Effects of High-Frequency Atrial Pacing in Atypical Atrial Flutter and Atrial Fibrillation

Atypical atrial flutter has, hitherto, been relatively refractory totermination by rapid atrial pacing. High-frequency pacing (HFP) in theatrium, for termination of atrial flutter or atrial fibrillation (AF), andthe electrophysiologic effects related to it have not been examined. Weexamined the clinical efficacy, safety, and electrophysiologic mechanisms ofHFP using 50-Hz bursts at 10 mA applied at the high right atrium in patientswith atypical atrial flutter (group 1) or AF (group 2), using a prospectiverandomized study protocol. Four burst durations (500, 1000, 2000, and 4000ms) were applied at the high right atrium repetitively in random sequence in22 patients with spontaneous atrial flutter or AF. Local and distant rightand left atrial electrogram recordings were analyzed during and after HFP.HFP resulted in local and distant right and left atrial electrogramacceleration in 8 of 10 patients (80%) in group 1 but caused lessfrequent local atrial electrogram acceleration (6 of 12 patients) and nodistant atrial electrogram effects in group 2 (p < .05 versus group 1).The HFP protocol was effective in arrhythmia termination in 6 of 10patients in group 1 but in no patient in group 2 (p < .05 versus group1). Standard HFP protocol applied at the high right atrium can frequentlyalter atrial activation in both atria and can terminate atypical atrialflutter. Efficacy in AF is limited, probably due to limitedelectrophysiologic actions beyond the local pacing site.     

Early versus Late Atrial Fibrillation after Atrial Flutter Ablation

Introduction: Radiofrequency catheter ablation of atrial flutter (AFl) has high initial success with a 10–15% recurrence. Atrial fibrillation (AFib) after radiofrequency catheter ablation of AFl can occur but may be transient (lasting no more than four weeks). Methods: Of one hundred seventeen consecutive patients studied, one hundred and four consecutive patients with sustained, symptomatic AFl, as the predominant rhythm disturbance (some of whom had transient pre-ablation AFib), referred for radiofrequency catheter ablation, had clinical follow-up. All had evidence for successful AFl ablation. Patients were followed prospectively. Results: Over a mean follow-up of 28 months, 28 patients developed AFib after ablation of AFl [12 early AFib (<2 months) and 16 late AFib (>2 months)]. Seven of 12 (58%) patients in the early onset group reverted to normal sinus rhythm; none required long-term antiarrhythmic therapy. Only one (8%) developed permanent AFib. No patient in the late onset group remained in sinus rhythm without an antiarrhythmic drug. Three (19%) developed permanent AFib despite therapy among those with late onset AFib. Two (17%) patients with early onset AFib reverted to normal sinus rhythm with treatment versus 5 (31%) in the late onset group. Finally, only 2 patients (17%) with paroxysmal/persistent episodes of Afib from the early onset group stayed in normal sinus rhythm despite therapy, while 8 patients ( ± %) with paroxysmal/persistent AFib episodes from the late onset group required therapy to maintain normal sinus rhythm. Conclusion: Early onset AFib after ablation of AFl is likely to be transient and self-limited. Late onset AFib after ablation of AFl can persist and require chronic therapy.     

Spontaneous Transition from Atrial Fibrillation to Typical Atrial Flutter during Catheter Ablation of the Pulmonary Vein

A 71-year-old male patient was admitted for catheter ablation of the pulmonary veins to treat paroxysmal atrial fibrillation. Atrial fibrillation originating from the left superior pulmonary vein was induced after a pause of atrial pacing under isoproterenol infusion and became sustained. Spontaneous transition from atrial fibrillation to typical atrial flutter was noted after complete isolation of the pulmonary vein focus from the left atrium. Subsequently linear ablation of the cavotricuspid isthmus was created with completely bi-directional isthmus conduction block. We hypothesized that ectopic pulmonary vein focus played an important role in the spontaneous conversion of atrial fibrillation to typical atrial flutter, and complete isolation of the pulmonary vein could stop the spontaneous transition between the two atrial tachyarrhythmias.     

Coexistence of Intracardiac Atrial Flutter and Extracardiac Fibrillation

This report describes the coexistence of fibrillatory activity limited to an isolated left common pulmonary vein trunk with typical counterclockwise isthmus-dependent right atrial flutter in a patient undergoing a pulmonary vein isolation procedure.     

