High Dominant Frequency Sites Research Articles

Evaluating spatial disparities of rotor sites and high dominant frequency regions during catheter ablation for PersAF patients targeting high dominant frequency sites using non-contacting mapping.

Purpose: Several studies have emphasised the significance of high dominant frequency (HDF) and rotors in the perpetuation of AF. However, the co-localisation relationship between both attributes is not completely understood yet. In this study, we aim to evaluate the spatial distributions of HDF regions and rotor sites within the left atrium (LA) pre and post HDF-guided ablation in PersAF. Methods: This study involved 10 PersAF patients undergoing catheter ablation targeting HDF regions in the LA. 2048-channels of atrial electrograms (AEG) were collected pre- and post-ablation using a non-contact array (EnSite, Abbott). The dominant frequency (DF, 4–10 Hz) areas with DF within 0.25 Hz of the maximum out of the 2048 points were defined as “high” DF (HDF). Rotors were defined as PSs that last more than 100 ms and at a similar location through subsequent phase frames over time. Results: The results indicated an extremely poor spatial correlation between the HDF regions and sites of the rotors in pre-versus post-ablation cases for the non-terminated (pre: CORR; 0.05 ± 0.17. vs. post: CORR; −0.030 ± 0.19, and with terminated patients (pre: CORR; −0.016 ± 0.03. post: CORR; −0.022 ± 0.04). Rotors associated with AF terminations had a long-lasting life-span post-ablation (non-terminated vs. terminated 120.7 ± 6.5 ms vs. 139.9 ± 39.8 ms), high core velocity (1.35 ± 1.3 mm/ms vs. 1.32 ± 0.9 mm/ms), and were less meandering (3.4 ± 3.04 mm vs. 1.5 ± 1.2 mm). Although the results suggest a poor spatial overlapping between rotors’ sites and sites of AFCL changes in terminated and non-terminated patients, a higher correlation was determined in terminated patients (spatial overlapping percentage pre: 25 ± 4.2% vs. 17 ± 3.8% vs. post: 8 ± 4.2% vs. 3.7 ± 1.7% p < 0.05, respectively). Conclusion: Using non-contact AEG, it was noted that the correlation is poor between the spatial distribution of HDF regions and sites of rotors. Rotors were longer-lasting, faster and more stationary in patients with AF termination post-ablation. Rotors sites demonstrated poor spatial overlapping with sites of AFCL changes that lead to AF termination.

The association of complex fractionated atrial electrograms, high dominant frequency sites and atrial fibrillation

The association of complex fractionated atrial electrograms, high dominant frequency sites and atrial fibrillation

Complex fractionated atrial electrograms, high dominant frequency regions, and left atrial voltages during sinus rhythm and atrial fibrillation

BackgroundAblation targeting complex fractionated atrial electrograms (CFAEs) or high dominant frequency (DF) sites is generally effective for persistent atrial fibrillation (AF). CFAEs and/or high DF sites may exist in low-voltage regions, which theoretically represent abnormal substrates. However, whether CFAEs or high DF sites reflect low voltage substrates during sinus rhythm (SR) is unknown. MethodsSixteen patients with AF (8 with paroxysmal AF; 8, persistent AF) underwent high-density mapping of the left atrium (LA) with a 3-dimensional electroanatomic mapping system before ablation. The LA was divided into 7 segments and the mean bipolar voltage recorded during AF and SR, CFAEs (cycle lengths of 50–120ms), and DF sites were assessed in each segment with either a duo-decapolar ring catheter (n=10) or a 64-pole basket catheter (n=6). Low-voltage areas were defined as those of <0.5mV during AF and <1.0mV during SR. ResultsRegional mean voltage recorded from the basket catheter showed good correlation between AF and SR (r=0.60, p<0.01); however, the % low-voltage area in the LA recorded from the ring catheter showed weak correlation (r=0.34, p=0.05). Mean voltage was lower during AF than during SR (1.0mV [IQR, 0.5–1.4] vs. 2.6mV [IQR, 1.8–3.6], p<0.01). The regional and overall % low-voltage area of the LA was greater during AF than during SR (20% vs. 11%, p=0.05). CFAEs and high DF sites (>8Hz) did not correlate with % low-voltage sites during SR; however, CFAEs sites were located in high-voltage regions during AF and high DF sites were located in low voltage regions during AF. ConclusionsCFAEs and high DF areas during AF do not reflect damaged atrial myocardium as shown by the SR voltage. However, CFAEs and high DF sites may demonstrate different electrophysiologic properties because of different voltage amplitude during AF.

