School, San Paulo, Brazil; ∗∗∗∗∗∗∗Cardiac Arrhythmia Center, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; †††††††Cardiovascular Division, University of Miami Hospital, Miami USA; ‡‡‡‡‡‡‡Cardiovascular Division, Brigham and Women’s Hospital, Boston, MA, USA; ¶¶¶¶¶¶¶Cardiovascular Department, Ospedale dell’Angelo, Mestre-Venice, Italy; ∗∗∗∗∗∗∗∗Cardiology, Southlake Regional Health Center, Toronto, Canada; and ††††††††Department of Cardiology, Loyola University Medical Center, Chicago, IL, USA

Objectives The purpose of this study was to differentiate non–re-entrant junctional tachycardia (JT) and typical atrioventricular node re-entry tachycardia (AVNRT). Background JT may mimic AVNRT. Ablation of JT is associated with a lower success rate and a higher incidence of heart block. Electrophysiologic differentiation of these tachycardias is often difficult. Methods We hypothesized that JT can be distinguished from AVNRT based on specific responses to premature atrial complexes (PACs) delivered at different phases of the tachycardia cycle: when a PAC is timed to His refractoriness, any perturbation of the subsequent His indicates that anterograde slow pathway conduction is involved and confirms a diagnosis of AVNRT. A PAC that advances the His potential immediately after it without terminating tachycardia indicates that retrograde fast pathway is not essential for the circuit and confirms a diagnosis of JT. This protocol was tested in 39 patients with 44 tachycardias suggesting either JT or AVNRT based on a short ventriculo-atrial interval and apparent AV node dependence. Tachycardias were divided into 3 groups: clinically obvious AVNRT, clinically obvious JT, and clinically indeterminate rhythm. Results In the 26 cases of clinically obvious AVNRT, the sensitivity and specificity of the test were 61% and 100%, respectively. In the 9 cases of clinically obvious JT, the sensitivity and specificity were 100% and 100%, respectively. In the 9 cases of clinically indeterminate rhythm, the technique indicated AVNRT in 1 patient and JT in 7 patients, and the test was indeterminate in 1 patient. Conclusions The response to PACs during tachycardia can distinguish JT and AVNRT with 100% specificity in adult patients.

Cardiac resynchronization therapy (CRT) is a new therapy for patients with symptomatic heart failure (HF) resulting from systolic dysfunction. Numerous clinical investigations have demonstrated that in selected patients with ventricular dyssynchrony, CRT improved left ventricular function, functional status, and left ventricular ejection fraction (LVEF). Randomized clinical trials showed that in patients already on optimal medical therapy, CRT reduced morbidity and all-cause mortality. On the basis of the inclusion criteria and the results of these CRT trials, CRT is currently recommended, both in Europe and in the USA, for patients with NYHA functional Class III or IV heart failure, a LVEF ≤35%, and a QRS duration ≥160 ms (or ≥120 ms with other evidence of ventricular dyssynchrony) who are receiving chronic optimal medical therapy. However, several issues still remain unresolved: in particular, the benefit of CRT therapy has not been established in patients with mild HF (NYHA Class I or II), atrial fibrillation, minor conduction abnormality, or pacemaker dependence. In addition, ∼20–30% of patients do not respond to CRT. Considering that CRT is an invasive and costly procedure, identification of patients most likely to benefit from CRT is clearly a research priority.

Objectives We determined the contribution of multiple variables to predict arrhythmic death and total mortality risk in patients with coronary disease and left ventricular dysfunction. We then constructed an algorithm to predict risk of mortality and sudden death. Background Many factors in addition to ejection fraction (EF) influence the prognosis of patients with coronary disease. However, there are few tools to use this information to guide clinical decisions. Methods We evaluated the relationship between 25 variables and total mortality and arrhythmic death in 674 patients enrolled in the MUSTT (Multicenter Unsustained Tachycardia Trial) study that did not receive antiarrhythmic therapy. We then constructed risk-stratification algorithms to weight the prognostic impact of each variable on arrhythmic death and total mortality risk. Results The variables having the greatest prognostic impact in multivariable analysis were functional class, history of heart failure, nonsustained ventricular tachycardia not related to bypass surgery, EF, age, left ventricular conduction abnormalities, inducible sustained ventricular tachycardia, enrollment as an inpatient, and atrial fibrillation. The model demonstrates that patients whose only risk factor is EF ≤30% have a predicted 2-year arrhythmic death risk Conclusions Multiple variables influence arrhythmic death and total mortality risk. Patients with EF ≤30% but no other risk factor have low predicted mortality risk. Patients with EF >30% and other risk factors may have higher mortality and a higher risk of sudden death than some patients with EF ≤30%. Thus, risk of sudden death in patients with coronary disease depends on multiple variables in addition to EF.