Persistent Atrial Flutter in Patients Treated for Atrial Fibrillation with Amiodarone and Propafenone:

INTRODUCTION: Antiarrhythmic drugs have been reported to promote the conversion of atrial fibrillation to atrial flutter in patients with paroxysmal atrial fibrillation. However, information about the electrophysiologic mechanism and response to radiofrequency ablation of these drug-induced atrial flutters is limited. Furthermore, the determinants of the development of persistent atrial flutter in patients treated for atrial fibrillation with antiarrhythmic drugs are still unknown. METHODS AND RESULTS: Among the 136 patients treated for atrial fibrillation with amiodarone (n = 96) or propafenone (n = 40), 15 (11%, mean age 65.5 +/- 12.3 years) were identified to have subsequent development of persistent atrial flutter based on surface ECG characteristics during antiarrhythmic drug treatment. The mean interval between the beginning of drug treatment and the onset of atrial flutter was 5.0 +/- 5.5 months. Intracardiac mapping and entrainment studies revealed that 11 patients had counterclockwise typical atrial flutter, and 4 had clockwise typical atrial flutter. All 15 patients underwent successful ablation with creation of complete bidirectional isthmus conduction block. After a mean follow-up of 12.3 +/- 4.2 months, 14 (93%) of 15 patients who underwent successful ablation and continued taking antiarrhythmic drugs have remained in sinus rhythm. Univariate analysis of clinical variables demonstrated that only atrial enlargement was significantly related to the occurrence of persistent atrial flutter. CONCLUSION: In patients with atrial fibrillation, persistent typical atrial flutter might occur during antiarrhythmic drug treatment, and atrial enlargement was a risk factor for the development of such an arrhythmia. Radiofrequency ablation and continuation of pharmacologic therapy offered a safe and effective means of achieving and maintaining sinus rhythm.     

Discrimination of Sinus Rhythm, Atrial Flutter, and Atrial Fibrillation Using Bipolar Endocardial Signals

Discrimination of NSR, AFL, and AF. Introduction : Analysis of endocardial signals obtained from an electrode located in the right atrium as realized in newly designed dual chamber, implantable cardioverter defibrillators might be used to provide additional therapeutic options, such as overdrive pacing or low-energy atrial cardioversion for the treatment of concomitant atrial flutter (AFL) or atrial fibrillation (AF). Therefore, we developed a computer algorithm for discrimination of normal sinus rhythm (NSR), AFL, and AF that may lead to adequate differential therapy of atrial tachyarrhythmias in an automated mode.
Methods and Results : During an electrophysiologic study, bipolar endocardial signals from the high right atrium were obtained in 28 patients during sustained AFL or AF and after restoration of NSR. A total of 286 data segments of 5-second duration were recorded (NSR: 96, AFL: 86, AF: 104). Mean atrial cycle length (MCL), standard deviation of mean atrial cycle length (SDCK), and index of irregularity (IR). defined as the ratio between MCL and SDCL, were calculated for each data segment. A cutoff of 315 msec for MCL allowed discrimination of NSR from atrial tachyarrhythmias with 100% sensitivity and specificity. For discrimination of AF from AFI- by using SDCL, a cutoff value of 11.5 msec led to a sensitivity of 99% and a specificity of 90%. Best discrimination of AF from AFL was found for the criterion IR ≥ 7.5%, resulting in a sensitivity of 100% with a specificity of 95% for AF detection.
Conclusion : The investigated algorithm provides discrimination of NSR, AFL, and AF with high sensitivity and specificity. Incorporation of this algorithm in an implantable automated antitachycardia device may lead to adequate differential therapy in patients suffering from spontaneous episodes of AF and AFL.     