Invasive management of atrial fibrillation

AbstractAtrial fibrillation (AF), the most common sustained cardiac arrhythmia, affects 1% of the general population with increased incidence in the elderly population and is an important contributor to population morbidity and mortality. This article reviews the current invasive management of AF. Pulmonary vein isolation (PVI) is the cornerstone of current ablation techniques for the treatment of paroxysmal atrial fibrillation (AF). Despite proven PVI, a subset of patients still experience recurrent arrhythmia, mostly due to a higher prevalence of non‐PV triggers. PVI is associated with worse arrhythmia‐free survival in patients with persistent AF than those with paroxysmal AF. Accumulating data have shown that elimination of atrial fibrillation 9 (AF) sources (rotors or rotational activity, drivers, electrograms with continuous activity) should be the goal in persistent AF ablation. Pulmonary vein isolation, linear lesions, and complex fractionated atrial electrograms (CFAEs) ablation have shown limited efficacy in patients with persistent AF. A combined approach using voltage, CFAEs, and dominant frequency (DF) mapping may be helpful for the identification of AF sources and subsequent focal substrate modification. The fibrillatory activity is maintained by intramural reentry centered on fibrotic patches. Voltage mapping may assist in the identification of fibrotic areas. Stable rotors display the higher DF and possibly drive AF. Furthermore, the single rotor is usually consistent with organized AF electrograms without fractionation. It is therefore quite possible that rotors are located at relatively “healthy islands” within the patchy fibrosis. This is supported by the fact that high DF sites have been negatively correlated with the amount of fibrosis. CFAEs are located in areas adjacent to high DF. In conclusion, patchy fibrotic areas displaying the maximum DF along with high organization index and the lower fractionation index are potential targets of ablation. Prospective studies are required to validate the efficacy of substrate modification in left atrial ablation outcomes.Answer questions and earn CME: https://wileyhealthlearning.com/Activity2/4469458/Activity.aspx

Post-operative atrial fibrillation is associated with a pre-existing structural and electrical substrate in human right atrial myocardium

BackgroundPost-operative atrial fibrillation (POAF) is a major health economic burden. However, the precise mechanisms in POAF remain unclear. In other forms of AF, sites of high dominant frequency (DF) in sinus rhythm (SR) may harbour ‘AF nests’. We studied AF inducibility in relation to substrate changes using epicardial electrograms and cardiomyocyte calcium handling in the atria of AF naïve patients. MethodBipolar electrograms were recorded from the lateral right atrial (RA) wall in 34 patients undergoing coronary surgery using a high-density array in sinus rhythm (NSR). RA burst pacing at 200/500/1000ms cycle lengths (CL) was performed, recording episodes of AF>30s. Co-localised RA tissue was snap frozen for RNA and protein extraction. ResultsElectrograms prolonged during AF (76.64±29.35ms) vs. NSR/pacing (p<0.001). Compared to NSR, electrogram amplitude was reduced during AF and during pacing at 200ms CL (p<0.001). Electrogram DF was significantly lower in AF (75.87±23.63Hz) vs. NSR (89.33±25.99Hz) (p<0.05), and NSR DF higher in AF inducible patients at the site of AF initiation (p<0.05). Structurally, POAF atrial myocardium demonstrated reduced sarcolipin gene (p=0.0080) and protein (p=0.0242) expression vs. NSR. Phospholamban gene and protein expression was unchanged. SERCA2a protein expression remained unchanged, but MYH6 (p=0.0297) and SERCA2A (p=0.0343) gene expression was reduced in POAF. ConclusionsHuman atrial electrograms prolong and reduce in amplitude in induced peri-operative AF vs. NSR or pacing. In those sustaining AF, high DF sites in NSR may indicate ‘AF nests’. This electrical remodelling is accompanied by structural remodelling with altered expression of cardiomyocyte calcium handling detectable before POAF. These novel upstream substrate changes offer a novel mechanism and manifestation of human POAF.