INTRODUCTION Continuous mobile cardiac outpatient telemetry (MCOT) may have several advantages over traditional ambulatory monitoring systems in the diagnostic evaluation of symptoms such as palpitations, dizziness, and syncope. However, only limited published data are available showing its advantages. METHODS AND RESULTS We reviewed the records of 122 consecutive patients evaluated using MCOT for palpitations, presyncope/syncope, or to monitor the efficacy of a specific antiarrhythmic therapy. Ten of 17 patients (59%) studied for presyncope/syncope had a diagnosis made with MCOT. Eight of these 17 patients had a previous negative evaluation for presyncope/syncope and five had an event correlated with the heart rhythm during the monitoring period. Nineteen patients monitored for palpitations or presyncope/syncope were asymptomatic during monitoring but had a prespecified arrhythmia detected. When MCOT was used as the first ambulatory monitoring system to evaluate palpitations (n = 18), 73% of patients correlated their symptoms with the underlying cardiac rhythm. Seven of 21 patients monitored for medication titration had dosage adjustments during outpatient monitoring. CONCLUSIONS MCOT can detect asymptomatic clinically significant arrhythmias, and was especially useful to identify the cause of presyncope/syncope, even in patients with a previous negative workup. This outpatient monitoring system allows patients to undergo daily medication dose titration in the outpatient setting, thus avoiding hospitalization.

Several randomized controlled trials and meta-analyses have demonstrated improved freedom from atrial fibrillation with intraoperative atrial ablation. However, the increased bypass time and the risk for ablation-related complications should be weighed against the benefits in the decision-making. It is important to establish reasonable criteria to define candidates for surgical ablation. Furthermore, the efficacy and short- and long-term risks related to surgical ablation need to be considered. This article reviews the data on surgical ablation of atrial fibrillation as it pertains to these important issues. As shown the evidence does not support surgical ablation at the time of coronary artery bypass graft in some patients.

New Antiarrhythmic Agents for Prevention and Treatment of AF. Rhythm control could become the preferred treatment strategy for atrial fibrillation (AF) if the available antiarrhythmic agents were more effective and safe. A subanalysis of the AFFIRM trial data suggested that rhythm control, if achieved without the adverse effects related to antiarrhythmic medications, may offer a significant survival advantage over rate control. This article reviews the new investigational pharmacologic and dietary agents being considered for the prevention and treatment of AF. Dronederone is a benzofurane similar to amiodarone, but without the iodine component, and is devoid of many of the amiodarone systemic toxicities. Azimilide is a delayed rectifier potassium channel blocker with use-dependent effects. Agents that target the ultra rapid component of the delayed rectifier potassium current (I Kur ) have atrial myocyte specific properties and may be devoid of QT prolongation and torsade de pointes in clinical usage. Newer agents being studied also include fish oil, gap junction modulators, 5HT4 receptor antagonists, angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, and HMG CoA reductase inhibitors. There is considerable hope that at least some of these agents will ultimately be available for more effective and safe clinical treatment and prevention of AF.

Rhythm and Rate Control in Patients with AF. A recent series of randomized prospective clinical trials that compared rate control with rhythm control in patients with atrial fibrillation (AF) found no significant difference in primary outcome between the two strategies. However, these trials lacked clear criteria for defining “successful” rate or rhythm control. Various measures have been used to gauge the success of antiarrhythmic drug therapy, including time to first recurrence of AF, any AF recurrence, AF burden, and a reduction in symptoms. Determining the success of antiarrhythmic therapy can be relatively straightforward by using how patients feel during therapy as a key endpoint. Most patients are satisfied with a major reduction in symptomatic AF episodes and can live comfortably with occasional episodes of AF. For those who are bothered by even infrequent, brief AF episodes, a treatment regimen that eliminates nearly all AF recurrences is required, although often hard to achieve. Catheter ablation may be necessary to achieve a successful outcome in these patients. Suppression of AF in a patient at high risk of stroke does not, however, remove the need for concomitant warfarin therapy. The endpoints of ventricular rate control are not clear, and the recently published rhythm versus rate control trials lacked standard criteria for judging acceptable rate control. One relatively simple method is to try and achieve a 24-hour heart rate that mimics expected normal sinus rhythm. It is important to achieve good rate control to minimize symptoms and the risk of tachycardia-mediated cardiomyopathy. (J Cardiovasc Electrophysiol, Vol. 17

