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Introduction: Inappropriate shocks remain a highly challenging complication of implantable cardioverter defibrillators (ICD). We examined whether automatic wireless remote monitoring (RM) of ICD, by providing early notifications of triggering events, lowers the incidence of inappropriate shocks., Methods and Results: We studied 433 patients randomly assigned to RM (n = 221; active group) versus ambulatory follow-up (n = 212; control group). Patients in the active group were seen in the ambulatory department once a year, unless RM reported an event requiring an earlier ambulatory visit. Patients in the control group were seen in the ambulatory department every 6 months. The occurrence of first and further inappropriate shocks, and their causes in each group were compared. The characteristics of the study groups, including pharmaceutical regimens, were similar. Over a follow-up of 27 months, 5.0% of patients in the active group received ≥1 inappropriate shocks versus 10.4% in the control group (P = 0.03). A total of 28 inappropriate shocks were delivered in the active versus 283 in the control group. Shocks were triggered by supraventricular tachyarrhythmias (SVTA) in 48.5%, noise oversensing in 21.2%, T wave oversensing in 15.2%, and lead dysfunction in 15.2% of patients. The numbers of inappropriate shocks delivered per patient, triggered by SVTA and by lead dysfunction, were 74% and 98% lower, respectively, in the active than in the control group., Conclusion: RM was highly effective in the long-term prevention of inappropriate ICD shocks., (© 2014 Wiley Periodicals, Inc.)

Objective: To evaluate the safety and outcomes of mitral isthmus (MI) linear ablation with temporary spot occlusion of the coronary sinus (CS)., Background: CS blood flow cools local tissue precluding transmurality and bidirectional block across MI lesion., Methods: In a randomized, controlled trial (CS-occlusion = 20, Control = 22), MI ablation was performed during continuous CS pacing to monitor the moment of block. CS was occluded at the ablation site using 1 cm spherical balloon, Swan-Ganz catheter with angiographic confirmation. Ablation was started at posterior mitral annulus and continued up to left inferior pulmonary vein (LIPV) ostium using an irrigated-tip catheter. If block was achieved, balloon was deflated and linear block confirmed. If not, additional ablation was performed epicardially (power ≤25 W). Ablation was abandoned after ∼30 minutes, if block was not achieved., Results: CS occlusion (mean duration -27 ± 9 minutes) was achieved in all cases. Complete MI block was achieved in 13/20 (65%) and 15/22 (68%) patients in the CS-occlusion and control arms, respectively, P = 0.76. Block was achieved with significantly small number (0.5 ± 0.8 vs 1.9 ± 1.1, P = 0.0008) and duration (1.2 ± 1.7 vs 4.2 ± 3.5 minutes, P = 0.009) of epicardial radiofrequency (RF) applications and significantly lower amount of epicardial energy (1.3 ± 2.4 vs 6.3 ± 5.7 kJ, P = 0.006) in the CS-occlusion versus control arm, respectively. There was no difference in total RF (22 ± 9 vs 23 ± 11 minutes, P = 0.76), procedural (36 ± 16 vs 39 ± 20 minutes, P = 0.57), and fluoroscopic (13 ± 7 vs 15 ± 10 minutes, P = 0.46) durations for MI ablation between the 2 arms. Clinically uneventful CS dissection occurred in 1 patient, Conclusions: Temporary spot occlusion of CS is safe and significantly reduces the requirement of epicardial ablation to achieve MI block. It does not improve overall procedural success rate and procedural duration. Tissue cooling by CS blood flow is just one of the several challenges in MI ablation., (© 2012 Wiley Periodicals, Inc.)

Background: The "sequential ablation" strategy for persistent AF is aimed at progressive organization of AF until the rhythm converts to sinus rhythm or atrial tachycardia (AT). During ablation of an AT, apparently seamless transitions from one organized AT to another occur. The purpose of our study was to quantify the occurrence and the mechanism of this transition., Methods and Results: Twenty-nine of 90 patients undergoing ablation for persistent AF had multiple AT during the procedure and constitute the study group. Thirty-nine direct transitions from one AT to another during ablation were observed classified in four types: type I (79.4%), i.e., a direct transition of a faster to a slower tachycardia without significant intervening pause; type II (7.69%)--transition after intervening ectopy or longer pause; type III (10.26%)--A slower AT accelerated; type IV (2.56%)--alteration of activation sequence but with no change on CL., Conclusions: Transition to a second AT occurs frequently in the midst of ablation of AT in persistent AF patients. This transition occurs most commonly abruptly within the range of a single cycle length of the original AT. This is best explained by a continuation of AT that was "present" simultaneously with the pretransition tachycardia, being "entrained" (for a reentrant tachycardia) or "overdriven" for an automatic focal tachycardia. The presence of multiple tachycardia mechanisms active simultaneously would be consistent with the eclectic pathophysiology of persistent AF., (© 2010 Wiley Periodicals, Inc.)

