Tsair Kao

Consistency of complex fractionated atrial electrograms during atrial fibrillation

BACKGROUND Temporal variation in complex fractionated atrial electrograms (CFAEs) exists during atrial fibrillation (AF). OBJECTIVE This study sought to quantify the variation in CFAEs using a fractionation interval (FI) algorithm and to define the shortest optimal recording duration required to consistently characterize the magnitude of the fractionation. METHODS Twenty-seven patients undergoing AF mapping in the left atrium were studied. The FI and frequency analysis were performed at each mapped site for recording durations of 1 to 8 seconds. The magnitude of the fractionation was quantified by the FI algorithm, which calculated the mean interval between multiple, discrete deflections during AF. The results from each duration were statistically compared with the maximal-duration recording, as a standard. The FI values were compared with the dominant frequency values obtained from the associated frequency spectra. RESULTS The FIs obtained from recording durations between 5 and 8 seconds had a smaller variation in the FI (P < .05) and, for those sites with a FI < 50 ms, the fractionation was typically continuous. The fast-Fourier Transform spectra obtained from the CFAE sites with recording durations of >5 seconds harbored higher dominant frequency values than those with shorter recording durations (8.1 +/- 2.5 Hz vs. 6.8 +/- 0.98 Hz, P < .05). The CFAE sites with continuous fractionation were located within the pulmonary veins and their ostia in 77% of patients with paroxysmal AF, and in only 29% of patients with nonparoxysmal AF (P < .05). CONCLUSION The assessment of fractionated electrograms requires a recording duration of > or =5 seconds at each site to obtain a consistent fractionation. Sites with the shortest FIs consistently identified sites with the fastest electrogram activity throughout the entire left atrium and pulmonary veins.

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.

Electrophysiological Characteristics and Catheter Ablation in Patients With Paroxysmal Right Atrial Fibrillation

Background—Catheter ablation of the right atrial (RA) substrate has had variable efficacy in curing paroxysmal atrial fibrillation (PAF), suggesting that RA substrate ablation can play an important role in the treatment of atrial fibrillation (AF) in some patients. The aim of this study was to investigate the electrophysiological characteristics and ablation strategy and its results in a specific group of patients with paroxysmal RA-AF. Methods and Results—The study population consisted of 13 patients (8 men; age, 64±15 years) with drug-refractory (2±1 drugs), frequent episodes of PAF. Provocation maneuvers did not reveal any ectopic beat–initiating AF. However, rapid atrial pacing easily induced AF. Activation mapping during sinus rhythm, atrial pacing, and AF was visualized by using a noncontact mapping system. Noncontact mapping revealed RA reentry (6 patients with single-loop circuits and 7 with double-loop circuits) with conduction through channels between lines of block, crista terminalis gaps, and the cavotricuspid isthmus, which could be identified during sinus rhythm and atrial pacing, resulting in fibrillatory conduction in other parts of the RA. The consistency of wavefront activation was confirmed by frequency analysis from equally distributed mapping sites in the RA. Short lines of ablation lesions were aimed at the conduction channels between the lines of block, crista terminalis gaps, and the cavotricuspid isthmus, resulting in bidirectional block. AF was eliminated in 11 (85%) of 13 patients, and those 11 patients with acute success were free of AF without any antiarrhythmic drugs during the long-term follow-up period (16±6 months). Conclusions—RA ablation still can cure selected patients with PAF. Linear ablation of the RA substrate guided by the electrophysiological characteristics of RA-AF is an effective approach for treating this specific group of patients with AF.

Spatiotemporal Organization of the Left Atrial Substrate After Circumferential Pulmonary Vein Isolation of Atrial Fibrillation

Background—There is a paucity of data regarding the mechanism of maintaining atrial fibrillation (AF) after pulmonary vein isolation (PVI) in patients with AF. The aim of this study was to examine the impact of circumferential PVI on the left atrial (LA) substrate characteristics. Methods and Results—Seventy-two AF patients (age, 53±11 years) underwent mapping and catheter ablation using an NavX system. The biatrial characteristics such as the complex fractionated atrial electrograms (CFEs; based on fractionated intervals) and frequency analysis (based on dominant frequencies) were mapped before and after PVI. PVI with electric isolation was performed in all patients. In the 45 patients who did not respond to PVI, the continuous CFEs (>8 seconds, 18±18% and 12±17% of the LA sites, before and after PVI, respectively, P=0.02), degree of LA fractionation (mean fractionated interval: 75.6±14.3 msec versus 87.3±16.7 msec, P=0.001), and mean LA dominant frequencies (6.92±0.88 Hz versus 6.58±0.91 Hz, P=0.001) decreased after PVI. Complete PVI altered the distribution of the CFEs toward the LA anteroseptum, mitral annulus, and LA appendage regions. A persistent presence of continuous CFEs in the vicinity of the dominant frequencies sites (observed in 53% patients) correlated with a higher procedural AF termination rate for the CFE ablation (63% versus 23%, P<0.05). Conclusions—Complete PVI eliminated some CFEs in the LA and altered the distribution of the CFEs. The persistent presence of CFEs before and after PVI in the vicinity of the high frequency sites is important for AF maintenance after PVI.

