Telemetry of Intracardiac Electrograms: Applications in Spontaneous and Induced Arrhythmias

In order to demonstrate the feasibility of dysrhythmia analysis by means of noninvasive intracardiac telemetry, a custom-modified AFP DDD pulse generator was attached to temporary pacing electrodes in 15 patients undergoing electrophysiology studies for a variety oftacliy- or bradyarrhythmias. Intracardiac atrial and ventricular electrograms were obtained during induction, termination, and drug intervention in patients with these arrhythmias. The telemetered computer-generated hardcopy tracings compared favorably to those obtained through a standard multichannel physiological recorder, and thus confirmed the accuracy of the technique. Therefore, microprocessor-based telemetry ofintracardiac electrograms may have a prominent role in the design of multifunction devices for both bradycardias and tachycardias     

The Complementary Role of Electrogram, Event Marker, and Measured Data Telemetry in the Assessment of Pacing System Function

Increasing numbers of pulse generators have one or more features that assist in the diagnostic evaluation of the pacing system. Interrogation of programmed parameters, measured lead and battery data, telemetry of event markers, endocardial electrograms, diagnostic data concerning the frequency of pacing and the presence or absence of spontaneous arrhythmias all facilitate the ease with which the pacing system is evaluated and the patient managed. The utility of these features is illustrated from five separate cases demonstrating the value of the individual features and how they may complement one another in extremely complicated pacing system problems.     

Use of correlation waveform analysis in discrimination between anterograde and retrograde atrial electrograms during ventricular tachycardia

INTRODUCTION: Discriminating between ventricular tachycardia (VT) with 1:1 ventriculoatrial association and sinus tachycardia can be difficult, even when assisted by intracardiac tracings. In this study, we used a new computer algorithm to perform correlation waveform analyses on intracardiac atrial electrograms to help distinguish between VT and sinus tachycardia. METHODS AND RESULTS: Electrophysiologic studies of 28 patients (22 men; age 66 +/- 14 years) with inducible VT and mean ejection fraction of 37% +/- 16% were analyzed. A template of an intracardiac high right atrial electrogram was obtained during sinus rhythm (SR). Atrial electrograms during SR and VT were compared with the template using the new algorithm, and correlation coefficients (rho) were generated. The correlation coefficient of SR beats with the template was 96.4% +/- 3.4%. During VT with AV dissociation and persistent SR, rho was 94.5% +/- 3.7% (P = NS). During VT with 1:1 retrograde conduction, rho was 70.6% +/- 11.3% (P < 0.0001). At a cutoff of 85%, rho had positive and negative predictive values of 99% and 96%, respectively. CONCLUSION: Our findings indicate that the new algorithm can reliably separate between anterograde and retrograde atrial activation during VT. It can, therefore, discriminate between sinus tachycardia and VT with 1:1 ventriculoatrial conduction and may be useful in preventing inappropriate shocks from dual chamber defibrillators.     

The Novel Electrophysiology of Complex Fractionated Atrial Electrograms: Insight from Noncontact Unipolar Electrograms

