Electrogram Mapping Research Articles

Electrogram dispersion mapping for repeat ablation in patients with persistent atrial fibrillation

Abstract Background/Introduction While pulmonary vein isolation (PVI) is a key guideline endpoint for atrial fibrillation (AF) ablation, strategies for repeat ablation are debated, particularly when PVs are isolated. Electrogram dispersion mapping identifies dynamic substrates using existing catheters, remote from the PVs and may confer benefit to additional ablation. Purpose To describe the outcome of repeat ablation using electrogram mapping to identify areas of mechanistic significance in persistent AF patients. Methods Patients undergoing repeat ablation for persistent AF were recruited from two international centers. A five spline catheter was used to mark areas of electrogram dispersion before any ablation using previously described criteria. After confirming PVI, or re-isolation of PVs if necessary, ablation of all dispersion areas was performed. If termination to atrial tachycardia (AT) occurred, this was mapped using conventional methods. Patients who terminated to sinus underwent reinduction pacing protocols to map any further AT or AF inducible. Patients were followed up at 12 months with continuous event monitors, and beyond 12 months based on local guidelines. Results In total, 167 AF patients were enrolled: age 66 ± 8 yrs; 32% female; mean LA diameter 4.8 cm. PVI was present in 108 (64%) of patients. All patients underwent LA mapping, and 75 (45%) underwent right atrial (RA) mapping. Patients had an average of 3.2 LA and 1.4 RA ablation sites. The total number of dispersion sites in patients was similar in patients with and without PVI, (4.1 ± 2 and 3.6 ± 1 respectively). AF terminated in 144 patients (86%), with an overall conversion to sinus rhythm obtained by ablation in 42% of the patients. Patients were followed for an average of 2.92 ± 0.9 years. At 12 months, 159 (95%) patients were AF free, and 124 (74%) remained free of atrial arrhythmia. Of those patients, only 8 (5%) had AF, with 35 (21%) recurring with AT or atrial flutter (AFL). Of the 70 patients who terminated to sinus with repeat ablation, only 2 (2.9%) recurred with AF and 26 (37.1%) had recurrence of atrial arrhythmia (AF/AT/AFL) as a whole throughout the entire follow-up period (P<0.05). Patients with and without PVI at redo procedure did not have a statistically significant difference in recurrence of AF (Figure 1, P = 0.80) nor recurrence of atrial arrhythmia (Figure 2, P = 0.63) during total follow up time by log rank test. Conclusions In a difficult to treat population of persistent AF patients requiring a repeat ablation procedure, electrogram mapping led to rates of freedom from AF at 12 months similar to first time ablation series. Additionally, those with PVI present at time of procedure had similar benefit from this approach compared to those with reconnected veins. This is the largest demonstration of a technique that confers benefit in a PVI isolated subgroup of purely redo ablations for persistent AF.Figure 1:Percent AF FreeFigure 2:Percent AF/AT/AFL Free

Electroanatomical mapping-guided left bundle branch area pacing in patients with structural heart disease and advanced conduction abnormalities.

Left bundle branch area pacing (LBBAP) can be technically challenging and fluoroscopy-intense. Three-dimensional electroanatomical mapping (EAM) facilitates non-fluoroscopic lead navigation and electrogram mapping. We sought to prospectively evaluate the feasibility, safety, and outcomes of routine EAM-guided LBBAP in patients with structural heart disease (SHD) and advanced conduction abnormalities. Consecutive patients with SHD and conduction abnormalities who underwent an attempt at EAM-guided LBBAP were included. The feasibility, safety, procedural, and mid-term outcomes were evaluated. Electrical, echocardiographic, and clinical parameters were assessed at implantation and last follow-up. Thirty-two patients (68 ± 18 years; 19% female) were included, of which 75% had intrinsic QRS > 150 ms, 53% left bundle branch block, and 25% right bundle branch block. Primary EAM-guided LBBAP was successful in 29 patients (91%). The procedural duration was 95 (70-110) min, total fluoroscopy time 0.93 (0.40-1.73) min, and total fluoroscopy dose 35.4 (20.5-77.2) cGy cm2. Paced QRS duration (QRSd) was significantly shorter than intrinsic QRSd (121.9 ± 10.7 vs. 159.2 ± 34.4 ms; P < 0.001) and remained stable during the mean follow-up of 7.0 ± 5.9 months. The LBBAP capture threshold was 0.57 ± 0.23 V/0.4 ms at implantation and remained low during follow-up (0.58 ± 0.18 V/0.5 ± 0.2 ms; P = 0.877). Overall left ventricular ejection fraction improved significantly from 44.2 ± 14.3% at baseline to 49.4 ± 13.1% at follow-up (P = 0.009), New York Heart Association class from 2.4 ± 0.6 to 1.8 ± 0.6 (P = 0.002), respectively. No complications occurred that required intervention. Routine near-zero fluoroscopy EAM-guided LBBAP can safely be performed in patients with SHD and advanced conduction abnormalities with high success rates and favourable mid-term outcomes. Further studies are needed to investigate whether the use of EAM improves the overall outcome of conduction system pacing and to identify specific patient populations who benefit the most from EAM-guided lead implantation.

