Substitutional photoluminescence modulation in adducts of a europium chelate with a range of alkali metal cations: a gas-phase study.

We present gas-phase dispersed photoluminescence spectra of europium(III) 9-hydroxyphenalen-1-one (HPLN) complexes forming adducts with alkali metal ions ([Eu(PLN)3M](+) with M = Li, Na, K, Rb, and Cs) confined in a quadrupole ion trap for study. The mass selected alkali metal cation adducts display a split hypersensitive (5)D0 → (7)F2 Eu(3+) emission band. One of the two emission components shows a linear dependence on the radius of the alkali metal cation whereas the other component displays a quadratic dependence thereon. In addition, the relative intensities of both components invert in the same order. The experimental results are interpreted with the support of density functional calculations and Judd-Ofelt theory, yielding also structural information on the isolated [Eu(PLN)3M](+) chromophores.

Dynamical matrix diagonalization for the calculation of dispersive excitations.

The solid state exhibits a fascinating variety of phases, which can be stabilized by the variation of external parameters such as temperature, magnetic field and pressure. Until recently, numerical analysis of magnetic and/or orbital phases with collective excitations on a periodic lattice tended to be done on a case-by-case basis. Nowadays dynamical matrix diagonalization (DMD) has become an important and powerful standard method for the calculation of dispersive modes. The application of DMD to the interpretation of inelastic neutron scattering (INS) data on dispersive magnetic excitations is reviewed. A methodical survey of calculations employing spin-orbit and intermediate coupling schemes is illustrated by examples. These are taken from recent work on rare earth, actinide and transition metal compounds and demonstrate the application of the formalism developed.

Magnetic structure of GdCu(6).

Hot neutron diffraction has been used to study the magnetic structure of GdCu(6). Long range antiferromagnetic order with a propagation vector of (h 0 0) has been determined below the Néel temperature T(N) = 16 K from the neutron powder refinement. The magnetic moments are oriented normal to the a direction, which is in agreement with previously reported results of bulk experiments. Mean field model calculations suggest that the magnetic structure is a helix.

Success of Radiofrequency Catheter Ablation of Atrial Fibrillation: Does Obesity Influence the Outcomes?

Background: Catheter ablation of atrial fibrillation (AF) is an increasingly popular therapeutic option for symptomatic patients who have failed multiple antiarrhythmic drugs (AADs). Patients of higher body mass index often fail direct current cardioversion. The role of body mass index (BMI) on the success of AF ablation is not well understood. Methods: We prospectively studied 511 patients who underwent AF ablation at the Cleveland Clinic Foundation between 2002 and 2005. Patients were divided into four classes based on their BMI: Class I ( 25); Class II (25.1-30); Class III (30.1-35) and Class IV (>35). These groups were compared for baseline demographic and clinical characteristics. Any recurrence of AF after 3 months of ablation was considered as failure. All classes were followed for at least 12 months and rates of failure were compared. Results: Based on their BMI, 25% of patients were assigned to class I, 37% in class II, 21% in class III and 16% in class IV. Patients of higher classification (class III or IV) were more likely to be male (p<0.001), diabetic (p<0.001), smokers (p=0.002), with coronary artery disease (=0.018), left atrial enlargement (p=0.015) and longstanding AF (p=0.007). Severity of obesity as measured by BMI had a direct correlation to early (p=0.05) and late (p=0.01) recurrence of AF. Conclusion: Obesity is significantly associated with long-term AF recurrence after catheter ablation. Higher incidence of smoking & left atrial enlargement may possibly contribute to higher failure rates in this sub-group of patients.

Atrial fibrillatory cycle length: computer simulation and potential clinical importance.