Unipolar Characteristics of CFAEs. Background: The noncontact mapping (NCM) system possesses the merit of global endocardial recording for unipolar and activation mapping. Objective: We aimed to evaluate the unipolar electrogram characteristics and activation pattern over the bipolar complex fractionated atrial electrogram (CFAE) sites during atrial fibrillation (AF). Methods: Twenty patients (age 55 ± 11 years old, 15 males) who underwent NCM and ablation of AF (paroxysmal/persistent = 13/7) were included. Both contact bipolar (32–300 Hz) and NCM virtual unipolar electrograms (0.5–300 Hz) were simultaneously recorded along with the activation pattern (total 223 sites, 11 ± 4 sites/patient). A CFAE was defined as a mean bipolar cycle length of ≤ 120 ms with an intervening isoelectric interval of more than 50 ms (Group 1A, n = 63, rapid repetitive CFAEs) or continuous fractionated activity (Group 1B, n = 59, continuous fractionated CFAEs), measured over a 7.2‐second duration. Group 2 consisted of those with a bipolar cycle length of more than 120 ms (n = 101). Results: The Group 1A CFAE sites exhibited a shorter unipolar electrogram cycle length (129 ± 11 vs 164 ± 20 ms, P < 0.001), and higher percentage of an S‐wave predominant pattern (QS or rS wave, 63 ± 13% vs 35 ± 13%, P < 0.001) than the Group 2 non‐CFAE sites. There was a linear correlation between the bipolar and unipolar cycle lengths (P < 0.001, R = 0.87). Most of the Group 1A CFAEs were located over arrhythmogenic pulmonary vein ostia or nonpulmonary vein ectopy with repetitive activations from those ectopies (62%) or the pivot points of the turning wavefronts (21%), whereas the Group 1B CFAEs exhibited a passive activation (44%) or slow conduction (31%). Conclusions: The bipolar repetitive and continuous fractionated CFAEs represented different activation patterns. The former was associated with an S wave predominant unipolar morphology which may represent an important focus for maintaining AF. (J Cardiovasc Electrophysiol, Vol. 21, pp. 640‐648, June 2010)     

Holter Recordings with Continuous Marker Annotation to Evaluate Pacemaker Function

Background: Pacemaker marker annotations facilitate the interpretation of device behavior in addition to ECG recordings. However, they are only available in conjunction with a programmer. We studied the diagnostic value of a prototype Telemetry Holter Decoder (THD), providing continuous marker annotations on a conventional Holter. Methods: The study included 20 patients with VDD or DDDR pacemakers. A 24‐hour Holter was performed using the THD. Marker annotations are transmitted from the pacemaker to the THD, which transforms them into analog signals, which are recorded on one of the Holter channels. Results: During a total recording time of 458 hours, high quality marker annotations were retrieved for every patient. Artefacts disturbed the recordings during 184 min (0.67%). The THD provided information not discernible on the ECG: intermittent atrial undersensing during sinus rhythm (1096 times). Atrial tachycardias, not visible on the ECG, were detected in 2 patients. The activation of tachycardia response algorithms was clearly annotated in 11,516 events. A total of 8875 PVC's occurred, 57.8% of which were classified incorrectly in the event counters as conducted or fusion beats. Atrial far‐field sensing or VA conduction was demonstrated 4294 times. Electromagnetic interferences, not visible on the ECG, could be seen three times. Conclusion: Recording of continuous high‐quality marker annotation on a conventional Holter is feasible. The THD provides important information on device behavior, even in patients assumed to have regular device function, and shows to be clearly superior to ECG interpretation alone. Such data can be used for improved programming, troubleshooting and for the validation of new algorithms. A.N.E. 2002;7(1):22–28     

Measuring the Complexity of Atrial Fibrillation Electrograms

AF Electrogram Complexity. Introduction: Complex fractionated atrial electrograms (CFAE) have been identified as targets for atrial fibrillation (AF) ablation. Robust automatic algorithms to objectively classify these signals would be useful. The aim of this study was to evaluate Shannon's entropy (ShEn) and the Kolmogorov‐Smirnov (K‐S) test as a measure of signal complexity and to compare these measures with fractional intervals (FI) in distinguishing CFAE from non‐CFAE signals. Methods and Results: Electrogram recordings of 5 seconds obtained from multiple atrial sites in 13 patients (11 M, 58 ± 10 years old) undergoing AF ablation were visually examined by 4 independent reviewers. Electrograms were classified as CFAE if they met Nademanee criteria. Agreement of 3 or more reviewers was considered consensus and the resulting classification was used as the gold standard. A total of 297 recordings were examined. Of these, 107 were consensus CFAE, 111 were non‐CFAE, and 79 were equivocal or noninterpretable. FIs less than 120 ms identified CFAEs with sensitivity of 87% and specificity of 79%. ShEn, with optimal parameters using receiver‐operator characteristic curves, resulted in a sensitivity of 87% and specificity of 81% in identifying CFAE. The K‐S test resulted in an optimal sensitivity of 100% and specificity of 95% in classifying uninterpretable electrogram from all other electrograms. Conclusions: ShEn showed comparable results to FI in distinguishing CFAE from non‐CFAE without requiring user input for threshold levels. Thus, measuring electrogram complexity using ShEn may have utility in objectively and automatically identifying CFAE sites for AF ablation. (J Cardiovasc Electrophysiol, Vol. 21, pp. 649‐655, June 2010)     

