Left Atrial Sites Research Articles

15. Measurement of esophageal temperature at two separate sites during pulmonary vein ablation

Pulmonary vein ablation (PVA) has been used to treat persistent supraventricular arrhythmias, in which a cardiologist first isolates and then thermally ablates the source of the arrhythmia1. Since the esophagus is in close proximity to the left atrium, heat induced injury to the esophagus may occur2. Although the incidence is low, the mortality rate is high. Luminal esophageal temperature (ET) monitoring is one of the most effective measures to minimize the risk of injury3. In this retrospective study, we elected to analyze temperature changes during PVA at two different temperature monitoring sites in the esophagus. The anesthetic technique was standardized and utilized general anesthesia, endotracheal intubation and an arterial line. ET monitors were placed at two mid-atrial locations, ET1 and ET2 separated by 1–1.5 inches in the esophagus, as determined by cardiologist using fluoroscopy. Temperatures at both ET1 and ET2 locations were recorded simultaneously when radio-frequency ablation was performed at different left atrial sites. The peak ET was recorded at each location. In particular, the increase over baseline ET and the difference between ET1 and ET2, were noted. Twenty five patients were studied. Ablation sites in the left atrium included the anterior, posterior, inferior regions and the pulmonary veins. The most significant increases in temperature were seen during ablation of the posterior left atrium ranging from 0.1 to 4.0 degrees. However, in 20 out of 25 patients, measurements of ET1 ≠ ET2. The absolute value of difference of temperature between ET1 and ET2 ranged from 0.4 to 3.8, with a mean of 1.3 and a standard deviation of 1.1. These findings suggest that measurement of temperature at two separate esophageal locations is more sensitive that one location in detecting temperature increases during PVA. The ablating electrode during PVA moves from different areas within the left atrium, and therefore, a wide area of temperature measurement is needed for more accurate monitoring. Furthermore, the most significant increases in temperature occurred when ablation performed in the posterior left atrium, adjacent to the esophagus. The implications of these observations suggest that one location of temperature measurement may not be accurate enough in detecting a “true” esophageal temperature. Further studies are needed to verify these findings in a prospective study and to ascertain whether this has any patient safety ramifications for preventing esophageal injury.

Sinus rhythm restoration and arrhythmia noninducibility are major predictors of arrhythmia-free outcome after ablation for long-standing persistent atrial fibrillation: a prospective study.

The impact of restoring sinus rhythm (SR) by initial ablation in patients with long-standing persistent atrial fibrillation (LSPAF) is not fully established. The purpose of this study was to investigate the prognostic value of SR restoration at the initial procedure and arrhythmia noninducibility at the final repeat procedure for long-term outcome. A total of 203 patients (22% female; age 59 ± 9 years) underwent stepwise catheter ablation for LSPAF. The procedural end-point of SR restoration was achieved in 50% of patients. During follow-up (median 48 months) and after 1.7 procedures per patient, 72% of patients were free from arrhythmia off antiarrhythmic drugs. Failure to restore SR was independently predicted by left atrial (LA) long-axis diameter ≥68 mm (relative risk [RR] 1.55, P = .03], proportion of high-voltage LA sites <20% (RR 1.62, P = .02), and left atrial appendage (LAA) atrial fibrillation cycle length (AFCL) <155 ms (RR 1.5, P = .05). Arrhythmia recurrence after the initial procedure was predicted by SR nonrestoration (RR 2.99, P <.000001) and LAA AFCL ≥155 ms (RR 1.90, P = .0002). Arrhythmia recurrence after the final procedure was predicted by SR nonrestoration at the initial procedure (RR 2.83, P = .0007), persistent AF duration ≥24 months (RR 2.74, P = .002), LAA outflow velocity <40 cm/s (RR 2.21, P = .006), and LAA AFCL ≥155 ms (RR 1.92, P = .02). In 115 patients with repeat procedure(s), failure to achieve arrhythmia noninducibility at the final procedure (19% of patients) was associated with arrhythmia recurrence (RR 8.9, P < .000001). SR restoration at the initial procedure and arrhythmia noninducibility at the last repeat procedure were major predictors of arrhythmia-free outcome after ablation for LSPAF.

Electrogram morphology recurrence patterns during atrial fibrillation.