Abstract 16024: High Frequency Driving Sites are Anchored by Fibrotic Regions in Chronic Atrial Fibrillation

Introduction: Stable high frequency sources and rotors have been described to drive episodes of atrial fibrillation (AF) but the mechanism for their stability is unknown. We used a chronic animal model of AF to test the hypothesis that fibrosis anchors sites of high frequency activation during AF, which may drive the arrhythmia.. Methods: Endocardial electrograms were measured with a Constellation catheter (Boston Scientific) placed in the left atrium (LA) of chronic AF dogs (n=6) (AF &gt; 12 months). An EnSite (St. Jude) geometric shell was then fused with a LA wall created by segmenting a high resolution T1 Mapping MRI. Regions with the lowest 10% T1 in the LA wall, used as a surrogate measure of fibrosis, were included on the LA wall segmentation. Fibrosis densities were calculated from histology and correlated with T1 Mapping MRI. Electrograms recorded during AF were processed to determine the dominant frequency (DFs) at each recording site. A probability map with the highest 10% DF value for each minute of AF at each of the sites was created to determine the stability of the DF during the 30 min AF episode. Results: Each AF animal had at least one site of high DF which was stable for at least 22.5 (75%) of a 30-minute AF episode and 82% of the high DF sites stabilized within 2 mm of a region of fibrosis (chi square test, p &lt; 0.05). The mean DF was 8.5±1.2 Hz and the highest DF sites showed an average DF of 10.3±1.1 Hz. The region of T1 Mapping MRI detected fibrosis of the LA wall had an average value of 283±32 ms whereas the rest of the LA had an average value of 463±79 ms. Histology confirmed that that T1 Mapping MRI detected fibrosis had more fibrosis than other LA regions. (25±1% vs. 13±2%). Conclusions: Fibrosis developed during chronic AF may provide a substrate that anchors sites of high DF. Cardiac T1 Mapping MRI provides a means to determine such fibrotic sites noninvasively. Ablating these sites may reduce the stability of these high frequency sources and eliminate the drivers of persistent AF.

Catheter ablation of persistent atrial fibrillation: The importance of substrate modification.

Accumulating data have shown that elimination of atrial fibrillation (AF) sources should be the goal in persistent AF ablation. Pulmonary vein isolation, linear lesions and complex fractionated atrial electrograms (CFAEs) ablation have shown limited efficacy in patients with persistent AF. A combined approach using voltage, CFAEs and dominant frequency (DF) mapping may be helpful for the identification of AF sources and subsequent focal substrate modification. The fibrillatory activity is maintained by intramural reentry centered on fibrotic patches. Voltage mapping may assist in the identification of fibrotic areas. Stable rotors display the higher DF and possibly drive AF. Furthermore, the single rotor is usually consistent with organized AF electrograms without fractionation. It is therefore quite possible that rotors are located at relatively "healthy islands" within the patchy fibrosis. This is supported by the fact that high DF sites have been negatively correlated to the amount of fibrosis. CFAEs are located in areas adjacent to high DF. In conclusion, patchy fibrotic areas displaying the maximum DF along with high organization index and the lower fractionation index are potential targets of ablation. Prospective studies are required to validate the efficacy of substrate modification in left atrial ablation outcomes.

Abstract 16295: Human Epicardial Bipolar Electrograms Prolong and Reduce in Amplitude Prior to Induction of Peri-Operative Atrial Fibrillation and Are Related to Sites of High Electrogram Dominant Frequency in Sinus Rhythm