Bedside Recordings of His-Bundle Electrograms Using Conventional Twelve-Lead Surface Electrocardiography

Bedside Recording of His Potentials. Introduction: Endocavitary His-bundle electro-grams are usually recorded using high fidelity amplifiers and special filters.
Methods and Results: To evaluate whether similar recordings could be obtained using a 12-lead surface electrocardiograph, we compared recordings obtained during an electrophysiologic study in 33 patients to those obtained by connecting the two poles of the bipolar catheter, used during the study as the His catheter, to the right and left arm leads of the surface electrocardiograph. We recorded His-bundle electrograms using both techniques in all patients. There were no differences in measurements obtained between the two techniques.
Conclusion: His-bundle electrograms can be recorded reliably with a conventional electro-gram without sophisticated systems.     

心房复杂碎裂电图的发生机制及临床意义

心房颤动(房颤)时心房电图会呈现特征性的复杂碎裂电图。多个研究认为复杂碎裂电图反映了局部折返激动,且与心脏自主神经兴奋有密切的关系。目前复杂碎裂电图指导临床射频消融治疗房颤已取得较高成功率,进一步证实复杂碎裂电图代表了房颤的基质。     

Intraprocedural Use of Ibutilide to Organize and Guide Ablation of Complex Fractionated Atrial Electrograms: Preliminary Assessment of a Modified Step‐Wise Approach to Ablation of Persistent Atrial Fibrillation

Ibutilide Guided CFAE Ablation. Introduction: While able to achieve clinical success, the current step‐wise approach to persistent atrial fibrillation (AF) ablation requires considerable “substrate” ablation and frequently mandates multiple procedures to address consequent atrial tachycardias (ATs). An alternative strategy minimizing the amount of ablation while maintaining clinical success would be desirable. We hypothesize that intraprocedural administration of a low‐dose antiarrhythmic drug (AAD) during AF will organize areas of passive activation and not affect areas critical to AF maintenance, thereby potentially minimizing the ablation lesion set. Methods and Results: Eleven patients (age = 55 ± 6 years; LA = 48 ± 15 mm; median AF duration = 3 years) with persistent AF undergoing catheter ablation were enrolled in this exploratory prospective observational study. After pulmonary vein (PV) isolation, a mean cycle length (mCL) map was created and areas with mCL <120 ms were considered to represent complex fractionated atrial electrograms (CFAE). Ibutilide (0.25–1.0 mg) was then administered and a second mCL map created. Ablation lesions were placed at CAFE sites identified after ibutilide administration. Activation and/or entrainment mapping was employed to address ATs. The endpoint of ablation was achieving sinus rhythm. The average LA mCL increased (146 vs 165 ms, P = 0.01) and the LA CFAE surface area decreased after ibutilide administration. Additional ablation organized AF to either sinus rhythm or AT in 10/11 (91%) patients. After a median follow up of 455 days, 8 of 11 (72%) patients were free from AF. Three patients underwent a repeat ablation procedure (average 1.27 ablations/patient). Conclusions: Ibutilide administration may organize atrial activity and facilitate AF termination during ablation while minimizing the ablation lesion set. (J Cardiovasc Electrophysiol, Vol. 21, pp. 608‐616, June 2010)     

The electrophysiological effects of intravenous magnesium on human sinus node, atrioventricular node, atrium, and ventricle

