Functional substrate mapping of atrium in patients with atrial scar: A novel method to predict critical isthmus of atrial tachycardia.

Atrial tachycardia (AT) is a common rhythm disorder, especially in patients with atrial structural abnormalities. Although voltage mapping can provide a general picture of structural alterations which are mainly secondary to prior ablations, surgery or pressure/volume overload, data is scarce regarding the functional characteristics of low voltage regions in the atrium to predict critical isthmus of ATs. Recently, functional substrate mapping (FSM) emerged as a potential tool to evaluate the functionality of structurally altered regions in the atrium to predict critical sites of reentry. Current evidence suggested a clear association between deceleration zones of isochronal late activation mapping (ILAM) during sinus/paced rhythm and critical isthmus of reentry in patients with left AT. Therefore, these areas seem to be potential ablation targets even not detected during AT. Furthermore, abnormal conduction detected by ILAM may also have a role to identify the potential substrate and predict atrial fibrillation outcome after pulmonary vein isolation. Despite these promising findings, the utility of such an approach needs to be evaluated in large-scale comparative studies. In this review, we aimed to share our experience and review the current literature regarding the use of FSM during sinus/paced rhythm in the prediction of re-entrant ATs and discuss future implications and potential use in patients with atrial low-voltage areas.

Anaesthetic management of paediatric patients undergoing electrophysiology study and ablation for supraventricular tachycardia: A focused narrative review.

Every year, 80,000-100,000 ablation procedures take place in the United States and approximately 1% of these involve paediatric patients. As the paediatric population undergoing catheter ablation to treat dysrhythmia is constantly growing, involvement of anaesthesiologists in the cardiac electrophysiology laboratory is simultaneously increasing. Compared with the adult population, paediatric patients need deeper sedation or general anaesthesia (GA) to guarantee motionlessness and preserve comfort. As a result, the anaesthesiologist working in this setting should keep in mind heart physiopathology as well as possible interactions between anaesthetic drugs and arrhythmia. In fact, drug-induced suppression of accessory pathways (APs) conduction capacity is a major concern for completing a successful electrophysiology study (EPS). Nevertheless, the literature on this topic is scarce and the optimal type of anaesthesia in EPS and ablation procedures in children is still controversial. Thus, the main goal of the present review is to collect the literature published so far on the effects on cardiac conduction tissue of the drugs commonly employed for sedation/GA in the cath lab for EPS and ablation procedures to treat supraventricular tachycardia in patients aged <18 years.

High density mapping of atrial tachycardia in patients post cardiac surgery.

Mapping and ablation of atrial tachycardia (AT) in patients who have had prior cardiac surgery can be a challenge for clinical electrophysiologists. High density mapping (HDM) technology has been widely used in these patients because it provides a better characterization of the substrate and the mechanisms with an unprecedented high resolution. In this review, we summarize how the latest HDM technologies can reveal the mechanism of AT in different types of patients post-cardiac surgery and guide a specifically tailored ablation strategy.

High density mapping of complex atrial tachycardia in patients after cardiac surgery.

To provide an overview of the current application of high-density mapping (HDM) in the mechanism of complex atrial tachycardias (ATs). Complex ATs are frequently scar-related, after history of previous cardiac surgery and large scars. These scar-related ATs are difficult to manage medically and frequently recur after electrical cardioversion. HDM technologies have enabled rigorous elucidation of AT mechanisms in patients post cardiac surgery. This article showed the application of HDM technology in complex ATs from the mechanisms of complex ATs, the development of HDM technology, and the identification of scars or critical isthmus from HDM. HDM-guided approach is highly effective for identifying the ATs mechanism and critical isthmus.

The Use of Local Activation Timing Histogram in Ablation of Focal and Re-Entrant Atrial Tachycardias.