Introduction: The influence of the autonomic nervous system on the pathogenesis of complex fractionated atrial electrograms (CFAE) during atrial fibrillation (AF) is incompletely understood. This study evaluated the impact of pharmacological autonomic blockade on CFAE characteristics., Methods and Results: Autonomic blockade was achieved with propanolol and atropine in 29 patients during AF. Three-dimensional maps of the fractionation degree were made before and after autonomic blockade using the Ensite Navx system. In 2 patients, AF terminated following autonomic blockade. In the remaining 27 patients, 20,113 electrogram samples of 5 seconds duration were collected randomly throughout the left atrium (10,054 at baseline and 10,059 after autonomic blockade). The impact of autonomic blockade on fractionation was assessed by blinded investigators and related to the type of AF and AF cycle length. Globally, CFAE as a proportion of all atrial electrogram samples were reduced after autonomic blockade: 61.6 +/- 20.3% versus 57.9 +/- 23.7%, P = 0.027. This was true/significant for paroxysmal AF (47 +/- 23% vs 40 +/- 22%, P = 0.003), but not for persistent AF (65 +/- 22% vs 62 +/- 25%, respectively, P = 0.166). Left atrial AF cycle length prolonged with autonomic blockade from 170 +/- 33 ms to 180 +/- 40 ms (P = 0.001). Fractionation decreases only in the 14 of 27 patients with a significant (>6 ms) prolongation of the AF cycle length (64 +/- 20% vs 59 +/- 24%, P = 0.027), whereas fractionation did not reduce when autonomic blockade did not affect the AF cycle length (58 +/- 21% vs 56 +/- 25%, P = 0.419)., Conclusions: Pharmacological autonomic blockade reduces CFAE in paroxysmal AF, but not persistent AF. This effect appears to be mediated by prolongation of the AF cycle length.

Background: Atrial tachycardia (AT) occurring following catheter ablation of persistent atrial fibrillation (AF) may be challenging to map and ablate because their mechanism and location is unpredictable and may be multiple in an individual patient., Methods and Results: A prospective cohort of 128 consecutive patients presenting 246 AT in the context of prior AF ablation was investigated. Using activation and entrainment mapping and applying the consensus definition of AT, we evaluated a deductive diagnostic approach based on up to three steps: (1) cycle length regularity, (2) search for macroreentry (i.e., involving >2 separate atrial segments), and (3) if macroreentry excluded, search for focal origin giving a centrifugal activation of the atria. A total of 238/246 (97%) sustained AT (mean cycle length [CL] 284 +/- 87 ms) were successfully mapped (single AT, 51 pts; multiple AT, 77 pts) with a diagnostic time of 10 +/- 8 min per tachycardia. AT were macroreentrant in 109 (46%) and focal in 129 (54%). Of the latter, only 34 focal AT originated from a discrete point site fulfilling the consensus criteria, while a distinct mechanism, localized reentry (AT that was neither macro reentry nor focal), was identified in 95. Localized reentry was defined by (1) electrograms covering >or=75% of the cycle length of AT within an area covering a single or 2 contiguous segments, (2) postpacing interval (PPI) < 30 ms at the site, (3) an identifiable zone of slow conduction, and (4) centrifugal activation of the atrium from the area., Conclusions: This prospective study demonstrates the feasibility of rapid and accurate identification of all types of postablation AT in a large cohort of patients and describes the dominant role of localized reentry as a novel mechanism of AT.

Introduction: A patent foramen ovale (PFO) is located at the anterior and superior part of the anatomical interatrial septum, the area that is targeted during transseptal puncture. This study sought to investigate the impact of accessing the left atrium via a PFO on paroxysmal AF ablation., Methods: From March 2004, 203 patients (55 +/- 11 years) underwent catheter ablation for paroxysmal AF (80 +/- 71 months), with the endpoint being electrical isolation of all pulmonary veins (PV) and AF noninducibility. The presence of a PFO was determined by both transesophageal echocardiography and catheter probing. Procedural difficulty was evaluated by radiofrequency (RF), procedural, and fluoroscopic durations. Clinical follow-up was also investigated., Results: A PFO was detected in 27 patients (13%) by transesophageal echocardiography and in 22 additional patients (total 49 patients, 24%), by catheter probing (P < 0.001). A PFO was associated with longer total RF applications (57 +/- 19 vs 51 +/- 18 min, P = 0.04) and RF applications to isolate the PVs (42 +/- 16 vs 35 +/- 12 min, P = 0.001). Procedural and fluoroscopic times were unaffected. Seventy-three patients (36%) required a second procedure; there was no difference in the number of PV reconnections (1.3 vs 1.8 veins, P = NS). After a mean follow-up of 19 +/- 9 months, 194/203 patients (96%) were free of AF, with no difference in patients in whom a PFO had been used., Conclusion: Although isolation of PVs is longer, overall procedural duration and success is not affected when using a PFO compared with a transseptal puncture. The presence of a PFO is underestimated by transesophageal echocardiography with brachial injection when compared with catheter probing.