Electrophysiologic Characteristics of a Dilated Atrium in Patients with Paroxysmal Atrial Fibrillation and Atrial Flutter

This study investigated the difference of atrial electrophysiologic characteristics between a normal and dilated atrium and compared them among patients with paroxysmal atrial fibrillation and flutter. Twenty-seven patients with paroxysmal atrial fibrillation and 28 patients with paroxysmal atrial flutter were divided into four subgroups, according to the presence of a normal atrium or bilateral atrial enlargement. Thirty patients without atrial arrhythmia (20 patients with normal atrium and 10 patients with bilateral atrial enlargement) were included in control group. The atrial refractoriness in patients with a dilated atrium was longer than those with normal atrial size. In patients with paroxysmal atrial fibrillation and patients of control group, the P-wave duration and interatrial conduction velocity with or without atrial enlargement were similar. However, in patients with paroxysmal atrial flutter, P-A_PCS (86 ± 10 ms vs. 73 ± 9 ms, p < 0.05) and P-A_DCS (109 ± 9 ms vs. 95 ± 9 ms, p < 0.05) in patients with a dilated atrium were longer than in patients with a normal atrium. The patients with paroxysmal atrial fibrillation or atrial flutter all demonstrated longer P-wave duration and interatrial conduction time than control group. Among the groups with a normal atrium or a dilated atrium, atrial refractoriness in patients with paroxysmal atrial flutter was shorter than that in control group. Moreover, in the patients with a normal atrium, the potential minimal wavelength in control group (6.6 ± 1.7) was longer than that of paroxysmal atrial fibrillation (5.3 ± 1.1), or atrial flutter (5.0 ± 1.2). These findings suggest that atrial electrophysiologic characteristics of a dilated atrium were different from those of normal atrium, and these changes were different between paroxysmal atrial fibrillation and flutter. Multiple factors are considered to be related to the genesis of atrial tachyarrhythmias.     

Higher Rate of Recurrent Atrial Flutter and Atrial Fibrillation Following Atrial Flutter Ablation After Cardiac Surgery

Atrial Flutter After Cardiac Surgery . Introduction: Atrial flutter (AFL) is common after cardiac surgery. However, the types of post‐cardiac surgery AFL, its response to catheter‐based radiofrequency ablation, and its relationship to atrial fibrillation (AF) are unknown. Methods and Results: We retrospectively studied all patients who underwent mapping and ablation for AFL after cardiac surgery from January 1990 to July 2004. One hundred randomly selected patients without prior cardiac surgery (PCS) who underwent mapping and ablation of AFL served as the control population. A total of 236 patients formed the study population (mean age 62 + 13 years, 22% female) and 100 patients formed the control population (mean age 60 + 13 years, 25% female). The majority of patients without PCS had cavo‐tricuspid isthmus (CTI)‐dependent AFL when compared to patients with PCS (93% vs 72%, respectively, P < 0.0001). In contrast, scar‐related AFL was more common in patients with PCS as compared to patients without PCS (22% vs 3%, P < 0.0001). Predictors of scar related AFL in multivariable regression analysis included PCS and left‐sided AFL. Acute success rates and complications were similar between the groups. When compared to patients with AFL ablation without PCS, those that had AFL after PCS had higher rates of recurrence of both AFL (1% vs 12%, P < 0.0001; mean time to recurrence 1.85 years) and AF (16% vs 28%, P = 0.02; mean time to recurrence 2.67 years). Conclusion: Despite ablation of AFL, patients with PCS have a higher rate of AFL and AF when compared to patients without PCS who underwent ablation of atrial flutter during long‐term follow‐up. (J Cardiovasc Electrophysiol, Vol. pp. 760‐765, July 2010)     

Nonpharmacologic Approaches to the Treatment of Atrial Fibrillation and Atrial Flutter

Nonpharmacologic Approaches to Atrial Fibrillation and Flutter. The high prevalence of atrial fibrillation, the associated morbidity and mortality, the absence of safe and effective drug therapy, and an increased understanding of the pathophysiologic basis of atrial fibrillation and flutter have collectively led to the development of novel nonpharmacologic treatments for the management of these arrhythmias, including the CORRIDOR and MAZE surgical procedures, catheter-based ablation and modification of AV conduction, catheter-based ablation of atrial flutter and fibrillation, and internal atrial defibrillation. These surgical and catheter-based techniques offer potentially curative therapy while sparing the long-term risks of antiarrhythmic drug therapy. For patients with typical atrial flutter, catheter ablation affords cure rates in excess of 70%. As technological innovations further facilitate identification and ablation of the critical isthmus in the floor of the right atrium, success rates should improve substantially. For patients with atrial fibrillation, AV junction ablation with implantation of a rate-responsive ventricular pacemaker should be considered palliative therapy, as should modification of AV junction conduction. The MAZE procedure offers very high cure rates, but because it currently involves open heart surgery, patient selection is critical. Catheter-based procedures emulating aspects of the MAZE procedure may one day offer cure rates comparable to those of the surgery itself, but additional research and technological development are necessary to further define and refine the minimal effective procedure, and then to facilitate the placement of contiguous, full-thickness lesions in precise three-dimensional configurations. In the interim, the implantable automatic atrial defibrillator may offer a means for rapidly restoring sinus rhythm without the risks of long-term antiarrhythmic drug therapy.     

