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Abstract Objectives  We aimed to test the maximum voltage-guided cavotricuspid isthmus (CTI) ablation technique during ongoing atrial flutter. Background  Former pathological and electrophysiological studies clarified that the cavotricuspid isthmus is composed of distinct muscular bundles, which are responsible for the conduction of electrical activation. Based on this observation, a maximum voltage-guided ablation technique (MVGT) was developed. This technique was assessed during pacing from the coronary sinus and was reported to be a feasible method to reach bidirectional isthmus block without the need for a complete anatomic ablation line. Methods  This was a prospective, randomized single center study. Twenty patients underwent CTI ablation during atrial flutter. In group I (10 pts) CTI ablation was performed with complete anatomical ablation line. In group II (10 pts) ablation was guided by the highest amplitude potentials on the CTI sequentially until bidirectional isthmus block was reached. The following parameters were compared: acute success rate, procedure time, fluoroscopy time, number of radiofrequency (RF) applications and total RF duration. Results  In all patients, atrial flutter terminated during ablation. Bidirectional isthmus block could be achieved in all pts. Procedure time was shorter in group II (107 � 40 vs 68 � 19 min, p p p  Conclusions  (1) The major finding of this study is that MVGT is a feasible method even during ongoing atrial flutter. (2) Our data confirm that MVGT is an effective technique for CTI ablation with considerable decrease in procedure and fluoroscopy times. [ABSTRACT FROM AUTHOR]

This randomized study aims to compare the left atrial (LA) lesion size, function, and tissue damage following pulmonary vein isolation (PVI) by high-power short-duration (HPSD) radiofrequency (RF) and second-generation cryoballoon (CB2) ablation. We enrolled 40 patients with paroxysmal atrial fibrillation who underwent PVI by HPSD RF (n = 21) or CB2 (n = 19). Every patient underwent LA CT angiography and transthoracic echocardiography (TTE) to assess the LA anatomy and function. Biomarker levels (hs-cTnT, hs-CRP, LDH) were compared pre- and post-procedurally. Pre- and post-ablation high-density mapping (HDM) was performed. The isolation area was defined under 0.2 mV bipolar voltage (low voltage area, LVA). We calculated the post-PVI LVA/LA surface ratio using LA CT-HDM merge images. At 3-month follow-up, TTE was performed to assess the changes in LA function. Post-ablation hs-cTnT level was significantly higher in the RF group (RF: 1249 ± 469 ng/L, CB2: 995 ± 280 ng/L, p = 0.024). Post-PVI hs-CRP (RF: 9.53 ± 10.30 mg/L, CB2: 12.36 ± 5.76 mg/L, p = 0.034) and LDH levels (RF: 349.9 ± 65.6 U/L, CB2: 451.6 ± 91.3 U/L, p < 0.001) were significantly higher following CB2 ablation. Post-PVI LVA/LA surface ratios were 8.37 ± 6.42% in the RF group and 13.58 ± 8.92% in the CB2 group (p = 0.022). LA function did not change significantly after the PVI procedure. Our data indicate that second-generation cryoballoon ablation produces a significantly larger LA lesion size compared to “point-by-point” HPSD radiofrequency. Both techniques preserve LA function. The myocardial component of tissue loss appears to be higher using HPSD radiofrequency ablation, with less collateral damage.

Purpose: Iatrogenic atrial septal defect (IASD) after catheter ablation (CA) for atrial fibrillation (AF) due to transseptal puncture (TSP) can occur. The aim of this prospective study was to describe the incidence of IASD and to detect any cerebrovascular accident (CVA) after radiofrequency (RF) and cryoballoon (CB) CA., Methods: Between July 2014 and September 2016, 94 patients (pts) (RF; 48, CB; 46, 30 (31.9%) women, mean age = 60 ± 9.7 years) with paroxysmal AF were enrolled who underwent CA procedure for the first time. During RF ablation a single (n = 30, 62.5%) or double (n = 18, 37.5%) TSP was performed. Transoesophageal echocardiography before the procedure and at the 3-month and 12-month follow-up (FU) was accomplished. During the FU period, we evaluated the occurrence of any postprocedural CVA., Results: At the 3-month FU, IASD was detected in 17/94 (18.1%) pts; in 9/48 (18.8%) pts in the RF while in 8/46 (17.4%) pts in the CB group (p = 0.866), all of them with left-to-right shunt. In the RF group, 6/30 (20%) pts with a single TSP while 3/18 (16.7%) pts in the double TSP group had IASD (p = 0.780). 14/17 (82.4%) IASDs showed high spontaneous closure rate at the 12-month FU. None of the pts died or suffered from CVA., Conclusion: Persistent IASD can occur rather frequently following AF CA. No significant difference was observed between the RF and CB techniques concerning the presence of IASD at 3-month. IASDs showed a high spontaneous closure rate. No cerebral thromboembolic event was observed in the 12-month FU period.