Alonso-Garcia, Carina Blomstrom-Lundqvist, Guy de Backer, Marcus Flather, Jaromir Hradec, Committee for Practice Guidelines & Policy Conferences Members, Werner W. Klein, Angeles Gregoratos, Loren F. Hiratzka, Alice K. Jacobs, Richard O. Russell, Sidney C. Smith, Jr., ESC J. Gibbons, Elliott M. Antman, Joseph S. Alpert, David P. Faxon, Valentin Fuster, Gabriel Levy, Robert L. McNamara, Eric N. Prystowsky, L. Samuel Wann, D. George Wyse, Raymond Harry J. Crijns, Robert L. Frye, Jonathan L. Halperin, G. Neal Kay, Werner W. Klein, Samuel Committee Members, Valentin Fuster, Lars E. Ryden, Richard W. Asinger, David S. Cannom, Collaboration With the North American Society of Pacing and Electrophysiology Guidelines for the Management of Patients With Atrial Fibrillation) Developed in Committee for Practice Guidelines and Policy Conferences (Committee to Develop Association Task Force on Practice Guidelines and the European Society of Cardiology Executive Summary A Report of the American College of Cardiology/American Heart ACC/AHA/ESC Guidelines for the Management of Patients With Atrial Fibrillation

We report a case of atrioventricular reentrant tachycardia (AVRT) using a concealed para-Hisian accessory pathway for retrograde conduction, which also required anterograde conduction over the AV nodal slow pathway to maintain the tachycardia. The shortest VA interval during AVRT (70 ms) was noted at a site with His bundle electrogram amplitude of 0.25 mV. The AVRT was cured by radiofrequency ablation of the AV nodal slow pathway without affecting accessory pathway conduction. The patient has not reported any sustained palpitations at 2 years after ablation while receiving no medications. The case presented in this report illustrates a para-Hisian AVRT that was successfully eliminated by an unconventional approach of ablation of the atrial inputs to the AV nodal slow pathway.

The management of patients with atrial fibrillation involves three main areas: anticoagulation, rate control and rhythm control. Importantly, these are not mutually exclusive of each other. Anticoagulation is necessary for patients who are at a high risk of stroke; for example, those who are older than 75 years, or those who have hypertension, severe left ventricular dysfunction, previous cerebrovascular events, or diabetes. It is now clear that patients who are at a high risk of stroke require long-term anticoagulation with warfarin regardless of whether a rate-control or rhythm-control strategy is chosen. One possible exception might be patients who are apparently cured with catheter ablation. Several published trials comparing rate-control and rhythm-control strategies for the treatment of patients with atrial fibrillation have shown no difference in mortality between these approaches. The patients enrolled in these studies were typically over 65 years of age. Data comparing rate and rhythm strategies in patients who are younger than 60 years of age are limited. For more elderly patients, it seems reasonable to consider rate control as a primary treatment option and to reserve rhythm control for those who do not respond to rate control. For younger patients, we prefer to start with a rhythm-control approach and to reserve rate-control approaches for patients in whom antiarrhythmic drugs, ablation, or both, do not ameliorate the symptoms.

Atrial fibrillation (AF), the commonest cardiac arrhythmia with an adverse prognosis, has an estimated prevalence of 0.4% in general population.1 The disease is associated with significant morbidity related to symptoms, heart failure, and thromboembolism.2 Although AF is generally considered a non–life-threatening arrhythmia, it was associated with a 1.5- to 1.9-fold excess mortality after adjustment for preexisting cardiovascular conditions in the Framingham Heart Study.3 In the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study, a strategy of heart rate control was equivalent to heart rhythm control in terms of quality of life and all-cause mortality but superior in reducing hospitalizations.4 Anticoagulation with warfarin is maintained in either strategy if the patient has risk factors for thromboembolism. The major reason to pursue sinus rhythm in patients with AF is to improve their symptoms and quality of life. No studies have shown a reduction in stroke or heart failure when rhythm control is attempted in patients with AF. Once the decision to achieve rhythm control in a given patient has been made, physicians have to determine the best means of achieving this objective. Multiple randomized trials have demonstrated a modest but highly significant efficacy for antiarrhythmic medications.5 The limited long-term efficacy and high incidence of side effects of antiarrhythmic medications have prompted physicians to consider nonpharmacological therapies for AF.6 It has also been postulated, in a retrospective subanalysis of the AFFIRM study, that a strategy to maintain sinus rhythm without the adverse effects of antiarrhythmic medications may confer a survival advantage.7 In a nonrandomized study, Pappone et al8 compared the outcomes in a selected group of 589 patients who underwent circumferential pulmonary vein ablation with 582 age- and gender-matched cohort patients who received antiarrhythmic medications to maintain sinus rhythm. After a median follow-up of …