The effects of intravenously (IV) administered magnesium chloride (MgCl) on electrophysiologic and electrocardiographic variables were studied in 13 patients undergoing a routine electrophysiologic assessment for clinical indications. An infusion of 12 mmol of MgCl was given during a 10-min period and relevant electrophysiologic variables were determined before and after the infusion. Serum Mg levels increased from 0.78 +/- 0.03 (mean +/- SEM) before to 1.52 +/- 0.08 ms after the infusion (p less than 0.0001). Magnesium treatment caused a significant prolongation in PR interval (from 151 +/- 8 to 174 +/- 8 ms, p less than 0.001) as well as in QRS duration (from 90 +/- 4 to 101 +/- 6 ms, p less than 0.05). Likewise, intra-atrial (PA) as well as atrioventricular (AV) nodal (AH) conduction times were significantly prolonged (from 33 +/- 3 to 46 +/- 3 ms, p less than 0.01, and from 85 +/- 6 to 94 +/- 6 ms, p less than 0.05, respectively). Mean effective and functional atrial refractory periods increased (from 228 +/- 8 to 256 +/- 10 ms, p less than 0.01 and from 292 +/- 9 to 320 +/- 11 ms, p less than 0.01, respectively), as did mean AV node functional refractory period (from 399 +/- 29 to 422 +/- 27 ms, p less than 0.02). No significant change occurred with regard to sinus node function (as estimated from heart rate, sinus node recovery time, and calculated sinoatrial conduction time) or ventricular refractoriness. It is concluded that IV Mg has several electrophysiologic effects that may be beneficial in the treatment/prevention of supraventricular tachyarrhythmias.     

Noncontact Endocardial Mapping: Reconstruction of Electrograms and Isochrones From Intracavitary Probe Potentials

Noncontact Endocardial Mapping. Introduction : Mapping endocardial activation and repolarization processes is critical to the study of arrhythmias and selection of therapeutic procedures. Previously, we developed methodology for reconstructing endocardial potentials from potentials measured with a noncontact, intracavitary probe. This study further develops and evaluates the ability of the approach to provide detailed information on the spatiotemporal characteristics of the activation process. Specifically, we reconstructed endocardial electrograms and isochrones throughout the activation process over the entire endocardium during a single beat.
Methods and Results : Cavity potentials were measured with a 65-electrode probe placed inside an isolated canine left ventricle. Endocardial potentials were measured simultaneously using 52 electrodes. Potentials were acquired during subendocardial pacing from different locations. Computed electrograms at various sites closely resemble the measured electrograms (correlation coefficient > 0.9 at 60% of the electrodes). Computed isochrones locate subendocardial pacing sites with 10-mm accuracy. Two pacing sites, 17 mm apart, were resolved. Critical regions, such as areas of isochrone crowding, were accurately reconstructed.
Conclusions : Results indicate the applicability of the approach to mapping the cardiac excitation process on a beat-by-beat basis without occluding the ventricle. The ability of locating electrical events (e.g., single or multiple initiation sites) is demonstrated. Importantly, the method is shown to be capable of reconstructing electrograms over the entire endocardium and determining nonuniformities of activation spread (e.g., areas of slow conduction). These capabilities are important to clinical application in the electrophysiology laboratory and experimental studies of arrhythmias in the intact animal.     

Impact of Pharmacological Autonomic Blockade on Complex Fractionated Atrial Electrograms

