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Objectives Our purpose was to investigate the impact of short-lasting atrial fibrillation (AF) on the electrophysiological properties of the atria and pulmonary veins (PVs) in patients devoid of AF. Background The presence of AF is associated with electrical remodeling processes that promote a substrate for arrhythmia maintenance in the atria, which has been termed “AF begets AF.” However, it is unclear whether those electrical alterations also occur in the PVs. Methods Thirty-five patients with a left-sided accessory pathway and without a prior history of AF were included. After successful ablation, the effective refractory periods (ERPs) and conduction times of the right atrium (RA), left atrium (LA), and the PVs were determined. Afterwards, AF was induced and maintained for a period of 15 min. Thereafter, the stimulation protocol was repeated. Results At baseline, the PVs had significantly longer ERPs than the atria. After exposure to AF, the ERPs of both the atria and the PVs decreased significantly. The ERPs of the PVs, however, decreased by a significantly greater extent than the ERPs of the atria (PVs: 248 ± 27 ms vs. 211 ± 40 ms, p Conclusions New-onset, short-lasting AF creates electrical characteristics similar to those of patients with AF. However, these alterations are pronounced in the PVs compared with the atria, indicating that “AF begets AF in the PVs” (Electrophysiological Properties of the Pulmonary Veins; NCT00530608).

Pulmonary veins (PVs) are the predominant sources of paroxysmal atrial fibrillation (AF), and electrical PV isolation has become an established interventional treatment for patients suffering from AF. There are a few cases describing PV tachycardias; however, mechanisms of PV arrhythmogenicity resulting in PV tachycardias remain incompletely understood. We report on a patient who underwent PV isolation for paroxysmal AF, in whom a persistent PV tachycardia was observed within an isolated vein. This tachycardia was stable in nature and different pacing manoeuvres revealed electrophysiological features consistent with reentry (Lasso displaying the entire tachycardia cycle length, concealed entrainment, overdrive termination, and induction by programmed stimulation) as the underlying mechanism.

Vorrangiges Ziel der Behandlung des Vorhofflimmerns ist die Pravention von Schlaganfallen. Obwohl die entsprechenden Risikofaktoren seit Jahren klar identifiziert sind, werden derzeit in Deutschland nur etwa die Halfte der Patienten mit Vorhofflimmern und entsprechender Indikation oral antikoaguliert. Die im Jahre 2006 publizierte neue Fassung der Leitlinien der amerikanischen und europaischen Fachgesellschaften legt ihren Empfehlungen bei Patienten mit „nichtvalvularem” Vorhofflimmern den CHADS2-Score zur Risikostratifizierung zugrunde, der sich in den klinischen Alltag einfach und schnell einbinden lasst. Neu ist bei diesen Leitlinien auch der erweiterte Entscheidungsspielraum bei intermediarem Risiko. Jetzt kann in diesen Fallen individuell abgewogen werden, ob eher eine Thrombozytenaggregationshemmung mit Acetylsalicylsaure oder eine orale Antikoagulation mit Vitamin-K-Antagonisten indiziert ist. Vor allem bei Letzterem ist eine entsprechende Therapietreue der Patienten essenziell, um das Schlaganfallrisiko tatsachlich reduzieren zu konnen. Dies gilt insbesondere fur altere Patienten, die ein erhohtes Risiko fur Thrombembolien, aber auch naturgemas ein gesteigertes Blutungsrisiko aufweisen. Bei alteren Patienten mit Vorhofflimmern und einem hohen Risiko fur das Auftreten einer kardiogenen Embolie sollte in der Regel primar eine orale Antikoagulation empfohlen werden. Prevention of ischemic stroke is the ultimate aim in patients with atrial fibrillation (AF). The risk factors for ischemic stroke in patients with atrial fibrillation have been clearly identified. Despite this, only half of all patients with atrial fibrillation and an indication were treated with oral anticoagulants. In the 2006 ACC/AHA/ESC-Guidelines, a new stroke risk classification scheme, known as CHADS2 (the letters standing for Cardiac Failure, Hypertension, Age, Diabetes, Stroke [Doubled]) was used for non-valvular AF. Especially in patients with intermediate risk, now there is more latitude for decisions. In contrast to previous guidelines, treatment with acetylsalicylate or oral anticoagulants is mandatory. The target intensity of anticoagulation involves a balance between prevention of ischemic stroke and avoidance of hemorrhagic complications especially in the elderly patient. Targeting the lowest adequate intensity of anticoagulation to minimize the risk of bleeding is particularly important for elderly AF patients. In elderly patients with a high risk for stroke, oral anticoagulation should be recommended usually.

