Isthmus Block Research Articles

Does the amount of atrial mass reduction improve clinical outcomes after radiofrequency catheter ablation for long-standing persistent atrial fibrillation? Comparison between linear ablation and defragmentation

BackgroundAlthough a large isolated surface area of the left atrium (LA) may improve the success rate of catheter ablation (CA) for paroxysmal atrial fibrillation (AF), little is known about the relation between clinical outcomes and the amount of atrial mass reduction (AMR: ratio of total isolated and ablated areas to LA surface area) in different ablation strategies for patients with long-standing persistent AF (L-PeAF). MethodsWe randomly assigned 119 consecutive L-PeAF patients to adjunctive linear ablation (n=60) or complex fractionated atrial electrogram (CFAE)-guided ablation (n=59) after circumferential antral pulmonary vein isolation (PVI). Linear lesions included roof and anterior lines with conduction block. LA defragmentation was performed with an automated CFAE-detection algorithm. Cavotricuspid isthmus block was performed in all patients. Creatine kinase-MB (CK-MB) and troponin-T levels were measured 1day post-CA. ResultsCK-MB and troponin-T levels were higher, ablation time was longer, and AMR was greater in the CFAE-guided ablation group than in the linear ablation group. AF termination during CA was more frequently observed in the linear ablation group than in the CFAE-guided ablation group (P=0.031). Twelve months after a single procedure, recurrence occurred in 16 (26.7%) patients with linear ablation and 27 (45.8%) patients with CFAE-guided ablation (P=0.023). On multivariate analysis, LA volume and ablation method were the only independent risk factors for arrhythmia recurrence. ConclusionConduction block through linear lines+PVI was an efficient ablation strategy for L-PeAF, whereas the AMR amount did not influence clinical outcomes.

Surgical outcome of Fontan conversion and arrhythmia surgery: Need a pacemaker?

Atrial tachyarrhythmias are frequent complications in the late period after the Fontan procedure, and important risk factors for a poor prognosis. The impact of Fontan conversion and arrhythmia surgery in failed Fontan patients has been described in many reports. We evaluated our experience with Fontan conversion procedures, concomitant arrhythmia surgery, and pacemaker implantation. We reviewed the hospital records of 25 consecutive patients who underwent a Fontan conversion procedure from January 2004 to March 2012. Twenty-four patients had arrhythmia surgery using cryoablation and radiofrequency ablation at the time of conversion. A bilateral atrial maze procedure was performed in 6 patients, right-side maze in 15, and isthmus block in 3. Three patients with a diagnosis of corrected transposition of the great arteries underwent simultaneous pacemaker implantation electively. There was no early death and one late death during a mean follow-up period of 21.2 months. Three tachyarrhythmia recurrences developed, and there were 4 occurrences of sinus bradycardia. Five of these patients required postoperative pacemaker implantation. The mid-term results of Fontan conversion and arrhythmia surgery in our institute were satisfactory. The occurrence of unexpected postoperative pacemaker requirement was high in the patients who underwent a right atrial or bilateral atrial maze procedure. Pacemaker or lead implantation is recommended for patients planned to undergo a right-side or full maze procedure.

Catheter ablation of atrial fibrillation in patients with hypertrophic cardiomyopathy