Traditional mapping of atrial fibrillation (AF) is limited by changing electrogram morphologies and variable cycle lengths. We tested the hypothesis that morphology recurrence plot analysis would identify sites of stable and repeatable electrogram morphology patterns. AF electrograms recorded from left atrial (LA) and right atrial (RA) sites in 19 patients (10 men; mean age 59 ± 10 years) before AF ablation were analyzed. Morphology recurrence plots for each electrogram recording were created by cross-correlation of each automatically detected activation with every other activation in the recording. A recurrence percentage, the percentage of the most common morphology, and the mean cycle length of activations with the most recurrent morphology were computed. The morphology recurrence plots commonly showed checkerboard patterns of alternating high and low cross-correlation values, indicating periodic recurrences in morphologies. The mean recurrence percentage for all sites and all patients was 38 ± 25%. The highest recurrence percentage per patient averaged 83 ± 17%. The highest recurrence percentage was located in the RA in 5 patients and in the LA in 14 patients. Patients with sites of shortest mean cycle length of activations with the most recurrent morphology in the LA and RA had ablation failure rates of 25% and 100%, respectively (hazard ratio 4.95; P = .05). A new technique to characterize electrogram morphology recurrence demonstrated that there is a distribution of sites with high and low repeatability of electrogram morphologies. Sites with rapid activation of highly repetitive morphology patterns may be critical to sustaining AF. Further testing of this approach to map and ablate AF sources is warranted.

Combined Dominant Frequency and Complex Fractionated Atrial Electrogram Ablation After Circumferential Pulmonary Vein Isolation of Atrial Fibrillation

Atrial substrates with high-dominant frequency (DF) and complex fractionated atrial electrogram (CFAE) sites have sources maintaining atrial fibrillation (AF) and are potential AF ablation targets. This study aimed to evaluate an approach of circumferential pulmonary vein isolation (PVI) followed by a DF and CFAE site ablation. Fifty consecutive AF patients (23 paroxysmal, 9 persistent, and 18 longstanding persistent) underwent ablation, using NavX. When AF continued after circumferential PVI, high-DF sites of ≥ 8 Hz and then continuous left atrial (LA) CFAE sites defined by fractionated intervals (FI) of ≤50 milliseconds including the coronary sinus and right atrium were targeted. A total of 45.1% of high-DF and 48.1% of continuous CFAE sites significantly decreased after PVI (P < 0.001). The mean LA DF and FI significantly decreased and prolonged, respectively, after PVI (P < 0.001). Only 14.1% of all high-DF sites after PVI overlapped with continuous CFAE sites. AF terminated at high-DF sites in 11 (22%) patients and continuous CFAE sites in 1 (2%). AF could be induced in only 8% of patients after the procedure. The mean LA DF value before ablation was significantly lower in those without recurrence (P = 0.003). AF freedom on antiarrhythmic drugs was 96% and 59%, respectively, in the paroxysmal and nonparoxysmal AF patients (89% persistent and 44% longstanding persistent) after 1 procedure over a 12-month follow-up. A combined high-DF and continuous CFAE site ablation in all chambers after circumferential PVI may be effective in the paroxysmal and persistent AF patients.

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Abstract 19176: Mapping of Electrogram Morphology Recurrence Patterns during Atrial Fibrillation

Introduction: Electrograms during atrial fibrillation (AF) are complex and seemingly chaotic. It is still unknown how to best analyze and utilize AF electrograms. Hypothesis: We hypothesize that the frequency and patterns of AF electrogram morphology recurrence determined by a modified recurrence plot (RP) analysis will show differences based on region in this pilot study. Methods: AF electrograms (&gt;16 s) recorded from documented left atrial (LA) and right atrial (RA) sites in 13 patients (10 male, 59±10 years old) prior to AF ablation were analyzed. A 100 ms window for each automatically detected activation was extracted and cross-correlated with every other activation in a 30-sec recording. The result was a set of NxN cross-correlation (CC) values, where N is the number of detected activations. These values were displayed in a two-dimensional RP. A recurrence index (RI), the percentage of the most common morphology, was also computed. A high RI likely indicates consistent activation directions at the site of bipolar electrogram recording. Results: Figure A is a RP example. The checker board pattern of alternating high and low CC values indicates periodic recurrences in morphologies (RI=70% for this example). The mean RI for all sites and all patients was 38±25%. The highest RI was found in the left superior LA in all 4 paroxysmal AF patients (85±18%, see Figure B). For 9 persistent AF patients, the highest RI was found in the RA (91±10%) in 5 patients and in the left superior LA (95±6%) in 4 patients. The persistent AF patients had higher maximum RIs in the RA than the paroxysmal AF patients (87±16 vs. 51±15%, p=0.01). Conclusion: Electrogram morphology with highest recurrence rates were most frequently found in the left superior LA, a common location for AF triggers. Further work is needed to determine whether high electrogram repeatability reflects AF driver activity and whether RPs could be used as part of an ablation strategy.