Background: External cardioversion is effective to terminate persistent atrial flutter. Biphasic shocks have been shown to be superior to monophasic shocks for ventricular defibrillation and atrial fibrillation cardioversion. The purpose of this trial was to compare the efficacy of rectilinear biphasic versus standard damped sine wave monophasic shocks in symptomatic patients with typical atrial flutter. Methods: 135 consecutive patients were screened, 95 (70 males, mean age 62 ± 13 years) were included. Patients were randomly assigned to a monophasic or biphasic cardioversion protocol. Forty-seven patients randomized to the monophasic protocol received sequential shocks of 100, 150, 200, 300 and 360 J. Forty-eight patients with the biphasic protocol received 50, 75, 100, 150 or 200 J. Results: First-shock efficacy with 50-Joule, biphasic shocks (23/48 patients, 48%) was significantly greater than with the 100-Joule, monophasic waveform (13/47 patients, 28%, p = 0.04). The cumulative second-shock efficacy with the 50- and 75-Joule, biphasic waveform (39/48 patients, 81%) was significantly greater than with the 100- and 150-Joule, monophasic waveform (25/47 patients, 53%, p < 0.05). The cumulative efficacy for the higher energy levels showed naturally no significant difference between the two groups. The amount of the mean delivered energy was significantly lower in the biphasic group (76 ± 39 J) compared to the monophasic one (177 ± 78 J, p < 0.05). Conclusions: For transthoracic cardioversion of typical atrial flutter, biphasic shocks have greater efficacy and the mean delivered current is lower than for monophasic shocks. Therefore, biphasic cardioversion with lower starting energies should be recommended.

The coronary sinus (CS) has been described as a substrate being involved in the atrial fibrillation (AF) process. However, there are no data describing the CS as a single source of AF. We report a patient with paroxysmal AF who demonstrated an arrhythmogenic focus within the proximal CS as single source initiating and driving AF. This discrete spot was characterized by a sharp "pulmonary vein-like " spike potential preceding every beat during AF and following the atrial potential during sinus rhythm. Radiofrequency ablation at that site led to elimination of the spike potential, disappearance and noninducibility of AF.

Objective: Catheter ablation of ventricular tachycardia (VT) after myocardial infarction (MI) can be complex and time-consuming. We only targeted the previously documented VTs and those with similar or longer cycle lengths. Methods: 30 patients with VTs after MI were included in the study. Voltage mapping was performed using an electro-anatomic mapping system (CARTOT). Stable VTs were mapped during tachycardia and unstable VTs during sinus rhythm. Results: Clinical VTs were stable in 16 (53%) and unstable in 14 (47%) patients, and ablation was successful in 11 (69%) and 9 patients (64%), respectively (p = 0.42). During follow-up (14 ± 6 months), 4 patients (25%) treated for stable and 6 (43%) for unstable VTs had recurrences (p = 0.82); ablation was successful in none and 2 (33%) of them, respectively. Non-target VTs were inducible in 11 (55%) of 20 patients after successful ablation and non-inducible in 9 (45%). During follow-up, inducibility of non-target VTs did not predict recurrences (9 vs. 11%, p = 0.88). Conclusions: Catheter ablation of VTs after MI can be successfully performed. Acute success rates seem to be similar for stable and unstable VTs. VTs faster than those documented clinically exert a minor effect on VT recurrences during follow-up.