Purpose: Cardiac resynchronization therapy (CRT) is an established therapeutic option in selected heart failure patients (pts). However, the transvenous left ventricular (LV) lead implantation remains ineffectual in a considerable number of pts. Transapical LV (TALV) lead implantation is an alternative minimally invasive, surgical, endocardial implantation technique. The aim of the present prospective study is to determine the long-term outcome, including the cerebral thromboembolic complications, of pts who underwent TALV lead placement., Methods: Twenty-six CRT candidates (19 men (78 %); mean age 61 ± 10 years) with a previously failed transvenous approach underwent TALV lead placement as a last resort therapy. The following data was collected: mortality rate, reoperation rate, and cerebrovascular event rate. Patients underwent a cerebral CT scan to determine any possible cerebrovascular event related to the presence of the TALV lead., Results: Eleven out of 26 (47 %) patients survived after a median follow-up of 40 ± 24.5 months. Major acute ischemic stroke occurred in two cases, while in one case transient ischemic stroke was observed. Cerebral CT scan examination performed in asymptomatic patients revealed chronic ischemic lesions with minimal extension in two patients. Reoperation occurred in one case due to TALV lead fracture., Conclusions: This is the first study reporting the long-term outcome, mortality, and thromboembolic event rate exclusively after TALV lead implantation. Patients who underwent TALV lead implantation have a comparable long-term mortality rate to conventional CRT, although a major ischemic cerebrovascular event after TALV lead implantation is worrisome and has an impact on the outcome.

Background: Population-based studies suggest that genetic factors contribute to sudden cardiac death (SCD)., Methods and Results: In the first part of the present study (Diagnostic Data Influence on Disease Management and Relation of Genetic Polymorphisms to Ventricular Tachy-arrhythmia in ICD Patients [DISCOVERY] trial) Cox regression was done to determine if 7 single-nucleotide polymorphisms (SNPs) in 3 genes coding G-protein subunits (GNB3, GNAQ, GNAS) were associated with ventricular tachyarrhythmia (VT) in 1145 patients receiving an implantable cardioverter-defibrillator (ICD). In the second part of the study, SNPs significantly associated with VT were further investigated in 1335 subjects from the Oregon SUDS, a community-based study analyzing causes of SCD. In the DISCOVERY trial, genotypes of 2 SNPs in the GNAS gene were nominally significant in the prospective screening and significantly associated with VT when viewed as recessive traits in post hoc analyses (TT vs CC/CT in c.393C>T: HR 1.42 [CI 1.11-1.80], P=0.005; TT vs CC/CT in c.2273C>T: HR 1.57 [CI 1.18-2.09], P=0.002). TT genotype in either SNP was associated with a HR of 1.58 (CI 1.26-1.99) (P=0.0001). In the Oregon SUDS cohort significant evidence for association with SCD was observed for GNAS c.393C>T under the additive (P=0.039, OR=1.21 [CI 1.05-1.45]) and recessive (P=0.01, OR=1.52 [CI 1.10-2.13]) genetic models., Conclusions: GNAS harbors 2 SNPs that were associated with an increased risk for VT in ICD patients, of which 1 was successfully replicated in a community-based population of SCD cases. To the best of our knowledge, this is the first example of a gene variant identified by ICD VT monitoring as a surrogate parameter for SCD and also confirmed in the general population., Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00478933., (© 2016 The Authors and Medtronic. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.)