Success Rate in Patients with Atrioventricular Nodular Re-Entrant Tachycarida (AVNRT) Slow Pathway Catheter Ablation with and without Junctional Rythym

Background and Aim: For successful radiofrequency ablation of atrioventricular nodal reentrant tachycardia (AVNRT), slow-pathway radiofrequency catheter ablation leads to junctional rhythm (JR) is now being considered as a very sensitive substitute end goal. During AVNRT RF ablation, a favorable result could be predicted based on the pattern of JR produced. Patients and Methods: This cross-sectional study was conducted on 64 patients presenting with symptomatic AVNRT and undergoing slow-pathway RF ablation in the Department of Cardiology, Hayatabad Medical Complex, Peshawar for the duration from January 2022 to June 2022. RF ablation of slow pathway was performed using a combined anatomical and electrogram mapping approach. Ablation was performed by controlling the temperature and delivering energy over 60 seconds at 60°C. In order to determine if the developed JR was successful, isoproterenol infusion was performed after every ablation pulse. Four different patterns of AVNRT inducibility were considered: intermittent, continuous, sparse, and transient. Position, pattern, and number of junctional beats were used to assess the success rate of ablation. SPSS version 28 was used for descriptive statistics. Results: Of the total patients, there were 36 (56.2%) women and 28 (43.8%) men. The overall mean age was 38.64 ± 18.36 years with an age range 16-80 years. The most prevalent symptom during AVNRT was palpitation found in 41 (64.1%) cases. The prevalence of pre-syncope, dyspnea, and syncope was 3.8%, 3.8%, and 3.4% respectively. The incidence of more than one symptoms were found in 21 (32.8%) patients. Almost all the patients displayed antegrade AH jumps and indicated dual AV nodal conduction. Out of total 156 RF, it took 114 (73.1%) RF energy applications to successfully ablate 38 (59.4%) patients with loss of AVNRT inducibility. About 126 (80.8%) patients developed JR with given specificity 42.6%, sensitivity 89.6%, and negative predictive value 61.8%. Conclusion: The present study found that the JR predicts the success of AVNRT RF ablation at a high level of sensitivity, but not to a specific degree. However, the findings indicate that its specificity may rise with the appearance of &gt; 14 total tight junctions beats. Furthermore, if the forecast of effective slow-route RF ablation in relation to the existence of JR remains not consistent adequate, its absence might be a trustworthy marker of the pathway needing greater energy application delivery to be abolished. Keywords: Atrioventricular nodular re-entrant tachycardia (AVNRT), Slow pathway catheter ablation, Junctional rhythm, success rate

Talk like a duck, walk like a duck: A cardiac surgeon's understanding of complex imaging in the management of atrial fibrillation.

The treatment of atrial fibrillation continues to evolve. The Heart Team Hybrid Ablation Approach is the latest iteration of Electrophysiology and Arrythmia surgeon collaboration that is focused on the treatment of complex (persistent and long-standing persistent) atrial fibrillation patients. Critical to this team approach is the ability to converse regarding atrial anatomy, atrial substrate and transmurality of ablation lesions. The cornerstone of these dialogs is advanced imaging techniques including; transesophageal echocardiography, enhanced magnetic resonance imaging, endocardial voltage mapping, and epicardial electrogram mapping. We herein review these techniques and their clinic implications.

Dynamic voltage attenuation identifies atrial fibrosis in a rabbit model: simultaneous assessment with optical mapping and contact electrogram mapping