Background— Insights gained from noncontact mapping of ventricular tachycardia (VT) have not been systematically applied to contact maps. This study sought to unify both techniques for an individualized approach to the patient with multiple ischemic VTs irrespective of cycle length. Methods and Results— For 12 consecutive patients with chronic myocardial infarction and recurrent VT, bipolar contact maps were acquired during sinus or paced rhythm. Additional noncontact maps were obtained during 48 induced VTs (cycle length 192 to 579 ms). Endocardial exit sites were superimposed on contact maps and verified by pace-mapping. Radiofrequency lesions were extended for critical borders defined by multiple neighboring exits and followed the isovoltage contour line of contact maps. Nine critical borders were identified in 8 patients and constituted the substrate for 31 VTs. The voltage at exit sites was 0.8 mV (range 0.1 to 2.3). Noncontact maps revealed 23±18% of isthmus conduction. Thirty-seven (77%) of all and 83% of clinically documented VTs were rendered noninducible irrespective of cycle length by application of 27 radiofrequency lesions (range 18 to 56). Spontaneous transitions between distinct VTs along critical borders were demonstrated in 4 patients. Pace-mapping reproduced the QRS morphology of 81% of VTs and was associated with successful ablation ( P P Conclusion— The combined approach of contact and noncontact mapping effectively defines critical borders as the substrate of multiple VTs without limitation for unstable VTs.

Aims To investigate the effectiveness of additional substrate modification (SM) by left atrial (LA) linear lesions as compared with pulmonary vein isolation (PVI) alone in patients with persistent atrial fibrilla- tion (AF) in a prospective randomized study. Percutaneous PVI has evolved as an accepted treatment for paroxysmal AF but seemed to be less effective in patients with persistent AF. The benefit of PVI alone and additional linear lesions has not been validated in a randomized study so far. Methods and results Sixty-two patients with persistent AF (median duration 7, range 1-18 months) were randomly assigned to either PVI alone (n ¼ 30) or additional SM (n ¼ 32) consisting of a roof line connecting both left superior and right superior PV and LA isthmus ablation between left inferior PV and mitral annulus. Procedures including SM were performed using a three-dimensional mapping system (EnSite NavX TM , St Jude Medical, St Paul, MN, USA). Anti-arrhythmic drugs were discontinued within 8 weeks after ablation in both groups. Follow-up included daily trans-telephonic ECG transmitted irrespective of the patient's symptoms. PVI was successful in 98% of all targeted veins in both groups. Additional SM did not increase fluoroscopy time (72.1+ 18.7 vs. 72.9+ 17.3 min, P ¼ 0.92) because of the use of three-dimensional navigation in the PVI þ SM group. AF recurrences within the first 4 weeks following ablation were more common after PVI alone (77%) than additional SM (44%, P ¼ 0.002). After a follow-up time of 487 (429-570) days, only 20% of patients undergoing stand alone PVI remained in sinus rhythm when compared with 69% following PVI combined with SM (P ¼ 0.0001). Two patients assigned to PVI þ SM experienced procedure-related complications (cardiac tamponade and minor stroke) which resolved without sequelae. Conclusion PVI alone is insufficient in the treatment of persistent AF. However, additional left linear lesions increase the success rate significantly. Early AF-relapses are associated with a negative outcome after PVI alone but not following additional SM.