Unlabelled: Women with Brugada Syndrome., Introduction: Spontaneous type-1 ECG has been recognized as a risk factor for sudden cardiac death (SCD) in Brugada syndrome (BrS), but studied populations predominantly consisted of men. We sought to investigate whether a spontaneous type-1 ECG pattern was also associated in women with severely symptomatic BrS. Other known risk factors were also examined for gender specificity., Methods: Patients with severely symptomatic BrS, defined as resuscitated SCD and/or appropriate implantable cardioverter-defibrillator (ICD) shock, were included from 11 European centers. Clinical data, investigation of family history, 12-lead ECG, and results of electrophysiological study (EPS) were collected. The average follow-up was 4 +/- 3 years., Results: Fifty-eight patients fulfilled the inclusion criteria (mean age 47 +/- 11 years, 8 women). Thirty-six men (72%) but only two women (25%) had a spontaneous type-1 ECG at baseline (P = 0.02). Maximal ST elevation before or after drug challenge was 3.7 +/- 1.3 mm in men versus 2.4 +/- 0.7 mm in women (P = 0.007). The proportion of patients with a family history of SCD or an SCN5A mutation was not significantly different between both groups. Of those patients with high-risk BrS who underwent EPS, 76%(12/25) of men and 50%(2/4) of women had a positive study., Conclusion: In contrast to men, most women with BrS and resuscitated SCD or appropriate ICD shock do not have a spontaneous type-1 ECG pattern. In addition, the degree of ST elevation is less pronounced in women than men. While women represent a lower-risk group overall, risk factors established from a predominantly male population may not be helpful in identifying high-risk females.

Introduction: The coronary sinus (CS) is a complex structure comprising a mesh of circumferential muscular fibers with oblique connections to both atria. We describe further evidence for the clinical importance of CS arrhythmogenicity in maintaining atrial fibrillation (AF) in humans., Methods: Since January 2004, following a sequential approach, the CS and the inferior left atrium were ablated in 144 patients with symptomatic drug refractory AF. Patients were included for analysis when this step resulted in the electrical dissociation of the CS from both atria with restoration of sinus rhythm, but with continued arrhythmic activity in the CS. The electrophysiologic mechanism of the confined arrhythmia was considered as focal activity (automaticity or triggered activity) by the presence of electrograms spanning less than 75% of the cycle length in the CS., Results: After restoration of sinus rhythm, four male patients (3% of the patients, three persistent and one permanent AF) were identified in whom arrhythmia continued within the CS. Repetitive activity confined to the disconnected CS was inconsistent in occurrence, as well as in duration (1 sec to 15 min) and cycle length (from 158 to 380 ms). For all four patients, electrogram mapping of the entire CS was compatible with a focal mechanism. In two patients, bursts alternating with slow dissociated activity suggested automaticity. In one patient, local activity consistently coupled to the previous sinus beat favored triggered activity., Conclusions: This study provides evidence that the CS may be a potential source of focal rapid activity maintaining AF.

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.

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.

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.

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.

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.

Background: Catheter ablation of atrial fibrillation (AF) is challenging in patients with long-standing persistent AF. The clinical outcome and subsequent arrhythmia recurrence after using an ablation method targeting multiple left atrial sites with the aim of achieving acute AF termination has not been characterized., Methods: Sixty patients (mean age: 53 +/- 9 years) with persistent AF (mean duration: 17 +/- 27 months) were prospectively followed after catheter ablation. Catheter ablation targeting the following sites was performed in a random sequence: (i) electrical isolation of all pulmonary veins (PV); (ii) disconnection of other thoracic veins; (iii) atrial ablation at sites possessing complex electrical activity, activation gradients, or short cycle lengths. Finally, linear ablation of the LA roof and mitral isthmus was performed if sinus rhythm was not restored following energy delivery to the above sites. At 1, 3, 6, and 12 months after ablation, patients underwent clinical review and 24-hour ambulatory ECG monitoring to identify asymptomatic arrhythmia. Repeat mapping and catheter ablation was performed in any patient experiencing recurrent atrial tachycardia (AT). Clinical success was defined as the absence of any sustained atrial arrhythmia., Results: AF terminated during ablation in 52 patients (87%). The fluoroscopy and procedural durations were 84 +/- 30 minutes and 264 +/- 77 minutes, respectively. Three months after ablation, sustained ATs were documented in 24 patients (associated with AF in 2). Mapping in 23 patients showed a single AT in 7 while multiple ATs were observed in 16. Macroreentry was confirmed to be due to gaps in the ablation lines, while focal ATs originated from discrete sites or isthmuses near the left atrial appendage, coronary sinus, pulmonary veins, or fossa ovalis; these sites were similar to those at which the greatest impact was observed on the fibrillatory process during the initial ablation procedure. After repeat ablation, at 11 +/- 6 months of follow-up, 57 patients (95%) were in sinus rhythm and 3 developed recurrent AF or AT. All patients in sinus rhythm demonstrated improved exercise capacity and all but 2 had evidence of atrial transport as assessed by Doppler echocardiography (mitral A wave velocity 34 +/- 17 cm/sec) by 6 months., Conclusion: Catheter ablation of long-lasting persistent AF associated with acute AF termination achieves medium to long-term restoration and maintenance of sinus rhythm in 95% of patients. Arrhythmia recurrence in the majority of patients is AT.

