Advances in Cardiac Electrophysiology.

Despite the global COVID-19 pandemic, during the past 2 years, there have been numerous advances in our understanding of arrhythmia mechanisms and diagnosis and in new therapies. We increased our understanding of risk factors and mechanisms of atrial arrhythmias, the prediction of atrial arrhythmias, response to treatment, and outcomes using machine learning and artificial intelligence. There have been new technologies and techniques for atrial fibrillation ablation, including pulsed field ablation. There have been new randomized trials in atrial fibrillation ablation, giving insight about rhythm control, and long-term outcomes. There have been advances in our understanding of treatment of inherited disorders such as catecholaminergic polymorphic ventricular tachycardia. We have gained new insights into the recurrence of ventricular arrhythmias in the setting of various conditions such as myocarditis and inherited cardiomyopathic disorders. Novel computational approaches may help predict occurrence of ventricular arrhythmias and localize arrhythmias to guide ablation. There are further advances in our understanding of noninvasive radiotherapy. We have increased our understanding of the role of His bundle pacing and left bundle branch area pacing to maintain synchronous ventricular activation. There have also been significant advances in the defibrillators, cardiac resynchronization therapy, remote monitoring, and infection prevention. There have been advances in our understanding of the pathways and mechanisms involved in atrial and ventricular arrhythmogenesis.

Catheter ablation of atrial fibrillation in very young adults: a 5-year follow-up study.

Aims: Catheter ablation is an established therapy for symptomatic atrial fibrillation (AF). However, outcome data on catheter ablation for AF in young adults is scarce. Methods and results: From 2005-2014, 85 consecutive young adults (mean age 31 ± 4 years; 69% men) with symptomatic paroxysmal AF (PAF, n = 52) and persistent (Pers) AF (n = 33) underwent pulmonary vein isolation (PVI) [±ablation of complex fractionated atrial electrograms/linear lesions in PVI non-responders] at our centre. Follow-up was based on outpatient visits including 24-h Holter-ECG at 3, 6 and, 12 months post ablation, and every 12 months thereafter. Recurrence was defined as any AF/atrial tachycardia episode >30s following a 3-month blanking period. Follow-up was available for 74/85 (87%) patients. After a median follow-up of 4.6 years (Q1: 2.6; Q3: 6.6) and a mean of 1.5 ± 0.6 (median 1, range 1-3) ablation procedures 84% [including 13% on previously ineffective antiarrhythmic drugs (AAD)] of patients were in stable SR. Single-procedural 1-year/5-year arrhythmia-free survival was 66% [95% confidence interval (CI): 56-78%]/44% (95% CI: 33-59%), respectively. Structural heart disease [SHD; hazard ratio (HR) 2.79 (95% CI 1.52-5.12), P = 0.001] and obesity [HR 1.10 (95% CI 1.00-1.21) per unit increase in body mass index >27 kg/m2, P = 0.05] independently predicted AF recurrence. Major complications occurred in 6/122 (4.9%) procedures (PV stenosis in 3, cardiac tamponade in 1, stroke in 1, and arterial-venous fistula in 1). Conclusion: In the majority of very young adults catheter ablation for AF is effective, and associated with an acceptable complication rate. SHD and obesity are predictors for AF recurrence in this population.

Insights into ablation of persistent atrial fibrillation: Lessons from 6-year clinical outcomes.