Background: The exact trigger/substrate interactions leading to post-operative AF are unknown. Sites of high DF in sinus rhythm are proposed to harbor ‘fibrillar myocardium’ or ‘AF nests’. We studied AF inducibility related to putative upstream substrate changes by characterising epicardial electrograms (EGM) in both time and frequency domains. Method: AF naïve patients (n=14) undergoing coronary artery bypass grafting (CABG) had bipolar electrograms recorded from the lateral right atria (RA) wall with a high density spiral catheter, sampled at 1kHz. RA burst pacing at cycle lengths (CL) of 200, 500 and 1000ms was performed with any episodes of AF &gt; 30s recorded. Electrograms were analysed using an average of 5 consecutive beats for duration, peak to peak amplitude, dominant frequency (DF) and activation time at all bipole pairs during every pacing drive train (total EGMs analysed 3430). Results: Bipolar EGM duration was significantly longer during AF (mean = 76.64ms, SD = 29.35ms) than all other CLs or NSR (p&lt;0.0001). There was no difference between CLs but a trend to longer EGM at 200ms CL. EGM amplitude was significantly smaller during AF (mean = 0.85mV, SD = 0.51mv) vs. 500ms CL and NSR (p&lt;0.0001) and at 200ms vs. 500ms CL (p&lt;0.05) and NSR (p&lt;0.0001). The EGM DF was significantly lower in AF (mean = 75.87Hz, SD = 23.63Hz) vs NSR (mean = 89.33Hz, SD = 25.99Hz) (p&lt;0.05) but not vs. pacing CLs. Activation time was significantly prolonged at 200ms CL (mean = 29.41ms, SD = 16.23ms) vs AF and NSR (p&lt;0.001 and 0.05 respectively). Conclusions: Human bipolar EGMs prolong and reduce in amplitude in induced peri-operative AF than in NSR or pacing. Atrial activation slows at 200ms CL, prior to initiation of AF. These changes are accompanied by high DF sites in NSR which may reveal underlying ‘AF nests’ even in non-remodelled atria. These novel peri-operative electrophysiological findings suggest upstream substrate changes which may predispose patients to post-operative AF.

Location of epicardial adipose tissue affects the efficacy of a combined dominant frequency and complex fractionated atrial electrogram ablation of atrial fibrillation.

Epicardial adipose tissue (EAT) is located adjacent to high dominant frequency (DF) sites. This study aimed to clarify the relationship between the EAT location and efficacy of a combined high DF site and continuous complex fractionated activation electrogram (CFAE) site ablation. Fifty-five patients with nonparoxysmal atrial fibrillation (AF) (26 (47%) persistent and 29 (53%) long-standing persistent) underwent pulmonary vein isolation followed by high DF site and continuous CFAE site ablation. High DF sites (DF ≥8 Hz) and continuous CFAE sites (fractionated intervals ≤50 ms) were targeted. The patients were divided into an AF-free group and an AF-recurrent group. The AF freedom rate on antiarrhythmic drugs in patients with persistent and long-standing persistent AF was 88.5% and 75.9% over a 12-month follow-up period, respectively. The total EAT, left atrial (LA)-EAT, and right atrial (RA)-EAT volumes did not indicate significant differences between the AF-free and AF-recurrent groups. In the LA, the overlap between high DF sites and EAT was larger in the AF-free group than in the AF-recurrent group (57.0% ± 33.3% vs 22.6% ± 23.3%; P < .01). However, this overlap did not differ between the AF-free and AF-recurrent groups in the RA (20.4% ± 28.2% vs 19.0% ± 24.4%; P = .91). The overlap between continuous CFAE sites and EAT did not differ between the 2 groups in both the LA and the RA. High DF sites that overlap with EAT may be important sources of AF. However, the contribution of EAT to the AF substrate may differ between the LA and the RA.

Distinctive patterns of dominant frequency trajectory behavior in drug-refractory persistent atrial fibrillation: preliminary characterization of spatiotemporal instability.

