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PubMed1991

Effects of posture, Valsalva maneuver and respiration on atrial flutter rate: an effect mediated through cardiac volume.

The effects of passive upright tilting from 0 degrees to +60 degrees (n = 27), Valsalva maneuver (n = 16) and respiration (n = 10) on the rate of atrial flutter were studied in 27 patients. After tilting to +60 degrees, the atrial flutter cycle length shortened in all patients from 247.5 +/- 7 to 236.7 +/- 6.9 ms (range of shortening 1 to 21 ms, p less than 0.001). The Valsalva maneuver (strain of 40 mm Hg) shortened the flutter cycle length during the strain (phase 2) from 242.2 +/- 4.6 to 230.5 +/- 5 ms (range of shortening 2 to 19 ms, p less than 0.001). In 10 patients whose respiration was monitored, the flutter cycle length consistently prolonged during inspiration and shortened during expiration. Combined beta-adrenergic and muscarinic receptor blockade in six patients did not significantly alter the flutter cycle length at rest or the effects of the various maneuvers on the changes in flutter cycle length. This study revealed that the atrial flutter cycle length can be shortened by passive upright tilting, the strain phase of the Valsalva maneuver and expiration. Changes in flutter cycle length were independent of autonomic tone, implying that by decreasing cardiac volume, these maneuvers affect characteristics of the atrial flutter circuit, thereby producing dynamic changes in the rate of atrial flutter.

Atrial Flutter↗
PubMed1995

Atrial flutter termination by overdrive transesophageal pacing and the facilitating effect of oral propafenone.

Transesophageal overdrive atrial pacing is effective and safe for atrial flutter termination. The influence of antiarrhythmic drug therapy on this procedure is controversial. In this study, we investigated whether oral propafenone may facilitate this procedure. Thirty patients with type I atrial flutter were randomized into 2 groups in which transesophageal pacing was attempted: group A, without treatment; and group B, after oral administration of propafenone 600 mg. Transesophageal pacing was effective in interrupting atrial flutter in 53% of patients (8 of 15) in group A and in 87% of patients (13 of 15) in group B. A significant lengthening of the flutter cycle was observed with respect to the baseline in patients given propafenone (261 +/- 23 vs 217 +/- 25, p < 0.01). Sinus rhythm resumed at a shorter paced cycle in group A patients (166 +/- 13 vs 187 +/- 14 ms, p < 0.01). The transesophageal threshold for stable atrial capture was significantly lower in group A (20.5 +/- 0.2 vs 23.3 +/- 1.2, p < 0.01). In no patient was the threshold for atrial capture higher than the pain threshold. We did not observe abrupt enhancement of atrioventricular conduction. We conclude that propafenone is effective and safe when used with transesophageal pacing in the termination of atrial flutter. The slowing effect of the drug on intraatrial conduction and the possible stabilizing effect on the reentry circuit appear to be outweighed by the positive effect of propafenone on the excitable gap of the circuit, facilitating its capture and accounting for the beneficial effect of the drug on arrhythmia termination.

Administration, Oral↗
PubMed1998

Impairment of left atrial appendage function after spontaneous conversion of atrial flutter.

This paper reports a patient in atrial flutter who spontaneously converted to sinus rhythm while undergoing a transesophageal echocardiogram. Atrial appendage flow velocities were noted to be significantly decreased after conversion to sinus rhythm. Spontaneous contrast also developed in the left atrium shortly after conversion. Spontaneous cardioversion may be associated with decreased mechanical activity of the left atrium and appendage, resulting in "stunning." This provides a possible explanation for the occurrence of thromboembolic events in patients without apparent thrombus before cardioversion.

Atrial Flutter↗
PubMed2000

Block of the lower interatrial connections: insight into the sources of electrocardiographic diversities in common type atrial flutter.

Whether the conduction disturbances of the interatrial connections play a role in the genesis of ECG variants of atrial flutter is almost completely unknown. We present a patient with typical counterclockwise atrial flutter in whom the ablation of the coronary sinus (CS) area during ongoing atrial flutter produced significant ECG changes without alterations in the activation sequence within the right atrium (RA). This case highlights the possible role of alterations of the interatrial connections in the genesis of atypical ECG manifestations of common type atrial flutter.

Aged↗
PubMed1997

Mechanism of initiation of atrial flutter in humans: site of unidirectional block and direction of rotation.