INTRODUCTION: Ablation of persistent atrial fibrillation (AF) is a potential treatment option for symptomatic patients. We sought to evaluate the critical role of circumferential pulmonary vein isolation (CPVI) in the ablation of persistent AF. METHODS AND RESULTS: A total of 341 ablation procedures were performed in 174 consecutive patients with persistent AF. CPVI was performed in all patients, additional ablation was only performed if electrical cardioversion failed after CPVI. During a median follow-up (FU) of 89 (63; 89) months, stable sinus rhythm was documented in 42/170 (25%) patients after a single procedure and in 111/164 (68%) patients after 1.9 ± 1.1 procedures. Stable SR was achieved in 40/75 (53%) patients in whom only CPVI was performed during the index and repeat procedures and in 71/89 (79%) patients with CPVI plus additional ablation. The main predictor for ablation success was duration of persistent AF before the index procedure (P < 0.001, HR ± CI: 1.608 [1.034, 1.103]). Responders to CPVI during the initial procedure had a significantly better multiple-procedure outcome after 42 months of FU compared to CPVI nonresponders (P  =  0.0365). Conversion during the index procedure had no impact on clinical outcomes (P  =  0.0903). Persistent AF regressed to paroxysmal AF in 16% of patients. CONCLUSIONS: We demonstrate a 25% single- and 68% multiple-procedure success in patients with persistent AF, while stable SR was achieved in 53% of patients with pure CPVI during all procedures and in 79% of patients with CPVI plus additional ablation. Only duration of persistent AF before ablation had a statistically significant impact on ablation outcome.

Mapping of ventricular arrhythmias using a novel noninvasive epicardial and endocardial electrophysiology system.

INTRODUCTION: The aim of this study was to assess the use of a novel noninvasive epicardial and endocardial electrophysiology system (NEEES) for mapping of ventricular arrhythmias. METHODS: Eight patients (2 females, mean age 50±17 years) with ischemic (n=3) and nonischemic (n=5) cardiomyopathy and inducible ventricular arrhythmias during electrophysiology study were enrolled. Noninvasive mapping of ventricular arrhythmias was performed using the NEEES based on body-surface electrocardiograms and computed tomography imaging data. Arrhythmia patterns were analyzed using noninvasive phase mapping. RESULTS: Macro-reentrant VT circuits were observed in 3 ischemic and 1 nonischemic cardiomyopathy patient, respectively. In the remaining 4 patients, phase mapping revealed relatively stable rotor activity and multiple wavelets. CONCLUSIONS: Noninvasive cardiac mapping was able to visualize the macro-reentrant circuits in patients with scar-related VT. In patients without myocardial scar only polymorphic VT or VF was inducible, and rotor activity and multiple wavelets were observed.

Noninvasive phase mapping of persistent atrial fibrillation in humans: Comparison with invasive catheter mapping.

BACKGROUND: A novel noninvasive epicardial and endocardial electrophysiology system (NEEES) to identify electrical rotors and focal activity in patients with atrial fibrillation (AF) was recently introduced. Comparison of NEEES data with results from invasive mapping is lacking. METHODS: Six male patients (59 ± 11 years) with persistent AF underwent cardiac mapping with the NEEES, which included the creation of isopotential and phase maps. Then patients underwent catheter mapping using a PentaRay NAV catheter and the CARTO 3 system. Signals acquired by the catheter were analyzed by customized software that applied the same phase mapping algorithm as for the NEEES data. RESULTS: In all patients, noninvasive phase mapping revealed short-lived electrical rotors occurring 1.8 ± 0.3 times per second and demonstrating 1-4 (mean 1.2 ± 0.6) rotation cycles. Most of these rotors (72.7%) aggregated in 2-3 anatomical clusters. In two patients, focal excitation from pulmonary veins was observed. Invasive catheter mapping in the dominant rotor aggregation sites and in the three control sites demonstrated the presence of electrical rotors with properties similar to noninvasively detected rotors. Spearman's correlation coefficient between rotor occurrence rate by noninvasive and invasive mapping was 0.97 (p < .0001). Mean rotors' cycle length at dominant aggregation sites, scores of their full rotations, and the proportion of rotors with clockwise rotation were not significantly different between the mapping modalities. CONCLUSION: In patients with persistent AF, phase processing of unipolar electrograms recorded by catheter mapping could reproduce electrical rotors as characterized by NEEES-based phase mapping.

Focal Impulse and Rotor Modulation for the Treatment of Atrial Fibrillation: Locations and 1 Year Outcomes of Human Rotors Identified Using a 64-Electrode Basket Catheter.