The role of substrates in the maintenance of persistent atrial fibrillation (persAF) remains poorly understood. The use of dominant frequency (DF) mapping to guide catheter ablation has been proposed as a potential strategy, but the characteristics of high DF sites have not been extensively studied. This study aimed to assess the DF spatiotemporal stability using high density noncontact mapping (NCM) in persAF. Eight persAF patients were studied using NCM during AF. Ventricular far-field cancellation was performed followed by the calculation of DF using Fast Fourier Transform. Analysis of DF stability and spatiotemporal behavior were investigated including characteristics of the highest DF areas (HDFAs). A total of 16,384 virtual electrograms (VEGMs) and 232 sequential high density 3-dimensional DF maps were analyzed. The percentage of DF stable points decreased rapidly over time. Repetition or reappearance of DF values were noted in some instances, occurring within 10 seconds in most cases. Tracking the HDFAs' center of gravity revealed 3 types of propagation behavior, namely (i) local, (ii) cyclical, and (iii) chaotic activity, with the former 2 patterns accounting for most of the observed events. DF of individual VEGMs was temporally unstable, although reappearance of DF values occurred at times. Hence, targeting sites of 'peak DF' from a single time frame is unlikely to be a reliable ablation strategy. There appears to be a predominance of local and cyclical activity of HDFAs hinting a potentially nonrandom temporally periodic behavior that provides further mechanistic insights into the maintenance of persAF.

Termination of atrial fibrillation by ablation of high-dominant frequency sites adjacent to epicardial adipose tissue

We report an interesting case in which atrial fibrillation (AF) was terminated during ablation of high-dominant frequency (DF) sites covered with epicardial adipose tissue (EAT). High-DF sites are known to be related to the center of focal-firing rotors or local reentry circuits. Therefore, this phenomenon suggests that EAT may be related to the development of dominant rotors maintaining AF.

Comparative distribution of complex fractionated atrial electrograms, high dominant frequency (HDF) sites during atrial fibrillation and HDF sites during sinus rhythm

Complex fractionated atrial electrograms (CFAEs) and high dominant frequency sites during atrial fibrillation (AF-HDF) are related to the maintenance of atrial fibrillation (AF). HDF sites in sinus rhythm (SR-HDF; as defined by frequencies of >70 Hz) are suggested to be abnormal atrial tissue. Relations between these electrophysiologic signals have not been elucidated. We investigated the relations between SR-HDF and CFAE and AF-HDF sites during AF. NavX-based maps of CFAE and left atrium (LA)/pulmonary vein (PV) dominant frequency (DF) during AF and DF maps during SR were created for 23 patients with AF (paroxysmal AF (PAF), n = 14; persistent AF (PerAF), n = 9). The extent of overlap between SR-HDF and CFAE sites was 51 ± 18 % (as calculated by the LA/PV segments containing both an SR-HDF site and a CFAE site/total LA/PV segments containing an CFAE site) and the extent of overlap between SR-HDF and AF-HDF sites was 50 ± 35 % (P = 0.7464). However, statistically poor agreement was noted for both (kappa values, 0.07 ± 0.19 and 0.08 ± 0.24, P = 0.8794). The extent of overlap did not differ between PAF and PerAF patients (SR-HDF and CFAE, 52 % (interquartile range (IQR), 42-59) versus 57 % (IQR, 33-67), P = 0.5842; SR-HDF and AF-HDF, 43 % (IQR, 25-85) versus 55 % (IQR, 13-83), P = 0.9465). The bipolar voltage amplitudes of SR-HDF, CFAE, and AF-HDF sites revealed normal voltage areas (1.6 mV (IQR, 0.8-2.7), 1.9 mV (IQR, 1.1-2.8), and 1.5 mV (IQR, 1.7-2.7), respectively). In both PAF and PerAF, most CFAE and AF-HDF sites did not correspond to the SR-HDF sites or low-voltage area during SR. Thus, most CFAE and DF signals during AF represent functional electrical activities rather than structural remodeling of the atria.