AIMS: Atrial fibrillatory cycle length (AFCL) is generally accepted as a surrogate marker for local refractoriness. In this study, a computer model and clinical data on human subjects undergoing catheter ablation for paroxysmal and persistent AF were used to determine the clinical potential of AFCL. METHODS AND RESULTS: Simulations were performed in a biophysical computer model of AF, induced from eight simultaneously active focal sources. Atrial fibrillatory cycle length persistence and termination were assessed in response to successively switching off the involvement of the eight sources. Electrophysiological data were obtained from 178 subjects undergoing catheter ablation of AF. Atrial fibrillatory cycle length, measured in the atria appendages using automated monitoring software, was studied to determine its clinical correlation, the complexity of the ablation procedure, and the AF termination success rate. Computer simulations showed an inverse relationship between the number of sources participating in AF maintenance and AFCL. Clinical data demonstrated a strong relationship between duration, degree of ablation, and AFCL, with shorter AFCL associated with more extensive ablation to terminate AF. Atrial fibrillatory cycle length was prolonged exponentially at each stage, with a critical cycle length of approximately 200 ms for AF conversion. CONCLUSION: Atrial fibrillatory cycle length is inversely associated with the number of sources participating in AF maintenance observed in the computer model. In addition, AFCL is an important predictor of baseline duration of the arrhythmia, type of AF, and ease of catheter ablation therapy to terminate AF.

Impact of catheter ablation of the coronary sinus on paroxysmal or persistent atrial fibrillation.

OBJECTIVES: This study evaluated the impact of catheter ablation of the coronary sinus (CS) region during paroxysmal and persistent atrial fibrillation (AF). BACKGROUND: The CS musculature and connections have been implicated in the genesis of atrial arrhythmias. METHODS: Forty-five patients undergoing catheter ablation of AF were studied. The CS was targeted if AF persisted after ablation of pulmonary veins and selected left atrial tissue. CS ablation was commenced endocardially by dragging along the inferior paramitral left atrium. Ablation was continued from within the vessel (epicardial) if CS electrograms had cycle lengths shorter than that of the left atrial appendage. RF energy was limited to 35 W endocardially and 25 W epicardially. The impact of ablation was evaluated on CS electrogram cycle length (CSCL) and activation sequence, atrial fibrillatory cycle length measured in the left atrial appendage (AFCL) and on perpetuation of AF. RESULTS: Endocardial ablation significantly prolonged CSCL by 17 +/- 5 msec and organized the CS activation sequence (from 13% of patients before to 51% after ablation); subsequent epicardial ablation further increased local CSCL by 32 +/- 27 msec (P < 0.001). AFCL prolonged significantly both during endocardial and epicardial ablation (median: 152 to 167 msec P = 0.03) and was associated with AF termination in 16 (35%) patients (46% of paroxysmal and 30% of persistent AF). AFCL prolongation > or =5 msec and/or AF termination was associated with more rapid activity in the CS region originally: P < or = 0.04. CONCLUSION: Catheter ablation targeting both the endocardial and epicardial aspects of the CS region significantly prolongs fibrillatory cycle length and terminates AF persisting after PV isolation in 35% of patients.

Effects of stepwise ablation of chronic atrial fibrillation on atrial electrical and mechanical properties.

OBJECTIVES: This study sought to evaluate the effects of stepwise catheter ablation of chronic atrial fibrillation (AF) on atrial electrical and mechanical properties. BACKGROUND: Although stepwise catheter ablation of chronic AF is associated with acute arrhythmia termination and a favorable clinical outcome, atrial tissue damage following the procedure has not been evaluated. METHODS: Forty patients who had previously undergone catheter ablation of chronic AF were studied. In the index procedure, termination of AF was achieved by catheter ablation alone in 36 of 40 patients (90%). Electroanatomical mapping was performed in sinus rhythm > or =1 month after the index procedure, during which the surface area of scar (bipolar voltage of <0.05 mV), low-voltage tissue (<0.5 mV), and atrial propagation were evaluated. Left atrial (LA) mechanical function was assessed by transthoracic echocardiography. RESULTS: Electroanatomical mapping showed areas of scar and low-voltage accounting for 31% +/- 12% and 32% +/- 17% of the total LA surface area respectively, with the ablated pulmonary vein region accounting for 20% +/- 4% of the LA surface area. The area of scar outside the pulmonary vein region represented 14% +/- 12% of the LA surface area using the initial randomized ablation strategy, and 6% +/- 8% (p = 0.02) using a specific ablation strategy. Atrial conduction was diversely affected by ablation with a wide range of LA conduction times observed (range 100 to 360 ms). The LA contraction was shown in all patients by the presence of late diastolic mitral flow (37 +/- 15 cm/s) and a mean LA active emptying fraction of 18 +/- 11%. At 9 +/- 5 months of follow-up, 39 patients (98%) were in sinus rhythm. CONCLUSIONS: Stepwise ablation achieving sinus rhythm in patients with chronic AF has a significant impact on LA electrical activity but is associated with recovery of LA function.