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): British Heart Foundation. Academy of Medical Sciences. Background Bipolar voltage amplitude is a widely-used clinical parameter in atrial electrophysiology procedures. However, voltage amplitude is variable, and it has been shown that increasing activation rate decreases bipolar voltage amplitude in patients with atrial fibrillation. It is not known whether such voltage attenuation is a marker of the presence of atrial fibrosis which could therefore be used to improve intra-procedural assessment of atrial cardiomyopathy. Purpose We sought to investigate the effect of increasing activation rate on bipolar voltage amplitude in both healthy and fibrotic left atrial tissue. Methods 10 New Zealand Rabbits were fed a high cholesterol diet (0.75%) for a period of 12 weeks to create an atrial fibrosis model. 10 Animals were fed normal chow. After terminal anaesthesia the heart was excised, and optical and voltage mapping of the excised left atrial tissue was performed. Blebbistatin was used to maintain cardiac stasis and the voltage sensitive dye RH237 was used for optical mapping. Voltage and optical recordings were made during pacing was from 3 different directions at rates from 2-6Hz and at 3 sites across the atrial tissue. Voltage amplitude was recorded as the mean amplitude over 10 beats during steady-state pacing. Optical recordings were used to measure conduction velocity and action potential characteristics. Only pacing runs showing 1:1 conduction were included in analysis. Atrial fibrosis was assessed using Masson’s Trichrome staining. Results The degree of atrial fibrosis was significantly greater in the atrial fibrosis model compared to healthy controls (15±3.24% vs. 9.74±4.98%, p=0.0069). Median voltage at base rate pacing of 2Hz was not significantly different between control and fibrotic atria (11.63mV, IQR 6.35mV vs. 10.3mV, IQR 6.81mV, p=0.71, respectively). Median voltage was significantly lower at 6Hz than at 2Hz in the control group (9.84mV, IQR 6.87mV, p=0.046). The degree of voltage attenuation between study groups was not significantly different between when pacing at 3hz or 4hz, whereas pacing at 5Hz and 6Hz showed significantly greater attenuation in fibrotic atria. At 5Hz the median reduction in amplitude from baseline in control vs fibrotic atria was 0.88mV, IQR 2.36mV vs 1.92mV, IQR 1.63mV (p=0.031). At 6 Hz the median reduction was 0.94mV, IQR 1.69mV vs 2.68mV, IQR 1.11mV, p=0.013 in control and fibrotic groups respectively. Discussion High cholesterol diet increased atrial fibrosis in a rabbit model. Bipolar voltage amplitude attenuation occurred in both control and fibrotic atria however the degree of voltage attenuation was significantly greater in fibrotic atria. These findings support the further evaluation of dynamic voltage attenuation for intraprocedural identification of atrial fibrosis.

Differentiating left bundle branch pacing and left ventricular septal pacing: An algorithm based on intracardiac electrophysiology.

Left bundle branch pacing (LBBP) is a new near-physiological pacing modality. Distinguishing left ventricular septal only pacing (LVSP) from nonselective LBBP still needs clarification. This prospective study sought to establish a differentiation algorithm to confirm LBBP. LBBP was attempted in consecutive patients. If direct LBB capture (LBBP) could not be confirmed, LVSP was considered to have been achieved. Intracardiac left ventricular (LV) activation sequence and activation time were analyzed using coronary sinus (CS) electrogram mapping. Electrophysiological parameters including S-CSmax, S-CSmin, LV lateral wall activation time, ΔLV, and LBB potential were compared between LBBP and LVSP. Stimulated LV activation time (S-LVAT) and stimulated QRS duration (S-QRSd) were also compared between the two groups. Multivariate logistic regression analysis was used to develop a prediction algorithm for LBBP. Of the 43 prospectively enrolled patients, 27 underwent LBBP and 16 underwent LVSP. All LBBP patients showed identical LV activation sequences to their intrinsic rhythm while no LVSP patients maintained their intrinsic sequence. S-CSmax, ΔLV, LV lateral wall activation time, and S-LVAT during LBBP were significantly shorter than those during LVSP. Combining LBB potential with S-LVAT had the largest area under the curve (AUC) of 0.985 for confirming LBBP with a sensitivity of 95.2% and a specificity of 93.7%. Compared with LVSP, LBBP preserves a normal LV activation sequence and better electrical synchrony. A combination of LBB potential with S-LVAT can be an effective and practical model to distinguish LBBP from LVSP during implantation in patients with normal LBB activation.

Impact of electroanatomical mapping-guided lead implantation on procedural outcome of His bundle pacing.