Prospective Clinical Evaluation of Programmed Atrial Stimulation Protocol for Induction of Sustained Atrial Fibrillation and Flutter

We sought to define a minimum standardized protocol for induction of atrial fibrillation [AF] and/or atrial flutter. In contrast to ventricular stimulation protocols, a stimulation protocol for induction of AF or atrial flutter has not been critically evaluated. Since suppression of inducible AF or atrial flutter is used as one of the endpoints of success of pharmacologic and ablation therapies, there is an obvious need to define minimally appropriate electrical stimulation protocol for induction of AF or atrial flutter. We prospectively evaluated 70 patients, 44 with spontaneous atrial flutter or AF and 26 controls without documented atrial arrhythmias. A standardized programmed stimulation protocol, which employed up to three atrial extrastimuli delivered at two atrial sites at two atrial drive pacing lengths, was used in attempt to reproduce sustained AF and atrial flutter. The study endpoint was induction of sustained (>30 s) AF or atrial flutter. Sustained AF or atrial flutter was induced in 39/44 (89%) patients and 2/26 (7%) of controls (p <0.01). The arrhythmia induced was atrial flutter in 19/21 (91%) of atrial flutter patients, AF in 17/18 (94%) AF patients, both atrial flutter and AF in 5 AF/atrial flutter patients (100%). Two patients with atrial flutter had both AF/atrial flutter and 1 patient with AF had atrial flutter induced. The arrhythmia was induced from first stimulation site in 37 patients (85%) using a single in 9 (20%) patients, double 18 (41%) patients and triple extrastimuli in 10 (23%) patients. Two patients (5%) required stimulation from second site with two and three extrastimuli, respectively. The overall sensitivity and specificity of this stimulation protocol were 89% and 92%, respectively with a positive predictive accuracy of 95%.Conclusions. 1. Up to three atrial extrastimuli and two atrial sites are needed to increase yield of AF/atrial flutter induction at electrophysiologic study. 2. Induction of either AF or atrial flutter correlates well with presence of a similar spontaneous arrhythmia. 3. A baseline determination of the induction mode may be desirable prior to evaluation of interventions directed at AF or atrial flutter.     

Induction of Atrial Fibrillation and Flutter in Dogs Using Methacholine

Systemic infusion of methacholine has been used to facilitate induction of atrial fibrillation. However, the dose-response relationship, reproducibility and effect of anesthetic agents on induction are not well understood. The use of methacholine to facilitate electrical induction of sustained (>10 minutes duration) atrial fibrillation or flutter was examined. In 25 dogs induction of atrial arrhythmias was attempted using a series of ten 50 Hz trains of 10 seconds duration delivered via an endocardial catheter in the baseline anaesthetized state and subsequently in the presence of graded doses of intravenous methacholine (maximum 5 µg/kg/min). Studies were repeated in 13 dogs to assess reproducibility. Twelve dogs (48%) had inducible sustained atrial flutter or fibrillation lasting greater than 10 minutes in the baseline state. During infusion of methacholine the remaining 13 (52%) dogs also had inducible sustained atrial flutter or fibrillation (mean infusion rate 1.6 ± 1.9 µg/kg/min). Induction of sustained atrial flutter or fibrillation was reproducible in all but one dog. The type of anesthetic did not significantly affect inducibility. Induction of prolonged atrial fibrillation or flutter is possible in the baseline anaesthetized state in approximately half of dogs using high frequency programmed electrical stimulation. The yield of inducible sustained atrial fibrillation or flutter with programmed stimulation during intravenous infusion of methacholine was increased to 100%. Induction of sustained atrial fibrillation or flutter was highly reproducible.     

