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Gender differences in J point height exist. Previous studies suggest male sex hormones mediate effects on cardiovascular disease through myocardial repolarization. Our objective was to assess whether male and female sex hormones are associated with J point amplitude in healthy subjects. We conducted a cross-sectional study of 475 healthy, mixed racial population of men, and premenopausal women (age 33 ± 9 years, 56% male). Baseline J point amplitude (JPA) was obtained from continuous surface electrocardiograms. Plasma testosterone (T), dihydrotestosterone, estrone, 17-estradiol (E2), and sex hormone-binding globulin were measured. A free testosterone index (FTI) was calculated. Multivariate regression analysis stratified by gender and electrocardiographic lead location was used to determine independent predictors of maximum JPA. Regression analysis demonstrated FTI levels were positively associated with JPA in lateral leads (β = +0.01, p <0.05) in men but not in women. Total testosterone was positively associated with anterior electrocardiographic lead JPA in women (β = +0.5, p <0.02), but not in men. E2 was positively associated with inferior lead JPA (β = +1.2, p <0.03) in men but not in women. Total testosterone levels were positively associated with JPA in anterior leads (β = +0.054, p <0.05) in women. Male volunteers in the highest tertile of FTI demonstrated greater lateral JPA compared with the lowest tertile (p <0.05). Women in the highest tertile of FTI demonstrated greater anterior lead JPA compared with the lowest tertile (p <0.05). In conclusion, in a young, healthy population, the female sex hormone E2 and an FTI are independent determinants of JPA in men, whereas T is associated with JPA in women., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Introduction: Dominant frequency (DF) analysis of electrocardiograms (ECGs) from patients with paroxysmal (PAF) and persistent (PeAF) atrial fibrillation has identified higher DFs in PeAF. We therefore hypothesized that among patients initially presenting to the emergency department (ED) with new onset AF, surface ECG features could differentiate PeAF from PAF., Methods and Results: Initial 12-lead ECGs from patients presenting to the ED with a first episode of symptomatic AF were analyzed. Following QRS-T subtraction, fast Fourier transform (FFT) analysis of the AF fibrillatory waves was performed to measure DF and organization index (OI). Median DF of all leads and the DF in the lead with maximum OI were determined. Maximum f wave amplitude and vector magnitudes were measured. One hundred sixty-one patients (age 59 ± 16 years, 68% men) were included in this analysis, of whom 96 (58%) spontaneously converted to sinus rhythm within 7 days (PAF group). The remaining 65 patients underwent cardioversion or remained in AF (PeAF group). ECG features (DF, OI, f wave amplitude, and vector magnitude) did not differ among PAF and PeAF patients., Conclusions: ECG features (DF, OI, amplitude, vector magnitude) do not differ among patients with PAF versus PeAF when the ECGs are obtained at the initial onset of symptoms. Thus, prior data showing higher DF in PeAF likely reflect electrophysiologic remodeling rather than a marker for any specific type of AF or extent of underlying substrate., (© 2017 Wiley Periodicals, Inc.)

