Prevention of ventricular fibrillation through de-networking of the Purkinje system: Proof-of-Concept Paper on the Substrate Modification of the Purkinje Network.

INTRODUCTION: Sudden cardiac death from ventricular fibrillation (VF) remains a major health problem worldwide. Currently, there are limited treatment options available to patients who suffer from episodes of VF. Because Purkinje fibers have been implicated as a source of initiation of VF, we are presenting the first paper of a series highlighting the promising results of substrate modulation through "De-Networking" of the Purkinje system preventing VF in patients without an alternative ablation strategy. METHODS AND RESULTS: We studied 10 consecutive patients (two female) all but one implanted with an ICD with documented VF or fast polymorphic Ventricular tachycardia (VT) (five patients without history of structural heart disease, two with ischemic cardiomyopathy, one with hypertrophic obstructive cardiomyopathy, one with dilated cardiomyopathy, and one with aortic valve disease). After 3D electroanatomical mapping, the left bundle branch (LBB) and left ventricular Purkinje potentials were annotated creating a virtual triangle with the apex formed by the distal LBB and the base by the most distal Purkinje potentials. Linear radiofrequency catheter ablation at the base of the triangle was performed, followed by ablation within the virtual triangle sparing the LBB and both fascicles ("de-networking"). All patients were treated without complications. During 1-year follow-up, only 2/10(20%) patients experienced recurrence in form of a single episode of polymorphic VT/VF. CONCLUSION: Catheter ablation of VF through "de-networking" of the Purkinje system in patients without overt arrhythmia substrate or trigger appears safe and effective and will require further study in a larger patient cohort.

"AF HeartTeam" Guided Indication for Stand-alone Thoracoscopic Left Atrial Ablation and Left Atrial Appendage Closure.

BACKGROUND: Traditional surgical treatment for patients with atrial fibrillation (AF) is performed via sternotomy and on cardiopulmonary bypass. It is very effective in regard to rhythm control, but remains unpopular due to its invasiveness. Truly endoscopic AF treatments have decreased the threshold for electrophysiologists (and cardiologists) to refer, and the reluctance of patients to accept a standalone surgical approach. Practice guidelines from around the world have recognized this as an acceptable therapeutic approach. Current guidelines recommend the HeartTeam approach in treating these complex AF cases. In this study we report our experience with AF HeartTeam approach for surgical stand-alone AF ablation. METHODS: The AF HeartTeam Program began in 2013, patients qualified for inclusion if either of the following was present: failed catheter ablation and/or medication, not suitable for catheter ablation, contraindication to anticoagulation, or patients preferring such an approach. All patients with a complex AF history were assessed by the AF HeartTeam, from which 42 patients were deemed suitable for a totally endoscopic AF procedure (epicardial ablation and LAA closure). Endpoints were intraoperative bidirectional block of the pulmonary veins and closure of left atrial appendage confirmed by transesophageal echocardiography (TEE). Post discharge rhythm follow-up was performed after 3 and 12, 24 and 36 months. Anticoagulation was discontinued 6 weeks after the procedure in patients after documented LAA closure. RESULTS: In total 42 patients underwent the endoscopic procedure (Median CHA2DS2-VASC=3 (1-6), HAS-BLED=2 (1-6)) for paroxysmal (15/42) and non-paroxysmal AF (27/42) respectively. Bidirectional block was obtained in all patients and complete LAA closure was obtained in all but one Patient on TEE (41/42). In one patient the LAA was not addressed due to extensive adhesions. Two patients underwent median sternotomy because of bleeding during the endoscopic surgery early in the series. There were no deaths. Procedure duration was a median of 124min (Range 83-211) and duration of hospitalization was median of 5 days (Range 3-12). During 36 months follow-up survival free of mortality, thromboembolic events or strokes was 100%. Twelve month freedom from atrial arrhythmia off anti-arrhythmic medication was 93% and 89% for paroxysmal and non-paroxysmal patients respectively. 6/42 patients who had an AF recurrence during the follow-up underwent touch-up catheter ablation. CONCLUSIONS: Atrial fibrillation heart team approach provides excellent outcomes for patients with AF. This approach is beneficial for patients after failed catheter ablation or not candidates for such and offers a very effective mid-term outcome data. In addition to effective rhythm control the protective effect of epicardial LAA closure may play an important role in effectively reducing stroke. The creation of an AF HeartTeam as recommended by the guidelines insures unbiased therapies and provides access to this minimally invasive but effective therapeutic option for AF patients.