Background: The relative contributions of different atrial regions to the maintenance of persistent atrial fibrillation (AF) are not known., Methods: Sixty patients (53 +/- 9 years) undergoing catheter ablation of persistent AF (17 +/- 27 months) were studied. Ablation was performed in a randomized sequence at different left atrial (LA) regions and comprised isolation of the pulmonary veins (PV), isolation of other thoracic veins, and atrial tissue ablation targeting all regions with rapid or heterogeneous activation or guided by activation mapping. Finally, linear ablation at the roof and mitral isthmus was performed if sinus rhythm was not restored after addressing the above-mentioned areas. The impact of ablation was evaluated by the effect on the fibrillatory cycle length in the coronary sinus and appendages at each step. Activation mapping and entrainment maneuvers were used to define the mechanisms and locations of intermediate focal or macroreentrant atrial tachycardias., Results: AF terminated in 52 patients (87%), directly to sinus rhythm in 7 or via the ablation of 1-6 intermediate atrial tachycardias (total 87) in 45 patients. This conversion was preceded by prolongation of fibrillatory cycle length by 39 +/- 9 msec, with the greatest magnitude occurring during ablation at the anterior LA, coronary sinus and PV-LA junction. Thirty-eight atrial tachycardias were focal (originating dominantly from these same sites), while 49 were macroreentrant (involving the mitral or cavotricuspid isthmus or LA roof). Patients without AF termination displayed shorter fibrillatory cycles at baseline: 130 +/- 14 vs 156 +/- 23 msec; P = 0.002., Conclusion: Termination of persistent AF can be achieved in 87% of patients by catheter ablation. Ablation of the structures annexed to the left atrium-the left atrial appendage, coronary sinus, and PVs-have the greatest impact on the prolongation of AF cycle length, the conversion of AF to atrial tachycardia, and the termination of focal atrial tachycardias.

Occlusion of LCX During RF Catheter Ablation. We report a case of acute occlusion of the left circumflex coronary artery during catheter ablation in the coronary sinus to complete the linear lesion between the postero-lateral mitral annulus and the left inferior pulmonary vein for the treatment of atrial fibrillation.

Introduction: Ventricular fibrillation (VF) is the main mechanism of sudden cardiac death. The clinical precipitants of sudden cardiac death due to idiopathic VF are poorly characterized. Emerging evidence implicates triggers originating predominantly from the distal Purkinje arborization and the right ventricular outflow tract., Methods and Results: We report three patients without structural heart disease or repolarization abnormalities in whom a febrile illness was the only concurrent disease associated with unexpected sudden cardiac death due to VF storm. An automated defibrillator was implanted in all three patients. In one patient with persistent recurrent VF episodes, mapping demonstrated the origin of these triggers was from the Purkinje arborization of the anterior wall of the right ventricle. Ablation at a site of earliest activation during ectopy, where pace mapping was concordant and Purkinje potential preceded the onset of ventriculogram, resulted in suppression of all arrhythmias. After follow-up of 22, 9, and 18 months in the three patients, no ventricular arrhythmias have been recorded., Conclusion: We present a series of patients in whom an apparently benign febrile illness was associated with malignant ventricular arrhythmias in the absence of cardiac disease or other factors known to precipitate sudden cardiac death. Physicians should be aware of this possible phenomenon in cases of febrile illness associated with syncope.

Introduction: The incidence and characteristics of dissociated arrhythmia confined to the pulmonary vein (PV) following disconnection have not been described in a large number of patients with paroxysmal atrial fibrillation., Methods and Results: This was a prospective study of 152 patients (29 female, mean age 51 +/- 11 years) referred for catheter ablation of drug-refractory paroxysmal atrial fibrillation. Following ostial ablation, the rate and regularity of any dissociated venous activity was analyzed with and without isoproterenol infusion (to achieve a heart rate of 120-140 beats/min). Patients then were classified according to their venous dissociated activity. Group 1 consisted of patients in whom the dissociated PV spike had a slow rhythm >1,200 ms. Group 2 consisted of patients with spontaneous repetitive dissociated discharges confined in the vein with a cycle length <400 ms. A total of 384 PVs were ablated in 152 patients. Disappearance of all venous potentials was observed in 88% of the treated veins; at least one dissociated venous potential was observed in the remaining 12%. Group 1 activity was seen more often than group 2 (23 patients, mean cycle length 2,300 +/- 1,100 ms vs 13 patients, mean cycle length 179 +/- 77 ms). Dissociated PV arrhythmia was seen most often in the right superior PV (19%)., Conclusion: Dissociation as the endpoint of PV disconnection was observed in 12% of PVs. Due to the capricious nature of this activity, the actual incidence is almost certainly higher. The dissociated venous rhythm usually is slow and, less commonly, is rapid and repetitive.