OBJECTIVES: Using a standardized induction protocol, we investigated the mechanism of initiation of atrial flutter, before ablation, to determine the site of initiating unidirectional block and to test the hypothesis that the direction of rotation of atrial flutter depends on the pacing site from which it initiates. BACKGROUND: The high recurrence rate of atrial flutter after presumed successful ablation may be due to difficulty in reinduction after termination. In addition, induction of clockwise flutter is currently of unknown clinical importance. METHODS: Ten patients with documented typical flutter were studied before ablation. A standard protocol consisting of single and double extrastimuli followed by burst pacing was performed from four sites in the right atrium (high and low trabeculated and smooth right atrium) to assess efficacy at inducing atrial flutter. A 20-pole halo catheter placed around the tricuspid annulus and a decapole catheter placed in the coronary sinus were used for mapping during initiation to determine type of flutter induced and the site of unidirectional block during initiation. RESULTS: Atrial flutter was induced in 52 (6.2%) of 838 attempted inductions. Of these, 33 were counterclockwise and 20 were clockwise. Of the 20 inductions resulting in clockwise flutter, 18 were from the trabeculated right atrium, whereas all the counterclockwise inductions were from the smooth right atrium. In all but the two inductions, the site of unidirectional block was identified between the os of the coronary sinus and the low lateral right atrium for both counterclockwise and clockwise flutter, in the same isthmus at which ablation is targeted. CONCLUSIONS: Even in patients with clinical counterclockwise flutter, clockwise flutter is frequently induced before ablation and is dependent on the site of induction: Pacing from the smooth right atrium induces counterclockwise flutter, whereas pacing from the trabeculated right atrium induces clockwise flutter. The site of the unidirectional block during the initiation of either form of flutter is in the low right atrium isthmus.

Aged↗
PubMed1996

Results of radiofrequency catheter ablation for atrial flutter.

RF catheter ablation for symptomatic typical atrial flutter is associated with a high procedural success rate, but a second RF procedure may be required in up to one third of subjects, particularly those with right atrial enlargement. In those subjects with both established AF and flutter, RF ablation for atrial flutter may decrease the recurrence rate of AF. However, patients remain at risk for the development of newly documented AF, most likely secondary to the high incidence of underlying structural heart disease.

Aged↗
PubMed1996

Radiofrequency catheter ablation of common atrial flutter: comparison of electrophysiologically guided focal ablation technique and linear ablation technique.

OBJECTIVES: The purpose of this study was to study electrophysiologic characteristics and compare the electrophysiologically guided focal ablation technique and linear ablation technique in patients with common atrial flutter in a prospective randomized fashion. Background. Catheter ablation of the common atrial flutter circuit can be performed with different techniques. To date, these two techniques have not been compared prospectively in a randomized study. METHODS: Sixty patients with drug-refractory common atrial flutter were randomly assigned to undergo radiofrequency catheter ablation performed with the electrophysiologically guided focal ablation (Group I) or linear ablation technique (Group II). In Group I, radiofrequency energy was delivered to the site characterized by concealed entrainment with a short stimulus-P wave interval (<40 ms) and a postpacing interval equal to the atrial flutter cycle length. In Group II, continuous migratory application of radiofrequency energy was used to create two linear lesions in or around the inferior vena cava-tricuspid ring isthmus. Serial 24-h ambulatory electrocardiographic (Holter) and follow-up electrophysiologic studies were performed to assess recurrence of tachycardia and possible atrial arrhythmogenic effects. RESULTS: Successful elimination of the flutter circuit was achieved in 28 of 30 patients in Group I and 29 of 30 patients in Group II. More atrial premature beats and episodes of short run atrial tachyarrhythmias in the early period (within 2 weeks) after ablation were found in Group II. Recurrence rate (2 of 28 vs. 3 of 29) and incidence of new sustained atrial tachyarrhythmias (3 of 28 vs. 3 of 29) was similar in the two groups. Occurrence of recurrent atrial flutter and new sustained atrial tachyarrhythmias was related to associated cardiovascular disease and atrial enlargement in both groups. However, in Group II, the procedure time (104 +/- 17 vs. 181 +/- 29 min, p<0.01) were significantly shorter than those in Group I. CONCLUSIONS: Radiofrequency ablation of the common atrial flutter circuit was safe and effective with either the electrophysiologically guided focal ablation or linear ablation technique. However, the linear ablation technique was time-saving.

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PubMed1992

Role of prophylactic anticoagulation for direct current cardioversion in patients with atrial fibrillation or atrial flutter.