Cooled Versus Large-Tip Catheters for Flutter Ablation. introduction: Open cooled-tip and solid 8-mm-tip catheters have demonstrated safety and effectiveness for radiofrequency current (RFC) ablation of typical atrial flutter (AFL). However, data from prospective and randomized studies in this setting are lacking. Methods and Results: One hundred thirty consecutive patients (104 men; 61 ′ 11 years) with AFL were randomized to undergo RFC catheter ablation either using a solid 8-mm-tip catheter (group A, 65°C, 70 W, 60 s) or an open irrigated-tip catheter (group B, 65°C, 50 W, 60 s, 17 mL/min flow). Endpoint was bidirectional conduction isthmus block. In cases of repeated (two times) transient isthmus block; the catheter was changed (crossed over) to the catheter used in the other randomization arm, but patients remained in the original group following intention-to-treat analysis. The selected endpoint could be achieved in all patients after 12 ′ 6 RFC pulses in group A and 10 ′ 7 RFC pulses in group B (P = 0.11). Procedure times were longer (159 ′ 38 min vs 138 ′ 37 min, P = 0.002) and x-ray exposures higher in group A (fluoroscopy time 25 ′ 17 min vs 21 ′ 10 min, P = 0.08; x-ray dosage 3,133 ′ 2,576 cGy.cm 2 vs 2,326 ′ 1,405 cGy.cm 2 , P = 0.03). Transient isthmus block was observed in 23 group A patients and 12 group B patients (P = 0.03). Onset time of transient isthmus block ranged from 0.5 to 27 minutes. Repeated transient isthmus block occurred in 8 of the 23 patients in group A after 19 ′ 3 RFC applications. After crossover to the cooled-tip catheter, the endpoint was reached another 5 ′ 1 RFC pulses. In group B, all patients could be treated without change of ablation catheter. After a follow-up of 14 ′ 2 months, 2 patients (3%) in group A and 1 patient (1.5%) in group B presented with AFL recurrence. Conclusion: Open cooled-tip catheters are more effective than solid large-tip catheters for AFL ablation. The greater effectiveness is evident in cases showing repeated conduction recovery within the cavotricuspid isthmus. Primary use of open irrigated-tip catheters should be considered for AFL ablation.

Aims Beneficial effects of atrial fibrillation (AF) ablation have been demonstrated in patients with congestive heart failure (CHF) and significantly impaired left ventricular ejection fraction (LVEF). However, the impact of pulmonary vein isolation (PVI) on cardiac function in patients with paroxysmal AF and impaired LVEF remains under discussion. This study aimed to evaluate the impact of PVI for paroxysmal AF on cardiac function in patients with impaired LVEF using cardiac magnetic resonance imaging (CMRI). Methods and results A total number of 70 patients with paroxysmal AF and episodes � 24 h were scanned on a 1.5-T-CMRI before and 6 months after PVI during sinus rhythm. End-diastolic volume, end-systolic volume, and LVEF were determined by epicardial and endocardial measurements. Patients were categorized into two groups regarding cardiac function as assessed by CMRI: group 1 patients (n ¼ 18) with an LVEF , 50% and patients with an LVEF . 50% (group 2, n ¼ 52). Group 1 patients demonstrated a significant lower success rate than patients of group 2 after a follow-up of 152+ 40 days (50 vs. 73%, P , 0.05). Cardiac magnetic resonance imaging in group 1 patients demonstrated a significant improvement in cardiac function after AF ablation (41+ 6v s. 51+ 12%, P ¼ 0.004), whereas group 2 patients did not show significant differences (60+ 6v s. 59+ 9%, P ¼ 0.22) after a 6 months follow-up. Conclusion Pulmonary vein isolation improves cardiac function in patients with paroxysmal AF and impaired LVEF. These data suggest that an impaired LV function can be partially attributed to AF with short-lasting paroxysms.

