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Nonpharmacologic treatment of common atrial flutter guided by transient entrainment.

We attempted nonpharmacologic treatment for common atrial flutter in 7 patients, with direct current catheter ablation (CA) in 5 cases and cryoablation in 2 cases under the guidance of transient entrainment. Transient entrainment during common atrial flutter by pacing from the mid or low lateral right atrium (LLRA) revealed a long conduction time between the LLRA and the orifice of the coronary sinus (CSo) (73% to 121% of flutter cycle length). In 2 cases, fragmented electrograms were recorded at the low right atrial septum with durations of 150 msec and 155 msec, respectively. Because these fragmented electrograms were transiently entrained by rapid atrial pacing in the same manner as other atrial electrograms and were recorded in an area of long conduction, we believe that fragmented electrograms represent critical slow conduction. In 5 cases, CA was directed at this area. Three cases were successfully treated with 3 to 4 DC shocks of 100 J (follow up periods of 11.3, 4.5 and 3 months). Two cases which received 1 to 2 DC shocks of 100 J had recurrence of atrial flutter 6 and 4.7 months later, respectively. Two cases which showed atrial septal defect received surgical treatment. They were successfully treated with extended cryoablation in this same area (follow up periods of 26 and 9.2 months). In conclusion, extended ablation of an area of fragmented electrograms using transient entrainment may be an effective treatment for common atrial flutter.

Aged↗

Comparison of echocardiographic markers of embolism in atrial flutter and fibrillation: frequency of protruding atherosclerotic plaques in the thoracic aorta.

The potential additional embolic risk of protruding aortic plaques > or = 4 mm and left atrial abnormalities such as thrombus, spontaneous echocardiographic contrast (SEC), low left atrial appendage velocity, recently has been shown in patients with atrial fibrillation (AF). However, the presence and potential role of transesophageal echocardiographic (TEE)-detected protruding aortic plaques > or = 4 mm have not been systematically evaluated in patients with atrial flutter. Among 2493 patients evaluated by TEE, 271 consecutive patients with atrial flutter (n = 41) and AF (n = 230) > or = 2 days duration were included in the study. Clinical and echocardiographic characteristics in consecutive patients with atrial flutter were compared to those in patients with AF, especially atrial morphology and function and atherosclerotic disease of the thoracic aorta. Clinical characteristics of patients with atrial flutter and AF were similar with regard to age (68 +/- 13 and 67 +/- 12, P = 0.628), sex ratio (men, 66% and 54%, P = 0.212), and previous embolic events (5% and 15%, P = 0.126), respectively. The frequency of protruding atherosclerotic plaques > or = 4 mm (12% and 11%, P = 0.919) and SEC (15% and 14%, P = 0.847) in the thoracic aorta was similar in patients with atrial flutter and AF. Left atrial appendage area was smaller (3.1 +/- 0.7 and 6.0 +/- 3.0 cm(2), P = 0.001), left atrial appendage SEC was less frequent (17% and 37%, P = 0.024), and left atrial appendage emptying velocity was higher (47 +/- 10 and 30 +/- 10 cm/s, P = 0.030) in patients with atrial flutter as compared to those with AF. There was no difference between the two groups regarding left ventricular fractional shortening (30 +/- 10% and 33 +/- 13%, P = 0.630), rheumatic valvular disease (5% and 12%, P = 0. 301), left atrial diameter (43 +/- 7 and 45 +/- 8 mm, P = 0.134), right atrial area (16 +/- 4 and 17 +/- 6 cm(2), P = 0.384), left atrial SEC (39% and 53%, P = 0.124), or atrial thrombus ( 2% and 3%, P = 0.888) respectively. Our results point to the high prevalence of protruding atherosclerotic plaques in the thoracic aorta in patients with atrial flutter.

Aged↗

Acute myocardial infarction after radiofrequency catheter ablation of typical atrial flutter: histopathological findings and etiopathogenetic hypothesis.

The right atrial inferior cavotricuspid isthmus represents the targeting site for radiofrequency (RF) current application during ablation treatment of typical atrial flutter. Despite the vicinity of the right coronary artery (RCA) to the RF application site and the long energy exposure needed to achieve electrophysiological success, reports about direct thermal damage of the coronary vessel during ablation of the cavotricuspid isthmus are rare and anecdotal. The present is the first case report describing the cardiac macroscopic and histological examination in a patient who died of cardiac rupture, as a complication of a myocardial infarction occurring after a standard procedure of RF ablation of typical atrial flutter. In consideration of the proximity we found between the RF energy-dependent tissue damage and the RCA, thermal-related damage of RCA during ablation of typical atrial flutter should always be considered as a potentially harmful risk of the procedure.