INTRODUCTION: Pulmonary vein isolation (PVI) is currently the gold standard for catheter ablation of atrial fibrillation (AF). The mechanism for AF-maintenance is still controversial. The concept of rapidly activating spiral rotors perpetuating AF has led to the development of several rotor-mapping systems. We present our experience with focal impulse and rotor modulation (FIRM) using a 64-electrode basket catheter and computational system and evaluate its feasibility in conjunction with PVI to treat AF. METHODS AND RESULTS: Twenty-five patients underwent FIRM mapping and ablation to treat AF (paroxysmal = 10, 40%). A basket catheter was used for rotor identification within the right atrium (RA) then left atrium (LA). Radiofrequency energy was applied at and around each rotor core for 300 seconds and rotor-mapping and ablation was repeated until all rotors were eliminated before circumferential PVI was performed. Three (1.0, 4.0) rotors were identified per patient, predominantly in the LA (LA = 59). Note that 7/59 left-sided rotors were located 8/59 at the PV antrum. Twelve (48%) patients had either AF termination (termination = 6/12) or conversion to another rhythm, or cycle length (CL) prolongation ≥10% after rotor ablation. After a single procedure, 13 (52%) patients were free of atrial tachyarrhythmia after a follow-up period of 13 ± 1 months. CONCLUSION: Early results suggest that FIRM-ablation can terminate AF in a significant number of patients. Rotors were frequently identified in the PVs and PV antrum, supporting PVI as the cornerstone of AF ablation.

Durability of wide-area left atrial appendage isolation: Results from extensive catheter ablation for treatment of persistent atrial fibrillation.

BACKGROUND: Extensive ablation strategies are currently performed in addition to pulmonary vein isolation (PVI) to improve the clinical outcome of patients with drug-refractory persistent atrial fibrillation (AF). Ablation of complex fractionated atrial electrograms (CFAEs), linear lesions, and/or isolation of the left atrial appendage (LAA) are thought to improve arrhythmia-free survival. OBJECTIVE: The purpose of this study was to assess the durability of wide-area left atrial appendage isolation (LAAI) achieved by PVI, an anterior line, and a mitral isthmus line. METHODS: Seventy-one patients with intentional or incidental LAAI during repeat catheter ablation for treatment of persistent AF were included. The initial ablation strategy was PVI. Additional ablation strategies were performed only if PVI failed to maintain stable sinus rhythm. Durability of LAAI was assessed during a subsequent ablation procedure for arrhythmia recurrences (n = 23) or a subsequent percutaneous LAA closure (n = 48). RESULTS: LAAI was performed after a mean of 3 ± 1 procedures. Ablation strategies included circumferential PVI in 71 patients (100%), mitral isthmus line in 64 (90%), anterior line in 60 (85%), CFAE in 27 (38%), and roof line in 13 (18%). LAAI occurred after ablation and bidirectional block of LA linear lesions in 63 patients (89%) and during extensive CFAE ablation in 8 patients (11%). After a median of 105 [61;426] days, the LAA remained electrically isolated in 52 of 71 patients (73%). CONCLUSION: Wide-area LAAI after extensive catheter ablation for persistent AF is durable in the majority of patients. The potential clinical benefit of LAAI for maintaining stable sinus rhythm requires further investigation.

Apixaban, Rivaroxaban, and Dabigatran in Patients Undergoing Atrial Fibrillation Ablation.