Background. There are little comparative data on catheter ablation of paroxysmal atrial fibrillation (AF) using the contact force radiofrequency (CF-RF) catheter versus the second-generation cryoballoon (CB2). Methods and results. This is a single center, retrospective, nonrandomized study of 98 patients with symptomatic, drug-refractory paroxysmal AF who underwent their first PVI ablation using either the CB2 (n = 40) or CF-RF (n = 58). The mean age was 60 years with 63% men, a mean LA size of 42 mm. The procedure duration (74 ± 17 versus 120 ± 49 minutes p < 0.05) was shorter for CB2 group; the fluoroscopy time (14 ± 17 versus 16 ± 5 minutes, p = 0.45) was similar. Complete PVI was achieved in 96% of patients with RF-CF and 98% with CB2. Phrenic nerve palsies (2 transient and 1 persistent) occurred exclusively in the CB2 group and 1 severe, nonlethal complication (pericardial tamponade) occurred in the CF-RF group. At 24-month follow-up, the success rate, defined as freedom from AF/atrial tachycardia (AT) after a single procedure without antiarrhythmic drug, was comparable in CF-RF group and CB2 group (65.5% versus 67%, resp., log rank p = 0.54). Conclusion. Both the CB2 and the RF-CF ablation appeared safe; the success rate at 2 years was comparable between both technologies.

Background: Defibrillation testing by induction and termination of ventricular fibrillation is widely done at the time of implantation of implantable cardioverter defibrillators (ICDs). We aimed to compare the efficacy and safety of ICD implantation without defibrillation testing versus the standard of ICD implantation with defibrillation testing., Methods: In this single-blind, randomised, multicentre, non-inferiority trial (Shockless IMPLant Evaluation [SIMPLE]), we recruited patients aged older than 18 years receiving their first ICD for standard indications at 85 hospitals in 18 countries worldwide. Exclusion criteria included pregnancy, awaiting transplantation, particpation in another randomised trial, unavailability for follow-up, or if it was expected that the ICD would have to be implanted on the right-hand side of the chest. Patients undergoing initial implantation of a Boston Scientific ICD were randomly assigned (1:1) using a computer-generated sequence to have either defibrillation testing (testing group) or not (no-testing group). We used random block sizes to conceal treatment allocation from the patients, and randomisation was stratified by clinical centre. Our primary efficacy analysis tested the intention-to-treat population for non-inferiority of no-testing versus testing by use of a composite outcome of arrhythmic death or failed appropriate shock (ie, a shock that did not terminate a spontaneous episode of ventricular tachycardia or fibrillation). The non-inferiority margin was a hazard ratio (HR) of 1·5 calculated from a proportional hazards model with no-testing versus testing as the only covariate; if the upper bound of the 95% CI was less than 1·5, we concluded that ICD insertion without testing was non-inferior to ICD with testing. We examined safety with two, 30 day, adverse event outcome clusters. The trial is registered with ClinicalTrials.gov, number NCT00800384., Findings: Between Jan 13, 2009, and April 4, 2011, of 2500 eligible patients, 1253 were randomly assigned to defibrillation testing and 1247 to no-testing, and followed up for a mean of 3·1 years (SD 1·0). The primary outcome of arrhythmic death or failed appropriate shock occurred in fewer patients (90 [7% per year]) in the no-testing group than patients who did receive it (104 [8% per year]; HR 0·86, 95% CI 0·65-1·14; pnon-inferiority <0·0001). The first safety composite outcome occurred in 69 (5·6%) of 1236 patients with no-testing and in 81 (6·5%) of 1242 patients with defibrillation testing, p=0·33. The second, pre-specified safety composite outcome, which included only events most likely to be directly caused by testing, occurred in 3·2% of patients with no-testing and in 4·5% with defibrillation testing, p=0·08. Heart failure needing intravenous treatment with inotropes or diuretics was the most common adverse event (in 20 [2%] of 1236 patients in the no-testing group vs 28 [2%] of 1242 patients in the testing group, p=0·25)., Interpretation: Routine defibrillation testing at the time of ICD implantation is generally well tolerated, but does not improve shock efficacy or reduce arrhythmic death., Funding: Boston Scientific and the Heart and Stroke Foundation (Ontario Provincial office)., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Aims: Delivery of a ventricular extrastimulus shortly after the effective refractory period (ERP) of a sensed (coupled pacing; CP) or a paced (paired pacing; PP) ventricular event can instantly decrease the mechanical pulse rate (MPR) during rapidly conducting atrial fibrillation (AF). We compared the short-term rate-controlling effects of CP and PP during AF with rapid ventricular rates., Methods and Results: Sixteen patients with ongoing, spontaneous AF were examined. Mechanical pulse rate was registered via arterial pressure tracings. During CP a coupling interval (CI) of ERP+20 ms was used to reach an optimal haemodynamic effect. Paired pacing was started at a basic cycle length (CL) of 500 ms followed by an extrastimulus with an CI of ERP+20 ms. Drive train was changed at 50 ms increments until the lowest MPR was reached. Proarrhythmic effects were characterized by the number of premature ventricular complexes (PVCs). Mechanical pulse rate significantly decreased in all patients during CP (113 ± 9 vs. 58 ± 4/min). Using CP the controlled rhythm remained irregular (CL range: 896 ± 24-1452 ± 67 ms) while no PVCs were observed. With different drive trains PP resulted in different regular MPRs (range 62 ± 6-80 ± 4/min), but the lowest MPR achieved was significantly higher in the PP group than in the CP. Paired pacing caused premature beats in nine patients (56%) resulting in loss of continuous MPR control., Conclusions: Both CP and PP can reduce the MPR during rapidly conducting AF. Coupled pacing is more applicable, but PP has the advantage to achieve different target heart rates. Paired pacing has more proarrhythmic effects as compared with CP.