Aged↗

Factors associated with early atrial fibrillation after ablation of common atrial flutter. A single centre prospective study.

BACKGROUND: The occurrence of early atrial fibrillation (< or = 6 months) after ablation of common atrial flutter is of clinical significance. Variables predicting this evolution in ablated patients without a previous atrial fibrillation history have not been fully investigated. OBJECTIVES: The aim of the present study was: (1) to identify predictive factors of early atrial fibrillation (< or = 6 months) in the overall population following atrial flutter catheter ablation; (2) to identify predictive variables of early atrial fibrillation following (< or = 6 months) atrial flutter catheter ablation within a subgroup of patients without documented prior atrial fibrillation. METHODS: This study prospectively included 96 consecutive patients (age 65 +/- 13 years; 18 women) over a 12-month period. Their counterclockwise flutter was ablated by radiofrequency, by the same operator, with an 8-mm-tip catheter. Clinical, electrophysiological and echocardiographic data were collected and 27 variables were retained for analysis: age; gender; type of atrial flutter (permanent vs paroxysmal); symptom duration (months +/- SD); pre-ablation history of atrial fibrillation; structural heart disease; left ventricular ejection fraction (%); left atrial size (mm); cava--tricuspid isthmus dimension; septal isthmus dimension; systolic pulmonary pressure > or < or = 30 mmHg; right atrial area; left atrial area; isthmus block; number of radiofrequency applications (+/- SD); antiarrhythmic drugs at discharge; left ventricular diastolic diameter; left ventricular systolic diameter; left ventricular telediastolic volume; left ventricular telesystolic volume; A-wave velocity (cm . s(-1)); E-wave velocity (cm . s(-1)); E/A; isovolumetric relaxation time; E-wave deceleration time; significant mitral regurgitation and flutter cycle length (ms). RESULTS: Of the 96 consecutive ablated patients, early atrial fibrillation was documented in 16 patients (17%). Atrial fibrillation occurred 30 +/- 46 days (range 1 to 171 days) after ablation. Univariate analysis associated an early occurrence of atrial fibrillation with: atrial fibrillation history, left ventricular ejection fraction, left atrial size, left ventricular telesystolic volume, A-wave velocity, significant mitral regurgitation and flutter cycle length. Multivariate analysis using a Cox model found that the only independent predictors of early atrial fibrillation were left ventricular ejection fraction and pre-ablation history of atrial fibrillation. In the subgroup without prior atrial fibrillation history (n=63; 66%), the only independent predictor of early atrial fibrillation was the presence of a significant mitral regurgitation. CONCLUSIONS: In a subgroup of patients without atrial fibrillation history, 8% of patients revealed an early atrial fibrillation. Mitral regurgitation is a strong predictive factor of early atrial fibrillation occurrence with 80% sensitivity, 78% specificity and 98% negative predictive value. These data should be considered in post-ablation management.

Adult↗

Implanted atrial pacemakers for paroxysmal atrial flutter. Long-term efficacy.

Five patients with drug-resistant paroxysmal atrial flutter received permanent burst atrial pacemakers for the treatment of tachycardia. All patients had extensive electrophysiologic evaluations to determine the safety and efficacy of atrial pacing. The absence of prolonged spontaneous or electrically induced atrial fibrillation was also documented in all patients. Three pulse generators were patient activated (nonautomatic) and two were multiprogrammable and automatic. The atrial pacemakers terminated many attacks of paroxysmal atrial flutter safely and reliably in a follow-up period ranging from 24 to 60 months (average, 42). No major complications developed. In four patients, concomitant drug therapy was necessary, although to a lesser degree, to reduce the frequency of attacks and the ventricular rate. Our study documents the long-term efficacy and low risk associated with permanent-burst atrial pacing in the treatment of drug-refractory paroxysmal atrial flutter in selected patients.

Adult↗

Use of intraoperative mapping to optimize surgical ablation of atrial flutter.

