Clinical Implications of Brief Device-Detected Atrial Tachyarrhythmias in a Cardiac Rhythm Management Device Population: Results from the Registry of Atrial Tachycardia and Atrial Fibrillation Episodes.

BACKGROUND: The RATE Registry (Registry of Atrial Tachycardia and Atrial Fibrillation Episodes) is a prospective, outcomes-oriented registry designed to document the prevalence of atrial tachycardia and/or fibrillation (AT/AF) of any duration in patients with pacemakers and implantable cardioverter defibrillators (ICDs) and evaluate associations between rigorously adjudicated AT/AF and predefined clinical events, including stroke. The appropriate clinical response to brief episodes of AT/AF remains unclear. METHODS: Rigorously adjudicated electrogram (EGM) data were correlated with adjudicated clinical events with logistic regression and Cox models. Long episodes of AT/AF were defined as episodes in which the onset and/or offset of AT/AF was not present within a single EGM recording. Short episodes of AT/AF were defined as episodes in which both the onset and offset of AT/AF were present within a single EGM recording. RESULTS: We enrolled 5379 patients with pacemakers (N=3141) or ICDs (N=2238) at 225 US sites (median follow-up 22.9 months). There were 359 deaths. There were 478 hospitalizations among 342 patients for clinical events. We adjudicated 37 531 EGMs; 50% of patients had at least one episode of AT/AF. Patients with clinical events were more likely than those without to have long AT/AF (31.9% vs. 22.1% for pacemaker patients and 28.7% vs. 20.2% for ICD patients; P<0.05 for both groups). Only short episodes of AT/AF were documented in 9% of pacemaker patients and 16% of ICD patients. Patients with clinical events were no more likely than those without to have short AT/AF (5.1% vs. 7.9% for pacemaker patients and 11.5% vs. 10.4% for ICD patients; P=0.21 and 0.66, respectively). CONCLUSIONS: In the RATE Registry, rigorously adjudicated short episodes of AT/AF, as defined, were not associated with increased risk of clinical events compared with patients without documented AT/AF. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00837798.

Observations of pacemaker pulses in high-bandwidth electrocardiograms and Dower-estimated vectorcardiograms.

BACKGROUND: Electronic pacemaker pulses are poorly reproduced in computerized electrocardiogram (ECG) tracings, impairing both automated and human interpretation. In this study, a high-bandwidth system is used to examine ECG and vectorcardiogram characteristics of pacemaker pulses. METHODS: In 69 subjects with artificial pacemakers, electrocardiograms were recorded at 75,000 samples per second with a high-bandwidth ECG system (GE Healthcare, Milwaukee, WI). Vectorcardiograms, as estimated with the Dower transform, were examined. RESULTS: Pulse loops in the vectorcardiogram consisted of distinct discharge and recharge waves, with an angle difference of 174° ± 10° (mean ± SD) in 3 dimensions. Atrial pulses were on average oriented anteriorly, superiorly, and to the left; right ventricular pulses were oriented posteriorly, superiorly, and to the right; and left ventricular pulses were oriented posteriorly, inferiorly, and to the right. Other details of pacemaker pulses could be readily observed. CONCLUSIONS: The high-bandwidth ECG has the potential to improve interpretation of paced rhythms in computerized ECGs.

Improved pacemaker pulse detection: clinical evaluation of a new high-bandwidth electrocardiographic system.

BACKGROUND: This study compares the pacemaker pulse detection performance of the new high-bandwidth (hi-fi) electrocardiographic (ECG) acquisition system to a conventional system in a prospective clinical evaluation. METHODS: Electrocardiograms from 88 subjects with implanted pacemakers were recorded using different pacemaker programmed outputs and with different noise levels. Each ECG was recorded simultaneously from both systems. A cardiologist independently confirmed the clinically relevant ECGs. The pacemaker pulse detection sensitivity and positive predictive value (PPV) of each system were computed. The efficacy of each system was evaluated using a z test. RESULTS: For the independently confirmed reports, the hi-fi system was superior, with higher sensitivity (99.2% vs 83.2%, P < .0001) and higher PPV (100% vs 99.9%, P = .33), for the detection of pacemaker pulses. CONCLUSION: In a large group of subjects with implanted pacemakers and even in noisy conditions, the new hi-fi system was shown to improve pacemaker pulse detection sensitivity and PPV.