Epicardial Adipose Tissue and Neural Mechanisms of Atrial Fibrillation

In this issue of Circulation: Arrhythmia and Electrophysiology , Nagashima et al1 reported that there is higher epicardial adipose tissue (EAT) volume and greater serum inflammatory biomarker levels in patients with persistent atrial fibrillation (PerAF) than in patients with paroxysmal atrial fibrillation (PAF). Furthermore, they noted that high dominant frequency (DF) sites are located adjacent to EAT sites. The authors proposed 2 possible explanations for these findings. One is that EAT secretes proinflammatory cytokines that alter local atrial and pulmonary vein (PV) electrophysiology and facilitates the development of atrial fibrillation (AF). The second is that EAT contains abundant ganglionated plexi. Activation of the autonomic nerves in the ganglionated plexi facilitates the maintenance of AF. The results of the present study extended their previous observation on EAT2 by providing new data on the correlation between high DF sites and EAT sites. These novel observations provide new insights into the anatomic and physiological differences between PAF and PerAF. Article see p 676 After the initial diagnosis of PAF, there is a slow (5%–10% per year) but steady progression to chronic (permanent or persistent) AF.3 Baseline echocardiographic variables, age, cardiomyopathy, and heart rate are independently associated with progression to chronic AF. On the other hand, PerAF is also frequently the initial diagnosis without preceding PAF episodes. How often PerAF and permanent forms of AF are preceded by recurrent PAF remains unclear. Improving the understanding of PAF to PerAF progression may help secondary prevention efforts to reduce the complications associated with AF. Wijffels et al4 performed intermittent rapid atrial pacing in goats to study the progression of PAF to PerAF. They found that when AF is maintained artificially, the duration of the paroxysms progressively increases, becoming sustained after 1 to 3 weeks of AF. The transition from PAF to PerAF …

Does Location of Epicardial Adipose Tissue Correspond to Endocardial High Dominant Frequency or Complex Fractionated Atrial Electrogram Sites During Atrial Fibrillation?

Although increased epicardial adipose tissue (EAT) volume is known to be associated with increased prevalence of atrial fibrillation (AF), the exact mechanisms are unclear. Therefore, we investigated whether EAT locations were associated with high dominant frequency (DF) sites or complicated fractionated atrial electrogram sites during AF. Three-dimensional reconstruction computed tomography images depicting EAT volumes (obtained by 320-detector-row multislice computed tomography) were merged with NavX-based DF and complicated fractionated atrial electrogram maps obtained during AF for 16 patients with paroxysmal AF and for 18 patients with persistent AF. Agreement between locations of the EAT, especially EAT surrounding the left atrium, and of high DF or complicated fractionated atrial electrogram sites was quantified. In addition, serum biomarker levels were determined. EAT surrounding the left atrium volumes was significantly greater in patients with persistent AF than in patients with paroxysmal AF (52.9 cm(3) [95% CI, 44.2-61.5] versus 34.8 cm(3) [95% CI, 26.6-43.0]; P=0.007). Serum high-sensitivity C-reactive protein and interleukin-6 levels were significantly higher in persistent AF patients than in paroxysmal AF patients (median high-sensitivity C-reactive protein, 969 ng/mL [interquartile range, 307-1678] versus 320 ng/mL [interquartile range, 120-660]; P=0.008; median interleukin-6, 2.4 pg/mL [interquartile range, 1.7-3.2] versus 1.3 [interquartile range, 0.8-2.4] pg/mL; P=0.017). EAT locations were in excellent agreement with high DF sites (κ=0.77 [95% CI, 0.71-0.82]) but in poor agreement with complicated fractionated atrial electrogram sites (κ=0.22 [95% CI, 0.13-0.31]). Increased EAT volume and elevation of inflammatory biomarkers are noted in persistent AF rather than paroxysmal AF patients. High DF sites are located adjacent to EAT sites. Thus, EAT may be involved in the maintenance of AF.

Relationship among complex signals, short cycle length activity, and dominant frequency in patients with long-lasting persistent AF: A high-density epicardial mapping study in humans

Complex fractionated atrial electrograms (CFAEs) and regions of high dominant frequency (DF) both may identify sites critical to the maintenance of atrial fibrillation (AF). CFAEs may be defined by either (1) complex multicomponent electrograms (EGMs) and/or continuous electrical activity (multicomponent/continuous EGM) or (2) discrete high-frequency EGMs. The purpose of this study was to test if the 2 definitions of CFAE identify the same arrhythmia substrate and determine the relationship of CFAE to areas of high DF. High-density epicardial mapping of the posterior left atrium was performed in 10 patients with long-lasting persistent AF. Point-by-point analysis was performed to determine the spatial distribution and correlation of CFAE defined as either (1) multicomponent/continuous-EGMs or (2) AF cycle length <120 ms. Additionally, spatial analysis was performed to determine the relationship of high DF sites to CFAE sites defined by each of the 2 definitions. The percentage of sites deemed CFAE varied markedly between patients and was different depending on the definition of CFAE adopted. There was a poor correlation between CFAE defined by multicomponent/continuous EGMs and AF cycle length <120 ms (r = 0.18). High DF sites were arranged in clusters evenly distributed throughout the posterior left atrium, with 4.2 ± 1.0 high DF clusters per patient. Although there was poor point-by-point correlation between multicomponent/continuous EGMs and high DF sites (r = 0.107), spatial analysis revealed that 96% of multicomponent/continuous EGMs were found adjacent to and partially surrounding (≤5 mm) high DF sites. There is poor anatomic overlap between CFAE defined by multicomponent/continuous EGMs and CFAE defined by AF cycle length <120 ms. Multicomponent/continuous EGMs are found adjacent to and surrounding sites of high DF. Further studies are needed to determine the mechanisms responsible for these different signals.