Complete isolation of the pulmonary veins and posterior left atrium in chronic atrial fibrillation. Long-term clinical outcome.

AIMS: To evaluate the contribution of the posterior left atrium (LA) to chronic atrial fibrillation (AF). METHODS AND RESULTS: Twenty-seven patients with chronic-AF were studied. After pulmonary vein (PV) isolation, the posterior-LA was isolated by ablation joining the right- and left-PVs using an irrigated-tip catheter. Isolation was demonstrated by absent/dissociated posterior-LA activity and the inability to pace the region. Ablation impact was determined by the effect on cycle length (CL) and AF termination. Posterior-LA isolation was achieved using 35 +/- 12 min of radiofrequency with total fluoroscopic and procedural durations of 64 +/- 16 and 199 +/- 46 min, resulting in abolition of electrograms (n = 21) or autonomous activity (n = 6; CL 820 +/- 343 ms). AFCL increased from 156 +/- 28 ms to 162 +/- 27 ms with PV-isolation and to 175 +/- 32 ms by posterior-LA exclusion (P < 0.0001). AF persisted in all after PV-isolation and terminated in 5 (19%) during posterior-LA-isolation. After 10 +/- 6 months, 12 patients developed atrial tachycardia (four) or AF (eight); four underwent repeat posterior-LA-isolation, while the others required additional ablation/antiarrhythmics. After 21 +/- 5 months, 17 (63%) were in sinus rhythm following posterior-LA-isolation. CONCLUSION: This study demonstrates the feasibility of complete posterior-LA exclusion by catheter ablation. This strategy results in maintenance of sinus rhythm in 63% at 2 years follow-up.

Impact of varying ablation patterns in a simulation model of persistent atrial fibrillation.

BACKGROUND: Several strategies of endovascular ablation with varying success rates and proarrhythmic effects have been proposed to treat persistent atrial fibrillation (AF). Evaluation of ablation patterns by computer simulation provides a tool for examination of its effectiveness and side effects. METHODS AND RESULTS: A biophysical model of the human atria based on magnetic resonance imaging derived geometry and a membrane kinetics model was used. Uniform conduction properties were assigned to the monolayer surface representing the atria. After induction of AF by burst pacing, progressively broader ablation patterns were applied: (A) individual pulmonary vein isolation (PVI); (B) double ipsilateral PVI; (C) double PVI with a roofline; (D) double PVI with a lateral mitral isthmus line, and (E) double PVI with both linear lesions. In addition, the influence of incomplete linear lesions and dilated atria were simulated. The incidence of AF termination was found to increase from pattern (A) to (E). Atrial flutter rate increased with incomplete ablations and in dilated atria. CONCLUSION: Computer simulation of various ablation patterns in persistent AF is feasible and can reproduce clinical results of catheter ablation. This model can be used to develop and simulate new ablation patterns and anticipate success rates and potential adverse effects.

Dual-loop circuits in postoperative atrial macro re-entrant tachycardias.