The purpose of this study was to develop a surgical treatment for atrial flutter using intraoperative activation sequence mapping to minimize the surgical procedure necessary to ablate the flutter. A canine model (n = 10) of left atrial enlargement was developed by creating a shunt from the left subclavian artery to the left superior pulmonary vein. Sustained atrial flutter was easily induced in this model. The flutter consisted of a single reentrant circuit that rotated around one or two anatomic obstacles linked by a region of functional block. Epicardial templates, consisting of 252 bipolar electrodes, were used to record activation time maps. After localization of the reentrant circuit, surgical incisions were placed to interrupt the pathways. In all 10 animals, flutter could be induced and intraoperative mapping localized the reentrant circuit. Seven circuits were in the right atrium and three were in the left atrium. The operation ablated all of the preoperative circuits. However, in 5 of the animals, flutter originating from a new circuit could be induced. Activation sequence mapping before and after operation demonstrates that there are multiple potential reentrant pathways in this canine model of atrial flutter. Therefore, all potential pathways must be surgically interrupted to prevent inducibility of atrial flutter.

Animals↗

Atrial flutter can be terminated by a class III antiarrhythmic drug but not by a class IC drug.

In atrial flutter, chemical conversion with class I drugs is often unsuccessful, whereas class III drugs seem more promising. The different electrophysiological effects of these drugs may explain this discrepancy. To date, only experimental data show the differential effects of these drugs on conversion rate and atrial flutter cycle length. This study evaluates the effects of the class IC antiarrhythmic drug flecainide, and of dofetilide, a new class III drug, on conversion rate and flutter cycle length in patients with atrial flutter. Flecainide (11 patients) was given as an intravenous bolus of 2 mg.kg-1 in 10 min and dofetilide (10 patients) as a maximum intravenous bolus of 8 micrograms.kg-1 in 15 min. Baseline characteristics were comparable between both groups. Only one patient treated with flecainide converted to sinus rhythm. This patient showed the largest flutter cycle length increase (280 to 420 ms). By contrast, seven of the 10 patients treated with dofetilide converted to sinus rhythm. Patients treated with flecainide showed a significantly larger increase in atrial flutter cycle length at the end of the infusion compared to the dofetilide-treated patients (from 226 +/- 28 to 317 +/- 52 ms vs from 221 +/- 26 to 239 +/- 39 ms, respectively). In conclusion, dofetilide is more effective than flecainide in the conversion of atrial flutter to sinus rhythm, despite the fact that flecainide produced a more prolonged flutter cycle length. Thus, action potential prolongation in the absence of conduction slowing seems more effective in terminating human atrial flutter than depression of the excitability.

Anti-Arrhythmia Agents↗

A logical state model of circus movement atrial flutter role of anatomic obstacles, anisotropic conduction and slow conduction zones on induction, sustenance, and overdrive paced modulation of reentrant circuits.

Mapping studies of atrial flutter in both the canine sterile pericarditis model and the right atrial enlargement model commonly reveal single loop reentrant circuits in the lower posterior part of the right atrium. Functional bidirectional conduction block and natural anatomical obstacles comprise the central obstacle for reentrant impulse during circus movement atrial flutter. Because the relative roles of anatomical obstacles, in combination with functional barriers, anisotropic conduction, and slow conduction can not be readily assessed with current electrophysiological techniques, an atrial activation model was developed to study the mechanisms of circus movement atrial flutter. A discrete state model consisting of 4096 logically connected cardiac elements was used to simulate atrial activation; an inexcitable region simulating the inferior vena cava (IVC) was also incorporated in the model. Atrial flutter was induced by programmed premature stimulation. Anisotropic conduction velocity properties, regional variations in slow conduction, regional refractory gradients and stimulation parameters were specified for each simulation. The reentrant circuit generally consisted of a single reentrant impulse which circulated around a continuous line of functional bidirectional conduction block joined to the IVC. Rapid pacing, 5-30 ms shorter than the spontaneous reentrant cycle length, was applied to entrain and/or terminate the rhythm. The results of this study demonstrate that patterns of initiation, entrainment, termination and reinitiation of circus movement atrial flutter mimic results from in vivo activation mapping studies. We find that sustained circus movement atrial flutter circuits depend on: 1) natural anatomical obstacles to stabilize reentrant circuits, and 2) anisotropic conduction properties to reduce the degree of functional conduction block needed to maintain circus movement. Rapid pacing of simulated circus movement atrial flutter demonstrated that the entrainment criteria can be satisfied in a two-dimensional syncytium.

Animals↗

Acute success and persistence of bidirectional conduction block in the cavotricuspid isthmus one month post cryocatheter ablation of common atrial flutter.