Background: Bipolar electrograms recorded during atrial fibrillation (AF) can have an appearance of chaotic/random behavior. The aim of this study was to use a novel electrogram morphology recurrence (EMR) analysis to quantify the level of order in the morphology patterns in AF., Methods: Rapid atrial pacing was performed in seven dogs at 600bpm for 3 weeks leading to sustained AF. Open chest high density electrical recordings were made in multiple atrial sites. EMR plots of bipolar electrograms at each site were created by cross-correlating morphologies of each detected activations with morphologies of every other activation. The following features of the EMR plots were quantified: recurrence rate (RR), determinism (DET), laminarity (LAM), average diagonal line length (L), trapping time (TT), divergence (DIV), and Shannon׳s entropy (ENTR). For each recording site, these measures were calculated for the normal sequence of morphologies and also after random shuffling of the electrogram orders., Results: Electrograms recordings from a total of 3961 sites had average cycle lengths of 104±22ms resulting in an average of 100±19 activations detected per 10-s recording and an average RR of 0.38±0.28 (range 0.02-1.00). Shuffling the order of the activation morphologies resulted in significant decreases in DET, LAM, L, TT, and ENTR and significant increases in DIV., Conclusions: EMR plots of AF electrograms show varying rates of recurrence with patterns that suggest an underlying deterministic structure to the activation sequences. A better understanding of AF dynamics could lead to improved methods in mapping and treating AF., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Introduction: The electrocardiogram (ECG) fibrillatory (f) wave characteristics in atrial fibrillation (AF) could provide important information regarding the efficacy of antiarrhythmic drug therapy., Methods and Results: To measure the effects of dofetilide on the surface ECG f wave characteristics in patients with persistent AF, baseline and post-drug (2 hours after first dose and after multiple doses) ECGs in 31 patients with persistent AF admitted for dofetilide loading were evaluated. A QRST template subtraction algorithm was used to yield an atrial ECG. Fast Fourier transform analysis was performed to evaluate the maximum organizational index (OI), the dominant frequency (DF) in the lead with max OI, the median DF for all leads, and the vector magnitude f wave amplitude. Dofetilide reduced DF in the lead with the max OI (6.32 ± 0.98 Hz at baseline vs. 4.83 ± 0.63 Hz after final dose, P < 0.0001) and median DF (6.46 ± 0.87 Hz vs. 4.92 ± 0.62 Hz, P < 0.0001). Dofetilide also increased the maximum OI from 0.52 ± 0.11 at baseline to 0.59 ± 0.11 after final dose (P = 0.02). Of the 29 patients with long-term follow-up, the 22 (76%) with recurrent AF on dofetilide had a lower baseline DF in the lead with the max OI (6.01 ± 1.08 vs. 6.89 ± 0.46; P = 0.05). The change in DF after dofetilide did not correlate with the change in QTc interval., Conclusions: The standard ECG can be used to assess atrial rate in AF. This may be useful to assess antiarrhythmic drug effects for treatment of AF., (© 2015 Wiley Periodicals, Inc.)

Background: Traditional mapping of atrial fibrillation (AF) is limited by changing electrogram morphologies and variable cycle lengths., Objective: We tested the hypothesis that morphology recurrence plot analysis would identify sites of stable and repeatable electrogram morphology patterns., Methods: 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., Results: 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)., Conclusion: 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., (Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Atrial fibrillation (AF) electrograms are characterized by varying morphologies, amplitudes, and cycle lengths (CLs), presenting a challenge for automated detection of individual activations and the activation rate. In this study, we evaluate an algorithm to detect activations and measure CLs from AF electrograms. This algorithm iteratively adjusts the detection threshold level until the mean CL converges with the median CL to detect all individual activations. A total of 291 AF electrogram recordings from 13 patients (11 male, 58 ± 10 years old) undergoing AF ablation were obtained. Using manual markings by two independent reviewers as the standard, we compared the cycle length iteration algorithm with a fixed threshold algorithm and dominant frequency (DF) for the estimation of CL. At segment lengths of 10 s, when comparing the algorithm detected to the manually detected activation, the undersensing, oversensing, and total discrepancy rates were 2.4%, 4.6%, and 7.0%, respectively, and with absolute differences in mean and median CLs were 7.9 ± 9.6 ms and 5.6 ± 6.8 ms, respectively. These results outperformed DF and fixed threshold-based measurements. This robust method can be used for CL measurements in either real-time and offline settings and may be useful in the mapping of AF.