Atrial Fibrillation/Flutter Induced by Implantable Ventricular Defibrillator Shocks:

Atrial Fibrillation/Flutter Induced by Defibrillator Shocks. Introduction : We evaluated the incidence and energy dependence of atrial fibrillation/flutter (AF) induced by implantable ventricular defibrillator shocks in 63 patients tested in the operating room or electrophysiology laboratory.
Methods and Results : Defibrillator shocks were epicardial monophasic in 32 patients, and through an Endotak® lead endocardial monophasic in 19 and biphasic in 12 patients. The epicardial and endocardial patient groups had similar clinical characteristics. A total of 517 defibrillator shocks were given. The epicardial group received 336 total defibrillator shocks and 10 ± 6 shocks (mean ± SD) per patient compared with the endocardial group, which received 181 total shocks and 6 ± 4 defibrillator shocks per patient (P = 0.004). In the epicardial group, AF occurred in 13 (41 %) patients and in 17 (5%) of the 336 shocks. No AF was induced with endocardial defibrillator shocks. The epicardial mean energy was 16 ± 9 J, lower than the endocardial mean energy of 20 ± 9 J (P < 0.004). In the epicardial monophasic group, energy correlated with AF induction. Each patient received 7 ± 6 defibrillator shocks < 15 J and 4 ± 2 shocks ≥ 15 J, yet AF occurred in only 2.3% versus 9.6% (P < 0.05) of defibrillator shocks < 15 J and ≥ 15 J, respectively. Of note, AF was not induced with energy < 4 J or > 31 J.
Conclusions : In the epicardial configuration, AF induction is energy dependent, with an apparent lower and upper limit of vulnerability. AF induction by defibrillator shocks delivered through an Endotak lead is very rare, possibly related to an apparent upper limit of vulnerability of less energy, avoidance of thoracotomy, or different energy field distribution.     

Dynamic Alterations in Right Atrial Activation During Atrial Fibrillation

Atrial fibrillation (AF) is usually considered to be a disorganized rhythm. However, several reports have described areas of organized right atrial (RA) activation during AF. We describe a patient with focal paroxysmal AF with a consistent pattern of organized RA activity despite typically disorganized left atrial activity. The sequence of RA activation varied, depending on which pulmonary vein foci initiated the AF.     

Reduced Cardioversion Thresholds for Atrial Fibrillation and Flutter Using the Rectilinear Biphasic Waveform

Background: The RLB waveform has been shown to be superior in overall efficacy to the MDS waveform for cardioversion of AF in one prospective study and one large retrospective analysis. However, little is known about the efficacy of the RLB waveform at lower energies.Objective: This study was undertaken to define the cardioversion thresholds for atrial fibrillation (AF) and flutter (FL) using the rectilinear biphasic (RLB) waveform and compare these to the cardioversion threshold using the conventional monophasic damped sine (MDS) waveform.Methods: All patients underwent transthoracic cardioversion of persistent AF and FL. We performed step-up cardioversion thresholds for AF in 180 RLB patients and 38 MDS patients and compared those results. We also performed cardioversion threshold determinations in 39 RLB patients with typical right atrial FL. For the RLB patients, an initial energy setting of 5 Joules (J) was selected, with increasing energy steps until success, up to 200J. The MDS energy sequence was 50 up to 360J.Results: The average selected energy threshold for AF using the RLB waveform was 70.6 J (median = 50 J) versus 193.4 J (median=150 J) for the MDS waveform (p < 0.001). For FL, the average cardioversion threshold using the RLB waveform was 33.2 J (median = 20 J; p < 0.001 vs. AF with the RLB waveform).Conclusions: Our results show that the transthoracic AF cardioversion threshold using the RLB waveform is significantly lower than the MDS waveform. As expected, the cardioversion threshold for FL was significantly lower than that of AF using the RLB waveform.     