Complex Fractionated Atrial Electrograms

Since its inception in the 1990s, catheter ablation of atrial fibrillation (AF) has been a continuously evolving procedure. Ablation strategies have adapted to advances in technology including new catheter designs, innovations in mapping systems, and alternative energy sources. Moreover, catheter ablation has stimulated and responded to an improved understanding of the mechanisms of initiation and perpetuation of AF. Over the past 15 years, many centers have spent considerable effort in defining optimal ablation strategies for elimination of paroxysmal and nonparoxysmal AF. Article see p 143 The pulmonary veins were recognized early by Haissaguerre et al1,2 as a frequent source of triggers for AF. Pulmonary vein isolation quickly became the cornerstone of catheter ablation of AF and sparked its rise as a promising tool to eliminate symptomatic and drug-refractory AF.3,4 This was first performed by ostial ablation, but, because of the risk of pulmonary vein stenosis and recognition of vital antral drivers, an antral pulmonary vein isolation (APVI) strategy evolved.3,5 Adjuvants to APVI have been proposed, including ablation of complex fractionated atrial electrograms (CFAE). Initial experience suggested that CFAE ablation is a viable stand-alone strategy,6 but this experience has not been reproducible.7 …

Relationship between High-Dominant Frequency Sites and the Impact of a Stepwise Linear Ablation on the Distribution of Complex Fractionated Electrograms

Background: Complex fractionated electrograms (CFE) and high-dominant frequency (DF) sites are considered to be maintainers of atrial fibrillation (AF). The purpose of this study was to determine the relationship between high-DF sites in the left atrium (LA) and the impact of a stepwise linear ablation in patients with AF. Methods: We compared LA-CFEs and DF maps acquired using NavX system before and after ablation in 30 AF patients (non-paroxysmal: 20). The maps were constructed from bipolar electrograms acquired from circular catheter during AF. The stepwise approach initially utilized a circumferential pulmonary vein isolation, followed by linear lesions including at the septum, roof, mitral annulus and ridge of the appendage. Results: A mean of 282±60 points were sampled. Multipolar-catheter mapping identified sites with high-DF (>9 Hz) in all patients (7.9±2.8/patient). Sixty-five% of the high-DF sites were on or adjacent to the ablation line. There was a significant reduction in the CFE burden after the stepwise ablation for both the regions with <120 ms (90% vs. 49%; P<.001) and <50 ms (65% vs. 8%; P<.0001), with a decrease in both the DF within the CS (7.0±1.3 vs. 5.1±1.1 Hz; P<.01) and CFE-surface area (44.2±21.5 vs. 6.0±5.3 cm2; P<.0001). Conclusion: Stepwise linear ablation lines have a higher incidence of neighboring high-DF sites, and this may be related to eliminating the majority of the CFE areas after the procedure. These findings have important implications for the substrate-based ablation strategies for AF.