Spatiotemporal Behavior of High Dominant Frequency During Paroxysmal and Persistent Atrial Fibrillation in the Human Left Atrium

Sites of high dominant frequency (DF(peak)) are thought to indicate the location of drivers of atrial fibrillation (AF), but characterization of their spatiotemporal distribution and stability, critical to their relevance as targets for catheter ablation, requires simultaneous global mapping of the left atrium. Noncontact electrograms recorded simultaneously from 256 left atrial sites during spontaneous AF were analyzed. After subtraction of the ventricular component, fast Fourier transform identified the DF at each site. Focal areas of DF(peak) were defined as those having a DF >20% above all neighboring sites. Twenty-four patients with spontaneous AF (11 paroxysmal and 13 persistent) were studied. In paroxysmal AF, sites of DF(peak) (mean DF, 11.6±2.9 Hz) were observed in 100% of patients (present during 65% of the mapping period). In contrast, DF(peak) was detected in only 31% of patients with persistent AF (P<0.001) and for only 5% of the mapping period (P<0.001). In both groups, locations of DF(peak) varied widely in both consecutive and separated segments of AF (κ coefficient range, -0.07-0.22). Activation sequences around sites of DF(peak) did not demonstrate centrifugal activation that would be expected from focal drivers. Focal areas of high DF are more frequent in paroxysmal than persistent AF, are spatiotemporally unstable, are not the source of centrifugal activation, and are not, therefore, indicative of fixed drivers of AF. In the absence of spatiotemporal stability, the success of ablation at sites of DF(peak) cannot be explained by elimination of fixed drivers.

Effects of inter-electrode spacing on complex fractionated atrial electrograms and dominant frequency detection

The influence of inter-electrode spacing (IES) on complex fractionated atrial electrograms (CFAEs) and dominant frequency (DF) detection was assessed. Bipolar electrograms were recorded via an octapolar catheter (2-mm electrode spacing) from left atrial CFAEs sites in 17 atrial fibrillation patients. The CFE-mean was calculated at IES of the electrode pairs 1-2, 1-3, 1-4, 1-5, and 1-6. The DF, regularity index (RI), and organization index (OI) were simultaneously analyzed. The CFE-mean decreased as the IES increased (from 71 ± 15 ms of IES 1-2 to 61 ± 8 ms of IES 1-3, 57 ± 6 ms of IES 1-4, 57 ± 8 ms of IES 1-5, and 58 ± 9 ms of IES 1-6, respectively; IES 1-2 vs. 1-3 to 1-6, P < 0.01). The DF was unchanged (6.6 ± 1.6 Hz for all; P > 0.99). However, the RI decreased as the IES increased (from 0.30 ± 0.11 to 0.26 ± 0.11, 0.23 ± 0.11, 0.22 ± 0.12, and 0.20 ± 0.12; IES 1-2 vs. 1-3 to 1-6, P < 0.01), as did the OI (from 0.39 ± 0.14 to 0.34 ± 0.12, 0.32 ± 0.13, 0.29 ± 0.13, and 0.28 ± 0.13; IES 1-2 vs. 1-3 to 1-6, P < 0.01). A wider IES might detect dyssynchronous activations, leading to a reduced CFE-mean and RI and OI. Therefore, bipolar signals recorded with a narrower IES might be preferable to more precisely localizing CFAEs and DF sites.