The need for prophylactic anticoagulation to prevent embolism before direct current cardioversion is performed for atrial fibrillation or atrial flutter is controversial. To examine this issue further, a retrospective review was undertaken to assess the incidence of embolic complications after cardioversion. The review involved 454 elective direct current cardioversions performed for atrial fibrillation or atrial flutter over a 7 year period. The incidence rate of embolic complications was 1.32% (six patients); the complications ranged from minor visual disturbances to a fatal cerebrovascular event. All six patients had atrial fibrillation, and none had been on anticoagulant therapy (p = 0.026). The duration of atrial fibrillation was less than 1 week in five of the six patients who had embolic complications. Baseline characteristics of patients with a postcardioversion embolic event are compared with those of patients who did not have an embolic event. There was no difference in the prevalence of hypertension, diabetes mellitus or prior stroke between the two groups, and there was no difference in the number of patients who were postoperative or had poor left ventricular function. Left atrial size was similar between the two groups. No patient in the embolic group had valvular disease. No patient with atrial flutter had an embolic event regardless of anticoagulant status; therefore, anticoagulation is not recommended for patients with atrial flutter undergoing cardioversion. Prophylactic anticoagulation is pivotal in patients undergoing elective direct current cardioversion for atrial fibrillation, even those with atrial fibrillation of less than 1 week's duration.

Anticoagulants↗
PubMed1998

Conversion efficacy and safety of intravenous ibutilide compared with intravenous procainamide in patients with atrial flutter or fibrillation.

OBJECTIVES: This multicenter study compared the efficacy and safety of ibutilide versus procainamide for conversion of recent-onset atrial flutter or fibrillation. BACKGROUND: Ibutilide fumarate is an intravenous (IV) class III antiarrhythmic agent that has been shown to be significantly more effective than placebo in the pharmacologic conversion of atrial flutter and fibrillation to sinus rhythm. Procainamide is commonly used for conversion of recent-onset atrial fibrillation to normal sinus rhythm. METHODS: One hundred twenty-seven patients (age range 22 to 92 years) with atrial flutter or fibrillation of 3 h to 90 days' (mean 21 days) duration were randomized to receive either two 10-min IV infusions of 1 mg of ibutilide fumarate, separated by a 10-min infusion of 5% dextrose in sterile water, or three successive 10-min IV infusions of 400 mg of procainamide hydrochloride. RESULTS: Of the 127 patients, 120 were evaluated for efficacy: 35 (58.3%) of 60 in the ibutilide group compared with 11 (18.3%) of 60 in the procainamide group had successful termination within 1.5 h of treatment (p < 0.0001). Seven patients were found to have violated the protocol and were not included in the final evaluation. In the patients with atrial flutter, ibutilide had a significantly higher success rate than procainamide (76% [13 of 17] vs. 14% [3 of 22], p=0.001). Similarly, in the atrial fibrillation group, ibutilide had a significantly higher success rate than procainamide (51% [22 of 43] vs. 21% [8 of 38], p=0.005). One patient who received ibutilide, which was found to be a protocol violation, had sustained polymorphic ventricular tachycardia requiring direct current cardioversion. Seven patients who received procainamide became hypotensive. CONCLUSIONS: This study establishes the superior efficacy of ibutilide over procainamide when administered to patients to convert either atrial fibrillation or atrial flutter to sinus rhythm. Hypotension was the major adverse effect seen with procainamide. A low incidence of serious proarrhythmia was seen with the administration of ibutilide occurring at the end of infusion.

Aged↗
PubMed2006

Blanked atrial flutter in patients with cardiac resynchronization therapy: clinical significance and implications for device programming.