Aims Rhythm follow-up after catheter ablation of atrial fibrillation (AF ablation) is mainly based on Holter electrocardiogramm (ECG), tele-ECG or on patients symptoms. However, studies using 7-day Holter or tele-ECG follow-up revealed a significant number of asymptomatic recurrences. Thus, the aim of this study was to analyse continuous atrial recordings in pacemaker patients with an incorporated Holter function before and after AF ablation in order to determine all AF recurrences and thereby the ‘real’ success rates. Methods and results The study comprised 37 patients (64.6 ± 10 years) with prior pacemaker/implantable cardioverter defibrillator (ICD) implantation including an atrial Holter function referred for AF ablation. Holter data were obtained and correlated to patients’ symptoms before and every 3-month after AF ablation. AF recurrence was defined as an atrial high frequency episode of less than 330 ms (180 b.p.m.) lasting longer than 30 s. The ablation procedure consisted of pulmonary vein isolation (PVI) in patients with paroxysmal atrial fibrillation (PAF, n = 20) and additional substrate modification aiming arrhythmia termination in patients with persistent or inducible AF after PVI as well as in patients with a history of long-lasting persistent AF (PersAF, n = 17). The mean atrial Holter monitoring period was 7.4 ± 3.3 months before and 13.5 ± 4.2 months after ablation with an overall AF burden of 33.7% prior to ablation. During follow-up, AF burden decreased from 17.3–0.65% ( P = 0.001) in PAF patients and from 57.4 to 13.9% ( P = 0.024) in patients with PersAF. Complete AF freedom was observed in 85% (17 patients) of PAF patients and 59% (10 patients) in patients with PersAF. The absence of symptoms correlated well with documented freedom of AF. Conclusion In the present study we could show, that freedom from AF can be achieved by catheter ablation in a high percentage of patients even with PersAF. Continuous atrial monitoring reveals AF ablation success rates comparable with those assessed by clinical evaluation. Symptomatic freedom of AF correlated well with the actual freedom of AF at least in this highly symptomatic patient cohort.

AP localization can be predicted by analyzing the polarity of the delta wave, QRS polarity, and R/S ratio in patients with Wolff-Parkinson-White syndrome. However, the estimation of AP location is limited in patients with concealed pathways during atrioventricular reentrant tachycardias (AVRT). Thus, we analyzed retrograde P-wave polarity during orthodromic AVRT and developed an algorithm to predict the localization of concealed accessory pathways (AP).A total number of 131 patients with a single AP and inducible orthodromic AVRT were included. The initial 61 patients were analyzed retrospectively for algorithm development, whereas 70 patients were evaluated prospectively. The retrograde P-wave polarity was analyzed by subtracting the superimposing T-wave during orthodromic AVRT using custom-designed software. Four leads of the surface electrocardiogram (ECG) were identified to accurately distinguish AP locations assigned to four different regions around each AV annulus: I, aVR, aVL, and V(1). Lead V(1) was used to differentiate right (negative or isoelectric) from left (solely positive) APs. Retrograde P-wave in lead I was negative in left posterior APs exclusively and became more positive with an AP location shifting towards right anterior. P-wave polarity in lead aVR demonstrated a shift from a positive polarity from left APs to isoelectric in right APs. The opposite direction (shift from positive to isoelectric) was observed for lead aVL. The subsequently developed algorithm for concealed AP localization using these surface ECG leads demonstrated a high sensitivity, specificity, and positive predictive value particularly for common AP localizations (left posterior and inferior, and right septal) when applied in a prospective fashion.Concealed AP localization can be accurately predicted by the analysis of retrograde P-wave polarity during orthodromic AVRT using the algorithm derived from the presented study.