Background: Epicardial pacing lead implantation is the currently preferred surgical alternative for left ventricular (LV) lead placement. For endocardial LV pacing, we developed a fundamentally new surgical method. The trans-apical lead implantation is a minimally invasive technique that provides access to any LV segments. The aim of this prospective randomized study was to compare the outcome of patients undergoing either trans-apical endocardial or epicardial LV pacing., Methods: In group I, 11 end-stage heart failure (HF) patients (mean age 59.7 ± 7.9 years) underwent trans-apical LV lead implantation. Epicardial LV leads were implanted in 12 end-stage HF patients (group II; mean age 62.8 ± 7.3 years). Medical therapy was optimized in all patients. The following parameters were compared during an 18-month follow-up period: LV ejection fraction (LVEF), LV end-diastolic diameter (LVEDD), LV end-systolic diameter, and New York Heart Association (NYHA) functional class., Results: Nine out of 11 patients responded favorably to the treatment in group I (LVEF 39.7 ± 12.5 vs 26.0 ± 7.8%, P < 0.01; LVEDD 70.4 ± 13.6 mm vs 73.7 ± 10.5 mm, P = 0.002; NYHA class 2.2 ± 0.4 vs 3.5 ± 0.4, P < 0.01) and eight out of 12 in group II (LVEF 31.5 ± 11.5 vs 26.4 ± 8.9%, P = < 0.001; NYHA class 2.7 ± 0.4 vs 3.6 ± 0.4, P < 0.05). During the follow-up period, one patient died in group I and three in group II. There was one intraoperative LV lead dislocation in group I and one early postoperative dislocation in each group. None of the patients developed thromboembolic complications., Conclusions: Our data suggest that trans-apical endocardial LV lead implantation is an alternative to epicardial LV pacing., (©2011, The Authors. Journal compilation ©2012 Wiley Periodicals, Inc.)

Background: Coronary sinus lead placement for transvenous left ventricular (LV) pacing in cardiac resynchronization therapy (CRT) has a significant failure rate at implant and a considerable dislocation rate during follow-up. For these patients epicardial pacing lead implantation is the most frequently used alternative. Recent data support endocardial lead implantation through the atrial septum and the mitral valve, because this method provides further hemodynamic advantages. On the other hand transseptal CRT carries a significant risk for device related infective endocarditis of the mitral valve. The aim of this prospective, nonrandomized study was to demonstrate the feasibility of a fundamentally new approach for endocardial LV lead implantation., Methods: We performed 12 transapical LV lead implantations in 10 end-stage heart failure patients. In each operation an active fixation lead was placed into the LV cavity using standard Seldinger technique through the LV apex. By use of a J-shaped guide wire, the tip of the lead was positioned and fixed into the basal-lateral segment of the LV under fluoroscopy guidance. Pacing parameters were assessed and found to be optimal in all patients. The lead was conducted through the chest wall near the apex into a subcutaneous tunnel up to the pocket of the previously implanted device. After surgery the patients are anticoagulated with target anticoagulation level identical to mechanical valve prostheses., Results: In 8 patients there were no major or minor complications related to this new technique. During the follow-up period (mean 7.2 +/- 4.1 months) all patients responded favorably to the treatment. One lead dislocation and 1 pocket infection were detected; the lead repositioning and replacing could be performed without reopening of the pleural cavity., Conclusions: The potential advantages of this new technique are that it is minimally invasive, endocardial, and does not involve the mitral valve. LV lead repositioning can also be performed minimally invasively.