Manifestation of left atrial events and interatrial frequency gradients in the surface electrocardiogram during atrial fibrillation: contributions from posterior leads.

BACKGROUND: In most patients, atrial fibrillation (AF) is initiated and maintained by pulmonary vein foci, but the relationship between left atrial (LA) events and the surface electrocardiogram (ECG) is largely unknown. We investigated whether LA events are reflected in the surface ECG and whether additional information can be obtained from recording posterior leads in patients with AF. METHODS AND RESULTS: In 10 patients undergoing radiofrequency ablation of AF, we identified 103 5-second segments with a significant frequency gradient between right (RA) and left (LA) intraatrial electrograms, or with frequency changes from segment to segment in the same patient. QRS-T cancellation methods were used to isolate atrial activity in the surface ECG and peak frequencies were computed. Peak frequencies of different posterior leads were very similar (6.0 +/- 1.3 Hz for V10, 6.0 +/- 0.9 Hz for V9, 5.9 +/- 1.4 Hz for V8, 6.0 +/- 1.3 Hz for V7). We found a strong correlation between V1 and RA and between V9 and LA, 0.89 and 0.88, respectively, while the lowest correlation was found between lead V1 and LA, 0.62, P < 0.0001. Magnitude-squared coherence values were highest between V1 and RA and between V9 and LA. CONCLUSION: We have demonstrated that, by recording additional surface ECG leads from posterior locations, RA and LA electrical events and interatrial frequency gradients can be monitored noninvasively.

Derivation of orthogonal leads from the 12-lead electrocardiogram. Performance of an atrial-based transform for the derivation of P loops.

The objective of this study was the evaluation of the accuracy of Dower inverse transform for the derivation of the P wave in orthogonal leads. We tested the accuracy of Dower transform on the P wave and compared it with a P-wave-optimized transform in a database of 123 simultaneous recordings of electrocardiograms and vectorcardiograms. This new transform achieved a lower error when we compared derived vs true measured P waves (mean +/- SD, 12.2 +/- 8.0 VRMS) than Dower transform (14.4 +/- 9.5 Root mean squared voltage) and higher correlation values (Rx, 0.93 +/- 0.12; Ry, 0.90 +/- 0.27; Rz, 0.91 +/- 0.18; vs Dower: Rx, 0.88 +/- 0.15; Ry, 0.91 +/- 0.26; Rz, 0.85 +/- 0.23). We conclude that derivation of orthogonal leads for the P wave can be improved by using an atrial-based transform matrix.

The relationship between programmed pacemaker pulse amplitude and the surface electrocardiogram recorded amplitude: application of a new high-bandwidth electrocardiogram system.

BACKGROUND: Recording and displaying outputs from electronic pacemakers with electrocardiogram (ECG) recorders typically used in clinical practice have presented a number of technical limitations. We have recently reported on a new high-bandwidth ECG system and have shown that it is capable of reproducing accurate pulse amplitudes and durations from the body surface. In the present work, we have used our data to calculate a transform function between the programmed pacemaker output voltage and the amplitude on the body surface. METHODS: We recorded 3 high-bandwidth (75,000 samples per second) ECGs from each of 100 pacemaker patients at 3 different programmed outputs. Each pacemaker pulse was isolated using the criterion standard annotations, and the pulses were transformed from the 8 independent leads to an XYZ vector using the Dower transform. The magnitude of the vector was calculated. Linear regression techniques were used to learn a transfer function over the records of the first 50 patients. These results were tested against the second 50 patients. RESULTS: The measured pacemaker pulse vector magnitude has a linear relationship to the programmed pacemaker amplitude on a per-patient basis for most of the patients in the training database. The linear transform models were tested against the testing set with an R(2) metric of 0.38 for the atrial pulses and 0.54 for the right ventricular pulses. CONCLUSION: Understanding the relationship between the generated pacemaker pulses and the measurements at the body surface will help drive specifications for pacemaker pulse detection among the various device manufactures.