BACKGROUND: Activation mapping is often used to differentiate focal from re-entrant arrhythmias. This can be challenging but is critical to ablation success. The local activation time (LAT) histogram, which depicts point distribution over isochronal segments, may help characterize arrhythmia mechanisms and identify an optimal ablation strategy. OBJECTIVES: This study aimed to investigate features of the LAT histogram associated with the focal vs re-entrant mechanism of atrial tachycardias (ATs) and the use of the LAT histogram in the identification of target ablation sites. METHODS: We retrospectively evaluated cases of focal and re-entrant ATs performed at a single academic tertiary care center for which activation mapping was performed using CARTO 3 version 7 software (Biosense Webster). Baseline patient, arrhythmia, and procedural characteristics as well as LAT histogram features were evaluated for each case. LAT histogram-guided ablation targets were also compared against actual ablation sites. RESULTS: Among 52 ATs assessed, 17 were focal, and 35 were re-entrant. Tachycardia cycle length was significantly shorter in re-entrant than in focal ATs (288.2 milliseconds [Q1-Q3: 250-306.5 milliseconds] vs 370 milliseconds [Q1-Q3: 285-400 milliseconds], respectively; P = 0.006). LAT histograms contained more "valleys" in re-entrant than in focal ATs (3 [Q1-Q3: 2-4] vs 1 [Q1-Q3: 1-1]; P < 0.001). No focal ATs contained >2 and no re-entrant ATs contained <1 LAT valley(s). All successful ablation sites correlated with LAT histogram-suggested sites. CONCLUSIONS: LAT histograms can help distinguish focal from re-entrant Ats and identify effective ablation sites.

Electrophysiologic Determinants of Isoelectric Intervals on Surface Electrocardiograms During Atrial Tachycardia: Insights From High-Density Mapping.

BACKGROUND: Substrate abnormalities can alter atrial activation during atrial tachycardias (ATs) thereby influencing AT-wave morphology on the surface electrocardiogram. OBJECTIVES: This study sought to identify determinants of isoelectric intervals during ATs with complex atrial activation patterns. METHODS: High-density activation maps of 126 ATs were studied. To assess the impact of the activated atrial surface on the presence of isoelectric intervals, this study measured the minimum activated area throughout the AT cycle, defined as the smallest activated area within a 50-millisecond period, by using signal processing algorithms (LUMIPOINT). RESULTS: ATs with isoelectric intervals (P-wave ATs) included 23 macro-re-entrant ATs (40%), 26 localized-re-entrant ATs (46%), and 8 focal ATs (14%), whereas those without included 46 macro-re-entrant ATs (67%), 21 localized-re-entrant ATs (30%), and 2 focal ATs (3%). Multivariable regression identified smaller minimum activated area and larger very low voltage area as independent predictors of P-wave ATs (OR: 0.732; 95% CI: 0.644-0.831; P < 0.001; and OR: 1.042; 95% CI: 1.006-1.080; P = 0.023, respectively). The minimum activated area with the cutoff value of 10 cm2 provided the highest predictive accuracy for P-wave ATs with sensitivity, specificity, and positive and negative predictive values of 96%, 97%, 97%, and 95%, respectively. In re-entrant ATs, smaller minimum activated area was associated with lower minimum conduction velocity within the circuit and fewer areas of delayed conduction outside of the circuit (standardized ß: 0.524; 95% CI: 0.373-0.675; P < 0.001; and standardized ß: 0.353; 95% CI: 0.198-0.508; P < 0.001, respectively). CONCLUSIONS: Reduced atrial activation area and voltage were associated with isoelectric intervals during ATs.

Detailed analysis of tachycardia cycle length aids diagnosis of the mechanism and location of atrial tachycardias.

AIMS: Although the mechanism of an atrial tachycardia (AT) can usually be elucidated using modern high-resolution mapping systems, it would be helpful if the AT mechanism and circuit could be predicted before initiating mapping. OBJECTIVE: We examined if the information gathered from the cycle length (CL) of the tachycardia can help predict the AT-mechanism and its localization. METHODS: One hundred and thirty-eight activation maps of ATs including eight focal-ATs, 94 macroreentrant-ATs, and 36 localized-ATs in 95 patients were retrospectively reviewed. Maximal CL (MCL) and minimal CL (mCL) over a minute period were measured via a decapolar catheter in the coronary sinus. CL-variation and beat-by-beat CL-alternation were examined. Additionally, the CL-respiration correlation was analysed by the RhythmiaTM system. : Both MCL and mCL were significantly shorter in macroreentrant-ATs [MCL = 288 (253-348) ms, P = 0.0001; mCL = 283 (243-341) ms, P = 0.0012], and also shorter in localized-ATs [MCL = 314 (261-349) ms, P = 0.0016; mCL = 295 (248-340) ms, P = 0.0047] compared to focal-ATs [MCL = 506 (421-555) ms, mCL = 427 (347-508) ms]. An absolute CL-variation (MCL-mCL) < 24 ms significantly differentiated re-entrant ATs from focal-ATs with a sensitivity = 96.9%, specificity = 100%, positive predictive value (PPV) = 100%, and negative predictive value (NPV) = 66.7%. The beat-by-beat CL-alternation was observed in 10/138 (7.2%), all of which showed the re-entrant mechanism, meaning that beat-by-beat CL-alternation was the strong sign of re-entrant mechanism (PPV = 100%). Although the CL-respiration correlation was observed in 28/138 (20.3%) of ATs, this was predominantly in right-atrium (RA)-ATs (24/41, 85.7%), rather than left atrium (LA)-ATs (4/97, 4.1%). A positive CL-respiration correlation highly predicted RA-ATs (PPV = 85.7%), and negative CL-respiration correlation probably suggested LA-ATs (NPV = 84.5%). CONCLUSION: Detailed analysis of the tachycardia CL helps predict the AT-mechanism and the active AT chamber before an initial mapping.

