P wave separation after atrial compartment operation for atrial fibrillation

Surgically induced abnormalities in atrial conduction could result in unusual P wave changes. A 31-year-old woman underwent concomitant mitral valve surgery and atrial compartment operation for mitral stenosis and atrial fibrillation (AF). After operation, the AF was successfully converted to sinus rhythm, whereas an unusual electrocardiogram (ECG) with a discrete negative deflection before the T wave in V1 was noted. Electrophysiological study showed a marked conduction delay from the high right atrium (HRA) to the right atrial appendage (RAA) compartment, which resulted in a separation of P waves. The P wave preceding the QRS complex represented the activation of sinus node and the left atrial compartments, and the P at the vicinity of T wave represented the activation of RAA compartment. The conduction from HRA to RAA was worsened on HRA pacing at a faster rate, and improved after isoproterenol infusion. This report demonstrated that conduction across a surgically created isthmus in the atrium could be severely impaired and result in unusual P wave separation.     

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.     

Noncontact mapping-guided ablation of atrial flutter and enhanced-density mapping of the inferior vena caval-tricuspid annulus isthmus

Three-dimensional visualization of cardiac activation has become important in providing further insights into pathophysiological mechanisms of arrhythmias and to increase the efficacy of catheter ablation. The noncontact mapping enables a single beat analysis in a reconstructed geometry of the cardiac chamber. The aim of the study was to describe three-dimensional activation patterns and inferior vena caval-tricuspid annulus (IVC-TA) isthmus conduction characteristics in patients with atrial flutter and the noncontact guidance of the radiofrequency ablation of this arrhythmia. In 34 patients with atrial flutter, the noncontact probe was deployed in the RA. The global three-dimensional activation and the isthmus conduction (enhanced density mapping) were delineated during ongoing a trial flutter and paced rhythms. Ablation was performed nonfluoroscopically based on reconstructed anatomy and conduction patterns. Noncontact mapping was compared and validated with conventional multielectrode technique. IVC-TA isthmus ablation was completed successfully in 33 (97%) of 34 patients. In one patient a lower loop reentry around the inferior vena cava was depicted as a mechanism of atrial flutter. In another patient with positive flutter waves in inferior leads, an activation pattern typical of counterclockwise flutter was demonstrated in propagation maps. During a follow-up of 15.9 +/- 5.9 months, two atrial flutter recurrences occurred (5.8%). A gap of the resumed conduction through the IVC-TA isthmus was delineated as a mechanism of recurrence and ablated with one and three radiofrequency applications. Noncontact mapping allows construction of the global activation patterns in typical and atypical atrial flutter. It enables the nonfluoroscopic guidance of atrial flutter ablation and a comprehensive evaluation of the ablation results.     

Ectopic atrial rhythm with exit block following catheter ablation for focal atrial tachycardias in a patient with prior surgery for atrial septal defect

The patient was a 40-year-old woman with a history of surgery for atrial septal defect and catheter ablation for typical atrial flutter. An electrophysiological study was performed because she had palpitation and syncope. She had ectopic atrial rhythm originating from low lateral RA. Two focal atrial tachycardias ([1] superior vena cava-RA junction and [2] a lowposteroseptal RA) were successfully ablated. Following catheter ablation for the second atrial tachycardia, she developed junctional rhythm because ectopic atrial rhythm showed exit block. However, atrial activation of junctional rhythm could conduct into the ectopic atrial rhythm focus and reset the rhythm when atrial activation of junctional rhythm reached the blocked line after atrial refractoriness by preceding ectopic atrial rhythm.     

Impaired cardiac performance relating to delayed left atrial activation after atrial compartment operation for chronic atrial fibrillation

In the presence of a normal atrial systole and optimal AV delay, atrial kick contributes to a significant fraction of the stroke volume. This atrial contribution may be lost during atrial asystole or mismatch in the timing of atrial and ventricular contraction. A patient received atrial compartment operation for his chronic AF. Although the AF was successfully converted to sinus rhythm, the conduction from the right to left atrium was markedly delayed so that the left atrial and ventricular activations occurred almost simultaneously. This delay in left atrial activation resulted in impaired cardiac performance.     