Purpose: Atrial fibrillation (AF) is common in patients with hypertrophic cardiomyopathy (HCM) and known to predict adverse outcome. Radiofrequency catheter ablation represents a promising option to improve symptoms and outcome of these patients. The purpose of this study was to evaluate the long term effects of catheter ablation in AF patients with HCM. Methods: Twenty-five consecutive patients (19 male, age 53.4±8.0 years) with HCM undergoing pulmonary vein (PV) isolation with or without additional left atrial roof, mitral isthmus or cavotricuspid isthmus linear ablations for drug-refractory AF (16 paroxysmal AF) composed the HCM group of this study. Fifty non-HCM patients (38 male, age 53.5±8.3 years, 32 paroxysmal AF) matched for age, sex and types of AF were used as the control group. Ablation strategy used in control group was similar to that utilized in HCM group. Baseline characteristics, cardiac functional improvement and success rate of AF ablation during follow-up were compared. Results: All patients underwent ablation successfully without major complication. The left atrium (LA) was significantly larger in patients with HCM (47.38±7.51 vs. 40.36±7.98 mm in control group, P=0.001). Other baseline characteristics were comparable between two groups. AF-related symptoms were assessed by the European Heart Rhythm Association (EHRA) score which was 3.04±0.68 in HCM group and 2.54±0.68 in control group (P=0.003). Integrated long term follow-up data (3.39±1.17 years) were available in 20 patients of HCM group and 44 patients of non-HCM group. After an average of 1.1 procedures, sinus rhythm was retained in 9/20 (45%) patients with HCM and 32/44 (72.7%; p=0.032) patients without HCM. In HCM group, 8/9 patients were free from AF recurrence off anti-arrhythmic drug. Among patients in whom mitral isthmus (MI) linear ablation were performed, bidirectional isthmus block was achieved in 50% (4/8) of patients with HCM, comparing to 70.6% (12/17) in control group. After ablation, patients with HCM who maintained sinus rhythm showed remarkable improvement of NYHA cardiac functional categorization (1.1±0.3 vs. 1.6±0.5, P=0.035). Conclusions: AF-related symptoms are more severe in patients with HCM. Success rate of AF ablation remained low in this cohort. Restoration of sinus rhythm in HCM patients is associated with significant cardiac functional improvement.

Anatomical characteristics of mitral isthmus requiring ablation inside the coronary sinus for creation of complete linear block in patients with atrial fibrillation

Background: Radiofrequency energy delivery inside the coronary sinus (CS) is often required to achieve complete linear block at the mitral isthmus (MI). The purpose of this study is to elucidate the morphologic characteristics of the MI which may need ablating inside the CS. Method and results: Ninety-eight consecutive patients (mean age 64±11, 74 male [76%], 51 persistent AF [52%]) who underwent the first linear ablation at the MI during catheter ablation for AF/AT were enrolled in the study. All patients underwent 64-slice MDCT scanning prior to the procedure and its anatomical features of the MI were analyzed. Complete block along the mitral isthmus was achieved in 85 (87%) patients, of which 45 (53%) patients required radiofrequency ablation inside the CS (Group CS), and RF application was not required in the other 40 (47%) patients (Group Non-CS). There were no significant differences in the MI length, isthmus depth, CS diameter, CS cross-sectional area, and the distance between the CS and the MI. However, group CS patients were more likely to have interposed circumflex artery between the CS and the MI (40% vs. 18% p=0.02). Conclusion: Interposition of the circumflex artery between the MI and the CS is associated with a higher probability of requiring ablation inside the CS to achieve complete mitral isthmus block.

Impact of Stepwise Ablation on the Biatrial Substrate in Patients With Persistent Atrial Fibrillation and Heart Failure

Ablation of persistent atrial fibrillation can be challenging, often involving not only pulmonary vein isolation (PVI) but also additional linear lesions and ablation of complex fractionated electrograms (CFE). We examined the impact of stepwise ablation on a human model of advanced atrial substrate of persistent atrial fibrillation in heart failure. In 30 patients with persistent atrial fibrillation and left ventricular ejection fraction ≤35%, high-density CFE maps were recorded biatrially at baseline, in the left atrium (LA) after PVI and linear lesions (roof and mitral isthmus), and biatrially after LA CFE ablation. Surface area of CFE (mean cycle length ≤120 ms) remote to PVI and linear lesions, defined as CFE area, was reduced after PVI (18.3±12.03 to 10.2±7.1 cm(2); P<0.001) and again after linear lesions (7.7±6.5 cm(2); P=0.006). Complete mitral isthmus block predicted greater CFE reduction (P=0.02). Right atrial CFE area was reduced by LA ablation, from 25.9±14.1 to 12.9±11.8 cm(2) (P<0.001). Estimated 1-year arrhythmia-free survival was 72% after a single procedure. Incomplete linear lesion block was an independent predictor of arrhythmia recurrence (hazard ratio, 4.69; 95% confidence interval, 1.05-21.06; P=0.04). Remote LA CFE area was progressively reduced following PVI and linear lesions, and LA ablation reduced right atrial CFE area. Reduction of CFE area at sites remote from ablation would suggest either regression of the advanced atrial substrate or that these CFE were functional phenomena. Nevertheless, in an advanced atrial fibrillation substrate, linear lesions after PVI diminished the target area for CFE ablation, and complete lesions resulted in a favorable clinical outcome.