Implantable Atrial Defibrillator and Detection of Atrial Flutter

The implantable atrial defibrillator (IAD) is designed to detect and treat atrial fibrillation (AF) with low energy synchronized shocks. A patient with a history of persistent AF was implanted with an IAD after ineffective treatment with procainamide and sotalol. Through four months of follow-up, the IAD performed appropriate detection and treatment of AF. During the fifth month, the patient was put on flecainide in an attempt to minimize the AF recurrence rate. On flecainide the patient experienced typical atrial flutter which required IAD reprogramming for appropriate detection and therapy delivery. This case report examines the optimization of the IAD to detect atrial flutter. Six months of follow-up after optimization the IAD has shown appropriate detection of both atrial flutter and AF. During the entire follow-up period the IAD had appropriate detection of sinus rhythm (no false positive detection, i.e. sinus rhythm as AF).     

Ablation of Atrial Fibrillation at the Time of Cavotricuspid Isthmus Ablation in Patients With Atrial Flutter Without Documented Atrial Fibrillation Derives a Better Long‐Term Benefit

AF Ablation in Patients With Only Documentation of Atrial Flutter. Objectives: The aim of the study was to evaluate whether isolation of the pulmonary veins (PVs) at the time of cavotricuspid isthmus (CTI) ablation is beneficial in patients with lone atrial flutter (AFL). Background: A high proportion of patients with lone persistent AFL have recurrent episodes of atrial fibrillation (AF) after CTI ablation. However, the benefit of AF ablation in patients with only documentation of AFL has not been determined. Methods: Forty‐eight patients with typical lone persistent AFL (age 56 ± 6; 90% male) were randomized to CTI ablation (Group A; n = 25) or to CTI + PV isolation (PVI) (Group B; n = 23). In addition to PVI, some patients in group B underwent ablation of complex fractionated electrograms and/or creation of left atrial roof and mitral isthmus ablation line in a stepwise approach when AF was induced and sustained for more than 2 minutes. Mean follow‐up was 16 ± 4 months with a 48‐hour ambulatory monitor every 2 months. Results: There were no recurrences of AFL in either group. Six patients in group B (22%) underwent a stepwise ablation protocol. AF organized and terminated in 5 patients during ablation (83%). Complication rate was not significantly different among the groups. Twenty patients in group B (87%) and 11 patients in group A (44%) were free of arrhythmias on no medications at the end of follow‐up (P < 0.05). Conclusions: Ablation of AF at the time of CTI ablation results in a significantly better long‐term freedom from arrhythmias. (J Cardiovasc Electrophysiol, Vol. 22, pp. 34‐38, January 2011)     

Atrial Appendage Thrombosis Risk Is Lower for Atrial Flutter Compared with Atrial Fibrillation

Background

The risk of stroke and thromboembolism in atrial fibrillation is established. However, the evidence surrounding the risk of thromboembolism in patients with atrial flutter is not as clear. We hypothesized that atrial flutter would have indicators of less risk for thromboembolism compared with atrial fibrillation on transesophageal echocardiography, thereby possibly leading to a lower stroke risk.

Right Atrial Remodeling is More Advanced in Patients with Atrial Flutter Than with Atrial Fibrillation

Atrial Remodeling in Atrial Flutter. Introduction: Atrial fibrillation (AF) and atrial flutter (AFL) are related arrhythmias with common triggers, yet in individual patients either AF or AFL often predominates. We performed detailed electrophysiologic (EP) and electroanatomic (EA) studies of the right atrium (RA) in patients with AF and AFL to determine substrate differences that may explain the preferential expression of AF/AFL in individual patients. Methods: Patients with AF (n = 13) were compared to patients with persistent AFL (n = 10). Detailed studies were performed, and 3‐dimensional electroanatomic mapping studies were created and the RA was divided into 4 segments for regional analysis. Global, septal, lateral, anterior, and posterior segments were compared for analysis of: bipolar voltage; proportion of low‐voltage areas and areas of electrical silence; conduction times; and proportion of abnormal signals (fractionated signals and double potentials). Results: Compared to patients with AF, patients with AFL had (1) lower bipolar voltage and an increase in the proportion of low‐voltage areas; (2) an increase in the proportion of complex signals; and (3) prolongation of activation times. Conclusions: Patients with AFL showed more advanced remodeling than patients with AF with slowed conduction, lower voltage areas with regions of electrical silence, and a greater proportion of complex signals, particularly in the posterior RA. These changes facilitate the stabilization of AFL and may explain why some patients are more likely to develop AFL as a sustained clinical arrhythmia. (J Cardiovasc Electrophysiol, Vol. 23 pp. 1067‐1072, October 2012)