Predicting factors for atrial fibrillation acute termination during catheter ablation procedures: Implications for catheter ablation strategy and long-term outcome

BACKGROUND Termination of atrial fibrillation (AF) can be achieved by catheter ablation. It has been used as one of the procedural endpoints for AF ablation. OBJECTIVE The purpose of this study was to investigate the factors that predict AF termination and the association with long-term outcomes. METHODS Eighty-five consecutive AF patients (33 paroxysmal, 52 nonparoxysmal) underwent three-dimensional mapping and catheter ablation. A stepwise ablation approach included circumferential pulmonary vein (PV) isolation and left atrial (LA) linear ablation, followed by LA and right atrial (RA) electrogram-based (complex fractionated atrial electrogram) ablation. Clinical and electrophysiologic characteristics were assessed to evaluate the predictors of acute AF termination. RESULTS In univariate analysis, a diagnosis of paroxysmal AF, shorter AF history, absence of history of heart failure, smaller LA diameter, longer postablation coronary sinus cycle length, lower LA and RA mean dominant frequencies, lower RA max dominant frequency, and higher LA voltage were related to acute termination of AF during ablation. Multivariate analysis showed that smaller LA diameter and lower preablation mean RA dominant frequency were independent predictors of AF termination. Multivariate analysis also showed that larger LA diameter and the presence of RA non-PV ectopy during the index procedure could predict late recurrence during long-term (13 +/- 8 months) follow-up. CONCLUSION LA size and RA non-PV drivers are important for acute termination of AF and for long-term success. Careful selection of patients, extensive RA mapping, and LA ablation may enhance long-term ablation efficacy.

Spectral analysis of chronic atrial fibrillation and its relation to minimal defibrillation energy.

TAI, C‐T., et al.: Spectral Analysis of Chronic Atrial Fibrillation and Its Relation to Minimal Defibrillation Energy. The average rate of fibrillatory activity may reflect the global activation pattern of AF. Electrical cardioversion is the most effective method of converting chronic AF to sinus rhythm. The aim of this study was to investigate the relation between the minimal defibrillation energy requirement and the dominant frequency of chronic AF. Twenty‐nine patients with chronic AF (mean duration 57.9 ± 7.7 months) underwent external electrical cardioversion. Before cardioversion, the frequency content of the 60‐second AF in ECG lead V1 was quantified using digital signal processing. After band‐pass filtering, QRST complexes were cancelled using a recursive least squares algorithm. The resulting fibrillatory baseline signal was subjected to fast Fourier transform and was displayed as a power spectrum. The dominant AF frequency was found to range from 4.9 to 8.7 Hz (mean 6.7 ± 0.9 Hz). Twenty‐six patients had successful conversion of AF to sinus rhythm without immediate recurrence. There was a positive correlation between the minimal defibrillation energy and the dominant frequency of chronic AF (ρ= 0.414, P = 0.035). Thus, power spectral analysis of AF using the surface ECG is feasible and may be useful in predicting the minimal shock energy required for successful cardioversion of chronic AF.

Spectral analysis during sinus rhythm predicts an abnormal atrial substrate in patients with paroxysmal atrial fibrillation

BACKGROUND Regions of rapid and multiple deflections can be identified with high dominant frequency (DF) during sinus rhythm (SR). These areas may play a role in the perpetuation of atrial fibrillation (AF) and indicate an atrial substrate abnormality. OBJECTIVE The purpose of this study was to investigate the atrial substrate properties of the high-frequency sites in patients with paroxysmal AF. METHODS Forty patients (52 +/- 12 years of age) with paroxysmal AF were studied using a three-dimensional mapping system. Spectral analysis was performed on the bipolar electrograms in the left atrium (LA) during SR. Overall, 7708 electrograms were analyzed, and the DFs higher than 70 Hz were labeled as abnormal. RESULTS The regional distribution of the high-DF sites in the LA could be divided into two types. Type 1 includes high-DF sites existing only in the pulmonary veins (PVs; n = 19, 6.6 +/- 3.4 sites/patient). Type 2 includes high-DF sites in the LA or LA plus the PVs (n = 21, 11 +/- 5.6 sites/patient). In type 1, PV isolation (PVI) could eliminate the AF with negative AF inducibility testing after the PVI in 89% of patients. In type 2, additional LA substrate modification was needed in 81% of patients because sustained AF was induced after the PVI (P<.001, compared with type 1). Multivariate analysis showed that the lower mean voltage of the LA and high-frequency sites distribution both independently predicted a positive AF inducibility after the PVI (P<.05). CONCLUSIONS Spectral analysis during SR can detect an abnormal atrial substrate. A regional distribution of the high-DF sites predicts the efficacy of the PVI.