Aborted Sudden Cardiac Death Due to Radiofrequency Ablation Within the Coronary Sinus and Subsequent Total Occlusion of the Circumflex Artery

We report a case of aborted sudden cardiac death and subsequent development of malignant drug-refractory incessant ventricular tachycardia/fibrillation in a patient with acute coronary artery occlusion following radiofrequency ablation within the CS. Catheter ablation is a well-established therapy for treatment of atrial fibrillation (AF). In patients with longstanding persistent AF extensive left atrial ablation and ablation inside the coronary sinus (CS) is frequently performed. Perimitral flutter following AF ablation is the most common form of left atrial macroreentry, especially in patients with previous ablation of complex fractionated electrograms and incomplete linear lesion sets within the left atrium. Successful ablation of this type of tachycardia is generally difficult and in about 60-70% patients requires additional ablation within the CS to achieve termination of tachycardia or/and left atrial isthmus (LAI) block. A limited number of case reports have been published describing acute coronary artery occlusion during or immediately after LAI ablation within the CS. This case exhibits a potential lethal risk of radiofrequency ablation within the CS.

Long-term outcomes after radiofrequency catheter ablation of paroxysmal and persistent atrial fibrillation

Background : Short-term oucomes of radiofrequency (RF) catheter isolation of the pulmonary veins (PVs) in patients with paroxysmal or persistent atrial fibrillation (PAF/PEAF) are encouraging. However, long-term outcomes are not well defined. Therefore, we evaluated 3–5-year outcomes in our series of patients. Freedom from symptomatic AF/flutter/tachycardia recurrences with patients off antiarrhythmic drugs (AAD) was considered a treatment success. Methods : Consecutive patients with symptomatic PAF/PEAF and AAD failure, without significant structural heart disease, were prospectively recruited between September 2003 and November 2009. Irrigated-tip RF ablation catheter and Lasso catheter were used after standard trans-septal approach with X-ray fluoroscopic guidance. Ablation endpoints were: complete segmental/circumferential ostial and antral electrical PV isolation, non-PV foci ablation, and bi-directional flutter isthmus (FI) block when indicated. The procedure was repeated if AF/flutter/tachycardia recurred after 3-month blanking period. The suspected arrhythmia recurrences were evaluated by series of ECG/Holter recordings. Data were analyzed by t-, chi-square, and Fisher’s exact tests. P < 0.05 was considered statistically significant. Results : In 126 patients, median age 55 years (range 19–75), 94 men (75 %), 86 with PAF and 40 with PEAF (31 %), 207 procedures were performed: single in 63 (50 %), double in 48 (38 %), and multiple in 15. FI was ablated in 53 patients (42 %). Tamponade occurred in 4 (3 %). No PV stenosis, esophageal injury, or stroke were detected clinically in 115 patients (91 %) during 36-month (13–89) follow-up. We achieved treatment success in 69 patients (61 %), partial success with a significant reduction of AF/flutter/tachycardia recurrences on AAD in 13 patients (12 %), and in 33 patients (27 %) the procedure was not successful. Overall, 73 % of our patients had long-term benefit. Outcomes were better in patients with PAF vs. PEAF (84 % vs. 48 %, p < 0,001), in younger age, in those without concomitant diseases, and in those with normal PV anatomy. These results were maintained in the subgroup of 58 patients over 56 months of follow-up: 35 (60 %), 6 (11 %), and 17 (29 %), respectively. Conclusions : Lasso-guided RF irrigated-tip segmental/circumferential PV isolation is a safe and long-term successful treatment of PAF in the majority of our patients. The method needs improvements in patients with PEAF, possibly with the introduction of new technologies.