Differences in Repeating Patterns of Complex Fractionated Left Atrial Electrograms in Longstanding Persistent Atrial Fibrillation as Compared With Paroxysmal Atrial Fibrillation

Complex fractionated atrial electrograms (CFAE) are morphologically more uniform in persistent longstanding as compared with paroxysmal atrial fibrillation (AF). It was hypothesized that this may result from a greater degree of repetitiveness in CFAE patterns at disparate left atrial (LA) sites in longstanding AF. CFAEs were obtained from recording sites outside the 4 pulmonary vein (PV) ostia and at a posterior and an anterior LA site during paroxysmal and longstanding persistent AF (10 patients each, 120 sequences total). To quantify repetitiveness in CFAE, the dominant frequency was measured from ensemble spectra using 8.4-second sequences, and repetitiveness was calculated by 2 novel techniques: linear prediction and Fourier reconstruction methods. Lower prediction and reconstruction errors were considered indicative of increasing repetitiveness and decreasing randomness. In patients with paroxysmal AF, CFAE pattern repetitiveness was significantly lower (randomness higher) at antral sites outside PV ostia as compared with LA free wall sites (P < 0.001). In longstanding AF, repetitiveness increased outside the PV ostia, especially outside the left superior PV ostium, and diminished at the LA free wall sites. The result was that in persistent AF, there were no significant site-specific differences in CFAE repetitiveness at the selected LA locations used in this study. Average dominant frequency magnitude was 5.32 ± 0.29 Hz in paroxysmal AF and higher in longstanding AF, at 6.27 ± 0.13 Hz (P < 0.001), with the frequency of local activation approaching a common upper bound for all sites. In paroxysmal AF, CFAE repetitiveness is low and randomness high outside the PVs, particularly the left superior PV. As evolution to persistent longstanding AF occurs, CFAE repetitiveness becomes more uniformly distributed at disparate sites, possibly signifying an increasing number of drivers from remote PVs.

Neural Mechanism of Atrial Fibrillation: Insight from Global High Density Frequency Mapping

It has been demonstrated that intrinsic cardiac autonomic activation of ganglionated plexi (GPs) exhibits a frequency gradient from the center to the periphery with limited mapping. We aimed to use a global mapping tool (Ensite Array) to identify the frequency distribution and clarify the interaction between the extrinsic/intrinsic autonomic systems. A mid sternal thoractomy was performed in anesthetized dogs. High frequency stimulation (20 Hz, 0.1 ms duration) was applied to locate the GPs and achieve vagosympathetic stimulation (VNS). There were 4 major GPs, which were located near the 4 pulmonary vein (PV) ostia, and a third fat pad (SVC-Ao) GP that was located near the superior vena cava (SVC)-right atrial (RA) junction. Without VNS (n = 12), the left atrial (LA) mean (8.20 ± 0.11 vs 7.95 ± 0.30 Hz, P = 0.04) and max (9.86 ± 0.28 vs 9.43 ± 0.29 Hz, P = 0.03) DFs were higher during the PV ostial GP stimulation than the SVC-Ao GP stimulation. The LA max DFs were located not only at the primary GPs but also the nearby secondary PV ostial GPs. The RA mean DF (8.36 ± 0.05 vs 7.99 ± 0.19 Hz, P = 0.04) was higher during SVC-Ao GP stimulation than PV ostial GP stimulation. The max DF was located inside the SVC during SVC-Ao GP stimulation and at the RA septum during PV ostial GP stimulation. With VNS (n = 12), the LA mean and max DFs between the PV ostial and SVC-Ao GP stimulation were similar. The DF distribution shifted to non-GP LA sites during both the PV ostial and SVC-Ao GP stimulation. The findings indicate that the AF was caused by an interaction between the PV ostial GPs during intrinsic autonomic stimulation, whereas the non-GP LA sites were responsible for the AF induced by an extrinsic neural input.