Short-term dynamics in fibrillatory wave characteristics at the onset of paroxysmal atrial fibrillation in humans.

INTRODUCTION: The purpose of this study was to investigate the magnitude and time course of fibrillatory wave dynamics during spontaneous onset of paroxysmal atrial fibrillation (AF). METHODS: We studied fibrillatory waves in Holter recordings of paroxysmal AF with regard to the fibrillation-free interval (FFI) preceding each episode. RESULTS: For 38 episodes of paroxysmal AF in 20 patients, dominant frequency (DF) ranged from 4.4 to 6.8 Hz (5.5 +/- 0.5 Hz). Long-FFI episodes showed a gradual increase in DF over the first 4 minutes (P < .0001). Short-FFI episodes showed an increase only from the first to the second minute (P < .003). For all 7 patients exhibiting both long-FFI and short-FFI episodes, short-FFI episodes had a higher initial DF (P < .002). CONCLUSION: The dynamics during onset and their relation to the FFI are consistent with the influence of short-term electrophysiological changes and their reversal. These findings have implications for the timing of antifibrillatory interventions.

Atrial electrograms improve the accuracy of tachycardia interpretation from ICD and pacemaker recordings: The RATE Registry.

BACKGROUND: Tachycardia diagnoses from implantable device recordings ultimately depend on the analysis of captured electrograms (EGMs). The degree to which atrial EGMs improve tachycardia discrimination, dependent on the level of expertise of the medical professional involved, remains uncertain. OBJECTIVE: The purpose of this article was to determine whether atrial EGM recordings improve tachycardia discrimination and whether this improvement, if any, varies for professionals with different levels of training. METHODS: Expert-adjudicated supraventricular tachycardia (SVT) and ventricular tachycardia (VT) dual-chamber EGMs (DEGMs) from the Registry of Atrial Tachycardia and Atrial Fibrillation Episodes in the Cardiac Rhythm Management Device Population were provided to electrophysiology specialists, electrophysiology fellows (EPF), and nurse practitioners or physician assistants (NPPA). Each participant diagnosed 112 EGM episodes presented in random sequence (61 VTs and 51 SVTs) and independently categorized each as "SVT," "VT," or "uncertain" in 2 stages. First, participants analyzed ventricular EGMs (VEGMs) alone (atrial channel covered). Second, the tracings were randomized and reanalyzed with atrial EGMs exposed. The diagnostic accuracy of VEGMs alone vs DEGMs was assessed for each group. RESULTS: For all 3 groups, diagnostic accuracy improved significantly (>20% for VTs and >15% for SVTs; P < .01 for all) when DEGMs were provided. Electrophysiology specialists diagnosed VTs more accurately than did EPF and NPPA (VEGM: 73.1%±7.6% vs 58.7%±15.5% and 56.1%±14.1%; P < .01; DEGM: 98.0%±2.7% vs 90.8%±16.0% and 80.3%±7.4%; P < .01). EPF diagnosed VTs more accurately than did NPPA only when DEGMs were provided. There was no significant intergroup difference in SVT diagnoses. CONCLUSION: DEGMs are superior to VEGMs alone for tachycardia discrimination at all levels of expertise. The level of training affects diagnostic accuracy with and without atrial EGMs.

Practice standards for electrocardiographic monitoring in hospital settings: an American Heart Association scientific statement from the Councils on Cardiovascular Nursing, Clinical Cardiology, and Cardiovascular Disease in the Young: endorsed by the International Society of Computerized Electrocardiology and the American Association of Critical-Care Nurses.