Our purpose was to investigate the impact of short-lasting atrial fibrillation (AF) on the electrophysiological properties of the atria and pulmonary veins (PVs) in patients devoid of AF.The presence of AF is associated with electrical remodeling processes that promote a substrate for arrhythmia maintenance in the atria, which has been termed "AF begets AF." However, it is unclear whether those electrical alterations also occur in the PVs.Thirty-five patients with a left-sided accessory pathway and without a prior history of AF were included. After successful ablation, the effective refractory periods (ERPs) and conduction times of the right atrium (RA), left atrium (LA), and the PVs were determined. Afterwards, AF was induced and maintained for a period of 15 min. Thereafter, the stimulation protocol was repeated.At baseline, the PVs had significantly longer ERPs than the atria. After exposure to AF, the ERPs of both the atria and the PVs decreased significantly. The ERPs of the PVs, however, decreased by a significantly greater extent than the ERPs of the atria (PVs: 248 +/- 27 ms vs. 211 +/- 40 ms, p0.001; LA: 233 +/- 23 ms vs. 214 +/- 20 ms, p = 0.004; RA: 226 +/- 29 ms vs. 188 +/- 20 ms; p = 0.003). After AF exposure, the PVs demonstrated a significant conduction slowing whereas the atria did not (PVs: 125 +/- 33 ms vs. 159 +/- 37 ms, p0.001; LA: 129 +/- 26 ms vs. 130 +/- 24 ms, p = NS; RA: 192 +/- 36 ms vs. 196 +/- 32 ms, p = NS). Finally, AF was more frequently induced after the presence of AF, particularly by pacing in the PVs (14% vs. 49%, p = 0.001).New-onset, short-lasting AF creates electrical characteristics similar to those of patients with AF. However, these alterations are pronounced in the PVs compared with the atria, indicating that "AF begets AF in the PVs" (Electrophysiological Properties of the Pulmonary Veins; NCT00530608).

External cardioversion is effective to terminate persistent atrial flutter. Biphasic shocks have been shown to be superior to monophasic shocks for ventricular defibrillation and atrial fibrillation cardioversion. The purpose of this trial was to compare the efficacy of rectilinear biphasic versus standard damped sine wave monophasic shocks in symptomatic patients with typical atrial flutter.135 consecutive patients were screened, 95 (70 males, mean age 62 +/- 13 years) were included. Patients were randomly assigned to a monophasic or biphasic cardioversion protocol. Forty-seven patients randomized to the monophasic protocol received sequential shocks of 100, 150, 200, 300 and 360 J. Forty-eight patients with the biphasic protocol received 50, 75, 100, 150 or 200 J.First-shock efficacy with 50-Joule, biphasic shocks (23/48 patients, 48%) was significantly greater than with the 100-Joule, monophasic waveform (13/47 patients, 28%, p = 0.04). The cumulative second-shock efficacy with the 50- and 75-Joule, biphasic waveform (39/48 patients, 81%) was significantly greater than with the 100- and 150-Joule, monophasic waveform (25/47 patients, 53%, p0.05). The cumulative efficacy for the higher energy levels showed naturally no significant difference between the two groups. The amount of the mean delivered energy was significantly lower in the biphasic group (76 +/- 39 J) compared to the monophasic one (177 +/- 78 J, p0.05).For transthoracic cardioversion of typical atrial flutter, biphasic shocks have greater efficacy and the mean delivered current is lower than for monophasic shocks. Therefore, biphasic cardioversion with lower starting energies should be recommended.

Aims In the setting of right ventricular outflow tract-tachycardia (RVOT-T), data about long-term follow-up (FU) with respect to the therapeutic strategies are missing. All patients (pts) referred to our institution during the last 20 years for the treatment of RVOT-T were studied in a retrospective analysis to assess mortality and efficacy of treatment. Methods and results One hundred and thirty-three patients (77 female; 39 ± 13 years) with sustained RVOT-T were included in this study. At the time of first presentation, diagnosis of RVOT-T was made by complete invasive and non-invasive diagnostic assessment, including electrophysiology study and two-dimensional echocardiography. After 135 ± 68 months (median 136, range 29–248), patients were invited to undergo clinical assessment. Of the 133 pts, 127 (95%) survived and six (5%) died from non-cardiac disease. Anti-arrhythmic (AA) drugs were given to 62 of the 133 pts (47%); of them 32 (52%) had recurrences during follow-up. The mean time to recurrence was 10.02 years (95% CI 7.46–12.59). The other 71 study patients (53%) underwent catheter ablation. The procedure was successful in 58 pts (82%). During follow-up, 30 (52%) of the 58 successfully treated patients had recurrences of RVOT-T. The mean time to recurrence was 6.28 years (95% CI 4.96–7.6). RVOT-T recurrences were similar in morphology to those treated previously in 33% and different in 67% of cases. Conclusions Long-term follow-up in patients with RVOT-T is favourable. Catheter ablation is effective in this setting. However, late recurrences with similar or different morphology may arise in half of the patients after initially successful treatment. AA drug therapy is a valid initial therapeutic option, since it is effective in about half of the patients.