Junctional Tachycardia: A Critical Reassessment.

Junctional tachycardia (JT) is typically considered to have an automatic mechanism originating from the distal atrioventricular node. When there is 1:1 retrograde conduction via the fast pathway, JT would resemble the typical form of atrioventricular nodal re-entrant tachycardia (AVNRT). Atrial pacing maneuvers have been proposed to exclude AVNRT and suggest a diagnosis of JT. However, after excluding AVNRT, one should consider the possibility of an infra-atrial narrow QRS re-entrant tachycardia, which can exhibit features that resemble AVNRT as well as JT. Pacing maneuvers and mapping techniques should be performed to assess for infra-atrial re-entrant tachycardia before concluding that JT is the mechanism of a narrow QRS tachycardia. Distinguishing JT from typical AVNRT or infra-atrial re-entrant tachycardia has notable implications regarding the approach to ablation of the tachycardia. Ultimately, a contemporary review of the evidence on JT raises some questions as to the mechanism and source of what has traditionally been considered JT.

Single-beat global atrial mapping facilitates the treatment of short-lived atrial tachycardias and infrequent premature atrial contractions.

BACKGROUND: Short runs of atrial tachycardias (ATs) and infrequent premature atrial contractions (PACs) are difficult to map and ablate using sequential electrophysiology mapping techniques. The AcQMap mapping system allows for highly accurate mapping of a single atrial activation. OBJECTIVES: We aimed to test the value of a novel dipole charge density-based high-resolution mapping technique (AcQMap) in the treatment of brief episodes of ATs and PACs. METHODS: Data of all patients undergoing catheter ablation (CA) using the AcQMap mapping system were reviewed. RESULTS: Thirty-one out of 219 patients (male n = 8; female n = 23) had short runs of ATs (n = 23) and PACs (n = 8). The mean procedural time was 155.3 ± 46.6 min, with a mean radiation dose of 92.0 (IQR 37.0-121.0) mGy. Total radiofrequency application duration 504.0 (271.0-906.0) s. Left atrial localization of ATs and PACs was identified in 45.1% of the cases, right atrium localization in 45.1%, and septal origins in 9.8% of the cases. Acute success was achieved in 30/31 (96.8%), and recurrence during the follow-up developed in six patients (19.4%), including four patients with PACs and two patients with short-lived ATs. One patient presented procedure-related groin hematoma as minor complication. CONCLUSION: Brief episodes of highly symptomatic ATs and infrequent PACs can be mapped using charge density mapping and successfully ablated with high acute and long-term success rates.

Treatment of atrial tachycardia arising after superior transseptal approach mitral valve surgery: Insights from ultra-high-density mapping to prevent atrioventricular block.

INTRODUCTION: Mitral valve surgery employing a superior transseptal approach (STA) is associated with arrhythmogenicity and intra-atrial conduction delay, despite being optimal for visualization of the surgical field. It is sometimes difficult to treat atrial tachycardias (AT) that arise after STA. To investigate AT circuits that arise after STA in detail in order to identify the optimal ablation line, using ultra-high-resolution mapping (UHRM). METHODS: We retrospectively analyzed 12 AT from 10 patients (median age 70 years, nine males) who had undergone STA surgery. The tachycardias were mapped using the Rhythmia mapping system (Boston Scientific, Natick, Massachusetts). RESULTS: The 12 STA-related AT (STA-AT) circuits were classifiable as follows according to location of the optimal ablation line: (1) peri-septal incision STA-AT (n = 3), (2) cavotricuspid isthmus (CTI) dependent STA-AT (n = 7), and (3) biatrial tachycardia (n = 2). Radiofrequency (RF) application terminated 11 of the 12 STA-AT. We found that difference in STA-AT circuit type was due to characteristics of the septal incision line made for STA. UHRM was important in identifying optimal ablation sites that did not create additional conduction disturbances in the right atrium (RA). CONCLUSIONS: ATs after STA involve complex arrhythmia circuits due to multiple and long incision lines in the RA. Accurate understanding of the arrhythmia circuit and sinus conduction in the RA after STA is recommended for treating post-surgical tachycardia in a minimally invasive manner.