BACKGROUND: Atrial arrhythmias are frequently observed in patients with heart failure and may be a primary cause for decompensation during cardiac resynchronization therapy (CRT). The accurate detection of organized atrial tachyarrhythmias poses a challenge to the function of mode-switching biventricular pacemakers/defibrillators. METHODS: The purpose of the study was to determine retrospectively the incidence of blanked atrial flutter and mode switch failure (2:1 lock-in), and to look for factors predisposing to this problem. A total number of 65 patients with CRT devices has been followed regularly over 18 +/- 12 months. Five patients were excluded because of chronic atrial fibrillation and reprogramming to VVIR mode. RESULTS: Seven out of 60 patients (12%) were diagnosed with blanked atrial flutter at unscheduled device interrogation. Sustained biventricular pacing at a median rate of 125/min-mimicking sinus tachycardia-resulted in rapid deterioration of heart failure and hospitalization. Mode switch failure occurred due to coincidence of every second flutter wave with atrial blanking. The group with 2:1 lock-in was programmed to longer atrial blanking times (143 +/- 34 ms vs 105 +/- 32 ms; P = 0.026) and AV intervals (126 +/- 8 ms vs 107 +/- 29; P = 0.001) than the group without lock-in. Other clinical characteristics examined did not differ between the two groups apart from a previous history of atrial fibrillation (P = 0.032). CONCLUSION: Blanked atrial flutter with rapid ventricular pacing is a clinically important problem in heart failure patients treated with CRT devices. Efforts should be made to avoid this complication by atrial lead implantation without ventricular farfield oversensing, by programming short PVAB and AV intervals, and by implementation of dedicated device algorithms.

Aged↗
PubMed2006

Long-term symptomatic benefit after radiofrequency catheter ablation for atrial flutter despite a high incidence of post-procedural atrial fibrillation.

OBJECTIVE: A high proportion of patients develops atrial fibrillation (AF) after ablation for atrial flutter (AFL). Radiofrequency ablation for AFL therefore would only be useful if it leads to a better quality of life despite this high incidence of AF post-ablation. METHODS: All patients who underwent AFL ablation in our centre before March 2002 (n=203) were contacted by letter a median of 2.3 years after their ablation. Sixty-eight percent answered the questionnaire polling the perceived benefits of the procedure. The results were stratified according to the presenting arrhythmia before the ablation: only AFL, predominantly AFL, predominantly AF or class Ic-III AFL. RESULTS: Despite a 60% incidence of AF, 84% considered the procedure to be beneficial during the 1st year and 77% during the 2nd year post-ablation. Patients with predominantly AF before the procedure showed significantly less overall improvement than the 3 other groups (50% and 33% after I year and 2 years, p< 0.01) and a smaller reduction in palpitations (50% and 29% after I year and 2 years, p < 0.01). The benefit of an ablation was also significantly less in patients who developed AF post-ablation than in patients who were completely arrhythmia free (75% versus 98% 1st year, 58% versus 91% 2nd year; p 0.01); nevertheless 75% of these patients reported fewer palpitations and 56% tolerated symptoms better than before. CONCLUSIONS: Despite a high incidence of AF after AFL ablation, the majority of patients considered the intervention beneficial. Only in patients with predominantly AF before ablation the procedure does not seem beneficial.

Analysis of Variance↗
PubMed2002

[Comparative analysis of results of two techniques of ablation for typical atrial flutter].

AIM: To compare efficacy of two techniques of ablation for typical atrial flutter: 'old' which end point was impossibility of arrhythmia reinduction and 'novel' aimed at change of sequence of right atrial excitation during coronary sinus ostium pacing for verification of isthmus block after ablation of the inferior vena cava-tricuspid valve isthmus. METHOD: Retrospective analysis of results of 122 procedures of catheter ablation for common atrial flutter. RESULTS: Efficacy of both methods was similar but the use of the 'novel' technique was associated with shorter overall duration of a procedure and fluoroscopy time, lesser number of applications required for successful ablation, and lower rates of induction of atrial fibrillation and of atrial flutter recurrences.

Atrial Flutter↗
PubMed1978

Prolonged atrial conduction. A major predisposing factor for the development of atrial flutter.

Electrophysiological studies were performed during sinus rhythm on 21 patients who had demonstrated the spontaneous occurrence of sustained atrial flutter. The purpose was to determine if atrial conduction disease is a prediposing factor for the development of atrial flutter. Patients with atrial enlargement were excluded from the series. The control group consisted of 11 age-matched patients with normal electrocardiograms and electrophysiology studies. The flutter group showed prolongation of the mean right intra-atrial conduction time at 50 msec (control of 37 msec, P less than 0.05), the mean interatrial conduction time at 92 msec (control of 44 msec, P less than 0.001) and the mean P wave duration at 132 msec (control of 112 msec, P less than 0.01). The flutter group also demonstrated a higher incidence of sinus node dysfunction and ventricular conduction disease compared to the control group. These data indicate that patients who develop atrial flutter have atrial conduction disease. Atrial conduction disease appears to be 1) a major prediposing factor for the development of atrial flutter and 2) a part of the fibro-degenerative conduction disease spectrum.