INTRODUCTION: Data on the novel oral anticoagulants (NOACS) during catheter ablation (CA) of atrial fibrillation (AF) are still limited. This study evaluated the periprocedural major complications (MC) of CA of AF, and compared Apixaban, Dabigatran, and Rivaroxaban with continuous phenoprocoumon. METHODS AND RESULTS: A total of 444 patients (mean age = 65.1 ± 9.4 years; 283 [64%] male) with paroxysmal (n = 180 [41%]), persistent (n = 256 [58%]), or longstanding-persistent AF were enrolled. CA was performed in all patients using radiofrequency energy in conjunction with a 3D-mapping system. MCs were defined according to the current guidelines. Continuous phenprocoumon-therapy was administered in 120/444 (27%) patients (group 1) and 324/444 (73%) patients were treated with NOACs (group 2; Dabigatran: n = 51 [15.7%]; Rivaroxaban: n = 193 [59.6%]; Apixaban: n = 80 [24.7%]). Procedure times were comparable between groups 1 and 2 (128.2 ± 39.7 minutes vs. 129.7 ± 51.2 minutes; P = 0.77). CHA2 DS2-Vasc (3.0 [2.0, 4.0)] vs. 2.0 [1.0, 3.0]; P < 0.01) and HASBLED scores (2.0 [2.0, 2.5] vs. 2.0 [1.0, 2.0]; P = 0.002) were higher in group 1 patients. The incidence of MCs in the overall group was 8/444 (2%) and was equally distributed between groups 1 and 2 (2/120 [2%] vs. 6/324 [2%], P = 0.90). The incidence of MCs was comparable between the three different NOACs. There were no significant differences between patients with and without MCs with regard to age, CHA2 DS2-Vasc-score or HASBLED-score. CONCLUSIONS: The major complication rate between all three NOACs currently available and continuous phenprocoumon during AF ablation seem to be comparable. Complication rates were similar between patients treated with the three different available NOACs.

Focal impulse and rotor modulation using the novel 64-electrode basket catheter: electrogram characteristics of human rotors.

AIMS: Ablation of fractionated electrograms (EGMs) has been performed to eliminate areas of slow conduction in atrial fibrillation (AF). The rotor hypothesis suggests that rapidly activating spiral waves perpetuate and maintain AF. This study describes the EGM characteristics of AF rotors, using the novel 64-electrode basket catheter. METHODS AND RESULTS: Twenty-five patients (male n = 16) with AF (paroxysmal n = 10) underwent focal impulse and rotor modulation. A 3.5 mm irrigated-tip ablation catheter was placed at the identified rotor core and EGMs were analysed for amplitude, characteristics (single-EGM, fractionated-EGM, and continuous-EGM), and cycle length over 10 s. A total of 72 rotors were identified [right atrium (RA) = 13, left atrium (LA) = 59]. Seven rotors were excluded from EGM analysis due to location in the pulmonary veins. Single-EGMs were more frequent in the RA compared with the LA (8 (61.5) vs. 12 (23.1); P < 0.01) and EGM amplitudes were smaller in LA rotors when compared with RA rotors (0.14 (0.08-0.17) mV vs. 0.19 (0.15-0.29) mV; P = 0.029). In patients with persistent AF, single-EGMs were observed more often in the right-sided rotors compared with left-sided rotors (4 (57.1) vs. 5 (14.3); P = 0.012), and EGM amplitudes were smaller in patients with persistent AF compared with paroxysmal atrial fibrillation (PAF) patients (0.15 (0.09-0.19) mV vs. 0.22 (0.17-0.47) mV; P = 0.03). Furthermore, the prevalence of fractionated- EGMs was higher in patients with persistent AF compared with PAF patients (31/42 (73.8) vs. 9/23 (39.1); P = 0.03). CONCLUSION: There are no characteristic rotor-EGM potentials. Rotor-EGM characteristics are different between the RA and LA. Although rotors are not associated with abnormal EGMs, rotor-EGMs in persistent AF were more fractionated with lower amplitudes compared with that in PAF.

Modified energy settings are mandatory to minimize oesophageal injury using the novel multipolar irrigated radiofrequency ablation catheter for pulmonary vein isolation.