An unusual case of non-reentrant atrioventricular nodal tachycardia.

INTRODUCTION: Although uncommonly encountered, dual atrioventricular nodal non-reentrant tachycardia (DAVNNRT) is a well-described arrhythmia that can manifest in patients with dual atrioventricular nodal pathways physiology. This arrhythmia is characterized on electrocardiogram (ECG) by a single P wave followed by two conducted QRS complexes (so-called "double fire"), and on intracardiac electrograms by a single atrial electrogram followed by two separate His deflections and ventricular electrograms. METHODS/RESULTS: We report a rare case of "triple-fire" atrioventricular non-reentrant tachycardia in which a patient was found to have three distinct atrioventricular nodal pathways and multiple triple fire responses, both on surface ECG and intracardiac electrograms. CONCLUSION: Multiple pathways physiology and it's clinical ramifications are discussed.

Mapping and ablation of left atrial roof-dependent tachycardias using an ultra-high resolution mapping system.

BACKGROUND: Left atrial roof-dependent tachycardias (LARTs) are common macroreentrant atrial tachycardias (ATs). We sought to characterize clinical LARTs using an ultra-high resolution mapping system. METHODS: This study included 22 consecutive LARTs in 21 patients who underwent AT mapping/ablation using Rhythmia systems. RESULTS: Three, 13, 4, and 2 LART patients were cardiac intervention naïve (Group-A), post-roof line ablation (Group-B), post-atrial fibrillation ablation without linear ablation (Group-C), and post-cardiac surgery (Group-D), respectively. The mean AT cycle length was 244 ± 43 ms. Coronary sinus activation was proximal-to-distal or distal-to-proximal in 16 (72.7%) ATs. The activation map revealed 13 (59.1%) clockwise and 9 (40.9%) counter-clockwise LARTs. A 12-lead synchronous isoelectric interval was observed in 10/19 (52.6%) LARTs. The slow conduction area was identified on the LA roof, anterior/septal wall, and posterior wall in 18, 6, and 2 ATs, respectively. Twenty concomitant ATs among 13 procedures were also eliminated, and peri-mitral AT coexisted in 7 of 9 non-group-B patients. In group-B, the conduction gap was predominantly located on the mid-roof. Sustained LARTs were terminated by a single application and linear ablation in 6 (27.3%) and 9 (40.9%), while converting to other ATs in 7 (31.8%) LARTs. Complete linear block was created without any complications in all, however, ablation at the mid-posterior wall was required to achieve block in 4 (18.2%) procedures. During 14.0 (6.5-28.5) months of follow-up, 17 (81.0%) and 19 (90.5%) patients were free from any atrial tachyarrhythmias after single and last procedures. CONCLUSIONS: The LART mechanisms were distinct in individual patients, and elimination of all concomitant ATs was required for the management.

Supraventricular tachycardia associated with severe diabetic ketoacidosis in a child with new-onset type 1 diabetes mellitus.

Diabetic ketoacidosis is one of the most serious and common complications of diabetes, with between 15 and 70% of new-onset type 1 diabetes mellitus worldwide presented with diabetic ketoacidosis. Supraventricular tachycardia, however, is an infrequent complication of diabetic ketoacidosis. We present the case of a child with a new-onset type 1 diabetes mellitus with supraventricular tachycardia as a complication of paediatric diabetic ketoacidosis. The patient received intravenous fluid resuscitation, insulin, and potassium supplementation and subsequently developed stable supraventricular tachycardia initially, confirmed on a 12-lead electrocardiogram despite a structurally normal heart and normal electrolytes. Vagal manoeuvers failed to achieve sinus rhythm. The patient went into respiratory distress and was intubated, for mechanical ventilation. She received one dose of adenosine with successful conversion to sinus rhythm and a heart rate decreased from 200 to 140 beats per minutes. We conclude that supraventricular tachycardia can occur as a complication of diabetic ketoacidosis, including in new-onset type 1 diabetes mellitus. Furthermore, a combination of acidosis, potassium derangement, falling magnesium, and phosphate levels may have precipitated the event. Here, we report a case of supraventricular tachycardia as a complication of paediatric diabetic ketoacidosis.