Conventional His bundle pacing (HBP) can be technically challenging and fluoroscopy-intense, particularly in patients with His-Purkinje conduction disease (HPCD). Three-dimensional electroanatomical mapping (EAM) facilitates non-fluoroscopic lead navigation and HB electrogram mapping. We sought to assess the procedural outcome of routine EAM-guided HBP compared with conventional HBP in a real-world population and evaluate the feasibility and safety of EAM-guided HBP in patients with HPCD. We included 58 consecutive patients (72 ± 13 years; 71% male) who underwent an attempt to conventional (EAM- group; n = 29) or EAM-guided (EAM+ group; n = 29) HBP between June 2019 and April 2020. The centre's learning curve was initially determined (n = 40 cases) to define the conventional control group and minimize outcome bias favouring EAM-guided HBP. His bundle pacing was successful in 26 patients (90%) in the EAM+ and 27 patients (93%) in the EAM- group (P = 0.64). The procedure time was 90 (73-135) and 110 (70-130) min, respectively (P = 0.89). The total fluoroscopy time [0.7 (0.5-1.4) vs. 3.3 (1.4-6.5) min; P < 0.001] and fluoroscopy dose [21.9 (9.1-47.7) vs. 78.6 (27.2-144.9) cGycm2; P = 0.001] were significantly lower in the EAM+ than EAM- group. There were no significant differences between groups in His capture threshold (1.2 ± 0.6 vs. 1.4 ± 1.0 V/1.0 ms; P = 0.33) and paced QRS duration (113 ± 15 vs. 113 ± 17 ms; P = 0.89). In patients with HPCD, paced QRS duration was similar in both groups (121 ± 15 vs. 123 ± 12 ms; P = 0.77). The bundle branch-block recruitment threshold tended to be lower in the EAM+ than EAM- group (1.3 ± 0.7 vs. 1.8 ± 1.2 V/1.0 ms; P = 0.31). No immediate procedure-related complications occurred. One patient (2%) experienced lead dislodgement during 4-week follow-up. Implementation of routine EAM-guided HBP lead implantation is feasible and safe in a real-world cohort of patients with and without HPCD and results in a tremendous reduction in radiation exposure without prolonging procedure time or increasing procedure-related complications.

Abstract 16896: Electrogram Morphology Recurrence to Characterize Drivers of Persistent Atrial Fibrillation: Findings at Initial versus Redo Catheter Ablation

Background: Electrogram (EGM) morphology recurrence (EMR) mapping of persistent atrial fibrillation (PeAF) quantifies consistency of activation at each site and is expected to be high and rapid near drivers of PeAF. Objective: To compare EMR in the left (LA) and right atrium (RA) in patients undergoing first- vs second-time PeAF catheter ablation (CA). Methods: Multisite bipolar EGM mapping of the LA (265±153 sites) and RA (224±148 sites) prior to CA for PeAF was performed in 40 patients (29 males, age 63±9 yrs, CHA2DS2-VASc 2.4±1.5, LVEF 48±12%) undergoing first (Group 1, n=31) or second-time (Group 2, n=9) CA. After cross-correlation of each automatically detected EGM with every other EGM in the recording, the most recurrent EGM morphology was identified and its frequency (Rec%) and cycle length of recurrence (CL R ) were computed (figure). The minimum CL R sites were identified. Results: In group 1, shortest CL R was in the LA in 26 patients (84%) and RA in 5 patients (16%). In the LA, there were 1 (n=23), 2 (n=2), or 3 (n=1) areas of shortest CL R , most commonly in the pulmonary veins (PV; n=19). In the RA, there was only 1 area of shortest CL R . Minimum CL R was 174.1±25.4 ms (LA-179.6±37.4 vs RA-207.9±34.5, p=0.0004), with Rec% 95±10%. In group 2, shortest CL R was in the LA in 5 patients and RA in 5 patients (56%)– one had both LA and RA. In the LA/RA, there were 1 (n=3/4) or 2 (n=2/1) areas of shortest CL R . The most common LA site was non-PV (6/7, 85.7%). The minimum CL R was 182.1±26.2ms (LA-190.8±36.2 vs RA-196.0±30.5, p=0.6), with Rec% 96±5%. Conclusion: In 61% of patients undergoing initial CA for PeAF, EMR identified LA drivers in the PVs which may explain why PV isolation has been reported to have 50-60% success rates in PeAF. In patients undergoing a 2 nd ablation for PeAF, EMR identified predominantly nonPV drivers with even distribution of shortest CL R between RA and LA and diminished CL R gradient between the LA and RA. EMR may be a useful mapping tool to characterize potential drivers of PeAF.

In-silico pace-mapping using a detailed whole torso model and implanted electronic device electrograms for more efficient ablation planning

BackgroundPace-mapping is a commonly used electrophysiological (EP) procedure which aims to identify exit sites of ventricular tachycardia (VT) by matching ventricular activation patterns (assessed by QRS morphology) at specific pacing locations with activation during VT. However, long procedure durations and the need for VT induction render this technique non-optimal.To demonstrate the potential of in-silico pace-mapping, using stored electrogram (EGM) recordings of clinical VT from implanted devices to guide pre-procedural ablation planning. MethodSix scar-related VT episodes were simulated in a 3D torso model reconstructed from computed tomography (CT) imaging data, including three different infarct anatomies mapped from infarcted porcine imaging data. In-silico pace-mapping was performed to localise VT exit sites and isthmuses by using 12-lead electrocardiogram (ECG) signals and different combinations of EGM sensing vectors from implanted devices, through the creation of conventional correlation maps and reference-less maps. ResultsOur in-silico platform was successful in identifying VT exit sites for a variety of different VT morphologies from both ECG correlation maps and corresponding EGM maps, with the latter dependent upon the number of sensing vectors used. We also showed the added utility of both ECG and EGM reference-less pace-mapping for the identification of slow-conducting isthmuses, uncovering the optimal algorithm parameters. Finally, EGM-based pace-mapping was shown to be more dependent upon the mapped surface (epicardial/endocardial), relative to the VT origin. ConclusionsIn-silico pace-mapping can be used along with EGMs from implanted devices to localise VT ablation targets in pre-procedural planning.