Background: There is a heightened risk of sudden cardiac death related to exercise and the postexercise recovery period, but the precise mechanism is unknown. We have demonstrated that sympathoexcitation persists for ≥45 minutes after exercise in normals and subjects with coronary artery disease (CAD). The purpose of this study is to determine whether this persistent sympathoexcitation is associated with persistent heart rate variability (HRV) and ventricular repolarization changes in the postexercise recovery period., Methods and Results: Twenty control subjects (age 50.7 ± 1.4 years), 68 subjects (age 58.2 ± 1.5 years) with CAD and preserved left ventricular ejection fraction (LVEF), and 18 subjects (age 57.6 ± 2.4 years) with CAD and depressed LVEF underwent a 16-minute submaximal bicycle exercise protocol with continuous ECG monitoring. QT and RR intervals were measured in recovery to calculate the time dependent corrected QT intervals (QTc), the QT-RR relationship, and HRV. QTc was dependent on the choice of rate correction formula. There were no differences in QT-RR slopes among the three groups in early recovery. HRV recovered quickly in controls, more slowly in those with CAD-preserved LVEF, and to a lesser extent in those with CAD-depressed LVEF., Conclusion: Despite persistent sympathoexcitation for the 45-minute recovery period, ventricular repolarization changes do not persist for that long and HRV changes differ by group. Additional understanding of the dynamic changes in cardiac parameters after exercise is needed to explore the mechanism of increased sudden cardiac death risk at this time., (© 2012, Wiley Periodicals, Inc.)

Early repolarization (ER) on a 12-lead electrocardiogram has recently been associated with ventricular tachyarrhythmias (VTAs) in patients without structural heart disease and in patients with healed myocardial infarction (MI). An association between ER and VTAs in the setting of acute ST-segment elevation MI (STEMI) has not been explored. In a single-center retrospective case-control design, 50 patients with STEMI complicated by VTAs (cases), defined as ventricular fibrillation, sustained ventricular tachycardia, or nonsustained ventricular tachycardia within 72 hours of the index hospitalization, were matched for age and gender with 50 subjects with STEMI without VTAs (controls). Electrocardiograms obtained an average of 1 year before STEMI were analyzed for ER pattern, defined as notching or slurring of the terminal QRS complex or J-point elevation >0.1 mV above baseline in ≥ 2 contiguous leads. A higher prevalence of ER was associated with VTAs overall in cases compared to controls (26% vs 4%, p = 0.01) and localized to anterior (16% vs 0%) and inferior (14% vs 2%, p = 0.07) leads but not lateral limb leads. Notching (10% vs 2%, p = 0.1) and J-point elevation (16% vs 0%) were more common in cases. Slurring was uncommon. ER was associated with VTAs (odds ratio [OR] 6.5, 95% confidence interval [CI] 1.5 to 28.8, p = 0.01), even after adjustment for creatine kinase-MB (OR 9.2, 95% CI 1.6 to 53.4, p = 0.01) and ejection fraction (OR 5.7, 95% CI 1.2 to 27.1, p = 0.03). In conclusion, ER is associated with VTAs in patients with STEMI even after adjustment for left ventricular ejection fraction or creatine kinas-MB levels. Larger prospective studies exploring potential associations and mechanisms of ventricular arrhythmogenesis with ER pattern are needed., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Objectives: This study sought to test the hypothesis that "virtual" electrophysiological studies (EPS) on an anatomic platform generated by 3-dimensional magnetic resonance imaging reconstruction of the left ventricle can reproduce the reentrant circuits of induced ventricular tachycardia (VT) in a porcine model of myocardial infarction., Background: Delayed-enhancement magnetic resonance imaging has been used to characterize myocardial infarction and "gray zones," which are thought to reflect heterogeneous regions of viable and nonviable myocytes., Methods: Myocardial infarction by coronary artery occlusion was induced in 8 pigs. After a recovery period, 3-dimensional cardiac magnetic resonance images were obtained from each pig in vivo. Normal areas, gray zones, and infarct cores were classified based on voxel intensity. In the computer model, gray zones were assigned slower conduction and longer action potential durations than those for normal myocardium. Virtual EPS was performed and compared with results of actual in vivo programmed stimulation and noncontact mapping., Results: The left ventricular volumes ranged from 97.8 to 166.2 cm(3), with 4.9% to 17.5% of voxels classified as infarct zones. Six of the 7 pigs in which VT developed during actual EPS were also inducible with virtual EPS. Four of the 6 pigs that had simulated VT had reentrant circuits that approximated the circuits seen with noncontact mapping, whereas the remaining 2 had similar circuits but propagating in opposite directions., Conclusions: This initial study demonstrates the feasibility of applying a mathematical model to magnetic resonance imaging reconstructions of the left ventricle to predict VT circuits. Virtual EPS may be helpful to plan catheter ablation strategies or to identify patients who are at risk of future episodes of VT., (Copyright © 2012 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Early repolarization, indicated on the standard 12-lead ECG, has recently been associated with idiopathic ventricular fibrillation in patients without structural heart disease. It is unknown whether there is an association between early repolarization and ventricular arrhythmias in the coronary artery disease (CAD) population., Methods and Results: Patients with CAD with implantable cardioverter-defibrillators in the healed phase of myocardial infarction were analyzed. In a case-control design, 60 patients who had ventricular arrhythmic events were matched for age and sex with 60 control subjects. ECGs were analyzed for early repolarization, defined as notching or slurring morphology of the terminal QRS complex or J-point elevation ≥0.1 mV above baseline in at least 2 lateral or inferior leads. Results were adjusted for left ventricular ejection fraction. Overall, early repolarization in 2 or more leads was more common in cases than control subjects (32% versus 8%, P=0.005). Early repolarization was noted more commonly in inferior leads (23% versus 8%, P=0.03), and a trend was noted in leads V(4) through V(6) (12% versus 3%, P=0.11). Early repolarization was uncommon in leads I and aVL in cases and control subjects (3% versus 0%). Notching was more common in cases than control subjects (28% versus 7%, P=0.008). Slurring and J-point elevation were not associated with ventricular arrhythmias., Conclusions: Early repolarization and, in particular, notching in the inferior leads is associated with increased risk of life-threatening ventricular arrhythmias in patients with CAD, even after adjustment for left ventricular ejection fraction. Our findings suggest early repolarization, and a notching morphology should be considered in a risk prediction model for arrhythmias in patients with CAD.