Introduction: Catheter ablation for atrial fibrillation (AF) is associated with prolonged fluoroscopy times. We prospectively evaluated the use of the LocaLisa three-dimensional nonfluoroscopic catheter imaging system with the aim of reducing fluoroscopy times during pulmonary vein (PV) disconnection., Methods and Results: Fifty-two patients with AF (47 men and 5 women, mean age 53 +/- 9 years) underwent disconnection of all four PVs guided by a circumferential mapping catheter. The LocaLisa navigation system was used for real-time three-dimensional nonfluoroscopic imaging of the circumferential mapping catheter and ablation catheter electrodes in 26 patients. Procedural parameters were compared with those of a control group consisting of 26 patients in whom only standard fluoroscopy was used. PV disconnection was performed similarly in both groups by circumferential ablation around the ostia, with the endpoint of disconnecting left atrium to PV breakthroughs. The cumulative duration of radiofrequency (RF) energy delivery, procedural time, and fluoroscopy time required for PV disconnection were compared. Successful disconnection was achieved in all PVs, without acute complications. There was no significant difference in cumulative RF energy delivery: 34.8 +/- 11.4 minutes for the nonfluoroscopic imaging group versus 38.2 +/- 10.5 minutes for the control group. The fluoroscopy time required for disconnection of all four PVs was significantly lower in the LocaLisa group than in the control group: 8.4 +/- 4.3 minutes versus 23.7 +/- 9.7 minutes (P < 0.0001). There also was a significant difference in the mean time taken for PV disconnection: 46.5 +/- 12.0 minutes for the nonfluoroscopic imaging group versus 66.3 +/- 18.9 minutes for the control group (P < 0.0001)., Conclusion: By allowing continuous three-dimensional monitoring of ablation and mapping catheter position and orientation, the LocaLisa nonfluoroscopic imaging system significantly reduces fluoroscopy and PV disconnection times.

Introduction: Sustained atrial fibrillation (AF) is frequently encountered during pulmonary vein (PV) isolation. The aim of this study was to evaluate the feasibility and safety of PV isolation during sustained AF., Methods and Results: Thirty-seven patients (30 men, age 54 +/- 10 years) underwent Lasso-guided isolation of 87 PVs during sustained AF. Baseline PV electrogram patterns were classified into one of two types: organized, with consistent PV activation sequence; or disorganized, with constant variation of PV activation sequence. In disorganized activity, radiofrequency ablation was performed circumferentially around the Lasso while the earliest PV potential was targeted during organized activity. Complete left atrial (LA) to PV block during AF was identified by abolition or dissociation of all sharp potentials recorded within the vein. PV isolation then was verified during sinus rhythm. Baseline activation patterns of PV potential were organized in 32 PVs (37%) [more frequently in inferior veins than superior veins (53% vs 26%, P = 0.01)] and disorganized in 55 PVs (63%). In 59 of 87 PVs, isolation was begun and completed during AF. Radiofrequency ablation organized PV activation sequence in 75% prior to isolation. LA-PV block was confirmed during sinus rhythm in 54 (92%) of 59 PVs. In 28 of 87 PVs, sinus rhythm was restored before complete LA-PV block. Complete isolation was achieved in all 87 PVs without complications., Conclusion: PV isolation can be effectively and safely performed during sustained AF, preceded in most cases by organization of PV electrogram activity. This strategy may be the preferred alternative to multiple intraprocedural cardioversions.

Introduction: Catheter ablation of pulmonary veins (PV) for treatment of atrial fibrillation (AF) is limited by the disparate requirements of sufficient energy delivery to achieve PV isolation while avoiding PV stenosis. The aim of the present study was to evaluate the safety and efficacy of using an irrigated-tip catheter for systematic isolation of PV., Methods and Results: The study population consisted of 136 consecutive patients (109 men, mean age 52 +/- 10 years) with symptomatic, drug-refractory paroxysmal (122) or persistent (14) AF. Cavotricuspid isthmus ablation and systematic radiofrequency isolation of all four PVs (guided by a circumferential mapping catheter) was performed in all patients with a protocol using an irrigated-tip catheter. PV diameter was assessed by selective angiography. The electrophysiologic endpoint of PV isolation was achieved in 100% of patients. Bidirectional cavotricuspid isthmus block was achieved in 99% of patients. Moderate PV stenosis (50% narrowing) was observed in one patient (0.7%) without clinical consequence. No other complications were observed. Reablation procedures were required in 67 patients (49%). After a mean follow-up of 8.8 +/- 5.3 months, 81% of patients were free of AF clinical recurrence, including 66% not taking any antiarrhythmic drugs., Conclusion: Systematic radiofrequency ablation of PV using an irrigated-tip catheter in patients with atrial fibrillation allows complete isolation of all four PVs with a very low incidence of stenosis.