Electrophysiological characteristics of atrial tachycardia recurrence: Relevance to catheter ablation strategies in adults with congenital heart disease.

BACKGROUND: Catheter ablation outcomes for adults with congenital heart disease (ACHD) are described, but recurrence mechanisms remain largely unknown. OBJECTIVE: The purpose of this study was to identify the electrophysiological characteristics of atrial tachycardia (AT) recurrence in ACHD. METHODS: ACHD atrial tachycardia procedures over a 10-year period were explored for AT or atrial fibrillation (AF) recurrence. RESULTS: At 299 procedures in 250 ACHD (mean age 39 ± 15 years; 130 [52%] male), 464 ATs (360 intra-atrial reentrant tachycardia, 104 focal AT; median 2 [IQR 1-3] ATs per procedure) were targeted. Complete (n = 256 [86%]) or partial (n = 37 [12%]) success was achieved in 98% of procedures. Over a median of 3.0 (IQR 1.4-5.3) years of follow-up, 67 patients (27%) developed AT/AF recurrence after the index procedure. Repeat vs index tachycardias were more often focal AT (26/69 [38%] vs 73/378 [19%]; P < .001), demonstrated longer cycle length (325 ms vs 280 ms; P = .003), required isoproterenol (34/69 [50%] vs 121/378 [32%]; P = .03), and involved the pulmonary venous atrium (PVA)/septum (26/69 [38%] vs 67/378 [18%]; P < .001). AF history (hazard ratio [HR] 2.0; interquartile range [IQR] 1.2-3.4; P = .01), incomplete success (HR 3.6; IQR 2.1-6.4; P < .001), and PVA substrate (HR 2.1; IQR 1.2-3.5; P = .006) were independently associated with AT/AF recurrence. With complete index procedure success and no AF history, 5-year actuarial freedom from AT/AF and AT alone were 77% and 80%. CONCLUSION: After catheter ablation in ACHD, repeat ATs were more frequently focal, required isoproterenol administration, or involved intra-atrial reentrant tachycardia within the PVA or atrial septum. Negative factors were partial success, index PVA substrate, and remote history of AF. These data support aggressive pharmacological provocation to eliminate all inducible tachycardias and coexisting PVA substrates at index procedures for ACHD.

Ultra-high-density mapping and ablation strategy for multiple scar-related right atrial tachycardias in patients without previous cardiac surgery.

BACKGROUND: Catheter ablation of right atrial (RA) tachycardia in patients who have extensive spontaneous RA scarring is challenging due to the complex substrate and the potential for multiple inducible atrial tachycardias (ATs). METHODS: Eighteen patients with scar-related RA AT and no prior cardiac surgery were enrolled. A total of 52 different ATs (mean 3.2 ± 1.5 ATs per patient) were observed. We endeavored to complete activation maps for 45 ATs. RESULTS: By analyzing activation maps, we classified ATs into six categories. The discrepant location and extension of ESAs were associated with different AT mechanisms. CONCLUSIONS: Multiple scar-related RA ATs were observed in patients without previous cardiac surgery. The detailed activation patterns of these ATs could be clearly demonstrated by using an ultra-high-density mapping system.

Outcomes of supraventricular tachycardia ablation: Results from the Singapore ablation and cardiac devices registry.

BACKGROUND: The Singapore Cardiac Databank was designed to monitor the performance and outcomes of catheter ablation. We investigated the outcomes of paroxysmal supraventricular tachycardia (PSVT)-ablation in a prospective, nationwide, cohort study. METHODS: Atrioventricular nodal re-entrant tachycardia (AVNRT), atrioventricular re-entry tachycardia (AVRT), or atrial tachycardia (AT)-ablations in Singapore from 2010 to 2018 were studied. Outcomes include acute success, periprocedural-complications, postoperative pacing requirement, arrhythmic recurrence and 1-year all-cause mortality. RESULTS: Among 2260 patients (mean age 45 ± 18 years, 50% female, 57% AVNRT, 37% AVRT, 6% AT), overall acute success rates of PSVT-ablation was 98.4% and increased in order of AT, AVRT, and AVNRT (p < .001). Periprocedural cardiac tamponade occurred in two AVRT patients. A total of 15 pacemakers (6 within first 30-days, 9 after 30-days) were implanted (seven AV block, eight sinus node dysfunction [SND]), with the highest incidence of pacemaker implantation after AT-ablation (5% vs. 0.6% AVNRT vs. 0.1% AVRT, p < .001). Repeat ablations (0.9% AVNRT, 7% AVRT, 4% AT, p < .001) were performed in 78 (3.5%) patients and 13 (0.6%) patients died within a year of ablation. Among outcomes considered adjusting for age, sex, PSVT-type and procedure-time, AT was independently associated with 6-fold increased odds of total (adjusted odds ratio [AOR] 6.32, 95% confidence interval [CI] 1.95-20.53) and late (AOR 6.38, 95% CI 1.39-29.29) pacemaker implantation, while AVRT was associated with higher arrhythmic recurrence with repeat ablations (AOR 4.72, 95% CI 2.36-9.44) compared to AVNRT. CONCLUSIONS: Contemporary PSVT ablation is safe with high acute success rates. Long-term outcomes differed by nature of the PSVT.