The effect of the atrial pacing site on the total atrial activation time

The effect of dual site pacing for prevention of atrial fibrillation may be due to synchronization of right and left atrial activation. Little is known, however, about the effect of pacing from single right atrial sites on differences in interatrial conduction. Twenty-eight patients without structural heart disease were studied following radiofrequency catheter ablation of supraventricular arrhythmias. Pacing was performed using standard multipolar catheters from the presumed insertion site of Bachmann's bundle, the coronary sinus ostium, the high lateral right atrium, and the right atrial appendage (n = 8 patients). Bipolar recording was performed from the distal coronary sinus, the high and low lateral right atrium, and the posterolateral left atrium (n = 13 patients). The longest conduction time from each pacing to each recording site was considered the total atrial activation time for the respective pacing site. During high right atrial pacing, the total atrial activation time was determined by the conduction to the distal coronary sinus (118 +/- 18 ms), during coronary sinus ostium pacing by the conduction to the high right atrium (94 +/- 18 ms), and during Bachmann's bundle pacing by the conduction to the distal coronary sinus (74 +/- 18 ms). The total atrial activation time was significantly shorter during pacing from Bachmann's bundle, as compared to pacing from other right atrial sites. Thus, in normal atria, pacing from the insertion of Bachmann's bundle causes a shorter total atrial activation time and less interatrial conduction delay, as compared to pacing from other right atrial sites. These findings may have implications for alternative pacing sites for prevention of atrial fibrillation.     

Deglutition induced atrial tachycardia and atrial fibrillation

Deglutition induced supraventricular tachycardia is an uncommon condition postulated to be a vagally mediated phenomenon due to mechanical stimulation. Patients usually present with mild symptoms or may have severe debilitating symptoms. Treatment with Class I agents, beta blockers, calcium channel blockers, amiodarone and radiofrquency catheter ablation has shown to be successful in the majority of reported cases. We report the case of a 46-year-old healthy woman presenting with palpitations on swallowing that was documented to be transient atrial tachycardia with aberrant ventricular conduction as well as transient atrial fibrillation. She was successfully treated with propafenone with no induction of swallowing-induced tachycardia after treatment. This is also the first case to show swallowing-induced atrial tachycardia and atrial fibrillation in the same patient.     

Left atrial appendage isolation during ablation in the interatrial septum: Rapid recognition by continuous monitoring of appendage electrograms

Extensive atrial ablation in the setting of atrial fibrillation (AF) and atrial tachycardia (AT) can affect interatrial connections. A 76-year-old man with a history of tachycardia-induced cardiomyopathy and nine ablation procedures for AF/AT over 15 years presented with highly symptomatic recurrent AT. Previous ablation lesions included pulmonary vein isolation, left atrial posterior wall isolation, mitral isthmus line, cavotricuspid isthmus line, and the ablation of areas of fractionated electrograms. Electroanatomical mapping found the pulmonary veins and the left atrial posterior wall to be silent, as was the posterior interatrial septum and the mitral isthmus area. Activation mapping showed progression of electrograms in the left atrial appendage (LAA) from the septal aspect posteriorly, and in the coronary sinus from proximal to distal; implying the existence of a septal circuit, where extensive fractionation was noted. This was targeted, while monitoring conduction into the LAA using a multielectrode catheter. Ablation led to prompt termination of tachycardia and simultaneous LAA isolation. Immediate cessation of ablation led to recovery of conduction into LAA. Additional lesions in the interatrial septum were required to render the tachycardia noninducible, accompanied by temporary isolation of LAA. The ablation lesion sets employed while ablating AF and left AT can block many interatrial pathways, rendering conduction dependent on muscle bundles in the interatrial septum and, therefore, vulnerable to block by lesions in this area. LAA isolation has been associated with high incidence of LAA thrombus formation and stroke despite oral anticoagulation. Continuous observation of LAA electrograms during ablation can help to avoid this complication.     