Superior Vena Cava Reentry. High-resolution mapping of a tachycardia originating from the superior vena cava (SVC) in a patient with atrial fibrillation is described. Unidirectional circuitous repetitive activation encompassing the full tachycardia cycle length was documented around a line of block within the myocardial sleeve of the SVC. Intermittent conduction to the right atrium resulted in an irregular atrial tachycardia. Evidence of electrical heterogeneity and slow conduction persisted in sinus rhythm and was exaggerated by premature stimulation but did not reproduce the activation pattern during tachycardia. All the available evidence is best compatible with circus movement reentry within the SVC, with marked slow and anisotropic conduction responsible for the restricted dimensions of the reentrant circuit. These findings may suggest a similar substrate and arrhythmia mechanism in the myocardium of the pulmonary veins.

Lone atrial fibrillation (AF) is defined by the absence of identifiable causes of AF, but its hemodynamics have not been investigated. Twenty-eight patients with lone AF were compared with 14 control patients referred for Wolff-Parkinson-White ablation. Transthoracic and transesophageal echocardiography were performed to rule out structural heart disease, followed by transseptally performed complete hemodynamic evaluation of the left heart systolic and diastolic function. There was no evidence of diastolic dysfunction according to echocardiographic criteria in AF and control patients. There was no difference in echocardiographic measurements, except for a significantly higher inferosuperior left atrial dimension seen in the four-chamber apical view in AF patients (51+/-10 vs 40+/-6 mm, P = 0.03). Hemodynamic evaluation showed that end-diastolic left ventricular pressure and the nadir of the left atrial Y descent were significantly higher in lone AF patients versus controls: 13+/-5 versus 8+/-3 mmHg (P = 0.001) and 6.7+/-3 versus 4.6+/-2.7 mmHg (P = 0.05). Our results demonstrated the presence of diastolic left heart dysfunction in patients with so-called lone AF.

Introduction: We assessed the mode of reinitiation of atrial fibrillation (AF) after cardioversion and the efficacy of ablating these foci of reinitiation in patients with chronic AF., Methods and Results: Fifteen patients, 7 with structural heart disease, underwent mapping and catheter ablation of drug-resistant AF documented to be persistent for 5 +/- 4 months. In all patients, cardioversion was followed by documentation of P on T atrial ectopy and early recurrence, which allowed mapping of the reinitiating trigger or the source of ectopy. Radiofrequency (RF) ablation was performed at pulmonary vein (PV) ostia using a target temperature of 50 degrees C and a power limit of 30 to 40 W, with the endpoint being interruption of all local muscle conduction. A total of 32 arrhythmogenic PVs and 2 atrial foci (left septum and left appendage) were identified: 1, 2, and 3 or 4 PVs in 5, 3, and 6 patients. RF applications at the ostial perimeter resulted in progressively increasing delay, followed by abolition of PV potentials in 8, but potentials persisted in 6. A single ablation session was performed in 7 patients and 8 underwent two or three sessions because of recurrence of AF; ablation was directed at the same source due to recovery of local PV potential or at a different PV. No PV stenosis was noted either acutely or at repeated follow-up angiograms. Nine patients (60%) were in stable sinus rhythm without antiarrhythmic drugs at follow-up of 11 +/- 8 months. Anticoagulants were interrupted in 7 patients., Conclusion: PVs are the dominant triggers reinitiating chronic AF in this patient population. Elimination of PV potentials by ostial RF applications results in stable sinus rhythm in 60%. A larger group and longer follow-up are needed to investigate further the role of trigger ablation in curative therapy for chronic AF.

Introduction: The efficacy and outcome of cavotricuspid isthmus ablation guided by local electrogram-based criteria of linear block were prospectively assessed., Methods and Results: In 40-consecutive patients (age 65+/-11 years) with typical right atrial (RA) flutter (cycle length = 255+/-31 msec), radiofrequency (RF) energy was delivered at electrograms in the isthmus coinciding with the center of the ECG plateau until termination of flutter, followed by local assessment of isthmus conduction during slow rate low-lateral RA pacing. 'Gaps' in the ablation line were located in the form of single or fractionated potentials centered on the isoelectric intervals of adjacent double potentials and ablated. Complete linear isthmus block was defined by the achievement of a complete corridor of parallel double potentials from the right ventricle to the inferior vena cava edge. Applications of 11+/-7 RF applications were required in all patients to achieve a complete line of double potentials separated by an isoelectric interval of 120+/-26 msec (range 60 to 190). After 6+/-3 RF applications, 6 (15%) patients had evidence of isthmus block using indirect RA activation sequence mapping without a complete line of double potentials. 5+/-5 further RF applications of eliminated local conduction and achieved complete linear block without altering descending septal RA activation. Conduction recovery occurred in 20 (50%) patients--1.85 times per patient-indicated by reversed changes in local electrograms eliminated by further ablation of the recovered gaps. After discharge, two recurrences (5%) occurred during a follow-up of 16+/-2 months., Conclusion: Double potential mapping is an effective assessment modality for local isthmus conduction. Slow conduction limited to the ablation line is observed during ablation in 15% of patients.