Autonomic Blockade During Atrial Fibrillation . Introduction: The influence of the autonomic nervous system on the pathogenesis of complex fractionated atrial electrograms (CFAE) during atrial fibrillation (AF) is incompletely understood. This study evaluated the impact of pharmacological autonomic blockade on CFAE characteristics. Methods and Results: Autonomic blockade was achieved with propanolol and atropine in 29 patients during AF. Three‐dimensional maps of the fractionation degree were made before and after autonomic blockade using the Ensite Navx^® system. In 2 patients, AF terminated following autonomic blockade. In the remaining 27 patients, 20,113 electrogram samples of 5 seconds duration were collected randomly throughout the left atrium (10,054 at baseline and 10,059 after autonomic blockade). The impact of autonomic blockade on fractionation was assessed by blinded investigators and related to the type of AF and AF cycle length. Globally, CFAE as a proportion of all atrial electrogram samples were reduced after autonomic blockade: 61.6 ± 20.3% versus 57.9 ± 23.7%, P = 0.027. This was true/significant for paroxysmal AF (47 ± 23% vs 40 ± 22%, P = 0.003), but not for persistent AF (65 ± 22% vs 62 ± 25%, respectively, P = 0.166). Left atrial AF cycle length prolonged with autonomic blockade from 170 ± 33 ms to 180 ± 40 ms (P = 0.001). Fractionation decreases only in the 14 of 27 patients with a significant (>6 ms) prolongation of the AF cycle length (64 ± 20% vs 59 ± 24%, P = 0.027), whereas fractionation did not reduce when autonomic blockade did not affect the AF cycle length (58 ± 21% vs 56 ± 25%, P = 0.419). Conclusions: Pharmacological autonomic blockade reduces CFAE in paroxysmal AF, but not persistent AF. This effect appears to be mediated by prolongation of the AF cycle length. (J Cardiovasc Electrophysiol, Vol. pp. 766‐772, July 2010)     

Efficacy of Additional Ablation of Complex Fractionated Atrial Electrograms for Catheter Ablation of Nonparoxysmal Atrial Fibrillation

Background: The efficacy of ablation of complex fractionated atrial electrograms (CFEs) in the single ablation procedure for nonparoxysmal atrial fibrillation (AF) patients is not well demonstrated. The aim of this study was to compare the ablation strategies of pulmonary vein isolation (PVI) plus linear ablation with and without additional ablation of CFEs in these patients.
Methods: Consecutive 60 patients (49 ± 11 years old, 50 male, 10 female) with nonparoxysmal AF underwent catheter ablation guided by a NavX mapping system. A stepwise approach included a circumferential PVI and left atrial (LA) linear ablation followed by either the additional ablation of continuous CFEs in the LA/coronary sinus (the first 30 patients) or not (the second 30 patients), detected by an automatic algorithm.
Results: There was no difference in the baseline characteristics between the two groups. Complete PVI eliminated some continuous CFEs and altered the distribution of CFEs. Following PVI and linear ablation, the remaining continuous CFEs were identified in 7.9 ± 10% mapping sites of the LA and CS, and were ablated successfully with a procedural AF termination rate of 53%. With a follow-up of 19 ± 11 months, a Kaplan–Meier analysis showed that the patients with additional ablation of the CFEs had a higher rate of sinus rhythm maintenance. Multivariate analysis showed the single procedure success could be predicted by the procedural AF termination and the additional ablation of continuous CFEs in the LA/CS.
Conclusions: Ablation of continuous CFEs after PVI and LA linear ablation had a better long-term efficacy based on the results of single-ablation procedure.     

The Optimal Automatic Algorithm for the Mapping of Complex Fractionated Atrial Electrograms in Patients With Atrial Fibrillation

CFAEs and the Voltage.   Introduction: Catheter ablation of atrial fibrillation (AF) can be guided by the identification of complex fractionated atrial electrograms (CFAEs). We aimed to study the prediction of the CFAEs defined by an automatic algorithm in different atrial substrates (high voltage areas vs low voltage areas).
Methods and Results: This study included 13 patients (age = 56 ± 12 years, paroxysmal AF = 8 and persistent AF = 5), who underwent mapping and catheter ablation of AF with a NavX system. High-density voltage mapping of the left atrium (LA) was performed during sinus rhythm (SR) (248 ± 75 sites per patient) followed by that during AF (88 ± 24 sites per patient). The CFAE maps were based on the automatic-detection algorithm. "Operator-determined CFAEs" were defined according to Nademannee's criteria. A low-voltage zone (LVZ) was defined as a bipolar voltage of less than 0.5 mV during SR. Among a total of 1150 mapping sites, 459 (40%) were categorized as "operator-determined CFAE sites," whereas 691 (60%) were categorized as "operator-determined non-CFAE sites." The sensitivity and negative predictive value increased as the fractionated interval (FI) value of the automatic algorithm increased, but the specificity and positive predictive value decreased. The automatic CFAE algorithm exhibited the highest combined sensitivity and specificity with an FI of <60 ms for the sites inside the LVZ and FI < 70 ms for the sites outside the LVZ, when compared with a single threshold for both the high- and low-voltage groups combined (i.e., no regard for voltage) (ROC: 0.89 vs 0.86).
Conclusions: The clinical relevance of the CFAE map would be improved if the calculated index values were accordingly scaled by the electrogram peak-to-peak amplitude. (J Cardiovasc Electrophysiol, Vol. 21, pp. 21–26, January 2010)     