Epicardial ablation of ventricular tachycardia using pericardioscopy through submammary minimal thoracotomy.

The subxiphoid access became the standard technique for epicardial ablation of ventricular tachycardia. However, it may prove difficult in certain situations. Here, we report an alternative method of epicardial and endocardial ablation performed via submammary minimal thoracotomy guided by pericardioscopy. Two male patients with structural heart disease and incessant ventricular tachycardia were successfully ablated using this technique. The described technique can be considered as an alternative to the standard technique. Moreover, it permits real-time visualization of cardiac vessels and fat tissue, and is safe in terms of damage to the phrenic nerve or potential bleeding complications.

Catheter ablation of right ventricular outflow tract tachycardia: a simplified remote-controlled approach.

AIMS: Manual mapping and ablation of right ventricular outflow tract (RVOT) tachycardia may be associated with cardiac perforation and complicated by mechanically induced ventricular extrasystoles (VESs). The aim of this study was to assess remote-controlled magnetic (RCM) mapping and ablation of RVOT ventricular tachycardia (VT)/VES utilizing a soft magnetic catheter. METHODS AND RESULTS: Mapping and ablation of RVOT VT/VES were performed using the magnetic navigation system (MNS, Niobe II, Stereotaxis, St Louis, MO) in conjunction with a cardiodrive motor unit (Stereotaxis). A soft magnetic catheter (Celsius RMT, 4 mm solid tip, Biosense Webster, Diamond Bar, CA) was navigated to the RVOT using a sequence of pre-installed magnetic vectors. The primary endpoint was defined as successful RCM VT/VES ablation. Other parameters observed included RCM RVOT accessibility, mapping-induced mechanical VES, fluoroscopy time, complications, and arrhythmia recurrence. Thirteen consecutive patients (mean age: 50 ± 14 years; 10 females, 6 RVOT VT) underwent RCM mapping and ablation. The RVOT was reached in all patients utilizing solely the MNS. Successful RCM RVOT ablation was achieved in {12 of 13} (92.3%) patients. Mean procedure and fluoroscopy times were 116.5 ± 48.9 and 7.5 ± 4.3 min, respectively. Catheter-induced VES during RVOT mapping were observed in {1 in 13} patients (7.7%, three VES). No complications occurred. During a mean follow-up of 252 ± 211 days, clinical arrhythmia recurrence was observed in {1 in 13} (7.7%) patients. CONCLUSIONS: Automatic RCM RVOT access is feasible, while RVOT mapping and ablation appear to be safe, fast, and effective. The soft magnetic catheter rarely induces mechanical VES.

Long-term results of catheter ablation in paroxysmal atrial fibrillation: lessons from a 5-year follow-up.

BACKGROUND: Paroxysmal atrial fibrillation (AF) naturally progresses toward chronic AF at an estimated rate of 15% to 30% over a 1- to 3-year period. Pulmonary vein (PV) isolation is increasingly performed for the treatment of drug-refractory paroxysmal AF. The long-term data on clinical outcome after circumferential PV isolation are limited. METHODS AND RESULTS: From 2003 to late 2004, 161 patients (121 men; age, 59.8±9.7 years) with symptomatic paroxysmal AF and normal left ventricular function underwent circumferential PV isolation guided by 3-dimensional mapping and double Lasso technique. Right-sided and left-sided continuous circular lesions encircling the ipsilateral PVs were placed with irrigated radiofrequency energy. The procedure end point was the absence of all PV spikes for at least 30 minutes after PV isolation verified by 2 Lasso catheters placed within the ipsilateral PVs. Sinus rhythm was present in 75 patients (46.6%) after the initial procedure during a median follow-up period of 4.8 years (0.33 to 5.5 years). A second procedure was performed in 66 and a third procedure in 12 patients. Recovered PV isolation conduction was observed in 62 of 66 patients (94.0%) during the second and in 8 of 12 patients (66.7%) during the third procedure. After a median of 1 (1 to 3) procedure, stable sinus rhythm was achieved in 128 of 161 patients (79.5%), whereas clinical improvement occurred in an additional 21 of 161 patients (13.0%) during a median follow-up of 4.6 years (0.33 to 5.5 years). Four patients in stable sinus rhythm died during follow-up. Progression toward chronic AF was observed in 4 patients (2.4%); however, only 2 patients reported symptoms. CONCLUSION: In patients with paroxysmal AF and normal left ventricular function, circumferential PV isolation results in stable sinus rhythm in the majority of patients, and low incidence of chronic AF was observed after ablation during up to 5 years of follow-up.