Continuous CFEs in the Vicinity of High DF Sites Are Important for the Maintenance of AF

In nonparoxysmal atrial fibrillation (AF), ablation of these continuous complex fractionated atrial electrogram (CFE) after PVI as an adjunctive therapy to PVI had a better long-term efficacy. However, the adjunctive role of dominant frequency (DF) mapping during CFE ablation of AF has not been clarified. The study enrolled 50 nonparoxysmal AF patients who underwent mapping, pulmonary vein isolation, and CFE ablation. High density DF and CFE mapping were performed from the center of DFmax centrifugally to the rest of the LA. The LA substrate was classified into two types depending on the presence of intra-LA DF gradients as type 1 (more than 20% of the average DF) or type 2 (less than 20%). In type 1, maximal CFE and DF gradients were observed at the boundary (28%) or center (32%) of the DFmax region. In type 2 (40%), less intra-LA DF gradient was observed and a large proportion of continuous CFEs extended from the center of DFmax. The procedure termination rate and long-term sinus rhythm maintenance rate were lower in patients with a smaller DF gradient (P<0.05). In conclusion, we found that the spatial distribution of fractionated activity was associated with particular DF patterns in nonparoxysmal AF patients. Individual knowledge of spatial and temporal organization of fibrillation waves in each patient may help in identification of mechanism and the critical targets for AF.

Role of high dominant frequency sites in nonparoxysmal atrial fibrillation patients: Insights from high-density frequency and fractionation mapping

The adjunctive role of dominant frequency (DF) mapping during complex fractionated electrogram (CFE) ablation of atrial fibrillation (AF) has not been clarified. The purpose of this study was to investigate whether DF distribution or substrate properties are related to fibrillatory activity in the left atrium (LA) and to evaluate the effect of CFE ablation on the different patterns of DF distribution. The study enrolled 50 nonparoxysmal AF patients who underwent mapping, pulmonary vein isolation, and CFE ablation. High-density DF and CFE mapping were performed from the center of DF(max) centrifugally to the rest of the LA. The LA substrate was classified into two types depending on the presence of intra-LA DF gradients as type 1 (>20% of the average DF) or type 2 (<20% of the average DF). In type 1, maximal CFE and DF gradients were observed at the boundary (n = 14) or center (n = 16) of the DF(max) region. In type 2 (n = 20), less intra-LA DF gradient was observed (4.27 +/- 1.92 Hz vs 1.14 +/- 0.52 Hz for types 1 and 2, P <.001) and a large proportion of continuous CFEs extended from the center of DF(max) (19% +/- 11% and 42% +/- 15% of the LA for types 1 and type 2, P = .001). The procedure termination rate and long-term sinus rhythm maintenance rate were lower in patients with a smaller DF gradient (P <.05). The spatial distribution of fractionated activity was associated with particular DF patterns in nonparoxysmal AF patients. Patients with an evident intra-LA DF gradient responded better to pulmonary vein isolation and continuous CFE ablation.

High‐Density Mapping of Atrial Fibrillation in Humans: Relationship Between High‐Frequency Activation and Electrogram Fractionation

Sites of complex fractionated atrial electrograms (CFAE) and dominant frequency (DF) have been implicated in maintaining atrial fibrillation (AF); however, their relationship is poorly understood. Twenty patients underwent biatrial high-density contact mapping (507 +/- 150 points/patient) during AF. CFAE were characterized using software to quantify electrogram complexity (CFE-mean). Spectral analysis determined the frequency with greatest power and sites of high DF with a frequency gradient. CFE-mean was higher (less fractionated) for right compared with left atria (P < 0.001) and in paroxysmal compared with persistent AF (P < 0.001). DF was lower for right compared with left atria (P = 0.02) and in paroxysmal compared with persistent AF (P < 0.001). There was significant regional variation in DF in paroxysmal (P < 0.001) but not persistent AF. Highest DF points clustered together with 5.2 +/- 1.7 clusters/patient. Correlation between CFE-mean and DF was poor on a point-by-point basis (r =-0.17, P < 0.001), but moderate on an individual basis (r =-0.50, P = 0.03). Exploration of their spatial relationship demonstrated CFAE areas in close proximity (median 5 mm, IQR 2-10) to high DF sites; within 10 mm in 80% and 10-20 mm in 10%. Simultaneous activation mapping at these sites further supports this observation. Greater fractionation and higher DF are seen in persistent AF and left atria during AF. Preferential areas of high DF are observed in paroxysmal but not persistent AF. CFAE and DF correlate within an individual but not point-by-point. Exploration of their spatial relationship demonstrates CFAE in areas adjacent to high DF, and this is supported by activation mapping at these sites.