Characteristics of Complex Fractionated Electrograms in Nonpulmonary Vein Ectopy Initiating Atrial Fibrillation/Atrial Tachycardia

Background: Nonpulmonary vein (PV) ectopy initiating atrial fibrillation (AF)/atrial tachycardia (AT) is not uncommon in patients with AF. The relationship of complex fractionated atrial electrograms (CFAEs) and non‐PV ectopy initiating AF/AT has not been assessed. We aimed to characterize the CFAEs in the non‐PV ectopy initiating AF/AT. Methods: Twenty‐three patients (age 53 ± 11 y/o, 19 males) who underwent a stepwise AF ablation with coexisting PV and non‐PV ectopy initiating AF or AT were included. CFAE mapping was applied before and after the PV isolation in both atria by using a real‐time NavX electroanatomic mapping system. A CFAE was defined as a fractionation interval (FI) of less than 120 ms over 8‐second duration. A continuous CFAE (mostly, an FI < 50 ms) was defined as electrogram fractionation or repetitive rapid activity lasting for more than 8 seconds. Results: All patients (100%) with non‐PV ectopy initiating AF or AT demonstrated corresponding continuous CFAEs at the firing foci. There was no significant difference in the FI among the PV ostial or non‐PV atrial ectopy or other atrial CFAEs (54.1 ± 5.6, 58.3 ± 11.3, 52.8 ± 5.8 ms, P = 0.12). Ablation targeting those continuous CFAEs terminated the AF and AT and eliminated the non‐PV ectopy in all patients (100%). During a follow‐up of 7 months, 22% of the patients had an AF recurrence with PV reconnections. There was no recurrence of any ablated non‐PV ectopy during the follow‐up. Conclusion: The sites of the origin of the non‐PV ectopies were at the same location as those of the atrial continuous CFAEs. Those non‐PV foci were able to initiate and sustain AF/AT. By limited ablation targeting all atrial continuous CFAEs, the AF could be effectively eliminated.     

Nonlinear Analysis of Fibrillatory Electrogram Similarity to Optimize the Detection of Complex Fractionated Electrograms During Persistent Atrial Fibrillation

Nonlinear Analysis of Atrial Fibrillation . Introduction: Currently, the identification of complex fractionated atrial electrograms (CFEs) in the substrate modification is mostly based on cycle length‐derived algorithms. The characteristics of the fibrillation electrogram morphology and their consistency over time are not clear. The aim of this study was to optimize the detection algorithm of crucial CFEs by using nonlinear measure electrogram similarity. Methods and Results: One hundred persistent atrial fibrillation patients that underwent catheter ablation were included. In patients who required CFE ablation (79%), the time‐domain fibrillation signals (6 seconds) were acquired for a linear analysis (mean fractionation interval and dominant frequency [DF]) and nonlinear‐based waveform similarity analysis of the local electrograms, termed the similarity index (SI). Continuous CFEs were targeted with an endpoint of termination. Predictors of the various signal characteristics on the termination and clinical outcome were investigated. Procedural termination was observed in 39% and long‐term sinus rhythm maintenance in 67% of the patients. The targeted CFEs didn't differ based on the linear analysis modalities between the patients who responded and did not respond to CFE ablation. In contrast, the average SI of the targeted CFEs was higher in termination patients, and they had a better outcome. Multivariate regression analysis showed that a higher SI independently predicted sites of termination (≥0.57; OR = 4.9; 95% CI = 1.33–18.0; P = 0.017). Conclusions: In persistent AF patients, a cycle length‐based linear analysis could not differentiate culprit CFEs from bystanders. This study suggested that sites with a high level of fibrillation electrogram similarity at the CFE sites were important for AF maintenance. (J Cardiovasc Electrophysiol, Vol. 24, pp. 280‐289, March 2013)     