Remote-controlled magnetic pulmonary vein isolation using a new irrigated-tip catheter in patients with atrial fibrillation.

BACKGROUND: Lack of an irrigated-tip magnetic catheter has limited the role of remote-controlled magnetic navigation (Niobe II, Stereotaxis) for catheter ablation of atrial fibrillation (AF). METHODS AND RESULTS: A novel 3.5-mm-tip irrigated magnetic catheter (group 1, Thermocool Navistar RMT, Biosense Webster) was used for 3D left atrial reconstruction (CARTO RMT) and remote-controlled magnetic pulmonary vein isolation. A redesigned catheter was used in group 2. The primary end point was wide area circumferential pulmonary vein isolation confirmed by spiral catheter recording during ablation; secondary end points included procedural data, complications, and AF recurrence. Fifty-six consecutive patients [group 1: 28 patients, 22 males, age 64 (38 to 78) years, left atrium: 47 (34 to 52) mm; paroxysmal AF: n=21, persistent AF: n=7; group 2: 28 patients, 20 males, age 60 (24 to 78) years, left atrium: 40 (35 to 53) mm; paroxysmal AF: n=18, persistent AF: n=10] were included. The primary end point was achieved in a total of 52 of 56 (93%) patients. Median procedure duration was 315 (125 to 550) minutes (group 1: 370 [230 to 550] minutes; group 2: 243 [125 to 450] minutes). Median fluoroscopy exposure to the investigator was reduced by 31%. Tip charring in 17 of 28 (61%) and complications in 3 of 28 (11%) patients in group 1 resulted in a catheter redesign. Sinus rhythm was maintained by 35 of 50 (70%) patients during a median follow-up period of 545 (100 to 683) days. CONCLUSIONS: Remote-controlled magnetic AF ablation with real-time verification of pulmonary vein isolation is feasible with a comparable success rate to manual ablation. Safety improved after a redesign of the catheter.

Catheter ablation of long-standing persistent atrial fibrillation: a lesson from circumferential pulmonary vein isolation.

INTRODUCTION: Circumferential pulmonary vein isolation (CPVI) is associated with a high success rate in patients with paroxysmal and persistent atrial fibrillation (AF). However, in patients with long-standing persistent AF, the ideal ablation strategy still remains a matter of debate. METHODS AND RESULTS: Two-hundred and five patients underwent catheter ablation for long-standing persistent AF defined as continuous AF of more than 1-year duration. In a first step, all patients underwent CPVI. If direct-current cardioversion failed following CPVI, ablation of complex fractionated atrial electrograms (CFAEs) was performed. The goal was conversion into sinus rhythm (SR) or, alternatively, atrial tachycardia (AT) with subsequent ablation. A total of 340 procedures were performed. CPVI alone was performed during 165 procedures in 124 of 205 (60.5%) patients. In the remaining 81 patients, additional CFAE ablation was performed in 45, left linear lesions for recurrent ATs in 44 and SVC isolation in 15 patients, respectively, resulting in inadvertent left atrial appendage isolation in 9 (4.4%) patients. After the initial ablation procedure, 67 of 199 patients remained in SR during a mean follow-up of 19 ± 11 months. Six patients were lost to follow-up. After a mean of 1.7 ± 0.8 procedures, 135 of 199 patients (67.8%) remained in SR. Eighty-six patients (43.2%) remained in SR following CPVI performed as the sole ablative strategy. CONCLUSIONS: CPVI alone is sufficient to restore SR in 43.2% of patients with long-standing persistent AF. Multiple procedures and additional ablation strategies with a significant risk of inadvertent left atrial appendage isolation are often required to maintain stable SR.