Arrhythmia, Sinus↗
PubMedDate not supplied

[Transesophageal stimulation of the left cardiac atrium in treatment of atrial flutter].

Transesophageal stimulation of the left cardiac atrium in the treatment of paroxysmal atrial flutter was assessed. An attempt of such a therapy in paroxysmal atrial flutter involved 20 patients. Cardiac atrium was stimulated with overdrive technique, with single or pair of stimuli and multiple impulses of various frequency and duration. Reversal to sinus rhythm was achieved in 10 patients (in 3 out of them through phase of atrial fibrillation transitory). Results confirm therapeutical value of the transesophageal stimulation of the left cardiac atrium in atrial flutter.

Adult↗
PubMed2002

Usefulness of three-dimensional non-fluoroscopic mapping in the ablation of typical atrial flutter.

BACKGROUND: Catheter ablation of the cavo-tricuspid isthmus is rapidly becoming the first line of treatment in the management of atrial flutter. The standard procedure is usually performed under fluoroscopy guidance and relays on multisite endocardial recordings to assess the completeness of the isthmus conduction block. Despite the high rate of success there is, at follow-up, a considerable number of recurrences which could reflect the limitations of conventional assessment of conduction block across the isthmus. This new non-fluoroscopic mapping system allowing high density mapping along the entire length of the ablation line, could provide a more accurate way of verifying complete conduction block. The aim of the present study was to describe our overall results and long-term follow-up using a three-dimensional mapping system to guide radiofrequency ablation of typical atrial flutter. METHODS: A multipoint three-dimensional map of the cavo-tricuspid isthmus, septal and lateral atrial wall was performed in 87 patients prior to and following ablation for typical atrial flutter. Evidence of persisting gaps in the line of block was identified by visual inspection of the color-coded activation maps and these sites were re-ablated. The conduction sequence was also assessed with conventional bidirectional pacing and recording. The assess the reduction in fluoroscopy time, two groups of patients were compared: group A (14 patients) in whom the entire mapping-ablation procedure was guided by the three-dimensional system (Carto, Biosense-Webster, Diamond Bar, CA, USA) and group B (32 patients) in whom the same protocol was used but the procedure was guided by standard fluoroscopic imaging. RESULTS: Acute success was achieved in every patient. During bilateral isthmus pacing, the mean local activation time increased from 20.3 +/- 13.3 ms pre-ablation to 148.3 +/- 53.2 ms (p < 0.01) post-ablation with a mean difference of 120 +/- 31 ms. In 11 patients (9.2%) there was evidence of persisting conduction across the line of block despite evidence of reverse activation of the cavo-tricuspid isthmus by conventional pacing. A gap in the ablation line was identified and re-ablated. At a mean follow-up of 16.3 +/- 2.2 months, there were 5 (4.2%) recurrences of atrial flutter and 12 (10%) recurrences of isolated atrial fibrillation. Four of the 5 recurrences occurred in patients in whom ablation was guided by conventional fluoroscopy (group B). The fluoroscopy time was 4.2 +/- 1.5 min in group A and 27.2 +/- 8.2 min in group B (p < 0.001). CONCLUSIONS: Multipoint mapping of the ablation line following radiofrequency ablation of typical atrial flutter performed using the Carto system allows a more accurate assessment of the isthmus conduction block. This has the potential to reduce the recurrence rate to the level observed for other supraventricular tachycardias.

Atrial Flutter↗
PubMed1988

Effects of N-acetylprocainamide and recainam in the pharmacologic conversion and suppression of experimental canine atrial flutter: significance of changes in refractoriness and conduction.

The electrophysiologic determinants of the pharmacologic conversion and the prevention of atrial flutter are poorly defined. This study investigated the effects of pharmacologically induced changes in atrial conduction velocity and refractoriness, in the conversion and suppression of atrial flutter induced in the open-chest anesthetized dog by intercaval crush and rapid atrial pacing. The effects of an intravenous infusion of the new class III antiarrhythmic drug N-acetylprocainamide (30 mg/kg over 15 min) and the class Ic antiarrhythmic drug recainam (10 mg/kg over 20 min followed by 10 mg/kg/h) were evaluated. N-acetylprocainamide restored sinus rhythm in 10 of 15 (66%) dogs, while recainam converted only 2 of 10 (20%). N-acetylprocainamide prevented reinduction in 3 (20%), while recainam was effective in none. In the atria, N-acetylprocainamide induced significant increases in effective refractory period (+27%, p less than 0.01), functional refractory period (+22%, p less than 0.01), and in atrial flutter cycle length (+13%, p less than 0.01). Recainam increased effective refractory period (+28%, p less than 0.01), functional refractory period (+20%, p less than 0.01), conduction time at atrial paced cycle length of 150 msec (+70%, p less than 0.01) and atrial flutter cycle length (+56%, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Acecainide↗
PubMed1996

Electrophysiologic effects of the new class III antiarrhythmic drug dofetilide compared to the class IA antiarrhythmic drug quinidine in experimental canine atrial flutter: role of dispersion of refractoriness in antiarrhythmic efficacy.