The goals of electrocardiographic (ECG) monitoring in hospital settings have expanded from simple heart rate and basic rhythm determination to the diagnosis of complex arrhythmias, myocardial ischemia, and prolonged QT interval. Whereas computerized arrhythmia analysis is automatic in cardiac monitoring systems, computerized ST-segment ischemia analysis is available only in newer-generation monitors, and computerized QT-interval monitoring is currently unavailable. Even in hospitals with ST-monitoring capability, ischemia monitoring is vastly underutilized by healthcare professionals. Moreover, because no computerized analysis is available for QT monitoring, healthcare professionals must determine when it is appropriate to manually measure QT intervals (eg, when a patient is started on a potentially proarrhythmic drug). The purpose of the present review is to provide 'best practices' for hospital ECG monitoring. Randomized clinical trials in this area are almost nonexistent; therefore, expert opinions are based upon clinical experience and related research in the field of electrocardiography. This consensus document encompasses all areas of hospital cardiac monitoring in both children and adults. The emphasis is on information clinicians need to know to monitor patients safely and effectively. Recommendations are made with regard to indications, timeframes, and strategies to improve the diagnostic accuracy of cardiac arrhythmia, ischemia, and QT-interval monitoring. Currently available ECG lead systems are described, and recommendations related to staffing, training, and methods to improve quality are provided.

Relationship between pattern of occurrence of atrial fibrillation and surface electrocardiographic fibrillatory wave characteristics.

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.

Accelerometer-based body-position sensing for ambulatory electrocardiographic monitoring.

Our objective is to validate the ability of 3 appropriately placed accelerometers to determine body position during ambulatory electrocardiographic (ECG) monitoring and to demonstrate the clinical applicability of this method. During ambulatory (Holter) monitoring, the ability to know a patient's position (lying down, sitting, standing, or changing from one position to another) is important in the evaluation of common symptoms such as dizziness, palpitations, and syncope. Changes in body position are also known to alter the electrical axis of the heart, resulting in artifactual changes in QRS amplitude and ST-segment morphology. We have developed an ambulatory patient-monitoring instrument that, through the use of microfabricated accelerometers, can simultaneously record body-position information and 2 channels of ECG data. The accelerometers measure the effects of gravity and dynamic acceleration, allowing determination of a patient's orientation and movements. The accelerometer and ECG signals are input to a portable recorder and are filtered and digitized. Algorithms were developed to automatically determine body position. Ten healthy volunteers wore the device for 1 hour and followed a protocol of standing, sitting, walking, lying supine, and lying in the left and right lateral decubitus positions. An observer manually recorded times of position changes. Data were recorded and analyzed using software designed with MATLAB. The ability of the accelerometers and computer algorithms to determine body position was analyzed in terms of the sensitivity and specificity for each body position. The sensitivities for sitting, standing, walking, lying supine, lying right, and lying left were 98.8%, 99.2%, 95.5%, 99.1%, 98.9%, and 94.8%, respectively. The specificities were 99.7%, 99.4%, 99.6%, 99.0%, 99.8%, and 99.9%, respectively. The use of microfabricated accelerometers is a clinically feasible method to determine body position and can be applied to future studies correlating body position with ECG or other physiologic data.

Extraction of the magnetohydrodynamic blood flow potential from the surface electrocardiogram in magnetic resonance imaging.

The magnetohydrodynamic effect generates voltages related to blood flow, which are superimposed on the electrocardiogram (ECG) used for gating during cardiac magnetic resonance imaging (MRI). A method is presented for extracting the magnetohydrodynamic signal from the ECG. The extracted magnetohydrodynamic blood flow potential may be physiologically meaningful due to its relationship to blood flow. Removal of the magnetohydrodynamic voltages from the ECG can potentially lead to improved gating and diagnostically useful ECGs.

Comparison of self-gated cine MRI retrospective cardiac synchronization algorithms.