Transesophageal electrophysiology study in the diagnosis of dual atrioventricular nodal nonreentrant tachycardia.

"Double fire" is generally characterized by 1:2 atrioventricular conduction of sinus beats traveling down fast and slow pathways that result in double ventricular response. When this phenomenon repeats rapidly, dual atrioventricular nodal nonreentrant tachycardia (DAVNNT) occurs. We report a case of an irregular tachycardia with a comprehensive record that includes an electrocardiogram, a transesophageal electrophysiology study, and an intracardiac electrophysiology study. This is the first report of transesophageal electrophysiology study in the diagnosis of DAVNNT. A diagnosis of DAVNNT was deduced, and the patient was successfully treated with radiofrequency ablation of the slow pathway.

Low-Voltage-Area Ablation in Paroxysmal Atrial Fibrillation　- Extended Follow-up Results of the VOLCANO Trial.

BACKGROUND: The randomized controlled VOLCANO trial demonstrated comparable 1-year rhythm outcomes between patients with and without ablation targeting low-voltage areas (LVAs) in addition to pulmonary vein isolation among paroxysmal atrial fibrillation (PAF) patients with LVAsMethods and Results:An extended-follow-up study of 402 patients enrolled in the VOLCANO trial with PAF, divided into 4 groups based on the results of voltage mapping: group A, no LVA (n=336); group B, LVA ablation (n=30); group C, LVA without ablation (n=32); and group D, incomplete voltage map (n=4). At 25 (23, 31) months after the initial ablation, AF/atrial tachycardia (AT) recurrence rates were 19% in group A, 57% in group B, 59% in group C, and 100% in group D. Recurrence rates were higher in patients with LVAs than in those without (group A vs. B+C, P<0.0001), and were comparable between those with and without LVA ablation (group B vs. C, P=0.83). Among patients who underwent repeat ablation, ATs were more frequently observed in patients with LVAs (Group B+C, 50% vs. A, 14%, P<0.0001). In addition, LVA ablation increased the incidence of AT development (group B, 71% vs. C, 32%, P<0.0001). CONCLUSIONS: Patients with LVAs demonstrated poor long-term rhythm outcomes irrespective of LVA ablation. ATs were frequently observed in patients with LVAs, and LVA ablation might exacerbate the occurrence of iatrogenic ATs.

Identification of high priority focal activations in persistent atrial fibrillation using a novel mapping strategy.

Focal activation is believed to be an atrial fibrillation (AF) driver; however, little is known about whether all focal activations are necessary for AF persistence. The purpose of this study was to assess the electrical nature of focal activation and identify high-priority focal activations using a novel mapping system (CARTOFINDER). Thirty-five patients with persistent AF who underwent catheter ablation were assessed. Cycle length (CL) and CL standard deviation (CLSD) on unipolar recordings and voltage amplitude and electrogram morphologies on bipolar recordings were evaluated at all points of interest. The most frequent CL at each mapping site was defined as the dominant CL. We identified dominant focal activations (DFAs) that had a shorter dominant CL on the integrated CARTOFINDER map. The effect of elimination of DFAs on AF maintenance was assessed by the composite endpoint (termination to sinus rhythm, organization of the rhythm to atrial tachycardia, and AF CL slowing). In all, 450 focal activations were identified among 10,868 points, and 50.4% of focal activations were DFAs. Focal activations showed relatively long CL and regularity with short CLSD. Most focal activations showed an isoelectric baseline and were located outside of the fractionated electrogram area. Both DFAs and non-DFAs were typically observed in the normal voltage range. Elimination of DFAs was achieved in 19 (54.3%) patients, with a remarkable impact on AF maintenance (68.4% vs. 25.0%, p = 0.018). In conclusion, DFAs may play an important role in AF maintenance and could be an attractive therapeutic target for AF.