Background: Gold has excellent electrical conductive properties and creates deeper and wider lesions than platinum-iridium during radiofrequency (RF) ablation in vitro. We tested the maximum voltage-guided technique (MVGT) of cavotricuspid isthmus (CTI) ablation using two 8-mm tip catheters containing gold (group G) or platinum-iridium (group PI)., Methods: We enrolled 31 patients who underwent CTI ablation. In group G (n = 15) CTI ablation was performed with a gold-tip ablation catheter, while in group PI (n = 16) a platinum-iridium tip was used. Ablation was guided by CTI potentials with the highest amplitude until achievement of bidirectional block (BIB). If BIB was not achieved after 10 RF applications, RF was delivered via a 3.5-mm irrigated-tip catheter. Success rate, procedure duration, duration of fluoroscopic exposure, and number of RF applications were measured., Results: BIB was achieved in all patients in group G, while in group PI an irrigated tip was used in four patients (0% vs 25%, P < 0.001). These four patients required a total of 21 additional RF applications (5.25 +/- 2.22). Procedure time (56.4 +/- 12 vs 73.1 +/- 15 minutes P < 0.05) and fluoroscopic explosure (4.9 +/- 2.3 vs 7.1 +/- 3.8 minutes, P < 0.01) were shorter in group G than in group PI. Mean number of RF applications was lower (4.6 +/- 1.9 vs 6.6 +/- 3.1 P < 0.001) and total RF duration shorter (280 +/- 117 vs 480 +/- 310 seconds) in group G than in group PI. No difference was observed in the number of recurrences at a 6 month-follow up (1 in group G vs 1 in group PI)., Conclusion: Using the MVGT of CTI ablation, gold-tip catheters were associated with shorter procedural and fluoroscopic times, and fewer RF applications.

Alternative methods are necessary for cardiac resynchronization therapy when coronary sinus lead implantation fails. We aim to describe a fundamentally new approach using transapical implantation of an active fixation endocardial pacing lead. This technique is based on direct puncture of the left ventricular apex using the standard Seldinger technique. The tip of the lead is positioned with intracavital navigation under fluoroscopy. This method offers advantages for cardiac resynchronization because it is minimally invasive, provides endocardial pacing, and does not involve the mitral valve.

Coronary sinus lead placement for transvenous left ventricular (LV) pacing in cardiac resynchronization therapy (CRT) has a significant failure rate at implant and a significant dislocation rate during follow-up. For these patients, epicardial pacing lead implantation is the most frequently used alternative. The aim of this case report is to describe a fundamentally new approach for the endocardial LV lead implantation. An epicardial lead implantation was planned, but after thoracotomy, extensive pericardial adhesions were found. An active fixation lead was placed into the LV cavity using the standard Seldinger technique through the LV apex. After an uneventful post-operative period at the 3- and 6-month follow-up visits, the patient had effective CRT with unchanged pacing parameters. In conclusion, this is the very first report showing feasibility of transapical LV lead implantation.