AIMS: The multipolar irrigated radiofrequency (RF) ablation catheter (nMARQ™) is a novel tool for pulmonary vein isolation (PVI). We investigated the incidence of thermal oesophageal injury (EI) using the nMARQ™ for PVI. METHODS AND RESULTS: In the initial six patients (Group 1), RF was delivered at the posterior wall with a maximum duration of 60 s and a maximum power (maxP) of 20 W for unipolar ablation, and a maxP of 10 W for the bipolar ablation. In the latter 15 patients (Group 2), RF application was limited at the posterior wall to a maximum duration of 30 s and a maxP of 15 W for unipolar ablation a max P of 10 W for bipolar ablation. Oesophageal temperature monitoring was performed in all patients and ablation was terminated at a temperature rise >41°C. Endoscopy was carried out within 2 days post-ablation. Pulmonary vein isolation was performed during sinus rhythm and was successfully achieved in 83 of 84 PVs except the septal inferior vein in one patient. Charring was seen in 3 of 21 (14.3%) patients without any evidence of embolism. Phrenic nerve palsy occurred in one patient. Endoscopy revealed severe EI in 3 of 6 (50%) patients in Group 1 and in 1 of 15 patients (6.7%) in Group 2. Procedure times between Groups 1 and 2 were similar (228.3 ± 60.2 min vs. 221.3 ± 51.8 min; P = 0.79). CONCLUSION: An unexpectedly high incidence of thermal EI was noted following PVI using the nMARQ™ with the initial ablation protocol. However, the incidence of thermal EI can be sigificantly reduced with limited power and RF application time at the posterior left atrium.

Electrical isolation of a substrate after myocardial infarction: a novel ablation strategy for unmappable ventricular tachycardias--feasibility and clinical outcome.

AIMS: Catheter ablation can abolish clinical ventricular tachycardia (VT) in patients after myocardial infarction (MI). However, VT frequently recurs after ablation. The best ablation strategy is still unknown, particularly in patients with unmappable VTs. We hypothesized that isolation of the arrhythmogenic substrate would be a feasible and effective ablation strategy for the treatment of ischaemic VT. METHODS AND RESULTS: Twelve patients (54 ± 8 years, left ventricular ejection fraction, LVEF 32 ± 13%) underwent catheter ablation for sustained VT (anterior MI = 10, inferior MI = 2). All patients had recurrent defibrillator shocks, including electrical storms in seven patients, despite anti-arrhythmic drugs. During electrophysiological study, 3 ± 2 VTs were induced. Three-dimensional mapping of the left ventricle revealed a low-voltage (<1.5 mV) area with fractionated electrograms and late potentials, with a mean area of 62 ± 20 cm(2). Isolation of the entire low-voltage area was attempted with a circumferential line along the low-voltage area border-zone. Substrate isolation was successfully achieved in 6 of 12 (50%) patients. Focal discharge within the isolated area was demonstrated in three of six (50%) patients. During a median follow-up of 479 [297; 781] days, 8 of 12 patients (66.7%) remained free of VT recurrence after a single procedure. In five of the six patients (83.3%) with successful substrate isolation, there were no VT recurrences when compared with three of the six patients (50%) with no substrate isolation. CONCLUSION: Electrical isolation of the entire substrate is feasible and appears to be an effective treatment in patients with late VT after MI.

In vivo contact force analysis and correlation with tissue impedance during left atrial mapping and catheter ablation of atrial fibrillation.