The Agilis Sheath in Typical Atrial Flutter Ablation Trial

Background: In general is it believed that use of a deflectable sheath can enhance tissue contact or improve catheter manipulation for ablation of challenging cavotricuspid anatomy. We sought to determine if use of a St. JudeAgilis sheath®− lead to improvedcontact force, faster procedures or greater efficacy in typical right atrial flutter ablation. Method: We performed cavotricuspid isthmus ablation with a pressure sensing catheter on 20 patients with isthmus dependant flutter and randomised them to use, or no use of an Agilis sheath. For the purpose of contact force assessment, the isthmus was divided into peri-annular, mid isthmus and venacaval zones. The proceduralist was blinded to contact force readings and the end point of ablation was bidirectional isthmus block with >50% prolongation of the transisthmus interval. Results: After 10min of ablation, four patients in the control group crossed over to use of an Agilis sheath. On intention to treat analysis bidirectional isthmus block was achieved in 9/10 patients with use of the Agilis sheath and 10/10 patients without (p=NS). Results were as follows.

The National Heart Foundation of Australia Consensus Statement on Catheter Ablation as a Therapy for Atrial Fibrillation

Background: In general is it believed that use of a deflectable sheath can enhance tissue contact or improve catheter manipulation for ablation of challenging cavotricuspid anatomy. We sought to determine if use of a St. JudeAgilis sheath®− lead to improvedcontact force, faster procedures or greater efficacy in typical right atrial flutter ablation. Method: We performed cavotricuspid isthmus ablation with a pressure sensing catheter on 20 patients with isthmus dependant flutter and randomised them to use, or no use of an Agilis sheath. For the purpose of contact force assessment, the isthmus was divided into peri-annular, mid isthmus and venacaval zones. The proceduralist was blinded to contact force readings and the end point of ablation was bidirectional isthmus block with >50% prolongation of the transisthmus interval. Results: After 10min of ablation, four patients in the control group crossed over to use of an Agilis sheath. On intention to treat analysis bidirectional isthmus block was achieved in 9/10 patients with use of the Agilis sheath and 10/10 patients without (p=NS). Results were as follows.

Abstract 19728: Translesional Time to Determine Complete Bidirectional Block Across the Cavotricuspid Isthmus

Introduction: The goal of ablation of typical atrial flutter is to create complete bidirectional block across the cavotricuspid isthmus (CTI). The purpose of this study was to document whether there was a transisthmus time that is associated with complete bidirectional isthmus block (CBIB). Methods: Thirty consecutive patients who had CTI ablation procedures were assessed. A circular right atrial mapping catheter, coronary sinus catheter, and electroanatomical mapping were used in all patients. Before ablation, points were marked medial and lateral to the planned line and bidirectional conduction times were assessed. Post ablation bidirectional conduction times were assessed again at the points medial and lateral to the line. The translesional time (TL) was defined as the difference in bidirectional conduction time recorded lateral to the line from medial to the line. CBIB was verified by reversal of activation of the right atrium on the circular mapping catheter and/or documentation of widely spaced double potentials. Results: CBIB was achieved in 29/30 patients. The average baseline counterclockwise (CCW) conduction time across the CTI was 43 +/- 22 msec The average baseline clockwise (CW) conduction time was 42 +/- 16 msec. The average baseline TL was 10 msec CCW, and 9 msec CW. The longest baseline TL was 52 msec CCW and 28 msec CW . Post ablation, the average CCW conduction time was 149 msec, and CW was 150 msec in patients with CBIB. The average TL in patients with CBIB was 116 msec CCW and 111 msec CW. The shortest TL associated with CBIB was 90 msec CCW and 91 msec CW. The maximum TL associated with incomplete block was 68 msec. Conclusions: A bidirectional TL of greater 90 msec was predictive of CBIB after typical atrial flutter ablation, and could be used simplify assessment of CBIB during CTI ablation.