P1419Persistent atrial fibrillation terminates during ablation more often using dispersion mapping than with fractionated electrogram mapping

Abstract Introduction Persistent AF termination rates have increased since the advent of AF driver mapping, with a recent meta-analysis (Baykaner Circ AE 2018) of over 3200 patients showing improved 12 month freedom from AF/AT. However, recent randomised clinical trials have cast doubt on the efficacy of complex fractionated atrial electrograms (CFAE) based mapping strategies. We set out to study a consecutive single centre series pre-and post- use of spatio-temporal dispersion (STD) to identify termination rates between the two approaches. Methods We recruited consecutive patients over 18 months at a single high volume tertiary centre undergoing first redo ablation for persistent AF. Patients were all mapped using Pentarray to mark areas of substrate using the spatio-temporal dispersion (STD) method (Seitz JACC 2017). Ablation was performed by a single operator using catheters to standardise equipment and workflow, to enable true comparison of mapping and ablation results in a consecutive series. Results In total 38 patients were studied at redo ablation for persistent AF (age 69, 87% male, LA diameter 4.5cm). Termination of persistent AF to SR (30%) or AT (70%) was obtained in 30/38 (79%) of the group with STD based substrate ablation vs. 1/38 (3%) in patients mapped with CFAE targeting using identical equipment and operator (p &amp;lt; 0.001). Procedure time was no different between STD and CFAE based approaches (263 vs. 248 mins, p = ns). Figure shows STD patterns (red arrows) on Pentarray in a 67 year old man anterior to left inferior pulmonary vein (A), where ablation terminated AF to sinus rhythm. At 12 month follow up, 30/38 (79%) patients were in sinus rhythm with no AF detected on ECG or continuous monitoring. Conclusions In this single centre series of persistent AF ablations, the use of STD mapping increased rates of termination compared to a fractionation based mapping strategy alone, without increasing overall procedure time. Clinical outcome data suggest this translates into better 12 month clinical outcomes, and motivate prospective randomised trials to definitively study this technique. Abstract Figure.

Association of Left Atrial High-Resolution Late Gadolinium Enhancement on Cardiac Magnetic Resonance With Electrogram Abnormalities Beyond Voltage in Patients With Atrial Fibrillation.

Conflicting data have been reported on the association of left atrial (LA) late gadolinium enhancement (LGE) with atrial voltage in patients with atrial fibrillation. The association of LGE with electrogram fractionation and delay remains to be examined. We sought to examine the association between LA LGE on cardiac magnetic resonance and electrogram abnormalities in patients with atrial fibrillation. High-resolution LGE cardiac magnetic resonance was performed before electrogram mapping and ablation in atrial fibrillation patients. Cardiac magnetic resonance features were quantified using LA myocardial signal intensity Z score (SI-Z), a continuous normalized variable, as well as a dichotomous LGE variable based on previously validated methodology. Electrogram mapping was performed pre-ablation during sinus rhythm or LA pacing, and electrogram locations were coregistered with cardiac magnetic resonance images. Analyses were performed using multilevel patient-clustered mixed-effects regression models. In the 40 patients with atrial fibrillation (age, 63.2±9.2 years; 1312.3±767.3 electrogram points per patient), lower bipolar voltage was associated with higher SI-Z in patients who had undergone previous ablation (coefficient, -0.049; P<0.001) but not in ablation-naive patients (coefficient, -0.004; P=0.7). LA electrogram activation delay was associated with SI-Z in patients with previous ablation (SI-Z: coefficient, 0.004; P<0.001 and LGE: coefficient, 0.04; P<0.001) but not in ablation-naive patients. In contrast, increased LA electrogram fractionation was associated with SI-Z (coefficient, 0.012; P=0.03) and LGE (coefficient, 0.035; P<0.001) only in ablation-naive patients. The association of LA LGE with voltage is modified by ablation. Importantly, in ablation-naive patients, atrial LGE is associated with electrogram fractionation even in the absence of voltage abnormalities.

Utility of ripple mapping for identification of slow conduction channels during ventricular tachycardia ablation in the setting of arrhythmogenic right ventricular cardiomyopathy.