Electrophysiological Charactaristics of the Left Atrial Endocardial Surface Close to the Ganglionated Plexi during Atrial Fibrillation

Background: Complex Fractionated Atrial Electrogram (CFAE) can contribute to the substrate of atrial fibrillation (AF), and some investigators have proposed that CFAE reflects cardiac autonomic nerve system activity occurring in areas of ganglionated plexi (GP). In this study, we examined the electrophysiological charactaristics of the left atrial sites close to GP. Methods: We analyzed 17 patients refered to our institution for AF ablation. GP was sought by demonstrating parasympathetic response to high-frequency stimulation. If AF sustained, we measured the average AF cycle length at GP sites by using automated calculation systems. Furthermore in 8 cases, we conducted CFAE analysis at the whole area of the left atrium. Results: We could measure the average AF cycle length at 76 GP sites. The values were 30–176 ms (81.5±29.7 ms). At 8 of 76 (10.5%) GP sites, AF cycle length was longer than 120 ms. In 8 cases with entire left atrial CFAE analysis, the shortest AF cycle length in the left atrium was 30–54 ms (43.4±11.4 ms). We could not induce GP responses at the shortest AF cycle length sites except 2 cases. Conclusion: We could induce GP responses at the long AF cycle length sites (over 120 ms). In 6 of 8 cases with CFAE analysis, we could not find GP responses at the shortest AF cycle length sites in the left atrium. In this study, we suggest that CFAE does not always reflect the GP activity.

Relationship between P‐Wave Duration and Atrial Electromechanical Delay Assessed by Tissue Doppler Echocardiography

The aim of the study was to assess the relationship between P-wave duration on the surface electrocardiogram (ECG) and echocardiographic parameters of atrial electromechanical delay (EMD), as well as contraction synchrony during different atrial pacing modalities. In 57 patients with sinus node disease and prolonged sinus P-wave duration treated with multisite atrial pacing (MSAp), the EMD was measured by tissue Doppler in several left and right atrial sites during sinus rhythm, MSAp, and single-site pacing at right atrial appendage (RAAp), Bachmann's bundle (BBp) region, and coronary sinus (CSp) ostium. Regional atrial synchrony was calculated on the basis of EMD. P-wave duration was 141 ± 16, 120 ± 17, 138 ± 17, 144 ± 16, and 160 ± 19 ms during sinus rhythm, MSAp, BBp, CSp, and RAAp, respectively (P < 0.001 RAAp and MSAp vs other). P-wave duration correlated with all atrial EMDs as well as interatrial and intraleft atrial parameters of dyssynchrony. In multivariate analysis, the EMD in lateral left atrial wall was the strongest predictor of P-wave duration (β 0.41; P < 0.001). The relationship between P-wave duration and the atrial EMDs was most prominent during RAAp (all left atrial walls r > 0.51; P < 0.01) and BBp (all atrial walls r > 0.42; P < 0.05), while during sinus rhythm and CSp, only weak correlation between echo and ECG was found. Neither of the tissue Doppler parameters correlated with P-wave duration during MSAp. Interatrial dyssynchrony correlated with P-wave duration during sinus rhythm and RAAp and intraleft atrial dyssynchrony only during sinus rhythm. P-wave duration of the surface ECG is highly correlated with the atrial EMD, the relationship is specific for each pacing modality.

Electrophysiologic Studies and Radiofrequency Catheter Ablation of Ectopic Atrial Tachycardia in Children

Ectopic atrial tachycardia (EAT) often resists medical therapy, making radiofrequency catheter ablation (RFCA) the preferred treatment. This study reviewed the records of 35 patients who underwent electrophysiologic studies (EPS) and 39 RFCA procedures for EAT during a 10-year period. Of the 35 patients, 10 (28%) presented with decreased ventricular function and tachycardia-induced cardiomyopathy (TIC). The EAT originated on the right atrial side in 19 patients (54%) and on the left atrial side in the remaining 16 patients (46%). The right atrial sites included the right atrial appendage (RAA) (n = 9, 25%), the tricuspid annulus (n = 7, 20%), and the crista terminalis (n = 3). The left atrial sites included the left atrial appendage (LAA) (n = 6, 17%), the pulmonary veins (n = 5, 14%), the mitral annulus (n = 3), and the posterior wall of the left atrium (n = 2). The mechanism of all EAT probably is automaticity. All EATs could be abolished using RFCA. Follow-up data were available for all patients 2 to 8 years after RFCA. All 35 patients remained recurrence free, and ventricular function improved for all 10 patients with TIC. The origin of EAT in children differed from its origin in adults. The authors conclude that RFCA is a safe and effective treatment option for children with refractory EAT and should be considered early in the course of their illness.