Long-term clinical outcome following pulmonary vein isolation with high-intensity focused ultrasound balloon catheters in patients with paroxysmal atrial fibrillation.

AIMS: High-intensity focused ultrasound (HIFU) applied via a balloon catheter is a novel technology for pulmonary vein isolation (PVI) in patients with paroxysmal atrial fibrillation (PAF). The long-term success rate is unknown. METHODS AND RESULTS: Thirty-two patients (22 male, age 60 +/- 9 years) with a long history [5 (4;9) years] of drug refractory [3 +/- 1 anti-arrhythmic drugs (AADs)], symptomatic PAF were included into the analysis. Pulmonary vein isolation was performed using the first- and second-generation HIFU balloon catheters (ProRhythm, Ronkonkoma, NY, USA). Follow-up (F/U) included regular telephonic interviews, trans-telephonic Holter ECG, and event recording. Recurrence was defined as a documented or symptomatic AF episode >30 s without a blanking period. In total 101/116 targeted PVs (87%) were acutely isolated exclusively using HIFU. During a median F/U of 1400 (930;1568) days, 18 patients (56%) were free of AF without AAD after a single HIFU procedure. In nine patients with AF recurrence, 20 PVs exhibited electrical reconduction and re-isolation was performed using irrigated radiofrequency current (RFC) ablation. CONCLUSION: Patients treated with the first- and second-generation HIFU balloon catheters due to symptomatic PAF show long-term success rates similar to RFC-based PVI procedures. The major determinant of AF recurrence after HIFU treatment seems to be reconduction of previously isolated PVs. However, the favourable effectiveness is offset by the severe complications reported following HIFU treatment. This led to a halt of its clinical use.

Cryoballoon pulmonary vein isolation with real-time recordings from the pulmonary veins.

INTRODUCTION: Cryoballoon (CB) ablation represents a novel technology for pulmonary vein isolation (PVI). We investigated feasibility and safety of CB-PVI, utilizing a novel spiral catheter (SC), thereby obtaining real-time PV potential registration. METHODS: Following double transseptal puncture, a Lasso catheter (Biosense Webster, Diamond Bar, CA, USA) and the 28 mm CB were positioned within the left atrium. A novel SC (Promap, ProRhythm Inc., Ronkonkoma, NY, USA) was inserted through the lumen of the CB allowing PV signal registration during treatment. Time to PV conduction block was analyzed. If no stable balloon position was obtained, the SC was exchanged for a regular guide wire and PV conduction was assessed after treatment by Lasso catheter. RESULTS: In 18 patients, 39 of 72 PVs (54%) were successfully isolated using the SC. The remaining 33 PVs were isolated switching to the regular guide wire. Time to PV conduction block was significantly shorter in PVs in which sustained PVI was achieved as compared to PVs in which PV conduction recovered within 30 minutes (33 +/- 21 seconds vs 99 +/- 65 seconds). In 40 PVs, time to PV conduction block was not obtained because of: (1) PVI not being achieved during initial treatment; (2) a distal position of the SC; or (3) isolation with regular guide wire. No procedural complications occurred. CONCLUSION: Visualization of real-time PV conduction during CB PVI is safe, feasible, and allows accurate timing of PVI onset in a subset of PVs. Time to PV conduction block predicts sustained PVI. However, mechanical properties of the SC need to be improved to further simplify CB PVI.

Right ventricular rapid pacing in catheter ablation of atrial fibrillation: a novel application for cryoballoon pulmonary vein isolation.