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.

Cardiac electrical alternans have been associated with spontaneous ventricular arrhythmias during myocardial ischemia. The study aims were to use a new algorithm to measure depolarization and repolarization alternans from epicardial electrograms in an ischemia model and to evaluate which features are predictive of ventricular fibrillation (VF). The left anterior descending coronary artery was occluded in 21 dogs, of which 6 developed spontaneous VF. Four seconds of unipolar epicardial electrograms was recorded before and 5 min after occlusion from an 8 x 14-electrode plaque placed on the anterior left ventricle. Alternans amplitudes were estimated with a triangular wave-fitting algorithm and for each unipolar electrogram for various measurements of the QRS and ST-T wave amplitude. The root mean square error was computed for each fit. Receiver-operator characteristic curves were used to determine whether prevalence of alternans having estimated alternans amplitude-to-error ratio (A/E) above a given threshold could distinguish the dogs who had and did not have spontaneous VF. The prevalence of alternans after ischemia was highly predictive of VF when measured both during depolarization (sensitivity of 83% and specificity of 87%) and during repolarization (sensitivity of 100% and specificity of 73%). The optimal alternans A/E ranged from 1 to 4. There were no differences in the level of discordance or alternans amplitude between dogs who developed VF versus dogs who did not. The prevalence of alternans in the ventricles may be the key risk factor for developing VF during myocardial ischemia when short-term recordings are used.