New insights into typical atrial flutter ablation: extra-isthmus activation time on the flutter wave is predictive of extra-isthmus conduction time after isthmus block

Catheter ablation of typical atrial flutter (AFl) is succesful if double electrograms on the ablation line are widely separated. Nevertheless, a small interval may also be compatible with complete isthmus block. Predicting such a situation may avoid useless additionnal radiofrequency (RF) applications. We postulated that measuring the extra-isthmus activation time (EIAT) on the counterclockwise (CCW) flutter wave is correlated with the extra-isthmus conduction time after a proven block. Files of 76 patients (71 males, 71 ± 12 years) ablated for typical CCW AFl were reviewed. Ten had 2/1 conduction prohibiting reliable measurement. Three patients with proven crista terminalis shunt were also excluded. In the remaining 63 patients, EIAT was measured on the surface ECG before the first RF pulse from the beginning of the negative deflection of the F wave in lead III to the end of the positive deflection (or beginning of the plateau). After successful ablation and completion of block, right atrial (RA) CCW (during low septal pacing), and clockwise (CW) (during low lateral pacing) activation times were measured. Flutter cycle length was 247 ± 34 ms and EIAT was 142 ± 25 ms. A bidirectionnal isthmus block was obtained in all patients after an RF delivery time of 623 ± 546 s. At a pacing cycle length of 681 ± 71 ms, RA CCW and CW activation times were 147 ± 23 and 139 ± 26 ms, respectively. There was a good correlation between EIA, RA CCW (r = 0.75, p < 0.0001), and CW (r = 0.69, p = 0.0002) activation times. EIAT on the flutter wave is an easy and feasible measure. It is correlated with extra-isthmus RA conduction time after block completion. EIAT can be used as a measure to predict the post cavo-tricuspid isthmus block RA activation time.

Comparative Determination and Monitoring of Biomarkers of Necrosis and Myocardial Remodeling between Radiofrequency Ablation and Cryoablation

Biomarkers of necrosis and inflammation have been found raised after radiofrequency ablation (RF). There is scarce information on biomarkers' behavior after cryoablation. Our aim was to study biomarkers of necrosis, inflammation, and interstitial remodeling after two different approaches: RF versus cryoablation. We studied 22 consecutive patients with atrial flutter who underwent RF (10) or cryoablation (12). All patients underwent electrophysiological study and subsequent ablation. Peripheral samples were collected before the procedure, immediately after, the following day, 3 days, 1 week, 1 month, and 2 months after ablation. Samples were assayed for biomarkers of inflammation (high sensitive C-reactive protein [hs-CRP]) and tissue remodeling (C-propeptide of type I procollagen [CICP], matrix metalloproteinase 2 [MMP-2], matrix metalloproteinase 9 [MMP-9], and metallopeptidase inhibitor 1 [TIMP-1]). We also determined biomarkers of tissue necrosis (creatine kinase [CK], its MB isoenzyme, cardiac troponin I [TnI], and troponin T (TnT)] in samples obtained immediately after ablation, 6 hours postablation, and 12 hours postablation. Bidirectional isthmus block was achieved in all patients. We found significantly higher levels of CK, CK-MB, and TnI after cryoablation compared to RF ablation for all timing samples. These necrosis biomarkers showed significant differences depending on the time (all P < 0.001), and the interaction between the time and the used ablation approach (P = 0.005, P < 0.001, and P < 0.001, respectively). For patients who undergoing RF ablation, MMP-2 showed the greatest changes depending on the interaction between time and number of applications (P = 0.041), whereas for patients who undergoing cryoablation, CK was the most relevant biomarker depending on the interaction between time and number of applications (P = 0.006). We show higher levels of necrosis and myocardial injury biomarker after cryoablation versus RF. However, we found higher remodeling processes after RF. Our data support previous publications showing different lesion formation in cryoablation and RF.

Ablation of Atrial Flutter in Complex Congenital Heart Disease

This article describes the case of a 38-year-old male patient with a history of D-transposition of the great arteries (D-TGA) status post Mustard atrial switch procedure who presented with palpitations. Electroanatomic mapping and entrainment proved that the arrhythmia was typical atrial flutter in the pulmonary venous atrium. Ablation was performed via the retrograde route with confirmation of isthmus block. This case illustrates typical mapping and ablation of atrial flutter in a patient after Mustard repair of D-TGA.