Characterization of Atrial Activation (A-A) Intervals During Atrial Fibrillation Due to a Single Driver: Do They Reflect Atrial Effective Refractory Periods?

The mean, median, and minimum local atrial activation (A-A) intervals have been used to determine the local atrial effective refractory period (AERP) during atrial fibrillation (AF), the underlying assumption being that AF is due to multiple reentrant wavelets. We tested the hypothesis that when AF is due to a single, rapid, stable reentrant circuit (driver), the minimum and mean local A-A intervals will be similar at sites in the reentrant circuit, but will vary widely at sites with fibrillatory conduction, making these latter intervals unreliable indicators of AERP. During sustained AF due to a left atrial (LA) driver in 6 sterile pericarditis dogs, electrograms were recorded from 186 bipolar electrodes from both atria. A-A intervals were measured from each recording site during 1.2 seconds of AF. Minimum A-A intervals as well as temporal (within site) and spatial (between sites) variability were determined from all sites. A-A intervals from each site during AF demonstrated that (1) 90-100% of right atrial (RA) sites and 18-39% of LA sites showed considerable (SD > 6 ms) temporal variability; (2) RA and LA sites with fibrillatory conduction (SD > 6 ms) showed considerable (a) spatial variability (RA: 9-36 ms; LA: 5-27 ms) and (b) variability of the minimum A-A intervals (RA: 14-35 ms; LA 11-28 ms). During AF due to a driver, areas with fibrillatory conduction manifested considerable variability in the mean and the minimum A-A intervals. Therefore, it is unlikely that any of the A-A intervals reflect AERP.

Short-term disruption in regional left ventricular electrical conduction patterns increases interstitial matrix metalloproteinase activity.

Increased matrix metalloproteinase (MMP) abundance occurs with adverse left ventricular (LV) remodeling in a number of cardiac disease states, including those induced by long-standing arrhythmias. However, whether regionally contained aberrant electrical activation of the LV, with consequent dyskinesia, alters interstitial MMP activation remained unknown. Electrical activation of the LV of pigs (n = 10, 30-35 kg) was achieved by pacing (150 beats/min) at left atrial and LV sites such that normal atrioventricular activation (60 min) was followed by regional early LV activation for 60 min within 1.5 cm of the paced site and restoration of normal atrioventricular pacing for 120 min. Regional shortening (piezoelectric crystals) and interstitial MMP activity (microdialysis with MMP fluorogenic substrate) at the LV pacing site and a remote LV site were monitored at 30-min intervals. During aberrant electrical stimulation, interstitial MMP activity at the paced site was increased (122 +/- 4%) compared with the remote region (100%, P < 0.05). Restoration of atrioventricular pacing after the 60-min period of aberrant electrical activation normalized segmental shortening (8.5 +/- 0.4%), but MMP activity remained elevated (121 +/- 6%, P < 0.05). This study demonstrates that despite the restoration of mechanical function, disturbances in electrical conduction, in and of itself, can cause acute increases in regional in vivo MMP activation and, therefore, contribute to myocardial remodeling.

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

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. To develop optimal methods for estimating activation rates in paroxysmal and persistent AF. 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. 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. 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.

Unusual Left Atrial Thrombus Site Undetected by Trans-Oesophageal Echocardiography

Introduction: In the era of left atrial (LA) appendage occlusion devices being used on the premise of non-inferiority to warfarin for stroke risk with the hope of alleviating long term anticoagulation, we present a patient presenting for catheter ablation (CA) for atrial fibrillation (AF) with an atypical LA thrombus location.

High-density biatrial pacing protects against atrial fibrillation by synchronizing left atrial tissue