BACKGROUND: Cryoballoon ablation (Arctic Front, Cryocath) represents a novel technology for pulmonary vein isolation (PVI). The initial phase of a freeze is crucial for cryolesion formation which is determined by local temperature depending on blood flow. We investigated the impact of right ventricular rapid pacing (RVRP) on temperature kinetics in patients (pts) with paroxysmal atrial fibrillation (PAF). METHODS AND RESULTS: Right ventricular rapid pacing was performed from the RV apex. Absolute minimal temperature (MT, degrees C), temperature slopes [time (s) to 80% MT; dT/dt), area under the curve (AUC) and arterial blood pressure (ABP, mmHg) were compared (group I: with RVRP vs. group II: without RVRP). RVRP (mean duration 55 +/- 7 s) was performed in 11 consecutive PAF pts (41 PVs, age 58 +/- 9 years, LA size 44 +/- 6 mm, normal ejection fraction). Only freezes with identical balloon positions were analyzed (11/41 PVs). RVRP (cycle length 333 +/- 3 ms) induced a significant drop in ABP (group I: 45 +/- 3 mmHg vs. group II: 100 +/- 18 mmHg, p < 0.001). MT was not different between group I and group II (-45.0 +/- 4.4 vs. -44.3 +/- 3.4 degrees C, p = 0.46), whereas slope (38.0 +/- 4.6 s vs. 51.6 +/- 14.4 s, p = 0.0034) and AUC (1090 +/- 4.6 vs. 1181 +/- 111.2, p = 0.02) was significantly changed. In one pt, a ventricular tachycardia was induced. PVI was achieved in 41/41 PVs. CONCLUSION: Right ventricular rapid pacing significantly accelerates cryoballoon cooling during the initial phase of a freeze possibly suggesting improved cryolesions.

The 'single big cryoballoon' technique for acute pulmonary vein isolation in patients with paroxysmal atrial fibrillation: a prospective observational single centre study.

AIMS: Cryothermal energy (CTE) ablation via a balloon catheter (Arctic Front, Cryocath) represents a novel technology for pulmonary vein isolation (PVI). However, balloon-based PVI approaches are associated with phrenic nerve palsy (PNP). We investigated whether 'single big cryoballoon'-deployed CTE lesions can (i) achieve acute electrical PVI without left atrium (LA) imaging and (ii) avoid PNP in patients with paroxysmal atrial fibrillation (PAF). METHODS AND RESULTS: After double transseptal punctures, one Lasso catheter and a big 28 mm cryoballoon catheter using a steerable sheath were inserted into the LA. PV angiography and ostial Lasso recordings from all PVs were obtained. Selective PV angiography was used to evaluate balloon to LA-PV junction contact. CTE ablation lasted 300 s, and the PN was paced during freezing at right-sided PVs. Twenty-seven patients (19 males, mean age: 56 +/- 9 years, LA size: 42 +/- 5 mm) with PAF (mean duration: 6.6 +/- 5.7 years) were included. PVI was achieved in 97/99 PVs (98%). Median (Q(1); Q(3)) procedural, balloon, and fluoroscopy times were 220 min (190; 245), 130 min (90; 170), and 50 min (42; 69), respectively. Three transient PNP occurred after distal PV ablations. No PV stenosis occurred. Total median (Q(1); Q(3)) follow-up time was 271 days (147; 356), and 19 of 27 patients (70%) remained in sinus rhythm (3-month blanking period). CONCLUSION: Using the single big cryoballoon technique, almost all PVs (98%) could be electrically isolated without LA imaging and may reduce the incidence of PNP as long as distal ablation inside the septal PVs is avoided.

Inducibility of atrial tachyarrhythmias after circumferential pulmonary vein isolation in patients with paroxysmal atrial fibrillation: clinical predictor and outcome during follow-up.

AIMS: We investigated the presence and clinical outcome of inducibility of atrial tachyarrhythmias after circumferential pulmonary vein isolation (CPVI) in patients with paroxysmal atrial fibrillation (PAF). METHODS AND RESULTS: Sixty patients with symptomatic PAF underwent CPVI guided by 3D mapping and double Lasso technique. After achievement of CPVI, the induction was performed. The left atrium (LA) volume and the isolated LA area around the right and left-sided pulmonary veins were measured by the 3D mapping system. Sustained atrial tachyarrhythmias (>10 min) were induced after CPVI in 17 of 60 patients (28%). Patients with inducible atrial tachyarrhythmias had significantly smaller isolated areas when compared with the group with non-inducible tachyarrhythmias (16.7 +/- 2.3 vs. 18.8 +/- 2.9%, P < 0.05). After the initial procedure, recurrence occurred in 18 of 43 (42%) patients in the non-inducible group and in 7 of 17 (41%) in the inducible group during follow-up. A repeat procedure was performed in all 25 patients with recurrence. Five patients had a recurrence after the repeat procedure during 20.8 +/- 7.5 months, and there was no difference between the two groups. CONCLUSION: Inducibility of atrial tachyarrhythmias is associated with proportionally smaller isolated area and does not predict the clinical efficacy of CPVI in patients with PAF.