Short-Long Sequences Prior to Ventricular Tachycardia Onset: Analysis of VAST Trial Electrograms

Background: The recently published Ventricular Arrhythmia Suppression Trial (VAST) found no effect of rate-smoothing (RS) algorithm on frequency of ventricular tachycardia (VT) episodes in patients with implantable defibrillator. A similar recent trial reported an opposite result. In order to determine possible reasons for the discrepancy between the trials and achieve better understanding of events preceding VT onset, we analyzed stored device electrograms preceding 162 VT episodes from 50 VAST trial patients with dual-chamber devices.
Results: In this analysis, short-long sequences were more common prior to polymorphic VTs than before monomorphic VTs. The proportion of VT episodes preceded by short-long sequences was lower during randomization to RS ON (5.3% vs 31.3%, P < 0.001). For patients with multiple episodes of monomorphic VT, there was higher interpatient than intrapatient variability in preceding RR intervals. When adjusting for this similarity of RR interval sequences preceding VT onset in individual patients, the difference in proportion short-long sequences between RS ON and RS OFF programming was no longer significant.
Conclusion: Episodes of VT were preceded by stereotypic, patient-specific sequences of RR intervals in several VAST trial patients. RS reduced the percentage of VTs preceded by short-long sequences, but did not change overall VT incidence.     

Optimized Measurement of Activation Rate at Left Atrial Sites with Complex Fractionated Electrograms During Atrial Fibrillation

Local Activation Rate in Atrial Fibrillation. Background: Complex fractionated atrial electrograms (CFAE) have become targets for catheter ablation of atrial fibrillation (AF). Frequency components of AF signals have also become important markers for identifying potential mechanisms of AF, yet inaccuracies exist, particularly in standard dominant frequency (SDF) calculations especially at CFAE sites. We developed new methodology to improve accuracy of AF rate determinations at such recording sites. Objective: To develop optimal methods for estimating activation rates in paroxysmal and persistent AF. Methods: Electrograms were obtained from one right atrial, coronary sinus, and 6 left atrial (LA) endocardial regions manifesting CFAEs in paroxysmal (N = 7) and persistent (N = 7) AF patients. SDF was measured from 8.4 s intervals and compared to (1) optimized DF (ODF) calculated by optimizing the filter coefficients which maximized dominant frequency power, (2) autocorrelation (AC), with the rate estimated as the inverse of the signal phase shift generating the largest autocorrelation coefficient, and (3) ensemble average (EA), with the rate estimated by summing successive signal segments and selecting segment length yielding maximum power. Rate measurements were compared between groups, at baseline and with additive interference, having similar frequency content to the electrograms, to test the robustness of the different methods. Results: From pooled data (N = 168 recording sites), a significantly higher LA dominant frequency was found in persistent versus paroxysmal patients using each method (P < 0.001), with a mean value for all methods of 6.23 ± 0.08 Hz versus 5.32 ± 0.10 Hz, respectively. At the highest additive interference level, the rate measurement error was significantly greater in SDF as compared with EA (P = 0.010) and ODF (P = 0.035), and at all interference levels SDF had the largest error of any method. Conclusions: SDF appears less robust to additive interference, compared to the ODF and EA methods of estimating the activation rate at CFAE sites in this small group of patients. Use of optimized filter coefficients for DF measurement, or use of correlative methods such as EA, that reinforce the signal rather than filtering the noise, may improve calculation of activation rates. (J Cardiovasc Electrophysiol, Vol. 21, pp. 133‐143, February 2010)