Although frequency-domain analysis of heart rate variability (HRV) has been performed in the setting of exercise and recovery from exercise, the relationship of specific frequency components to sympathetic and parasympathetic inputs has not been validated in this setting. The aim of this study is to evaluate the relationship of frequency components of HRV to sympathetic and parasympathetic modulation in the setting of recovery after exercise using selective autonomic blockade. Normal subjects (n = 27, 17 men, 53 +/- 7 yr old) underwent bicycle stress testing on four separate days. On day 1, a baseline study without autonomic blockade was performed. On days 2 through 4, either beta-adrenergic, parasympathetic, or double blockade was administered during exercise and completed 3 min before recovery. Continuous ECG was recorded for 5 min starting from the end of exercise. Time- and frequency-domain measures of HRV were computed for each of the five 1-min segments of RR intervals. Parasympathetic blockade significantly decreased all the HRV measures compared with baseline (P < 0.02 for all). Root mean square of successive differences of RR intervals (rMSSD) was increased by beta-adrenergic blockade (P < 0.0002). All the HRV measures except rMSSD showed increases with time after the first minute of recovery. The low frequency-to-high frequency ratio did not respond to autonomic blockade or to recovery time, consistent with the expected changes in sympathovagal influence. Root mean square (detrended SD) and rMSSD were highly correlated with the square root of the total power (r = 0.96) and high-frequency power (r = 0.95), respectively. Although there are marked reductions in the frequency-domain measures in recovery versus rest, the fluctuations in the low- and high-frequency bands respond to autonomic blockade in the expected fashion. Time-domain measures of HRV were highly correlated with frequency-domain measures and therefore provide a computationally more efficient assessment of autonomic influences during recovery from exercise that is less susceptible to anomalies of frequency-domain analysis.

Traditional analyses have assumed that cardiac electrical activity is reflected on the surface ECG without distortion as the signal passes through the body tissues. This study aims to explore the frequency dependence of thoracic attenuation of surface-recorded intracardiac electrical activity. Twenty patients (14 men, 55 +/- 15 yr of age) undergoing electrophysiological study were enrolled. Rectangular unipolar stimuli were applied from a catheter positioned in the right ventricular apical area and another in the posteroseptal area without contact with the myocardium. An orthogonal Frank-lead surface ECG and a unipolar intracardiac electrogram near the pacing site were recorded. Frequency domain characteristics of the signal-averaged pacing impulses were analyzed. Linear regression analysis showed significant frequency-dependent attenuation in the magnitude transfer functions (R(2) = 0.84-0.89, P < 0.0001) and good linear fit for the phase transfer characteristics (R(2) = 0.98-1.0, P < 0.0001). Age, physical dimension, and respiratory characteristics had significant effects on the magnitude and phase characteristics of the transfer functions. Application of models of the low- and high-slope transfer functions to signal-averaged ECGs from 33 subjects showed differences in the attenuation of P and T waves relative to the QRS.

Background: Atrial fibrillation (AF) is thought to be sustained by multiple reentrant wavelets or firing foci., Objective: The aim of this study was to compare the spectral domain characteristics in the left atrium (LA) and right atrium (RA) in two different models of AF., Methods: Rectangular 8 x 14 electrode arrays were placed on the LA and RA of 14 anesthetized dogs. AF episodes were induced with burst pacing and aconitine in each dog. For each model, AF was induced from the RA in six dogs and from the LA in six dogs. Dominant frequencies (DFs) were obtained using the fast Fourier transform of the unipolar recordings obtained from each electrode of the array. Standard deviation (SD) was used to compute the frequency dispersion within an atrium. Regularity of the signal was quantified using an organization index (OI)., Results: DFs were largest in the atrium where aconitine was applied. Aconitine AF had larger gradients than burst-pacing AF (5.0 +/- 4.5 vs. 0.9 +/- 1.0 Hz: P <.006). Aconitine AF when compared with burst-pacing AF had greater absolute LA-RA differences in the SD of DFs (2.3 +/- 1.9 vs. 0.2 +/- 0.2 Hz; P <.001) and in OI (0.11 +/- 0.07 vs. 0.06 +/- 0.07; P <.07)., Conclusions: Differences in frequency gradients and organization were observed during AF induced by burst pacing and aconitine. This suggests that different mechanisms of AF are possible and may be identified with frequency domain analysis.