BACKGROUND: Patients may develop dual-loop re-entrant atrial arrhythmias late after open-heart surgery, and mapping and catheter ablation remain challenging despite computer-assisted mapping techniques. OBJECTIVES: The purpose of the study was to demonstrate the prevalence and characteristics of dual-loop re-entrant arrhythmias, and to define the optimal mapping and ablation strategy. METHODS: 40 consecutive patients (mean (SD) age 52 (12) years) with intra-atrial re-entrant tachycardia (IART) after open-heart surgery (with an incision of the right atrial free wall) were studied. Dual-loop IART was defined as the presence of two simultaneous atrial circuits. After an abrupt tachycardia change during radiofrequency ablation, electrical disconnection of the targeted re-entry isthmus from the remaining circuit was demonstrated by entrainment mapping. Furthermore, the second circuit loop was localised using electroanatomical mapping and/or entrainment mapping. RESULTS: Dual-loop IART was demonstrated in eight (20%, 5 patients with congenital heart disease, 3 with acquired heart disease) patients. Dual-loop IART included an isthmus-dependant atrial flutter combined with a re-entry related to the atriotomy scar. The diagnosis of dual-loop IART required the comparison of entrainment mapping before and after tachycardia modification. Overall, 35 patients had successful radiofrequency ablation (88%). Success rates were lower in patients with dual-loop IART than in patients without dual-loop IART. Ablation failures in three patients with dual-loop IART were related to the inability to properly transect the second tachycardia isthmus in the right atrial free wall. CONCLUSIONS: Dual-loop IART is relatively common after heart surgery involving a right atriotomy. Abrupt tachycardia change and specific entrainment mapping manoeuvres demonstrate these circuits. Electroanatomical mapping appears to be important to assist catheter ablation of periatriotomy circuits.

The stepwise ablation approach for chronic atrial fibrillation--evidence for a cumulative effect.

Treatment options for atrial fibrillation (AF) have evolved from simple, fluoroscopy-guided pulmonary vein isolation for those patients with paroxysmal AF to complex, multi-modality procedures targeting not only anatomic structures but also electrophysiologic phenomena including complex fractionated electrograms, sites of dominant frequency and local non-venous drivers in patients with persistent and permanent AF. The stepwise ablation approach is a novel technique whereby structures contributing to initiation and maintenance of AF are sequentially targeted by radiofrequency ablation. Broadly divided into pulmonary veins, left atrial (LA) roof, left atrium (incorporating all anatomic regions of the chamber), mitral isthmus and non-LA structures, each region is targeted in sequence and the impact of ablation upon the global fibrillatory process assessed by measurement of AF cycle length (AFCL) at a site remote from the ablation target. In addition to pulmonary vein electrical disconnection and demonstrable complete conduction block across the roof and mitral isthmus lines (when performed), ablation is performed at those sites displaying continuous electrical and complex fractionated activity, with the endpoint of local organization, as well as at sites displaying electrograms consistent with focal sources driving AF. Ablation is accompanied by a cumulative increase in the AFCL prior to termination of AF by conversion either directly to sinus rhythm or to an atrial tachycardia which is then mapped conventionally and ablated. There is a ceiling of ablation within the LA beyond which further ablation is unlikely to result in a clinical benefit and should prompt evaluation of the contribution of the right atrium to maintenance of AF. The stepwise approach benefits from the integration of anatomic and electrophysiologic information to achieve a high level of success in termination of chronic AF by catheter ablation.

An approach to catheter ablation of cavotricuspid isthmus dependent atrial flutter.

Much of our understanding of the mechanisms of macro re-entrant atrial tachycardia comes from study of cavotricuspid isthmus (CTI) dependent atrial flutter. In the majority of cases, the diagnosis can be made from simple analysis of the surface ECG. Endocardial mapping during tachycardia allows confirmation of the macro re-entrant circuit within the right atrium while, at the same time, permitting curative catheter ablation targeting the critical isthmus of tissue located between the tricuspid annulus and the inferior vena cava. The procedure is short, safe and by demonstration of an electrophysiological endpoint - bidirectional conduction block across the CTI - is associated with an excellent outcome following ablation. It is now fair to say that catheter ablation should be considered as a first line therapy for patients with documented CTI-dependent atrial flutter.

Frequency mapping of the pulmonary veins in paroxysmal versus permanent atrial fibrillation.