Anatomic and electrophysiological differences between chronic and paroxysmal forms of common atrial flutter and comparison with controls:

Whether chronic typical atrial flutter differs from paroxysmal atrial flutter regarding electrophysiological properties of reentry pathways and cardiac function remains unknown. If so, can remodeling due to long duration of persistently rapid atrial or ventricular rates explain these changes? The aim of the study was to compare RA local conduction velocities and heart function parameters between three groups: (1) chronic atrial flutter, (2) paroxysmal atrial flutter, and (3) controls. The study evaluated 52 patients undergoing radiofrequency ablation for typical atrial flutter. There were 35 patients with chronic atrial flutter (62.7 ± 14 years) and 17 patients with paroxysmal atrial flutter (62.7 ± 10 years). Underlying structural heart disease was present in 20 (57%) of 35 chronic atrial flutter patients and in 7 (41%) of 17 paroxysmal atrial flutter patients (P = 0.1). Chronic atrial flutter duration was 10.9 ± 17 months and paroxysmal atrial flutter duration was 8.5 ± 10 (P = 0.06). RA conduction velocity measurements were carried out before ablation during sinus rhythm under pacing (600‐ms cycle length) with a 12‐pole steerable catheter positioned in the high lateral RA (poles 11‐12 [H6]), mid‐lateral RA (poles 9‐10 [H5]), and along the inferior vena caval tricuspid isthmus (poles 7‐8 [H4]; 5‐6 [H3]; 3‐4 [H2]) with its distal electrode pair at the coronary sinus origin (pole 1‐2 [H1]). Counter‐clockwise RA conduction velocities were assessed from H6 to H1 and clockwise RA conduction velocities from H1 to H6. After successful ablation, RA and LA areas, LV volumes, LVEF, inferior vena caval tricuspid annulus, and coronary sinus tricuspid annulus (septal isthmus) lengths were measured by two‐dimensional echocardiography. The control group included 12 patients without structural heart disease, referred for electrophysiological evaluation of AVN reentry. Counter‐clockwise RA conduction velocities at the inferior vena caval tricuspid isthmus were lower in chronic atrial flutter than in paroxysmal atrial flutter (H4, 1.19 ± 0.4 vs 1.89 ± 1 m/s, P = 0.0051; H3, 1.14 ± 0.4 vs 1.6 ± 0.7 m/s, P = 0.0015; H2, 1.16 ± 0.4 vs 1.53 ± 0.5 m/s, P < 0.0056 and H1, 1.2 ± 0.4 vs 1.5 ± 0.4 m/s, P = 0.03, respectively). Counter‐clockwise RA conduction velocities were identical at the high and mid‐lateral RA. Counter‐clockwise caval isthmus RA conduction velocities from H3 to H1 were significantly different between chronic atrial flutter and controls (H3, 1.14 ± 0.4 vs 1.7 ± 0.3 m/s, P = 0.0014; H2, 1.16 ± 0.4 vs 1.83 ± 0.4 m/s, P < 0.0001 and H1, 1.2 ± 0.4 vs 1.94 ± 0.4 m/s, P < 0.0001, respectively). A difference was found regarding clockwise isthmus RA conduction velocities between the two groups of atrial flutter and controls but not between chronic atrial flutter and paroxysmal atrial flutter. Respectively, chronic atrial flutter had greater RA and LA areas (24.5 ± 5 vs 13 ± 2 cm ² ; P < 0.0001 and 23 ± 5 vs 16 ± 3 cm ² , P < 0.0001), LV end‐systolic and end‐diastolic volumes (50 ± 25 vs 32 ± 13 cm ³ , P = 0.0084 and 112 ± 40 vs 85 ± 25 cm ³ , P = 0.01), septal isthmus length (21 ± 3 vs 13 ± 2 mm, P < 0.0001), and inferior vena caval tricuspid isthmus length (39 ± 6 vs 23 ± 5 mm; P < 0.0001). Chronic common atrial flutter is characterized by more prolonged counter‐clockwise conduction times and larger anatomic conduction pathways than the paroxysmal form, the causal relationship between electrophysiological and anatomic characteristics remains to be demonstrated.     