Mechanism of Induction of Atrioventricular Node Reentry. Introduction: AV node reentry (AVNRT) is typically induced with anterograde (Ant) block over the fast pathway (FP) and conduction over the slow pathway (SP), with subsequent retrograde (Ret) conduction over the FP. Rarely, a premature atrial complex (PAC) conducts simultaneously over the FP and SP to induce AVNRT (2 for 1). This study investigates the mechanism of 2 for 1 induction. Methods and Results: Of 192 consecutive patients (pts) undergoing posteroseptal radiofrequency ablation to treat AVNRT, 4 pts (2%) had 2 for 1 AVNRT induction. All needed isoproterenol for AVNRT initiation, and Ant conduction was over the SP during AVNRT. Controls (n = 15) were randomly selected from the remaining 188 pts and required isoproterenol to induce AVNRT with Ant block over the FP. For 2 for 1 versus control, respectively, there was no difference in mean age (55 vs. 46 yr), AVNRT cycle length (420 vs. 320 ms), or the Ant effective refractory period of the FP (320 vs. 344 ms). Of note, the PAC that induced AVNRT had a significantly longer AH interval over the SP in pts with 2 for 1 versus control (470 vs. 320 ms, P = 0.016), even though the A1A2 interval for induction was longer for 2 for 1 (315 vs. 260 ms, P = 0.003). Ret conduction over the SP was relatively poor in the 2 for 1 group as evidenced by 4/4 pts with induction of AVNRT during incremental ventricular pacing versus only 1/15 control pts (P < 0.001). Conclusion: The unique induction of AVNRT by a PAC with simultaneous conduction over the FP and SP is best explained by minimal to no retrograde invasion of the SP from the anterogradely conducted fast pathway impulse, and consistent with this observation is the initiation of slow/fast AVN reentry during incremental RV pacing.

Treatment of atrial fibrillation (AF) involves 3 major strategies: prevention of stroke, maintenance of sinus rhythm, and rate control [(1)][1]. Stroke is the most dreaded complication of AF, and its prevention is key. Anticoagulation with warfarin and the newer agents dabigatran, rivaroxaban, and

Introduction: Dofetilide is the newest drug approved by the United States Food and Drug Administration for the treatment of patients with atrial fibrillation (AF). Few data on the efficacy and safety of dofetilide in a diverse group of patients are available. The aim of this study was to evaluate the results of dofetilide in a consecutive series of 69 patients with AF. Methods and Results: Sixty-nine patients with persistent (n = 53) or paroxysmal (n = 16) AF were administered dofetilide in-hospital. Prior to starting dofetilide, all patients had been adequately anticoagulated, and concomitant agents contraindicated in the presence of dofetilide were discontinued. Heart rhythms were monitored continuously by telemetry in all patients. The initial dose, which was determined using the Cockroft-Gault calculated creatinine clearance, was 500 μg bid, 250 μg bid, and 125 μg bid in 51, 13, and 5 patients, respectively. Reductions in subsequent dosage occurred in 12 patients, 4 for QT prolongation. Dofetilide was discontinued in-hospital in 7 patients, 2 for adverse arrhythmic events and 3 for unacceptable QT prolongation. Twenty-seven (63%) of 43 patients in AF converted spontaneously to sinus rhythm. Fifty-eight patients were discharged receiving dofetilide treatment and were followed as outpatients for 21 ± 7 months. One third of patients continued to take dofetilide at 1 year. One patient had a cardiac arrest 1 day after hospital discharge. Conclusion: Dofetilide is a well-tolerated antiarrhythmic drug with a high conversion rate of AF to sinus rhythm. One third of patients maintained sinus rhythm at 1 year. Proarrhythmia can occur and initiation of therapy must be performed in-hospital. (J Cardiovasc Electrophysiol, Vol. 14, pp. S287-S290, December 2003, Suppl.)

Background— The aim of this study was to test the electrophysiological effects of continuous enhanced vagal tone on dual atrioventricular (AV) nodal and accessory pathways. Methods and Results— This study included 10 patients with typical, slow-fast AV nodal reentrant tachycardia (AVNRT) and 10 patients with AV reciprocating tachycardia. Electrophysiological data were measured before and during continuous vagal enhancement by using phenylephrine infusion (0.6 to 1.5 μg/kg per min). For patients with AVNRT, during phenylephrine infusion, 1:1 conduction times over the anterograde fast and slow and retrograde fast pathways were prolonged (453±64 to 662±120 ms, P P P P P Conclusions— Enhanced vagal tone produces disparate effects on the refractoriness of the slow and fast AV nodal conduction pathways, with the anterograde fast pathway being the most sensitive. These changes are conducive to induction of AVNRT with a premature atrial complex and may explain in part the relatively common occurrence of AVNRT during sleep or other periods of presumed increased parasympathetic tone.

Atrial fibrillation occurs commonly in the setting of congestive heart failure and, in fact can cause left ventricular dysfunction due to a rapid ventricular response over time, termed tachycardia-mediated cardiomyopathy. The combination of atrial fibrillation and congestive heart failure leads to a high risk of stroke for the patient and appropriate antithrombotic therapy can minimize this incidence of stroke. Stroke risk can be markedly reduced by treatment with warfarin and complications of anticoagulation minimized by close attention to maintaining the INR between 2.0 and 3.0.