Ripple mapping displays every deflection of a bipolar electrogram and enables the visualization of conduction channels (RMCC) within postinfarction ventricular scar to guide ventricular tachycardia (VT) ablation. The utility of RMCC identification for facilitation of VT ablation in the setting of arrhythmogenic right ventricular cardiomyopathy (ARVC) has not been described. We sought to (a) identify the slow conduction channels in the endocardial/epicardial scar by ripple mapping and (b) retrospectively analyze whether the elimination of RMCC is associated with improved VT-free survival, in ARVC patients. High-density right ventricular endocardial and epicardial electrograms were collected using the CARTO 3 system in sinus rhythm or ventricular pacing and reviewed for RMCC. Low-voltage zones and abnormal myocardium in the epicardium were identified by using standardized late-gadolinium-enhanced (LGE) magnetic resonance imaging (MRI) signal intensity (SI) z-scores. A cohort of 20 ARVC patients that had undergone simultaneous high-density right ventricular endocardial and epicardial electrogram mapping was identified (age 44 ± 13 years). Epicardial scar, defined as bipolar voltage less than 1.0 mV, occupied 47.6% (interquartile range [IQR], 30.9-63.7) of the total epicardial surface area and was larger than endocardial scar, defined as bipolar voltage less than 1.5 mV, which occupied 11.2% (IQR, 4.2 ± 17.8) of the endocardium (P < 0.01). A median 1.5 RMCC, defined as continuous corridors of sequential late activation within scar, were identified per patient (IQR, 1-3), most of which were epicardial. The median ratio of RMCC ablated was 1 (IQR, 0.6-1). During a median follow-up of 44 months (IQR, 11-49), the ratio of RMCC ablated was associated with freedom from recurrent VT (hazard ratio, 0.01; P = 0.049). Among nine patients with adequate MRI, 73% of RMCC were localized in LGE regions, 24% were adjacent to an area with LGE, and 3% were in regions without LGE. Slow conduction channels within endocardial or epicardial ARVC scar were delineated clearly by ripple mapping and corresponded to critical isthmus sites during entrainment. Complete elimination of RMCC was associated with freedom from VT.

Depolarization versus repolarization abnormality underlying inferolateral J-wave syndromes: New concepts in sudden cardiac death with apparently normal hearts

Early repolarization indicates a distinct electrocardiographic phenotype affecting the junction between the QRS complex and the ST segment in inferolateral leads (inferolateral J-wave syndromes). It has been considered a benign electrocardiographic variant for decades, but recent clinical studies have demonstrated its arrhythmogenicity in a small subset, supported by experimental studies showing transmural dispersion of repolarization. Here we review the current knowledge and the issues of risk stratification that limit clinical management. In addition, we report on new mapping data of patients refractory to pharmacologic treatment using high-density electrogram mapping at the time of inscription of J wave. These data demonstrate that distinct substrates, delayed depolarization, and abnormal early repolarization underlie inferolateral J-wave syndromes, with significant implications. Finally, based on these data, we propose a new simplified mechanistic classification of sudden cardiac deaths without apparent structural heart disease.

Mapping and Ablation of Idiopathic Ventricular Fibrillation.

Idiopathic ventricular fibrillation (IVF) is the main cause of unexplained sudden cardiac death, particularly in young patients under the age of 35. IVF is a diagnosis of exclusion in patients who have survived a VF episode without any identifiable structural or metabolic causes despite extensive diagnostic testing. Genetic testing allows identification of a likely causative mutation in up to 27% of unexplained sudden deaths in children and young adults. In the majority of cases, VF is triggered by PVCs that originate from the Purkinje network. Ablation of VF triggers in this setting is associated with high rates of acute success and long-term freedom from VF recurrence. Recent studies demonstrate that a significant subset of IVF defined by negative comprehensive investigations, demonstrate in fact subclinical structural alterations. These localized myocardial alterations are identified by high density electrogram mapping, are of small size and are mainly located in the epicardium. As reentrant VF drivers are often colocated with regions of abnormal electrograms, this localized substrate can be shown to be mechanistically linked with VF. Such areas may represent an important target for ablation.

Analytical approaches for myocardial fibrillation signals

Atrial and ventricular fibrillation are complex arrhythmias, and their underlying mechanisms remain widely debated and incompletely understood. This is partly because the electrical signals recorded during myocardial fibrillation are themselves complex and difficult to interpret with simple analytical tools. There are currently a number of analytical approaches to handle fibrillation data. Some of these techniques focus on mapping putative drivers of myocardial fibrillation, such as dominant frequency, organizational index, Shannon entropy and phase mapping. Other techniques focus on mapping the underlying myocardial substrate sustaining fibrillation, such as voltage mapping and complex fractionated electrogram mapping. In this review, we discuss these techniques, their application and their limitations, with reference to our experimental and clinical data. We also describe novel tools including a new algorithm to map microreentrant circuits sustaining fibrillation.