Impact of transisthmus linear ablation of typical atrial flutter on coronary sinus activation time

Complete or incomplete bidirectional isthmus conduction block after linear ablation of atrial flutter is difficult to interpret without detailed multiple electrodes mapping along the tricuspid annulus and the low right atrial isthmus area. The influence of isthmus block on the intraatrial septal and coronary sinus activation has not been assessed by endocardial mapping. This study was designed to analyze the intraartial and interatrial activation times in a retrospective fashion to investigate (1) whether isthmus conduction block can change the coronary sinus activation sequence during low lateral right atrial pacing, and (2) the correlation between change of coronary sinus activation time and isthmus conduction block. Sixty-five consecutive patients (mean age, 57 +/- 18 years) with clinically documented typical atrial flutter were studied. A 20-pole "Halo" catheter was placed around the tricuspid annulus including the entire low right atrial isthmus to verify complete bidirectional isthmus block. Activation time from ostium to distal coronary sinus (OCS-->DCS), and interatrial septum and isthmus activation times during right atrial pacing were analyzed and compared before and after incomplete or complete isthmus block. Complete bidirectional isthmus block was achieved in 50 (77%) patients. During low lateral right atrial pacing, linear ablation at low right atrial isthmus results in a significant delay of activation in all coronary sinus recording sites with greater extent at the ostium area without influence on interatrial septum activation in complete and incomplete isthmus conduction block. The difference of the OCS-->DCS interval before and after ablation, delta (OCS-->DCS), was well correlated with results of isthmus conduction block and significantly longer in patients with complete than those with incomplete isthmus block (34 +/- 11 vs 11 +/- 8 ms, P < 0.001), thereby allowing a value of 20 ms as a discriminative parameter to differentiate incomplete (< 20 ms) from complete (> or = 20 ms) isthmus counterclockwise conduction block with a sensitivity of 96% and a specificity of 88%. In conclusion, creation of a line of block at the inferior vena cava-tricuspid annulus isthmus could change coronary sinus activation sequence during low lateral right atrial pacing in sinus rhythm. The change of coronary sinus activation time after linear ablation, delta (OCS-->DCS), was well correlated with isthmus conduction block by using a value > or = 20 ms to discern complete counterclockwise isthmus block.     

Focal atrial tachycardia from the fossa ovalis in a patient with Bachmann's bundle block

We report the case of a patient with tracings during sinus rhythm compatible with block of the Bachmann's bundle and presenting with focal atrial tachycardia arising from the fossa ovalis with successful ablation on the right side of the septum. Upward activation of the left atrium has been related in this case to the block of the Bachmann's bundle and to the lack of transseptal conduction.     

"Left-variant" adenosine-sensitive atrial reentrant tachycardia ablated from the left coronary aortic sinus

Adenosine-sensitive reentrant atrial tachycardia (AT) is usually amenable to ablation at the right superoseptum near the His bundle. We report a case with "left-variant" adenosine-sensitive reentrant AT. The AT was reproducibly induced by atrial extrastimulation with negative correlation between the coupling interval and return cycle, and was terminated by atrial extrastimulation and bolus of 2 mg of adenosine 5'-triphosphate. Ablations at the right superoseptum were unsuccessful; however, the AT was successfully ablated from the left coronary aortic sinus (LCAS) where the earliest atrial activation was recorded. Ablation at the LCAS might be effective in this entity resistant to right-sided ablation.     

Conduction properties of the crista terminalis in patients with atrial flutter due to amiodarone therapy for atrial fibrillation