Background: Ablation during ongoing orthodromic reentry tachycardia (AVRT) and atrioventricular nodal reentry tachycardia (AVNRT) is not recommended using radiofrequency energy when the arrhythmia substrate is located in close proximity to the atrioventricular (AV) node due to a significant risk for inadvertent AV block. The aim of the study is to test the feasibility of ice mapping during tachycardias involving arrhythmia substrate located in close proximity to the AV node., Methods: This was a single-centre, prospective, randomized study. A total of 65 patients was screened and 30 patients with supraventricular arrhythmias were assigned either to a cryo or RF energy group after diagnosis of AVNRT (17 pts) or AVRT (13 pts) with an anteroseptal accessory pathway. RF ablation was performed using standard ablation techniques. In the cryo group, ice mapping was performed during tachycardia with cooling of the catheter tip temperature to a maximum of -40 degrees C. Ablation was performed only if ice mapping terminated the tachycardia without prolongation of the AV conduction., Results: The overall acute success rate was 84%, and was not different in the cryo and RF groups (85% vs. 82.4%, P = 0.43). Both fluoroscopy and the procedure times were comparable. There was a marked reduction in the mean number of applications in the cryo group [2 (1-6) vs. 7 (1-41), P = 0.002]. In one patient ablation was not attempted in the cryo group because of AV prolongation, and in two patients temporary second-degree AV block was observed in the RF group. After 12 months follow-up the long-term success rate was similar between the two groups., Conclusions: (I) Ice mapping is a feasible method to determine the exact location of accessory pathways and of the slow pathway during tachycardia. (2) Ice mapping performed during tachycardia causes less ablation lesions without increasing the procedure and fluoroscopy times.

Objectives: We aimed to test the maximum voltage-guided cavotricuspid isthmus (CTI) ablation technique during ongoing atrial flutter., Background: Former pathological and electrophysiological studies clarified that the cavotricuspid isthmus is composed of distinct muscular bundles, which are responsible for the conduction of electrical activation. Based on this observation, a maximum voltage-guided ablation technique (MVGT) was developed. This technique was assessed during pacing from the coronary sinus and was reported to be a feasible method to reach bidirectional isthmus block without the need for a complete anatomic ablation line., Methods: This was a prospective, randomized single center study. Twenty patients underwent CTI ablation during atrial flutter. In group I (10 pts) CTI ablation was performed with complete anatomical ablation line. In group II (10 pts) ablation was guided by the highest amplitude potentials on the CTI sequentially until bidirectional isthmus block was reached. The following parameters were compared: acute success rate, procedure time, fluoroscopy time, number of radiofrequency (RF) applications and total RF duration., Results: In all patients, atrial flutter terminated during ablation. Bidirectional isthmus block could be achieved in all pts. Procedure time was shorter in group II (107 +/- 40 vs 68 +/- 19 min, p < 0.01). Significantly less fluoroscopy was used in group II (22.6 +/- 10.6 vs 12.1 +/- 3.8 min, p < 0.01). There were less RF applications in group II (27.1 +/- 21.5 vs 5.9 +/- 2.4, p < 0.001)., Conclusions: (1) The major finding of this study is that MVGT is a feasible method even during ongoing atrial flutter. (2) Our data confirm that MVGT is an effective technique for CTI ablation with considerable decrease in procedure and fluoroscopy times.

Background: One of the crucial points during in most approaches developed for ablation of atrial fibrillation (AF) is the ability to identify the pulmonary vein (PVs) and to accurately locate their ostia., Objectives: The purpose of this case series was to investigate a simplified method for fusion of the multislice computer tomography (CT) derived 3D dataset with the electroanatomical map in order to facilitate the mapping procedure., Methods: In 5 consecutive patients (4 male) referred for catheter ablation of symptomatic drug-refractory paroxysmal atrial fibrillation contrast enhanced computer tomography was performed before the procedure and imported into an electroanatomical mapping system (Carto XP) using CartoMerge Image Integration Module. During the procedure a multipolar mapping catheter (Quick Star DS, Biosense Webster, Diamond Bar, CA, USA) was introduced to the coronary sinus (CS) to align the CSCT shell to the proper position. The CS potentials provided information to identify the ostium of the CS to achieve a more accurate fusion of the images. No mapping points were taken in the left atrium. The feasibility of the method was characterized by the distance of mapping points. Mapping, registration and outcome data were compared with a cohort of patients undergoing MRI image integration., Result: The mean distance between the mapping points taken in the CS by the Quick Star catheter and the CS CT surface was suitable (mean+/-SD, 1.4+/-0.3 mm). Full electrical isolation of the pulmonary veins could be achieved in all patients. The mean procedure and fluoroscopy time were 39 +/- 22 and 134 +/-38 min respectively, significantly decreased as compared to the MRI cohort., Conclusions: Highly accurate CT image and the electroanatomical map (EAM) fusion can be obtained by the Carto 3D electromanatomical mapping system using CS as the key anatomical structure for registration. Using this technique the mapping time of the left atrium can be reduced.