Prevalence and Types of Pitfall in the Assessment of Mitral Isthmus Linear Conduction Block

To identify and understand clinically encountered pitfalls in the assessment of transmitral conduction block using differential coronary sinus and left atrial appendage pacing techniques in patients with left mitral isthmus linear ablation. All the available assessments of mitral isthmus block were thoroughly reviewed in 271 mitral isthmus ablation procedures undertaken among 236 patients from October 2008 to April 2011. Bidirectional block was established in 186 of 271 (69%) procedures. Careful evaluation of electrograms recorded on the multipolar coronary sinus and ablation catheters was undertaken to identify and understand the characteristics of pitfall, if any. Pitfall was encountered in 55 of 271 (20%) procedures among 51 patients and categorized into 6 types (types 1, 3, 4, and 5 led to spurious diagnosis of block; types 2 and 6 led to erroneous diagnosis of absence of block). There were 14, 10, 17, 2, 15, and 3 (total=61) cases of pitfall types 1 through 6, respectively. Operator recognized 42 of 61 (69%) pitfalls intraprocedurally. Recognition of types 1 and 5 was difficult because of indiscernible electrograms at usual amplifier settings or presence of slow conduction mimicking block. Every fifth assessment of bidirectional block across mitral isthmus linear lesion using differential coronary sinus and left atrial appendage pacing techniques encounters a pitfall, which can lead to erroneous clinical diagnosis of block or absence of block. Recognition of pitfall during the procedure is feasible and necessitates careful distinction of far-field left atrium from the local coronary sinus electrograms besides appropriate adjustments in catheter position and pacing outputs.

Further Evidence for the “Muscle Bundle” Hypothesis of Cavotricuspid Isthmus Conduction: Physiological Proof, with Clinical Implications for Ablation

It has been suggested that the cavotricuspid isthmus (CTI) is composed of discrete muscle bundles with preferred paths of conduction. An ablation technique targeting high-voltage local electrograms (maximum voltage guided or MVG technique) has been described with the aim of preferentially targeting the muscle bundles. We hypothesized that the MVG technique could provide isthmus block even if the high voltage targets were clearly separated on different ablation lines. In contrast, conduction over a continuous sheet of muscle would require a single continuous ablation line. Twenty-two consecutive patients (mean age 65 ± 11.7, 5 females) underwent ablation using the MVG technique on 2 noncontiguous lines in the CTI. Ablation lesions were first applied at the septal aspect of the CTI, targeting only the ventricular (anterior) aspect of the annulus. A line distinctly lateral and noncontiguous to the first was then chosen to target high voltage potentials on the atrial (posterior) aspect of the CTI. Complete CTI block was achieved in all study patients without complication. A mean of 7.8 ± 3.7 ablation lesions were required. Mean ablation time was 401.0 ± 414.5 seconds. Two nonoverlapping incomplete lines of ablation in the CTI consistently lead to bidirectional conduction block. This further supports the hypothesis that conduction over the CTI occurs over discrete muscle bundles. These bundles can be targeted individually for ablation without the need to ablate a continuous line over the CTI.

“Dormant transisthmus conduction” revealed by adenosine after cavotricuspid isthmus ablation