Some patients with atrial fibrillation (AF) treated by antiarrhythmic drugs (AAD) can develop typical atrial flutter, but the mechanism is not clear. This study included 21 patients with AF. Group I (n = 7) had typical atrial flutter due to amiodarone therapy. Group II (n = 7) did not develop atrial flutter after amiodarone treatment. Group III (n = 7) did not receive AAD treatment. A 7 Fr, 20-pole electrode catheter was placed along the CT identified by fluoroscopy and intracardiac echocardiography. After restoration of the sinus rhythm, decremental pacing near the CT was performed until 2 to 1 atrial capture. Complete transverse conduction block was defined as the appearance of double potentials with opposite activation sequence along the CT. Focal transverse conduction delay was defined as the appearance of double potentials at > or = 2 recording sites. Focal transverse conduction delay was observed during pacing at the cycle length of 693 +/- 110 ms in group I, 360 +/- 97 ms in group II and 343 +/- 109 ms in group III (P = 0.001). Complete transverse conduction block was observed during pacing at the cycle length of 391 +/- 118 ms in group I and 231 +/- 23 ms in group II (P = 0.001), but not in group III. In conclusion, focal transverse conduction delay in the CT was common in patients with AF. A predisposition to the line of the conduction block in the CT might contribute to the conversion of AF to typical atrial flutter due to amiodarone therapy.     

Cyclic appropriate mode switching and inappropriate back switching of a biventricular pacemaker during atrial tachyarrhythmia

In patients with resynchronization devices and intact intrinsic AV conduction, atrial tachyarrhythmias may give rise to high ventricular rates, resulting in inhibition of (bi)ventricular pacing and concomitant lack of therapeutic effects of the device. This report presents a patient with atrial arrhythmias in whom mode switching and back switching of the biventricular pacemaker occurred, due to special timing of the atrial and ventricular deflections. This case report stresses the importance of strenuous treatment of atrial arrhythmias in patients with resynchronization devices.     

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.     

Basket catheter-guided three-dimensional activation patterns construction and ablation of common type atrial flutter

Construction of three-dimensional activation maps and evaluation of ablation-created bidirectional block in the tricuspid valve-inferior vena caval (TV-IVC) isthmus in patients with atrial flutter (AF) are difficult with conventional mapping technique. In 36 patients with type I AF (25 men, 11 women; mean age 62 +/- 10.5 years) a multielectrode basket catheter (BC) was deployed in the right atrium (RA). Out of 64 BC electrodes, 56 bipolar electrograms were derived. Three-dimensional activation patterns were constructed with a software program. Stable electrograms of satisfactory quality were obtained in 49 +/- 2 electrode pairs. Capture was possible in 36 +/- 3 of bipoles. In counterclockwise AF (CCW-AF) and clockwise AF (CW-AF) episodes, cycle lengths and TV-IVC isthmus conduction times were 248 +/- 26 ms and 251 +/- 23 ms, (P = 0.74) and 105 +/- 28 ms and 106 +/- 33 ms (P = 0.92), respectively. Conduction velocity in the TV-IVC isthmus was lower than in the anterior or septal limbs of the circuit, in counterclockwise or clockwise episodes. Double potentials were recorded in 94% of patients. Three-dimensional activation patterns were delineated and displayed as isochronal maps. The reentry circuit involved the TV-IVC isthmus, septal, and anterior walls and a part of the RA roof anterior to superior vena cava. Postablation isthmus conduction was evaluated through the sequence criteria, local electrogram-based criteria, and the analysis of three-dimensional activation patterns of the paced rhythms. The complete isthmus block was associated with a significant increase of the low anterior low septal conduction interval (152 +/- 29 vs 104 +/- 32 ms, P = 0.001) and the low septal-low anterior conduction interval (150 +/- 31 vs 107 +/- 33 ms, P = 0.001). Radiofrequency ablation was successful in 32 (90%) of 36 patients. In conclusion, the current mapping system enables construction of three-dimensional activation patterns and facilitates evaluation of the postablation TV-IVC isthmus block in patients with AF.     

Atrial activation analysis by surface P wave and multipolar esophageal recording after cardioversion of persistent atrial fibrillation