Background The accuracy of three-dimensional mapping systems is affected by cardiac contraction and respiration. Objective The study sought to determine relative motion of cardiac and thoracic structures to assess positional errors and guide the choice of an optimized spatial reference. Methods Motion of catheters placed at the coronary sinus (CS), pulmonary vein (PV) ostia, left atrial (LA) isthmus and roof, cavotricuspid isthmus (CTI), and right atrial appendage (RAA) were recorded for 30 patients using Ensite-NavX. The right subclavian vein, left brachiocephalic vein, azygos vein, pulmonary arteries, and a static reference were included. The displacement from a mean position was calculated for each pair of sites. Respiration effects were assessed by the shift of the motion curve during in- and expiration phases. Results The PVs showed a mean interpair displacement of 4.1 ± 0.2 mm and a shift of 5.0 ± 0.5 mm. Proximal CS references for all LA structures (4.0 ± 1.1 mm) were superior to the static reference (4.9 ± 0.7 mm; P = .01). In addition, the shift due to respiration was less pronounced at 3.5 ± 0.8 mm versus 4.9 ± 0.5 mm ( P = .004), respectively. Motion of extracardiac vessels was influenced by a mean shift of 6.8 ± 1 mm. The remote subclavian and brachiocephalic veins were more affected (7.6 ± 0.7 mm) than the pulmonary arteries (5.9 ± 0.4 mm; P = .002). For the CTI, a minimized mean displacement of less than 4.6 ± 2.0 mm relative to the proximal CS, RAA, and azygos vein was found. Conclusion Respiration is the major source of relative motion, which increases with distance from the heart. For LA procedures, a proximal CS reference position is superior to a static reference position.

Navigation System for Ablation of Typical AFL. Introduction: Ensite® NavX (NavX) is a novel mapping and navigation system that allows visualization of conventional catheters for diagnostic and ablative purposes and uses them to create a three-dimensional (3D) geometry of the heart. NavX is particularly suitable for ablation procedures utilizing an anatomic approach, as in the setting of common-type atrial flutter (AFL). The aim of this study was to compare NavX-guided and conventional ablation procedures for AFL. Methods and Results: Forty consecutive patients (32 male, 59 ′ 12 years) with documented AFL were randomized to undergo fluoroscopy-guided (group I, 20 patients) or NavX-guided (group II, 20 patients) ablation, including 3D isthmus reconstruction. The same catheter setup was used in both groups. The endpoint of bidirectional isthmus block was obtained in all patients. Compared to conventional approaches, NavX-guided procedures significantly reduced fluoroscopy time (5.1 ′ 1.4 min vs 20 ′ 11 min, P < 0.01) and total x-ray exposure (5.1 ′ 3.1 Gycm 2 vs 24.9 ′ 1.6 Gycm 2 , P < 0.01). Isthmus geometry reconstruction could be performed in all patients of group II. In 4 patients (20%) of group II, anatomic isthmus variations were detected by NavX. No significant differences in radiofrequency current applications and procedural times were found between the two groups. Conclusion: NavX technology allows geometry reconstruction of the cavotricuspid isthmus. NavX-guided ablation of AFL reduces total x-ray exposure compared to the fluoroscopy-guided approach but does not prolong procedure time.