Introduction: Atrial fibrillation (AF), the most common arrhythmia, is due to multiple simultaneous wavelets of reentry in the atria. The only available curative treatment is surgical, using atriotomies to compartmentalize the atria. Therefore, we investigated a staged anatomical approach using radiofrequency catheter ablation lines to prevent paroxysmal AF., Methods and Results: Forty-five patients with frequent symptomatic drug-refractory episodes of paroxysmal AF were studied. Progressively complex linear lesions were created by sequential applications of radiofrequency current in the right atrium and then in the left atrium if required. The outcome of the procedure was considered a success when the episodes of AF were either eliminated or recurred at a rate of no more than one episode (lasting < 6 hours) in 3 months. Patients who had no more than one episode per month were considered "improved." Right atrial ablation organized local electrical activity and led to stable sinus rhythm during the procedure in 18 (40%) of the 45 patients. However, sustained AF remained inducible in 40 of 45 patients, and the lesions failed to produce evidence of a significant linear conduction block/delay in all but four patients. There were no significant complications except for two transient sinus node dysfunctions. The procedure duration and fluoroscopic time were 248 +/- 79 and 53 +/- 22 min, respectively. Additional sessions were required in 19 patients to treat sustained right atrial flutter or arrhythmias linked to ectopic right or left atrial foci. During a mean follow-up of 11 +/- 4 months, right atrial ablation was successful in 15 (33%) patients, 6 without medication and 9 with a previously ineffective drug. Nine (20%) additional patients were improved. Ten patients with an unsuccessful outcome then underwent linear ablation in the left atrium. The procedure duration and fluoroscopy time were 292 +/- 94 and 66 +/- 24 min. A hemopericardium occurred in one patient. Two patients required reablation to treat ectopic atrial foci. Left atrial ablation terminated AF during the procedure in 8 patients, and sustained AF could not be induced in 5. Subsequent success was achieved in 6 (60%) patients, including 4 without medication, and 1 additional patient was improved., Conclusions: Successful radiofrequency catheter ablation of drug-refractory daily paroxysmal AF is feasible using linear atrial lesions complemented by focal ablation targeted at arrhythmogenic foci. Ablation only in the right atrium is a safe technique providing limited success, whereas linear lesions in the left atrium significantly increase the incidence of stable restoration of sinus rhythm, the inability to induce sustained AF, and the final success rate. The described technique is promising but must be considered preliminary because significant improvements are required to optimize lesion characteristics and shorten total procedure duration.

Introduction: The purpose of this study was to evaluate the efficacy and safety of radiofrequency (RF) catheter ablation of common atrial flutter and to determine the optimum target sites in a large series of patients. Three different approaches were used to target the ablation site. The first used a combined anatomic and electrophysiologic approach, whereas the second and the third approaches relied primarily on anatomic guidelines to target the critical area in the atrial flutter reentrant circuit located in the low right atrium., Background: Recent studies report the efficacy of RF current application in the low right atrial region to interrupt and prevent recurrences of common atrial flutter using either anatomic or electrophysiologic targets. However, larger groups of patients are required to confirm the efficacy of this technique and to specify the target sites., Methods and Results: Two hundred consecutive patients with drug-resistant common atrial flutter were studied. In the first 50 patients, target sites were localized using both anatomic landmarks and electrophysiologic parameters. The anatomic landmarks were area 1 between the tricuspid valve and inferior vena cava orifice; area 2 between the tricuspid valve and coronary sinus ostium; and area 3 between the inferior vena and coronary sinus. The electrophysiologic criterion was to ablate when there was an atrial electrogram occurring during the plateau phase (preceding F wave). The first targeted area was that giving the more stable catheter position. In the following 30 patients, we assessed the effect of RF energy application in a single line to area 1 in the first 10 patients, area 2 in the next 10, and area 3 in the last 10 patients. In the last 120 patients, RF energy was applied only in area 1 using repeated applications. RF energy of 12 to 30 W, or that achieving a temperature of 70 degrees C, was applied for 60 to 90 seconds at each site. The endpoint of the ablation procedure was interruption and noninducibility of common atrial flutter in the first 110 patients and additional isthmal block in 48 of the last 90 patients. Overall, atrial flutter was interrupted and rendered noninducible after a single session in 191 (95%) patients and could not be interrupted in 9 (4.5%) patients. The mean number of RF applications was 12 +/- 8. After a mean follow-up of 24 +/- 9 months, recurrences occurred in 31 (15.5%) patients, 26 of whom underwent a successful second or third session without further recurrences of atrial flutter. Atrial fibrillation not documented before the ablation was detected in 11 patients. On a retrospective analysis of the final successful site in the first group of 50 patients, the location was in area 1 in 39% of patients; area 2 in 36% of patients, and area 3 in 25% of patients. Atrial electrograms recorded at these sites showed a single spike pattern in 46% of patients, and double spike pattern (28%) or fractioned electrogram in 26% patients. When lines of RF lesions were placed at several sites, they produced a success rate of 70%, 40%, and 10% at areas 1, 2, and 3 respectively. In the last series of 120 patients, the procedure was successful in 119 patients: 92% of whom were successfully treated only by a linear lesion between the tricuspid annulus isthmus and the inferior vena cava, and the other 8% by additional applications near the coronary sinus ostium. No complications were observed., Conclusions: RF catheter ablation of atrial flutter can be done with a high success rate and is safe. The highest success rate is achieved with RF energy applied in the isthmus between the inferior vena cava orifice and the tricuspid valve. However, 15.5% of patients need multiple sessions to achieve success because of recurrence of flutter. Further follow-up is needed to evaluate the long-term effects of this procedure.