We studied atrial activation during sinus rhythm by combining 12-lead ECG and multipolar esophageal recordings in 30 patients after electrical cardioversion of persistent atrial fibrillation. The primary endpoint was to establish a correlation between atrial activation evaluated by the two methods. Total P wave duration and morphology in inferior leads identified three patterns: normal P wave, late-positive P wave, and late-negative P wave. Proximal and distal esophageal recording characterized the longitudinal direction of activation of the posterior left atrium. We distinguished three activation patterns: normal activation when the interatrial conduction time is normal and depolarizes in craniocaudal direction, delayed activation when the interatrial conduction time is prolonged and the craniocaudal activation is maintained, and finally reversed activation when the posterior left atrium depolarizes in a reversed caudocranial direction. Four patients showed a normal P wave and also had a normal esophageal activation. Twelve patients showed a prolonged P wave (associated with delayed esophageal activation in 10 patients and reversed activation in 2 patients); 14 patients had a late-negative P wave (all associated with a reversed esophageal activation). A high correlation existed between each pattern obtained by surface ECG and esophageal recording (P < 0.001) and between surface P wave duration and interatrial conduction time (R2 = 0.64, P < 0.001). Much information concerning atrial activation can be obtained by meticulous analysis of the P wave, particularly its terminal part. Multipolar esophageal recording can be used when surface ECG appears unclear.     

1:1 atrial flutter induced by flecainide,whilst the patient was at rest

Class Ic antiarrhythmic agents flecainide and propafenone are amongst the drugs most frequently prescribed to control atrial arrhythmias, in particular atrial fibrillation (AF). Despite being cited in some guidelines as a warning when using 1c antiarrhythmic agents, atrial flutter (AFl) with 1:1 atrioventricular conduction is rare in adults, with only small series reported in the literature, mainly including patients having 1:1 AFl during physical activity, and often associated with a predisposing factor, namely a dual AV nodal conduction pathway. We describe here a rare case of 1:1 AFl induced by flecainide, developing whilst the patients was resting in bed, in a 56?year old man who presented to the local Emergency Department (ED) complaining for palpitations due to acute-onset AF. After ED discharge, the patient was then evaluated in the Arrhythmologic Clinic of the Cardiology Department, and channellopaties were excluded. This case report should raise alertness in emergency physicians about this serious and potentially fatal side effect of flecainide, when using this drug for pharmacological cardioversion of AF.     

Radiofrequency ablation of a concealed right anterior accessory pathway associated with right atrial diverticulum in a child

A 9-year-old boy had refractory supraventricular tachycardia and a right atrial (RA) diverticulum as diagnosed by ultrafast computed tomography. An electrophysiological study under transesophageal echocardiography guidance revealed a concealed right anterior accessory pathway passing through the body of the RA diverticulum. Radiofrequency ablation was performed to eliminate retrograde ventriculoatrial conduction.     

Initial results of linear duty-cycled radiofrequency for atypical flutter and atrial tachycardia

Background: Duty‐cycled radiofrequency (DCRF) is increasingly used for ablation of atrial fibrillation (AF). Many patients also have atrial flutter (AFL). Recently, a linear multielectrode has been shown to create linear block at the cavotricuspid isthmus and in the left atrium (LA). Objective: To map and ablate atypical AFL and atrial tachycardias (ATs) in the right and LA using a linear multielectrode with DCRF. Methods: The linear multielectrode delivers DCRF at 20–45 W maximum in 1:1 unipolar/bipolar temperature‐controlled mode. Target temperatures were manually titrated to 60 °C in the LA, if power >5W indicated adequate passive cooling. Results: A total of 76 AT/AFL were targeted in 57 patients. Acute success was reached in 14/15 (93%) right AT, in 17/22 (77%) left atrial roof AFL, in 5/6 (83%) septal AFL, in 9/9 (100%) other left atrial AT, but only in 8/23 (35%) AFL from the mitral isthmus (which rose to 13/23 [57%] with additional use of irrigated radiofrequency). Nevertheless, freedom of AF/AFL 10 ± 6 months after a single procedure was documented in 92% of right AT, 71% of roof AFL, 73% for mitral AFL, and 60% of septal or other LA AT/AFL. No char formation was noted. However, frequent induction of AF and one case of asystole occurred during delivery of DCRF in a pacemaker patient. Conclusion: The linear multielectrode allows mapping and ablation of atypical AFL/AT. Freedom of AF/AT was reached in 60%–92% depending on localization and number of arrhythmias. Technical modifications will improve safety and efficacy. (PACE 2011; 34:1128–1137)