Introduction: Dominant frequency (DF) analysis of atrial electrograms has been used to characterize atrial fibrillation (AF). The aim of this study was to explore technical issues that may affect the estimation of local activation rate during AF using DF analysis., Methods and Results: Epicardial atrial electrograms recorded during AF from 10 dogs were used to evaluate the effects of unipolar versus bipolar recordings, bipolar electrode spacing, postrecording processing, far field ventricular depolarizations, ventricular template subtraction, and signal duration on DF analysis. Simulated electrograms were used to evaluate the effect of far field ventricular depolarizations and signal-to-noise ratio. DFs were compared with activation rates obtained by manual marking and the reproducibility of the DFs was evaluated. Bipolar electrograms were found to be preferable to unipolar electrograms. Preprocessing was a necessary step for bipolar signals, but also aided analysis of unipolar recordings. Ventricular far field depolarizations significantly affected DFs. Ventricular template subtraction helped DF analysis in signals with both minimal and significant ventricular components. A recording duration above 2 seconds was required for reliable DF measurements. Signal-to-noise ratios below 13 dB could also affect DF, particularly for signals with significant amplitude and frequency variation., Conclusions: Various factors affect DF analysis. Proper interpretation of DF analysis requires careful evaluation of the AF signals and robust processing techniques.

Dominant frequency analysis of atrial electrograms has been used to understand the pathophysiology of atrial fibrillation (AF). Although dominant frequency is an effective tool to estimate activation rate during AF, other factors besides activation rate may alter the results. Therefore, an adequate conceptual understanding of frequency domain analysis is required to properly use this technique and interpret the results. This review, while avoiding the use of formulas and equations, aims to explain fundamental theory of how signals can be decomposed into sine waves and how these sine waves relate to the activation rate detected from the electrograms. Through a series of examples and illustrations this relationship can be easily conceptualized. This will in turn allow the strengths and limitations of dominant frequency analysis to be better understood and improve its applicability to potential clinical usages.

Background: Dominant frequency analysis has become a widely used tool for studying the pathophysiology of atrial fibrillation (AF)., Objectives: The purpose of this study was to compare dominant frequency with atrial activation rates in the presence of changing activation intervals and amplitudes and the complex morphologies characteristic of AF electrograms., Methods: A combination of atrial electrograms recorded during persistent AF from 10 patients, atrial flutter electrograms with double potentials from 12 patients, and simulated electrograms were used in this study. Dominant frequencies were compared with the mean, median, and mode beat-to-beat activation rates obtained by electrogram marking., Results: Dominant frequency correlated well with, but did not specifically reflect, mean, median, and mode activation rates. Dominant frequencies were significantly impacted by frequency variation, combined amplitude and frequency variation, and ordering of the activation intervals. Averaging dominant frequency measurement of four consecutive signals improved reproducibility and agreement with mean and median activation rates. Signals with double potentials having longer delays between potentials were associated with harmonics chosen as the dominant frequency., Conclusion: Multiple dominant frequency measurements and scrutiny of the time and frequency domain signals are recommended to obtain accurate and reproducible values.

Objectives: The purpose of this study was to assess whether surface ECG fibrillatory (f)-wave characteristics reflect clinical variables, especially pattern of occurrence., Background: In clinically stable patients, f waves have fairly constant quantitative characteristics. Both electrophysiologic and structural remodeling might modify f waves., Methods: We analyzed f waves from 238 patients (120 men and 118 women; age range 30-97 years, mean 77 +/- 12) with atrial fibrillation identified by retrospective chart review as paroxysmal, persistent, or permanent fibrillation. Analysis was performed in the time and frequency domains on ECGs after QRS-T cancellation. Student's t-test and multivariate analysis were used for comparison., Results: The f waves of 12 patients taking rhythm control drugs had lower frequency ("slower" fibrillation) than the f waves of patients not taking such drugs (5.3 +/- 0.6 vs 6.0 +/- 0.7 Hz, P < .001). Of the 226 remaining patients, 59 were paroxysmal, 30 were persistent, and 72 were permanent; 65 had an unknown pattern. Paroxysmal and persistent patients were younger than permanent (74 +/- 12 and 72 +/- 15 vs 80 +/- 9 years, P < .002 for both). Paroxysmal, persistent, and permanent patients had different f-wave frequencies of 5.7 +/- 0.7, 6.1 +/- 0.8, and 6.2 +/- 0.6 Hz, respectively (P = .01 for paroxysmal vs persistent and P < .001 for paroxysmal vs permanent). Patients older than 77 years (mean age) had lower f wave frequency than those younger 77 years (6.0 +/- 0.7 vs 6.2 +/- 0.7 Hz, P = .01). Using multivariate analysis, the overall pattern-frequency relationship was significant (p = .014). There was a statistically significant inverse correlation between frequency and age (R = .27, slope = -0.017 Hz/year, P < .001)., Conclusions: ECG f-wave frequency reflects specific clinical variables, with higher frequency in permanent than paroxysmal fibrillation but lower frequency in older than younger patients. These findings are consistent with the idea that fibrillatory waves are modified by both electrophysiologic and structural remodeling.