Linear radiofrequency ablation at the cavotricuspid isthmus (CTI) is the treatment of choice for typical flutter. Despite a high acute success rate, reconduction through the CTI may occur in approximately 15% of patients and eventually lead to flutter recurrence. The purpose of this study was to test the hypothesis that injection of adenosine may reveal transient CTI reconduction and predict early relapse of permanent CTI conduction. Thirty-one patients with CTI-dependent flutter (mean age 65 ± 11 years, 87% male, ejection fraction 55% ± 11%) were included in the study. CTI ablation was performed using an open-irrigated ablation catheter. Bidirectional conduction block was confirmed using conventional criteria. Subsequently, transisthmus conduction was reevaluated after adenosine injection. During a 30-minute waiting period, permanent recovery of CTI conduction was monitored. During a mean follow-up of 6 ± 3 months, clinical recurrences of typical flutter were assessed. Bidirectional isthmus block was achieved in all patients. Injection of 16 ± 3 mg adenosine IV induced transient second- or third-degree AV block in all patients. An adenosine-induced brief sequence reversal at the right lateral wall occurred in 6 of 31 patients (19%) and revealed transient CTI reconduction. Among these 6 patients, 4 (67%) had permanent recovery of transisthmus conduction in the subsequent waiting period; the remaining 2 patients (33%) had clinical recurrence of common flutter. Importantly, no patient without adenosine-mediated dormant transisthmus conduction (25/31 [81%]) showed permanent recovery during the waiting period or clinical flutter recurrence during follow-up. Adenosine-induced "dormant transisthmus conduction" precedes early relapse of permanent CTI conduction. Patients without "dormant transisthmus conduction" develop no recovery of conduction during the postablation waiting period. Routine use of adenosine for assessment of ablation lines may help to reduce the clinical recurrence of the underlying arrhythmia.

Initial experience in ablation of typical atrial flutter using a novel three-dimensional catheter tracking system

Three-dimensional (3D) mapping has been established for clinical routine in an interventional electrophysiology (EP). Recently, a novel sensor-based 3D catheter tracking system has been introduced integrating 3D non-fluoroscopic catheter navigation into the environment of pre-recorded 2D fluoroscopy [MediGuide™ Technology (MG)]. We are reporting on the first clinical experience for ablation of typical atrial flutter. First we aimed to demonstrate safety and feasibility of this new technique. Secondly, procedural aspects such as effectiveness, procedure, and fluoroscopy time should be evaluated. Ten consecutive patients (100% male, age 68 ± 8 years) were ablated using MG technology. Two steerable diagnostic EP catheters (MediGuide Enabled Livewire™ Catheter, SJM) were used for coronary sinus cannulation and anatomical cavo-tricuspidal isthmus (CTI) reconstruction within the EnSite NavX™ System (NavX). Ablation was performed with a conventional 8 mm tip ablation catheter (IBI, SJM). In all 10 patients both sensor-equipped MG catheters could be tracked non-fluoroscopically. Successful anatomical CTI reconstruction was performed and complete isthmus block was documented after the ablation. Total procedure duration was comparable with conventional procedures (55 ± 8 min). Usage of the MG tracking system resulted in a fluoroscopy time of 2.5 ± 2 min. No adverse events occurred during the procedures. For the first clinical application of the MG technology in an interventional electrophysiology we found a stable system enabling excellent 3D orientation for spatial catheter positioning on the basis of underlying pre-recorded cine loops. Clinically, the MG technology allowed successful procedures with short fluoroscopy times, even though a sensor-equipped ablation catheter was not yet available for use in the study.

Feasibility of real-time magnetic resonance imaging-guided electrophysiology studies in humans

Magnetic resonance imaging (MRI) in the context of electrophysiology (EP) studies facilitates visualization of complex three-dimensional anatomy and the underlying arrhythmogenic substrate, real-time passive visualization of catheters, atrial and ventricular function and complications, as well as lesion visualization during the ablation without radiation. In the following we report on our first experience of a real-time MRI-guided EP study demonstrating current possibilities and drawbacks. Five consecutive patients (one male, four female; mean age 66 ± 11 years) with symptomatic arrhythmias, three patients with highly symptomatic typical atrial flutter, presented to our hospital for isthmus ablation, one patient for an EP study and one for slow pathway ablation in atrioventricular node re-entry tachychardia. The four ablations were performed successfully in a conventional EP laboratory and complete bidirectional isthmus block was confirmed in three patients with atrial flutter. After the procedure in the EP laboratory all five patients were transferred to a 1.5 T whole-body MRI scanner (Intera) for a diagnostic EP procedure. Two MRI compatible steerable diagnostic/ablation catheters (Vision) were inserted via the femoral sheaths and manipulated by an experienced electrophysiologist using a commercially available interactive real-time steady-state free precession sequence (repetition time = 3 ms, echo time = 1 ms, flip angle = 35°, slice thickness = 10 mm, frame rate = 8/s). All catheters could be placed successfully in the right atrium and ventricle, confirmed by intracardiac electrograms, using passive catheter tracking. Furthermore, simple programmed stimulation maneuvers were performed. During and after the procedure, no adverse effects were observed in any patients. To our knowledge, this is the first series of patients with real-time MRI-guided placement of multiple catheters with subsequent performance of stimulation maneuvers. Besides the mentioned benefits, this technology still encounters several limitations, which have to be solved before application in a routine clinical setting. Challenges arise from delineation of precise surface electrocardiogram recordings in the MRI setting along with intracardiac electrograms, easier handling and visualization of catheters, facilitation of immediate defibrillation in the MRI setting and implementation of an active catheter tracking system.