Frequency analysis of the fibrillatory activity from surface ECG lead V1 and intracardiac recordings: implications for mapping of AF

AIMS Fibrillatory waves observed in the surface electrograms may be a direct reflection of the electrophysiologic mechanism of the atrial fibrillation (AF). This study compared the fibrillatory waves in the surface ECG and the individual intracardiac mapping sites in different types of paroxysmal AF. METHODS AND RESULTS Thirty patients with paroxysmal AF originating from the pulmonary veins (PVs) or superior vena cava (SVC) were enrolled. Frequency analysis was performed on the intracardiac electrograms recorded from various mapping sites in both atria sequentially with simultaneous surface electrogram recordings. The SVC-AF patients had a trend toward a higher DF in ECG lead V1 when compared with the PV-AF patients (7.35 +/- 2.09 vs. 5.89 +/- 0.79 Hz, P = 0.018). The mean dominant frequency (DF) of the LA mapping sites in the PV-AF patients was higher than that in the SVC-AF patients (7.06 +/- 0.66 vs. 6.13 +/- 0.96 Hz, P = 0.009), whereas the mean DF of the RA mapping sites was similar between the two groups (5.84 +/- 0.80 vs. 6.26 +/- 1.11 Hz, P = NS). The intra-class correlation coefficient (ICC) between the mean DF of the RA sites and V1 was higher (r = 0.21, P = 0.02) when compared with the mean DF of the LA sites (r = -0.007, P > 0.05). Furthermore, the maximal ICC was observed in the anterolateral RA free wall (r = 0.84, P < 0.001) and not the other anatomic sites of the RA and LA. CONCLUSION The fibrillatory activity observed in ECG lead V1 correlated primarily with the activity of the anterolateral RA free wall and thus may be useful for detecting the AF source if it is close to that area.

Baroreflex sensitivity evaluation by Volterra Wiener model and the Laguerre expansion technique

This paper presents a Volterra-Wiener model and the Laguerre expansion technique to analyze the changes in heart rate interval, as modelpsilas output to the corresponding changes in systolic arterial blood pressure, as modelpsilas input. This new technique can not only find the baroreflex sensitivity (BRS) but also can assess the nonlinear and dynamic behavior of baroreflex from the identified model parameters. The performance of this new technique was compared with the measurements by sequence technique (SEQ) and alpha coefficient technique (Alpha) in 5 normal and 11 hypertension subjects. The BRS of hypertension subjects was 4.4 plusmn 2.0 ms/mmHg for SEQ, 4.6 plusmn 1.9 ms/mmHg for Alpha, and 2.9 plusmn 1.6 ms/mmHg for the new technique. For normal subjects, the BRS was 30.4plusmn12.4 ms/mmHg for SEQ, 25.8 plusmn 10.2 ms/mmHg for Alpha, and 17.5 plusmn 7.7 ms/mmHg for the new technique. The proposed new technique yielded a reasonable lower BRS estimation than existing noninvasive BRS techniques.

Nonlinear analysis of human atrial flutter and fibrillation using surface electrocardiogram

Atrial flutter and atrial fibrillation have different generating mechanisms in atrium. They are often cross-classified from the surface ECG. Nonlinear analysis has recently been applied to electrograms, and atrial arrhythmia is shown evidence that indicates the possibility of deterministic chaos. In this study, we applied methods from the theory of nonlinear dynamics to characterize electrograms of atrial flutter and fibrillation in humans. For typical flutter, nonlinear parameters were relatively smaller, and they presented higher values when in Af In atypical flutter, the magnitude of these nonlinear parameters was between those of typical flutter and Af Statistical analysis showed evidence that they exhibited a significant differentiation allowing the classification of these arrhythmias. By using the neural network classification, a desirable result was also obtained. Therefore, nonlinear analysis provided us an advantageous technique to discriminate among typical flutter, atypical flutter and Af electrograms from surface ECG.