Introduction: Fibrillatory waves on the surface ECG have been scrutinized to allow inferences about underlying mechanisms and pathophysiology, based on the premise that fibrillatory waves do not vary "randomly" but provide a consistent reflection of the underlying state of the atria in an individual patient. This premise is untested., Methods and Results: Ten standard ECGs were recorded over a 24-hour period in each of 20 clinically stable inpatients with atrial fibrillation. After QRS-T cancellation, the remainder fibrillatory waves were analyzed. Interpatient versus intrapatient differences in fibrillatory wave characteristics were evaluated by analysis of variance (ANOVA). The fibrillatory wave peak-to-peak amplitude of all the patients ranged from 0.06 to 0.35 mV, whereas 1 SD of the amplitude for each patient ranged from 0.004 to 0.053 mV. Short-term peak frequencies of all the patients ranged from 4.6 to 8.0 Hz, whereas 1 SD for each patient varied from 0.2 to 0.5 Hz. For these and all other parameters tested, interpatient differences were significantly greater compared to intrapatient differences (P < 0.0001)., Conclusion: Fibrillatory wave characteristics are repeatable from ECG to ECG over 24 hours for clinically stable patients, whereas substantial differences are present between patients. Further study of the relationship of such characteristics to pathophysiology and management decisions is valid and warranted.

Introduction: Multiple analysis techniques evaluate electrograms during atrial fibrillation (AF), but none have been established to guide catheter ablation. This study compares electrogram properties recorded from multiple right (RA) and left atrial (LA) sites. Methods: Multisite LA/RA mapping (281 ± 176/239 ± 166 sites/patient) was performed in 42 patients (30 males, age 63 ± 9 years) undergoing first (n = 32) or redo‐AF ablation (n = 10). All electrogram recordings were visually reviewed and artifactual signals were excluded leaving a total of 21 846 for analysis. Electrogram characteristics evaluated were cycle length (CL), amplitude, Shannon's entropy (ShEn), fractionation interval, dominant frequency, organizational index, and cycle length of most recurrent morphology (CLR) from morphology recurrence plot analysis. Results: Electrogram characteristics were correlated to each other. All pairwise comparisons were significant (p <.001) except for dominant frequency and CLR (p =.59), and amplitude and dominant frequency (p =.38). Only ShEn and fractionation interval demonstrated a strong negative correlation (r = −.94). All other pairwise comparisons were poor to moderately correlated. The relationships are highly conserved among patients, in the RA versus LA, and in those undergoing initial versus redo ablations. Antiarrhythmic drug therapy did not have a significant effect on electrogram characteristics, except minimum ShEn. Electrogram characteristics associated with ablation outcome were shorter minimum CLR, lower minimum ShEn, and longer mimimum CL. There was minimal overlap between the top 10 sites identified by one electrogram characteristic and the top 10 sites identified by the other 10 characteristics. Conclusion: Multiple techniques can be employed for electrogram analysis in AF. In this analysis of eight different electrogram characteristics, seven were poorly to moderately correlated and do not identify similar locations. Only some characteristics were predictive of ablation outcome. Further studies to consider electrogram properties, perhaps in combination, for categorizing and/or mapping AF are warranted. [ABSTRACT FROM AUTHOR]