Association of regional epicardial right ventricular electrogram voltage amplitude and late gadolinium enhancement distribution on cardiac magnetic resonance in patients with arrhythmogenic right ventricular cardiomyopathy: Implications for ventricular tachycardia ablation

Criteria for identification of anatomic ventricular tachycardia substrates in arrhythmogenic right ventricular cardiomyopathy (ARVC) on late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) are unclear. The purpose of this study was to define (1) the association of regional right ventricular (RV) epicardial voltage amplitude with the distribution of LGE; and (2) appropriate image signal intensity (SI) thresholds for ventricular tachycardia substrate identification in ARVC. Preprocedural LGE-CMR and epicardial electrogram mapping were performed in 10 ARVC patients. The locations of epicardial electrogram map points, obtained during sinus rhythm with intrinsic conduction or RV pacing, were retrospectively registered to the corresponding LGE image regions. Standardized SI z-scores (standard deviation distance from the mean) were calculated for each 10-mm region surrounding map points. In patient-clustered, generalized estimating equations models that included 3205 epicardial electroanatomic points and corresponding SI measures, bipolar (-1.43 mV/z-score; P <.001) and unipolar voltage amplitude (-1.22 mV/z-score; P <.001) were associated with regional SI z-scores. In contrast to the QRS-late potential (LP) interval (P = .362), the LP activation index, defined as electrogram duration divided by QRS-LP, was associated with regional SI z-scores (P <.001). SI z-score thresholds >0.05 (95% confidence interval -0.05 to 0.15) and <-0.16 (95% confidence interval -0.26 to 0.06) corresponded to bipolar voltage measures <0.5 and >1.0 mV, respectively. Increased RV gadolinium uptake is associated with lower epicardial bipolar and unipolar electrogram voltage amplitude. Standardized LGE-CMR SI z-scores may augment preprocedural planning for identification of low-voltage zones and abnormal myocardium in ARVC.

Combined Cryoballoon and Radiofrequency Ablation Versus Radiofrequency Ablation Alone for Long-Standing Persistent Atrial Fibrillation

BackgroundTo achieve sinus rhythm, ablation of long-standing persistent atrial fibrillation (LSPAF) usually requires substrate modification in addition to pulmonary vein isolation (PVI). In the present article, we aimed to compare clinical and substrate modification effects of 2 distinct PVI strategies during stepwise ablation in patients with LSPAF: (1) Combined approach: cryoballoon (CB) for PVI and radiofrequency (RF) ablation for substrate modification and (2) RF-only approach: RF ablation for both PVI and substrate modification. Materials and MethodsA total of 34 patients were divided into 2 groups: 19 in the combined group and 15 in the RF group. Left atrial (LA) complex fractionated atrial electrogram (CFAE) maps were acquired before and after PVI and compared between groups. The groups were compared for acute atrial fibrillation termination (AFT) rates and long-term arrhythmia-free survival. ResultsA significant reduction on total LA CFAE area was observed with PVI in both groups. In the CB group, when pulmonary veins were excluded, the reduction of LA CFAE area was the most significant on the posterior wall of left atrium and which was greater than in the RF group. Although the ratio of AFT was higher in the CB group (44% versus 33%, respectively), single-procedure arrhythmia-free survival at 1 year was comparable between groups (68% in the CB group versus 66% in the RF group). Times of total procedure, fluoroscopy and post-PVI RF were all shorter in the CB group. ConclusionsCB may cause greater substrate modification on the posterior wall and increase AFT rate during LSPAF ablation.

Conquest of Ventricular Tachycardia: Insights Into Mechanisms, Innovations in Management: Contribution of Mark E. Josephson, MD, to Clinical Electrophysiology.