INTRODUCTION: Cryoablation is successful in the treatment of common atrial flutter. Long-term clinical success is mainly dependent on persistence of bidirectional conduction block (BCB) in the inferior cavotricuspid isthmus (CTI). Only few data on persistence of BCB post cryoablation with the reported technique are available. This prospective study aimed to test efficacy of cryo energy and persistence of BCB in the CTI 1 month post cryoablation. METHODS: Cryoablation of the CTI was performed in 50 consecutive patients (64 +/- 12 years, 40 males) with symptomatic common atrial flutter using a novel 9 Fr 8-mm-tip catheter. BCB in the CTI 30 minutes following the final cryoapplication was the ablation endpoint. Thirty days post ablation, persistence of BCB was controlled by repeat electrophysiological study (EPS). RESULTS: In all patients BCB was achieved with a mean of 9 (IQR 7-17.5) cryo applications and a mean cryo time of 2,378 seconds (IQR 1,680-3,474 seconds). In 5 of 50 patients, common atrial flutter recurred within 1 month post cryoablation. In 30 of 32 recurrence-free patients, persistence of BCB was verified. In 2 patients, resumption of isthmus conduction was detectable. Including relapses, 81.1% of patients (30/37) showed persistence of BCB. No patients reported pain during cryoapplication. No procedural complications were observed. CONCLUSIONS: Cryoablation of the CTI using a large-tip catheter is feasible and safe in the treatment of common atrial flutter. Acute and short-term success rates are comparable to those reported for radiofrequency (RF) ablation. Besides short-term clinical success, the persistence of BCB demonstrates efficacy of the cryoablation technique.

Adult↗

Pathogenesis of atrial flutter.

It is now known that most cases of atrial flutter are due to reentrant excitation in the right atrium. In the usual reentrant circuit, the reentrant excitation wavefront travels up the interatrial septum and down the right atrial free wall. The boundaries of this reentrant circuit include on one side the tricuspid valve ring and on the other side an area of block, which is probably functional, in the region between the venae cavae. The latter area of block forms during the transitional atrial fibrillation rhythm of variable duration that almost always precedes the initiation of atrial flutter. An isthmus of conduction is also present in the reentrant circuit, and is bounded by the tricuspid ring and the inferior vena cava, the Eustachian ridge, and the coronary sinus. It is probable that an abnormal atrial tissue substrate is usually required. Reentrant circuits around a surgical incision in the atria or around the pulmonary veins (in whole or in part) may be also responsible for atrial flutter.

Atrial Flutter↗

Essential pathway of reentry in the canine model of atrial flutter. Analysis using radiofrequency ablation.

In humans, the isthmus in the low right atrium between the tricuspid annulus and the inferior vena cava or the coronary sinus ostium is a well-established target of catheter ablation of common atrial flutter. In the canine model of atrial flutter with a Y-shaped incision, the tricuspid annulus was thought to constitute the essential reentrant pathway. The present study was designed to determine whether the supravalvular tissue around the tricuspid annulus is essential to atrial flutter in the canine model with an intercaval obstacle on the basis of the results of radiofrequency ablation. Epicardial approach of radiofrequency ablation was tested in 4 groups of dogs. Group A (5 dogs): Single application of radiofrequency energy (20 W) for 5 sec to the mid right atrial free wall. Group B (9 dogs): One to two applications to the tricuspid annulus. A ligature was also placed encircling the tricuspid annulus from the supravalvular atrial tissue to the subvalvular ventricular tissue. Group C (9 dogs): Linear transverse applications to the mid right atrial free wall between the tricuspid annulus and the intercaval obstacle. Group D (10 dogs): The isthmus between the inferior vena cava and the tricuspid annulus was ablated. After the experiment, the heart was excised for anatomical and histological studies. Atrial flutter was never abolished in all dogs in Groups A and B. A ligature encircling the tricuspid annulus also failed to terminate atrial flutter in 2 dogs tested. In contrast, atrial flutter was successfully abolished in 6 dogs (67%) of Group C and in 7 dogs (70%) of Group D. Total energy delivered was significantly higher in Group C than in Group D (364 +/- 133 versus 139 +/- 65 joules, p < 0.003). The total energy required for successful ablation was related to the cross sectional area of the ablation site (r = 0.55, p < 0.05). These results indicate that the tricuspid annulus is not an essential part of the reentrant pathway in the canine model of atrial flutter with an intercaval obstacle. The entire atrial tissue between the anatomical barriers could be involved in the reentrant pathway, and should therefore be ablated transmurally for successful ablation.

Animals↗