Introduction: Catheter ablation of a case of incessant atrial fibrillation was attempted using linear right atrial lesions created by sequential applications of radiofrequency energy., Methods and Results: A 46-year-old patient had incessant episodes of atrial fibrillation. He had previously undergone successful radiofrequency catheter ablation of a common atrial flutter. Antiarrhythmic drugs including amiodarone and various drug combinations were ineffective. A 7-French specially designed 14-polar catheter with interelectrode distance of 3 mm was used to create linear lesions in the right atrium. Each electrode was 4 mm in length and able to transmit radiofrequency energy. Three linear lesions, two longitudinal and one transverse that connected the two longitudinal lesions, were created using 30 radiofrequency applications of 10 to 40 W. The final application interrupted an atrial fibrillation that had been persistent for 55 minutes. No sustained atrial fibrillation was inducible despite repeated pacing maneuvers. There was no complication. In short-term follow-up of 3 months, the patient has been free of arrhythmias without antiarrhythmic medication., Conclusion: Successful catheter ablation of human atrial fibrillation is feasible using linear atrial lesions created by radiofrequency energy delivery. Further studies are mandatory to ascertain the efficacy and safety of this procedure, as well as to assess different catheter techniques.

We present the case of a patient with episodes of supraventricular tachycardia and atrial dissociation that were terminated by either adenosine or verapamil. Involvement of an accessory pathway was shown by ventricular extrastimuli, elicited during His-bundle refractoriness, that interrupted the tachycardia or advanced the next His potential. The tachycardia circuit was demonstrated to be confined to the nodofascicular region based on the exclusion of surrounding tissues. Atrial activity, including that in the perinodal region, was totally dissociated during tachycardia. The lowest part of the circuit was determined to be located above the Hisian bifurcation, as multiple episodes with either a right or left bundle branch configuration during tachycardia did not modify the HH cycle. The ventricular septum summit was determined not to be involved, as no preexcitation was present during tachycardia or atrial pacing, and the right bundle branch was not part of the circuit. Radiofrequency current applied beneath the tricuspid valve at the His region successfully eliminated the nodofascicular connection with preservation of 1:1 AV conduction. The anatomical substrate underlying the abnormal connection may be either nodofasciculoventricular Mahaim fibers or a duality or dispersion of the nodo-Hisian conducting system.

Introduction: The purpose of this study was to test the feasibility of radiofrequency (RF) catheter ablation of localized mechanisms of atrial fibrillation (AF)., Methods and Results: Three patients underwent RF catheter ablation for drug-resistant atrial arrhythmias. The first two patients had either incessant atrial tachycardia or AF. In the first patient, the ECG pattern of AF was mimicked by a very rapid atrial focus, whereas in the second patient, AF was due to true degeneration of the atrial activity triggered by atrial tachycardia. In both patients, the ablation of atrial focus led to the clinical disappearance of AF. The third patient had frequent episodes of AF, which lasted several days or weeks, and two documented episodes of atrial flutter. Mapping during AF showed an irregular atrial rhythm in the atrial septum, particularly in the region surrounding the coronary sinus, whereas the entire lateral right atrial free wall exhibited a constantly organized rhythm. RF energy was applied between the tricuspid ring and both the inferior vena cava and the coronary sinus, resulting in inability to reinduce atrial flutter or sustained AF. A 6-month follow-up in this patient showed the disappearance of prolonged episodes of AF., Conclusion: The observations indicate that AF may be linked to "focal" mechanisms that can be treated by RF catheter ablation.

Catheter ablation techniques are now advocated as the first line of therapy for arrhythmias caused by accessory pathways (APs). The most common energy source is radiofrequency current, but technical characteristics vary. Several parameters can be used to determine the optimal target site: AP potential, AV time, atrial or ventricular insertion site, or unipolar morphology. Specific considerations are needed depending on AP location. Despite the different approaches described, there is no significant difference in the reported success rate, which is over 90%. However, the number of radiofrequency applications needed to achieve ablation appears to differ significantly, with median values from 3 to 8 reported. A combination of criteria related to both timing and direction of the activation wavefront or use of subthreshold stimulation could improve the accuracy of mapping. In patients with "resistant" APs, different changes in ablation technique must be considered during the procedure to achieve elimination of AP conduction. The incidence of complications in multicenter reports is close to 4%, with a recurrence rate of 8%. The long-term safety of catheter ablation requires further study.