BACKGROUND: The aim of this study was to evaluate in vivo contact force (CF) and the correlation of CF with impedance during left atrial 3-dimensional electroanatomical mapping and ablation. METHODS AND RESULTS: CF during point-by-point left atrial mapping was assessed in 30 patients undergoing atrial fibrillation ablation. Operators were blinded to the real-time CF data. Data were analyzed according to 11 predefined areas in the left atrial and 6 segments around the ipsilateral pulmonary veins. A total of 3475 mapping and 878 ablation points were analyzed. Median CF during mapping was 14.0g (6.5-26.2; q1-q3), ranging from 5.1g at the ridge to 29.8g at the roof. Median CF at the ridge and mitral isthmus were 5.1g and 6.9g, respectively. Extremely high CF ≥100g was noted in 24 points (0.7%). Median CFs during ablation around the right and left pulmonary veins were 22.8g (12.6-37.9; q1-q3) and 12.3g (6.9-30.2; q1-q3), respectively. The lowest median CFs were recorded at the anterior-superior and anterior-inferior segments of the left pulmonary veins (7.2g and 7.9g). Impedance values during mapping and impedance fall during ablation correlated with the applied CF (R(2)=0.16; P<0.001 and R(2)=0.04; P<0.001) although there was significant overlap. CONCLUSIONS: Excessively high and low CF values can be observed during left atrial mapping and ablation. The low CF obtained at the mitral isthmus and anterior segments of the left pulmonary veins may explain why reconnection after ablation occurs more frequently at these sites. CF and impedance do correlate; however, the impedance for a given CF ranges widely, limiting its use in clinical practice.

Long-term outcome after catheter ablation for left posterior fascicular ventricular tachycardia without development of left posterior fascicular block.

BACKGROUND: Catheter ablation of left posterior fascicular (LPF) ventricular tachycardia (VT) is commonly performed during tachycardia. This study reports on the long-term outcome of patients undergoing ablation of LPF VT targeting the earliest retrograde activation within the posterior Purkinje fiber network during sinus rhythm (SR). METHODS: This study retrospectively analyzed 24 consecutive patients (8 female; mean age 26 ± 11 years) referred for catheter ablation of electrocardiographically documented LPF VT. Programmed stimulation was performed to induce tachycardia, while mapping and ablation was aided by use of a 3D electroanatomical mapping system. Catheter ablation targeted the earliest potential suggestive of retrograde activation within the posterior Purkinje fiber network (retro-PP) recorded along the posterior mid-septal left ventricle during SR if LPF VT was noninducible. RESULTS: Overall, 21/24 (87.5%) patients underwent successful catheter ablation in SR targeting the earliest retro-PP, while 3/24 (12.5%) patients were successfully ablated during tachycardia. In none of the patients, ablation resulted in LPF block. No procedure-related complications occurred. After a median follow-up period of 8.9 (4.8-10.9) years, 22/24 (92%) patients were free from recurrent VT. CONCLUSION: In patients presenting with LPF VT, ablation of the earliest retro-PP along the posterior mid-septal LV during SR results in excellent long-term outcome during a median follow-up period of almost 9 years.

Monomorphic and polymorphic ventricular tachycardias arising from the His-Purkinje system: what do we know?

Monomorphic and polymorphic Purkinje-related ventricular tachycardias (VTs) may occur in patients with and without underlying structural heart disease. Monomorphic Purkinje-related VTs can be divided into different entities: verapamil-sensitive left fascicular VTs; bundle branch reentry tachycardias (BBRT); interfascicular VTs and focal Purkinje VTs. The most frequent fascicular VT is left posterior fascicular VT, characterized by macro-reentry within the posterior Purkinje network. However, the reentry may also be located in the anterior Purkinje network (left anterior fascicular VT). BBRT is also a macro-reentry-tachycardia, utilizing both the right and the left bundle branch as the antegrade and the retrograde limb and is often associated with pre-existing conduction disturbances in the specific conduction system. Interfascicular VT is rare and characterized by a macro-reentry within the left fascicles. BBRT and interfascicular VT may also occur in the same patient. In contrast to the mentioned macro-reentry mechanisms there are focal Purkinje-related VTs arising from the anterior or posterior Purkinje system. Focal Purkinje triggered premature ventricular contractions originating from the distal Purkinje arborization in patients without a structural heart disease, as well as in patients with known ischemic heart disease or an underlying channelopathy such as Brugada syndrome may induce polymorphic VTs. Catheter ablation is an effective treatment option for both monomorphic as well as polymorphic Purkinje-related VTs, often resulting in noninducibility and freedom from VT recurrence. A systematic analysis of the surface ECG and the intracardiac electrograms is essential for successful ablation of these heterogeneous and potentially curable VTs.