INTRODUCTION: The pulmonary veins (PVs) are a dominant source of triggers initiating atrial fibrillation (AF). While recent evidence implicates these structures in the maintenance of paroxysmal AF, their role in permanent AF is not known. The current study aims to compare the contribution of PV activity to the maintenance of paroxysmal and permanent AF. METHODS AND RESULTS: Thirty-four patients with paroxysmal AF (n = 20) or permanent AF (n = 14) undergoing ablation were studied. Prior to ablation, 32 seconds of electrograms were acquired from each PV and the coronary sinus (CS). The frequency of activity of each PV and CS was defined as the highest amplitude frequency on spectral analysis. The effects of ablation on the AF cycle length (AFCL) and frequency and on AF termination were determined. Significant differences were observed between paroxysmal and permanent AF. Paroxysmal AF demonstrates higher frequency PV activity (11.0 +/- 3.1 vs 8.8 +/- 3.0 Hz; P = 0.0003) but lower CS frequency (5.8 +/- 1.2 vs 6.9 +/- 1.4 Hz; P = 0.01) and longer AFCL (182 +/- 17 vs 158 +/- 21 msec; P = 0.002), resulting in greater PV to atrial frequency gradient (7.2 +/- 2.2 vs 4.2 +/- 2.9 Hz; P = 0.006). PV isolation in paroxysmal AF resulted in a greater decrease in atrial frequency (1.0 +/- 0.7 vs -0.05 +/- 0.4 Hz; P < 0.0001), greater prolongation of the AFCL (49 +/- 35 vs 5 +/- 6 msec; P < 0.0001), and more frequent AF termination (11/20 vs 0/14; P = 0.0007) compared to permanent AF. CONCLUSION: Paroxysmal AF is associated with higher frequency PV activity and lesser CS frequency compared to permanent AF. Isolation of the PVs had a greater impact on the fibrillatory process in paroxysmal AF compared to permanent AF, suggesting that while the PVs have a role in maintaining paroxysmal AF, these structures independently contribute less to the maintenance of permanent AF.

Characterization of conduction recovery across left atrial linear lesions in patients with paroxysmal and persistent atrial fibrillation.

BACKGROUND: Left atrial (LA) linear lesions are effective in substrate modification for atrial fibrillation (AF). However, achievement of complete conduction block remains challenging and conduction recovery is commonly observed. The aim of the study was to investigate the localization of gap sites of recovered LA linear lesions. METHODS AND RESULTS: Forty-eight patients with paroxysmal (n = 26) and persistent/permanent (n = 22) AF underwent repeat ablation after pulmonary vein (PV) isolation and LA linear ablation at the LA roof and/or mitral isthmus due to recurrences of AF or flutter. In 35 patients, conduction through the mitral isthmus line (ML) had recovered whereas roof-line recovery was observed in 30 patients. The gaps within the ML were distributed to the junction between left inferior PV and left atrial appendage in 66%, the middle part of the ML in 20%, and in 8% to the endocardial aspect of the ML while only 6% of lines showed an epicardial site of recovery. The RL predominantly recovered close to the right superior PV (54%) and less frequently in the mid roof or close to the left PV (both 23%). Reablation of lines required significantly shorter RF durations (ML: 7.24 +/- 5.55 minutes vs 24.08 +/- 9.38 minutes, RL: 4.24 +/- 2.34 minutes vs 11.54 +/- 6.49 minutes; P = 0.0001). Patients with persistent/permanent AF demonstrated a significantly longer conduction delay circumventing the complete lines than patients with paroxysmal AF (228 +/- 77 ms vs 164 +/- 36 ms, P = 0.001). CONCLUSIONS: Gaps in recovered LA lines were predominantly located close to the PVs where catheter stability is often difficult to achieve. Shorter RF durations are required for reablation of recovered linear lesions. Conduction times around complete LA lines are significantly longer in patients with persistent/permanent AF as compared to patients with paroxysmal AF.

Fibrillating areas isolated within the left atrium after radiofrequency linear catheter ablation.