INTRODUCTION: Previous studies suggest that class III antiarrhythmic drugs are more effective in reentrant arrhythmias because they prolong refractoriness (ERP) and wavelength and reduce dispersion of refractoriness compared to Class IA antiarrhythmic drugs, which slow conduction velocity (CV) in addition to their effects on refractoriness. METHODS AND RESULTS: To test this hypothesis, the Class III drug dofetilide and the Class IA drug quinidine were studied in the experimental canine crush-injury model of atrial flutter, utilizing right atrial multipoint programmed stimulation and activation mapping. In seven dogs dofetilide prolonged ERP by 23%, slowed CV by 9% at 200-msec cycle length (P < 0.001) and by 39% at 150-msec cycle length (P < 0.001), and increased wavelength by 11% (P < 0.02). Dofetilide reduced dispersion of ERP by 20% (P = 0.003) and adjacent electrodes with ERP difference > or = 20 msec by 76% (P < 0.001). Dofetilide slowed atrial flutter by 37% (P = 0.003) prior to terminating and suppressing it in all dogs. In eight dogs quinidine prolonged ERP by 14% (P < 0.001), slowed CV by 14% at 200-msec length cycle (P < 0.001) and by 19% at 150-msec cycle length (P < 0.001), and reduced wavelength by 2% (P = NS). Quinidine did not reduce dispersion of refractoriness. Quinidine slowed atrial flutter by 57% (P < 0.001), terminating and suppressing it in only three dogs. Efficacy of dofetilide was greater than quinidine (P = 0.026) and correlated with reduced dispersion of ERP (r = -0.653, P = 0.01), reduced adjacent electrodes with ERP difference > or = 20 msec (r = -0.637, P = 0.012), and prolonged wavelength (r = 0.61, P = 0.018). Dofetilide and quinidine terminated atrial flutter by similar mechanisms. Myocardial fiber orientation was nonuniform around the crush injury. CONCLUSIONS: Antiarrhythmic efficacy of dofetilide was greater than that of quinidine and correlated with drug-induced prolongation of wavelength and reduction in dispersion of refractoriness, effects produced only by dofetilide.

Action Potentials↗
PubMed2002

Conduction properties of the crista terminalis and its influence on the right atrial activation sequence in patients with typical atrial flutter.

The conduction properties of the crista terminalis (CT) and its influence on the right atrial activation sequence were analyzed in 14 patients with typical atrial flutter (AF). Atrial mapping was performed with 35 points of the right atrium during typical AF and during atrial pacing performed after linear ablation of inferior vena cava-tricuspid annulus (IVC-TA) isthmus. Atrial pacing was delivered from the septal isthmus at cycle lengths of 600 ms and the tachycardia cycle length (TCL). The right atrial activation sequence and the conduction interval (CI) from the septal to lateral portion of the IVC-TA isthmus were analyzed. During AF, the conduction block line (CBL) (detected by the appearance of double potentials along the CT and craniocaudal activation on the side anterior to CT) was observed along the CT in all patients. The TCL and CI during AF were 254 +/- 19 and 207 +/- 14 ms, respectively. During pacing at a cycle length of 600 ms, the CBL was observed along the CT in four patients, however, a short-circuiting activation across the CT was observed in the remaining ten patients. The CI during pacing at 600 ms was 134 +/- 38 ms, shorter than that during AF (P < .0001). During pacing at the TCL, the CBL was observed along the CT in all patients. The presence of the CBL along the CT prevented a short-circuiting activation across the CT and resulted in the same right atrial activation as observed during AF. With the formation of the CBL, the CI significantly increased to 206 +/- 17 ms and was not different from that during AF. These data suggest that the conduction block along the CT is functional. It was presumed that presence of conduction block at the CT has some relevance to the initiation of typical AF though it was not confirmed.

Aged↗