Intravenous Adenosine to Predict Conduction Recurrence in Cavotricuspid Isthmus Early After Ablation of Typical Atrial Flutter: Myth or Reality?

Early recovery of conduction (ER) after cavotricuspid isthmus (CTI) ablation for typical atrial flutter (AFl) occurs in approximately 10% of the patients. If not recognized, ER might lead to AFl recurrences. In this study, we hypothesized that intravenous adenosine (iADO) can be used to predict ER in the CTI immediately after RF ablation and distinguish functional block from the complete destruction of the CTI myocardium. We prospectively included 68 consecutive patients (age: 65 ± 14 years; male: 78%) referred in our centers for AFl ablation. Immediately after bidirectional isthmus block validation, a bolus of iADO was given during continuous pacing from the proximal coronary sinus. Patients with functional block revealed under iADO (iADO+) and those without (iADO-) were subsequently observed for a 30-minute waiting period (ER-) or until sustained recovery of the conduction through the CTI (ER+). Seven patients presented a persistent recovery (ER+, 10.3%, mean time to recovery: 14 ± 9 minutes). None of them presented even a transient resumption of conduction under iADO (iADO+: 0). With univariate analysis, we identified a heavy patient weight (>95 kg) as a predictor of ER (sensitivity: 71%). Adenosine does not predict early recovery in the CTI after linear ablation for atrial flutter. We found that a patient weight over 95 kg predicted early recovery of conduction through the CTI with a sensitivity of 71%.

Mitral Isthmus Ablation Using Steerable Sheath and High Ablation Power: A Single Center Experience

Mitral isthmus ablation is challenging. The use of steerable sheath and high ablation power may improve success rate. This single-center, prospective study enrolled 200 patients who underwent ablation for atrial fibrillation (AF), including mitral isthmus ablation. Mitral isthmus ablation was performed using an irrigated ablation catheter via a steerable sheath (endocardium: maximum power: 40/50 W limited to annular end, maximum temperature: 48 °C; coronary sinus [CS]: maximum power: 25/30 W, maximum temperature: 48 °C). Endpoint was bidirectional mitral isthmus block. Mitral isthmus block was acutely achieved in 182/200 patients (91%). Sixty-nine percent of patients required CS ablation. Mean total ablation time was 13 ± 6 minutes. There was 1 case of acute circumflex artery occlusion. Mean left atrium (LA) diameter was significantly bigger in patients with unsuccessful mitral isthmus ablation (49 ± 4 mm vs. 43 ± 6 mm; P = 0.0007). In redo procedures, the incidence of reconduction at the mitral isthmus, roof and cavotricuspid isthmus was 44%, 37%, and 29%, respectively. Overall incidence of perimitral flutter was 9%. Prior complex fractionated atrial electrogram ablation was a predictor for microreentrant atrial tachycardia (AT) whereas gaps in linear lesions predicted macroreentrant flutters. After a mean follow-up of 20 ± 9 months, 73% of patients remained free from AF or AT. We reported on a series of mitral isthmus ablation using steerable sheath and high ablation power (50 W). Larger LA diameter was a predictor of failure to achieve mitral isthmus block. The mitral isthmus had a moderately high incidence of re-conduction but was only associated with a relatively low incidence of perimitral flutter.