INTRODUCTION: Nonpulmonary vein sources have been implicated as potential drivers of atrial fibrillation (AF). This observational study describes regions of fibrillating atrial tissue isolated inadvertently from the left atrium (LA) following linear catheter ablation for AF. METHODS AND RESULTS: We report four patients with persistent/permanent AF who underwent pulmonary vein isolation with additional linear lesions and who presented with recurrent AF (mean AF cycle length [AFCL] 175-270 ms). Further catheter ablation resulted in the inadvertent electrical isolation of significant areas of the LA in which AF persisted at the same AFCL as was measured prior to disconnection, despite the restoration of sinus rhythm (SR) in all other left and right atrial areas, strongly suggesting that these islands were driving the remaining atria into fibrillation. The disconnected areas were located in the lateral LA, including the left atrial appendage (LAA) in three patients (limited to the LAA in one) and in the posterior LA in one patient. These isolated fibrillating regions represented 15-24% of the global LA surface, as estimated by electroanatomic mapping. CONCLUSION: Fibrillation can be maintained within electrically isolated regions of the LA following catheter ablation of AF, demonstrating the importance of atrial drivers in the maintenance of AF. Further mapping of these drivers is needed to characterize their mechanism and thereby allow for a more specific ablation strategy.

Phrenic nerve injury after atrial fibrillation catheter ablation: characterization and outcome in a multicenter study.

OBJECTIVES: The purpose of this study was to characterize the occurrence of phrenic nerve injury (PNI) and its outcome after radiofrequency (RF) ablation of atrial fibrillation (AF). BACKGROUND: It is recognized that extra-myocardial damage may develop owing to penetration of ablative energy. METHODS: Between 1997 and 2004, 3,755 consecutive patients underwent AF ablation at five centers. Among them, 18 patients (0.48%; 9 male, 54 +/- 10 years) had PNI (16 right, 2 left). The procedure consisted of pulmonary vein (PV) isolation in 15 patients and anatomic circumferential ablation in 3 patients, with additional left atrial lesions (n = 11) and/or superior vena cava (SVC) disconnection (n = 4). RESULTS: Right PNI occurred during ablation of right superior PV (n = 12) or SVC disconnection (n = 3). Left PNI occurred during ablation at the left atrial appendage. Immediate features were dyspnea, cough, hiccup, and/or sudden diaphragmatic elevation in 9, and in the remaining the diagnosis was made after ablation owing to dyspnea (n = 7) or on routine radiographic evaluation (n = 2). Four patients (22%) were asymptomatic. Complete recovery occurred in 12 patients (66%). Recovery occurred within 24 h in the two patients with left PNI and in one patient with right PNI occurring with SVC disconnection. In the other nine patients, right PNI recovery occurred after 4 +/- 5 months (1 to 12 months) with respiratory rehabilitation. After a mean follow-up of 36 +/- 33 months, six patients have persistent PNI (three with partial and three with no recovery). CONCLUSIONS: In this multicenter experience, PNI was a rare complication (0.48%) of AF ablation. Ablation of the right superior PV, SVC, and left atrial appendage were associated with PNI. Complete (66%) or partial (17%) recovery was observed in the majority.

Sites of focal atrial activity characterized by endocardial mapping during atrial fibrillation.

OBJECTIVES: The aim of the present study was to assess the feasibility of identifying sites of focal atrial activity by localized high-density endocardial mapping during atrial fibrillation (AF). BACKGROUND: Sites of focal activity in the left atrium have been demonstrated by epicardial mapping during AF. METHODS: Twenty-four patients (15 with paroxysmal, 3 with persistent, and 6 with permanent AF) underwent endocardial mapping during AF. A 20-pole catheter with five radiating spines was used to map both atria for 30 s in each of 10 pre-determined segments. A focal activity was defined as > or =3 atrial cycles with activation spreading from center to periphery of the mapping catheter. Catheter ablation was performed independent of the mapping results. RESULTS: Spontaneous focal activities were observed in 13 sites in the left atrium (9%; anterior 1, roof 2, posterior 6, inferior 4) in 12 patients (9 paroxysmal, 3 persistent). Focal activity was observed continuously (two sites) or intermittently (11 sites, median 5 episodes), and associated with shortening of the cycle length (from 183 +/- 33 ms to 172 +/- 29 ms; p < 0.05). The mean duration of an intermittent episode was 1.5 s (range 0.4 to 7.1 s). Atrial fibrillation terminated without ablation at the foci in all of 12 patients, but in 2 of them, re-initiated arrhythmia was successfully ablated at these foci. Nine of these 12 patients (75%) were arrhythmia-free without antiarrhythmic drugs during a follow-up period of 7.0 +/- 3.1 months. CONCLUSIONS: Termination of AF without ablation at the sites of atrial focal activity suggests that this activity may be triggered by impulses originating from other regions, such as the pulmonary veins.