### Mohammad Shenasa, MD Cardiac mapping has always been an integral part of basic and clinical electrophysiology. Indeed, direct cardiac mapping with recording of local electrograms has been used since the early 19th century, well before intracardiac catheter mapping.1,2 Walter H. Gaskell measured cardiac contraction to investigate the sequence of cardiac activation.1 Thomas Lewis used direct electrogram mapping in a dog model with atrial and ventricular arrhythmias (Figure 1).2 Intraoperative direct epicardial and endocardial mapping was later reported in patients with preexcitation syndromes and conduction disturbances, initially by the Amsterdam group3; however, systematic use of endocardial and epicardial mapping for ventricular tachycardia (VT) was pioneered by Josephson and colleagues at the University of Pennsylvania, although epicardial mapping was reported earlier by Fontaine et al.4–8 These reports greatly improved our understanding of pathophysiology and mechanisms of VT initially in patients with coronary artery disease and previous myocardial infarction. Intraoperative endocardial mapping revealed that reentry circuits were often localized on the endocardial surface or subendocardially and that resection of those regions eliminated the substrate of VT.9,10 These intraoperative studies led directly to the techniques we use in catheter ablation of VT today and has been applied to other VT substrates. Figure 1. Thomas Lewis’s activation map for direct electrogram recording in a dog heart.2 DBL indicates descending branch of left (coronary artery); DBR, descending branch of right (coronary artery); IVC, inferior vena cava; LA, left atrium; LV, left ventricle; PA, pulmonary artery; RA, right atrium; and SVC, superior vena cava. In modern interventional electrophysiology, cardiac mapping and imaging are integrated, and this merging is critical for success in complex ablation procedures. However, electrogram mapping remains an essential part of physiological understanding of the mechanism(s) of VT. The Penn group has set standards for …

Spatial reproducibility of complex fractionated atrial electrogram depending on the direction and configuration of bipolar electrodes: an in-silico modeling study.

Although 3D-complex fractionated atrial electrogram (CFAE) mapping is useful in radiofrequency catheter ablation for persistent atrial fibrillation (AF), the directions and configuration of the bipolar electrodes may affect the electrogram. This study aimed to compare the spatial reproducibility of CFAE by changing the catheter orientations and electrode distance in an in-silico left atrium (LA). We conducted this study by importing the heart CT image of a patient with AF into a 3D-homogeneous human LA model. Electrogram morphology, CFAE-cycle lengths (CLs) were compared for 16 different orientations of a virtual bipolar conventional catheter (conv-cath: size 3.5 mm, inter-electrode distance 4.75 mm). Additionally, the spatial correlations of CFAE-CLs and the percentage of consistent sites with CFAE-CL<120 ms were analyzed. The results from the conv-cath were compared with that obtained using a mini catheter (mini-cath: size 1 mm, inter-electrode distance 2.5 mm). Depending on the catheter orientation, the electrogram morphology and CFAE-CLs varied (conv-cath: 11.5±0.7% variation, mini-cath: 7.1±1.2% variation), however the mini-cath produced less variation of CFAE-CL than conv-cath (p<0.001). There were moderate spatial correlations among CFAE-CL measured at 16 orientations (conv-cath: r=0.3055±0.2194 vs. mini-cath: 0.6074±0.0733, p<0.001). Additionally, the ratio of consistent CFAE sites was higher for mini catheter than conventional one (38.3±4.6% vs. 22.3±1.4%, p<0.05). Electrograms and CFAE distribution are affected by catheter orientation and electrode configuration in the in-silico LA model. However, there was moderate spatial consistency of CFAE areas, and narrowly spaced bipolar catheters were less influenced by catheter direction than conventional catheters.

Impact of Catheter Contact Force on Human Left Atrial Electrogram Characteristics in Sinus Rhythm and Atrial Fibrillation.

During left atrial mapping, optimal contact parameters minimizing variation secondary to catheter contact are not established. Across 30 patients undergoing first-time atrial fibrillation ablation, 1965 stable mapping points (1409 atrial fibrillation, 556 sinus rhythm), comprising 8-s contact force (CF) and bipolar electrogram data were analyzed. Points were taken in groups at locations with CF or catheter orientation actively changed between acquisitions. Complexes were less positive at higher CF (Spearman ρ, -0.2; P<0.005, both rhythms). Increasing CF at a location significantly increased complex size, but only where initial CF was <10 g, and if the change was ≥4.5 g in sinus rhythm and ≥8 g in atrial fibrillation (P<0.0005, both rhythms): if initial CF was ≥10 g, no change was observed, regardless of CF change (P>0.05, both). Atrial ectopics during sinus rhythm were observed more frequently when CF was ≥10 g (P<0.0005). Increasing CF at a location was associated with an increase in the complex fractionated atrial electrogram interval confidence level score, but only if initial CF was <10 g and CF increased ≥8 g (P=0.003). The dominant frequency and organization index were unaffected by CF (P>0.1 for both). Changing catheter orientation from perpendicular to parallel in atrial fibrillation was associated with smaller, more positive complexes (P=0.001 for both), but no changes in complex fractionated atrial electrogram scores, dominant frequency or organization index (P>0.08 for each). During left atrial electrogram mapping, including complex fractionated atrial electrogram but not spectral parameter mapping, CF and catheter orientation influence results: consequently, mapping CFs should be ≥10 g to negate the influence of CF. URL: http://clinicaltrials.gov/. Unique identifier: NCT01587404.