Propagation velocity kinetics and repolarization alternans in a free-behaving sheep model of pacing-induced atrial fibrillation.

AIMS: Experimental models have reported conflicting results regarding the role of dispersion of repolarization in promoting atrial fibrillation (AF). Repolarization alternans, a beat-to-beat alternation in action potential duration, enhances dispersion of repolarization when propagation velocity is involved. METHODS AND RESULTS: In this work, original electrophysiological parameters were analysed to study AF susceptibility in a chronic sheep model of pacing-induced AF. Two pacemakers were implanted, each with a single right atrial lead. Right atrial depolarization and repolarization waves were documented at 2-week intervals. A significant and gradual decrease in the propagation velocity at all pacing rates and in the right atrial effective refractory period (ERP) was observed during the weeks of burst pacing before sustained AF developed when compared with baseline conditions. Right atrial repolarization alternans was observed, but because of the development of 2/1 atrioventricular block with far-field ventricular interference, its threshold could not be precisely measured. Non-sustained AF was not observed at baseline, but appeared during the electrical remodelling in association with a decrease in both ERP and propagation velocity. CONCLUSION: We report here on the feasibility of measuring ERP, atrial repolarization alternans, and propagation velocity kinetics and their potential in predicting susceptibility to AF in a free-behaving model of pacing-induced AF using the standard pacemaker technology.

Incidence and significance of far-field R wave sensing in a VDD-implantable cardioverter defibrillator.

BACKGROUND: A VDD-implantable cardioverter-defibrillator (ICD) provides atrioventricular (AV) synchronous stimulation when necessary and incorporates the advantages of dual chamber arrhythmia discrimination algorithms both at potentially lower costs and less periprocedural complications than a DDD-ICD system. A prerequisite for correct dual chamber ICD function is reliable atrial sensing. METHODS: We evaluated atrial near- and ventricular far-field sensing and its impact on the dual-chamber detection algorithm in 106 patients with a single-lead VDD-ICD during a 12-month follow-up period. RESULTS: Six hundred and thirty-nine follow-ups were included. Mean near-field amplitude was 3.82 +/- 1.76 mV; mean far-field amplitude was 0.31 +/- 0.15 mV. 46% of patients had far-fields >0.35 mV and 35% of patients showed atrial EGM markers corresponding to a ventricular far-field in at least one follow-up. Six hundred and forty-five tachycardia episodes were evaluated. Due to far-field sensing, three of 66 episodes (4.5%) of sinus tachycardia were misclassified as ventricular tachycardia (VT), leading to antitachycardia therapies. Delayed detection of VT was seen in a 12 of 323 episodes (3.7%) in five of 62 patients (8%) having VT events (delay 6.4 +/- 6.0 seconds (range 2-24 seconds)). Stable far-field amplitudes <0.2 mV in a follow-up had a high negative predictive value for the occurrence of malfunction during tachycardia-conversely, high far-field amplitudes or a high incidence of far-field markers are only moderately correlated with malfunction. CONCLUSIONS: Ventricular far-field sensing in a VDD-ICD is not uncommon, however, tachycardia detection by the dual chamber algorithm is not seriously impaired by far-field sensing.

[The implantable loop recorder]. / Holter implantable: reveal.

The implantable loop recorder developed by Medtronic (Reveal plus) is a small device inserted subcutaneously under local anesthesia in patients with syncope of unexplained origin. This device enables a single lead-ECG recording and has autonomy of two years. Memories are activated during episodes of bradycardia or tachycardia, either automatically or manually. Several studies have shown a high diagnostic rate reaching 50% and demonstrated its cost-effectiveness. There is also a significant reduction in syncopal episodes and a higher quality of life score in patients with syncope of unexplained origin.