Organization of frequency spectra of atrial fibrillation: relevance to radiofrequency catheter ablation.

INTRODUCTION: We hypothesized that the frequency spectra of fibrillatory electrograms may reflect the complexity of activities perpetuating atrial fibrillation (AF). To test this hypothesis, we evaluated the frequency spectra in patients with paroxysmal AF in relation to catheter ablation. METHODS AND RESULTS: This study comprised two protocols: 25 patients undergoing pulmonary vein (PV) isolation in protocol I, and 20 patients undergoing mitral isthmus linear ablation after PV isolation in protocol II. The mean of dominant frequency (DF) and organization index (the ratio of the area under the DF and its harmonics to the total power) were determined from 32-second recordings in the coronary sinus. In protocol I, a PV was considered "driver" of AF if isolation of the PV resulted in termination or slowing of AF (decrease in DF by > or =0.25 Hz). Twenty-one patients had AF termination during four PV isolation. Among these 21 patients, 13 patients with single driving PV showed significantly higher baseline organization index than eight patients with multiple driving PVs (0.45 +/- 0.08 vs 0.35 +/- 0.07, P = 0.009). Patients with multiple driving PVs showed a significant increase in the organization index to 0.45 +/- 0.11 (P < 0.05) after isolation of the initial driving PVs. In protocol II, the baseline organization index was significantly higher in seven patients who had termination of AF during mitral isthmus ablation than 13 patients who did not (0.50 +/- 0.10 vs 0.38 +/- 0.07, P < 0.008). The baseline DF was not associated with outcomes of ablation in both protocols. CONCLUSIONS: A higher organization index of atrial electrograms is associated with termination of AF during limited ablation. This parameter may be useful to anticipate the extent of ablation.

Flutter localized to the anterior left atrium after catheter ablation of atrial fibrillation.

INTRODUCTION: Organized atrial arrhythmias following atrial fibrillation (AF) ablation are typically due to recovered pulmonary vein (PV) conduction or reentry at incomplete ablation lines. We describe the role of nonablated anterior left atrium (LA) in arrhythmias observed after AF ablation. METHODS: A total of 275 consecutive patients with paroxysmal (n = 200) or chronic (n = 75) AF had PV isolation with/without additional linear ablation at the mitral isthmus (n = 106), LA roof (n = 23), or both (n = 88). Organized arrhythmias occurring after ablation were evaluated utilizing activation and entrainment mapping. RESULTS: Fourteen patients (11 female, 65 +/- 13 years, 10 chronic AF, 10 structural heart disease) demonstrated tachycardia localized to the anterior LA, an area not targeted by prior ablation. Eight had ECG features during sinus rhythm suggestive of impaired anterior LA conduction at baseline. These arrhythmias demonstrated a distinctive ECG flutter morphology in 7 of 10 (70%) with discrete -/+ or +/-/+ aspect in inferior leads. Mapping the anterior LA revealed electrograms spanning the entire tachycardia cycle length (325 +/- 125 msec). Entrainment was possible in all with a postpacing interval exceeding the tachycardia cycle length by 9 +/- 10 msec. Electroanatomic mapping in 6 demonstrated small reentrant circuits rotating clockwise in 4 and counterclockwise in 2. Low-amplitude, fractionated mid-diastolic potentials with long duration (200 +/- 80 msec) occupying 63 +/- 22% of the cycle length were targeted for ablation resulting in termination and subsequent noninducibility. CONCLUSION: Organized arrhythmias occurring after AF ablation can be due to reentrant circuits localized to the anterior LA, predominantly in females with chronic AF, structural heart disease, and abnormal atrial conduction. They are characterized by a distinctive surface ECG and highly responsive to RF ablation at the slow conduction area.