The induction and sustainability of atrial fibrillation (AF) are most commonly due to pulmonary vein (PV) triggers and left atrial (LA) substrate. We hypothesized that simultaneous pacing of the PV ostia, LA, and right atrium (RA) reduces AF susceptibility by synchronizing atrial activity. Mongrel dogs were rapidly paced and maintained in AF for 3 months before cardioversion. Pacing leads were then placed at PV ostia, LA, and RA sites. For single-site pacing (SSP), a drive train (S1) and premature stimulus (S2) were delivered from the same electrode. Multisite pacing (MSP) consisted of S1 at all leads simultaneously and S2 at one site. Pacing trials were performed with decremental S2 coupling intervals (CI) to endpoints of AF induction or refractoriness. AF induction was reduced by 40.0% with MSP vs. SSP (7.2% vs. 12.0%, p < 0.001). LA S2 sites were more likely to induce AF than RA sites (11.5% vs. 2.6%, p < 0.0001), with benefit of MSP over SSP at LA sites (8.6% vs. 14.6%, p < 0.0001). The CI for AF induction was longer with SSP vs. MSP (119.4 +/- 13.3 vs. 104.4 +/- 11.2 ms, p < 0.05). Atrial activation times were shortened with MSP vs. SSP (87.4 +/- 4.9 vs. 97.1 +/- 10 ms, p < 0.005). Atrial synchronization was shown by the decreased activation times with MSP. AF induction was reduced by 40.0% with MSP, supporting the hypothesis of decreased AF susceptibility with synchronization. This is the first study demonstrating AF protection with high-density pacing at LA sites associated with triggers and substrate for the induction and maintenance of AF.

The Relationship Between Electrogram Cycle Length and Dominant Frequency in Patients with Persistent Atrial Fibrillation

Sites of complex fractionated atrial electrograms (CFAE) with a short mean cycle length (MCL) and sites with a high dominant frequency (DF) have been advocated as targets for ablation in patients with persistent atrial fibrillation (AF). However, there are little data on the relationship between theses 2 markers. This study assessed the relationship between the DF and electrogram MCL after pulmonary vein (PV) isolation in patients with persistent AF. A total of 44 patients with persistent AF were studied. Four-second bipolar electrograms were obtained with a multielectrode mapping catheter at regions throughout the left atrium after isolation of the pulmonary veins, with analysis of the MCL and DF at each site. The DF was defined as the largest frequency peak within a 2.5- to 16-Hz spectral profile generated with fast Fourier transformation of the electrogram. A total of 9,262 electrograms from the 44 patients were analyzed. The average MCL and DF post-PV isolation were 135 +/- 24 ms and 6.1 +/- 0.6 Hz, respectively. There was a statistically significant but weak correlation between the MCL and DF (r = 0.21, P < 0.001). Additionally, analysis of this relationship within each patient did not demonstrate a strong correlation (range of r values per patient =-0.18 to 0.47). There is a poor correlation between the electrogram MCL and DF in patients with persistent AF. Ablation strategies targeting DF and those targeting CFAE are therefore unlikely to direct ablation toward similar left atrial sites. Comparative studies are necessary to determine the effectiveness of each strategy in guiding catheter ablation of persistent AF.

Dominant Frequency of Atrial Fibrillation Correlates Poorly With Atrial Fibrillation Cycle Length

Localized sites of high frequency during atrial fibrillation (AF) are used as target sites to eliminate AF. Spectral analysis is used experimentally to determine these sites. The purpose of this study was to compare dominant frequencies (DF) with AF cycle length (AFCL) of unipolar and bipolar recordings. Left and right atrial endocardial electrograms were recorded during AF in 40 patients with lone AF, using two 20-polar catheters. Mean age was 53+/-9.9 years. Unipolar and bipolar electrograms were recorded simultaneously during 16 seconds at 2 right and 4 left atrial sites. AFCLs and DFs were determined. QRS subtraction was performed in unipolar signals. DFs were compared with mean, median, and mode of AFCLs; 4800 unipolar and 2400 bipolar electrograms were analyzed. Intraclass correlation was poor for all spectral analysis protocols. Best correlation was accomplished with DFs from unipolar electrograms compared with median AFCL (intraclass correlation coefficient, 0.67). A gradient in median AFCL of >25% was detected in 16 of 40 patients. In 13 of 16 patients (81%) with a frequency gradient of >25%, the site with highest frequency was located in the left atrium (posterior left atrium in 8 patients). The site with shortest median AFCL and highest DF corresponded in 25% if unipolar and in 31% if bipolar electrograms were analyzed. DFs from unipolar and bipolar electrograms recorded during AF correlated poorly with mean, median, and mode AFCL. If a frequency gradient >25% existed, the site with highest DF corresponded to the site of shortest median AFCL in only 25% of patients. Because spectral analysis is being used to identify ablation sites, these data may have important clinical implications.