PURPOSE: To determine whether improved self-gating (SG) algorithms can provide superior synchronization accuracy for retrospectively gated cine MRI. MATERIALS AND METHODS: First difference, template matching, and polynomial fitting algorithms were implemented to improve the synchronization of MRI data using cardiac SG signals. Cine datasets were acquired during short-axis, two-, three-, and four-chamber cardiac MRI scans. The root-mean-square (RMS) error of SG synchronization positions compared to detected R-wave positions were calculated along with the mean square error (MSE) and peak signal-to-noise ratio (PSNR) comparing SG to electrocardiogram (ECG)-gated images. Overall image quality was also compared by two expert reviewers. RESULTS: RMS errors were highest for the first difference method for all orientations. Improvements for both template matching and cubic polynomial fitting methods were significant for two-, three-, and four-chamber scans. MSE values were lower and PSNR were significantly higher for the cubic method compared to the first difference method for all orientations. Reviewers scored the images to be of comparable quality. CONCLUSION: Template matching and polynomial fitting improved the accuracy of cardiac cycle synchronization for two-, three-, and four-chamber scans; improvements in SG synchronization accuracy were reflected in improvements in analytical image quality. Implementation of robust postprocessing algorithms may bring SG approaches closer to clinical utilization.

Abrupt changes in fibrillatory wave characteristics at the termination of paroxysmal atrial fibrillation in humans.

AIMS: We investigated the process of spontaneous termination of atrial fibrillation (AF) to determine its time course from the surface ECG. METHODS AND RESULTS: We studied fibrillatory waves in Holter recordings of paroxysmal and sustained AF. Following QRS-T cancellation dominant frequencies (DFs) were computed and the relationship of DF to termination was scrutinized. For 57 episodes of paroxysmal AF (PAF) in 24 patients, DF ranged from 4.4 to 6.5 Hz (5.2 +/- 0.4 Hz) compared to 5.8 to 7.4 Hz (6.6 +/- 0.6 Hz) for sustained AF recordings. Comparison of the atrial frequency of the ultimate to the penultimate second demonstrated a drop in frequency in 51 of 57 episodes, P < 0.00001. No comparable change was seen at longer time periods. Moments of comparably low frequency without termination were only occasionally seen in patients with PAF but not in patients with sustained AF. CONCLUSION: Low frequency fibrillation was found to be much more likely to terminate. Frequency changes preceding spontaneous termination were abrupt, in contrast to the gradual frequency drop reported with drug-induced termination. The analysis of fibrillatory wave characteristics and their change over time might be used to target specific moments for pacing therapy in patients with AF.

AHA scientific statement: practice standards for electrocardiographic monitoring in hospital settings: an American Heart Association Scientific Statement from the Councils on Cardiovascular Nursing, Clinical Cardiology, and Cardiovascular Disease in the Young: endorsed by the International Society of Computerized electrocardiology and the American Association of Critical-Care Nurses.

The goals of electrocardiographic (ECG) monitoring in hospital settings have expanded from simple heart rate and basic rhythm determination to the diagnosis of complex arrhythmias, myocardial ischemia, and prolonged QT interval. Whereas Computerized arrhythmia analysis is automatic in cardiac monitoring systems, computerized ST-segment ischemia analysis is available only in newer-generation monitors, and computerized QT-interval monitoring is currently unavailable. Even in hospitals with ST-monitoring capability, ischemia monitoring is vastly underutilized by healthcare professionals. Moreover, because no computerized analysis is available for QT monitoring, healthcare professionals must determine when it is appropriate to manually measure QT intervals (eg, when a patient is started on a potentially proarrhythmic drug). The purpose of the present review is to provide "best practices" for hospital ECG monitoring. Randomized clinical trials in this area are almost nonexistent; therefore, expert opinions are based upon clinical experience and related research in the field of electrocardiography. This consensus document encompasses all areas of hospital cardiac monitoring in both children and adults. The emphasis is on information clinicians need to know to monitor patients safely and effectively. Recommendations are made with regard to indications, time frames, and strategies to improve the diagnostic accuracy of cardiac arrhythmia, ischemia, and QT-interval monitoring. Currently available ECG lead systems are described, and recommendations related to staffing, training, and methods to improve quality are provided.

Atrial fibrillatory wave characteristics on surface electrogram: ECG to ECG repeatability over twenty-four hours in clinically stable patients.

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.

The effect of QRS cancellation on atrial fibrillatory wave signal characteristics in the surface electrocardiogram.

QRS cancellation methods have been used to analyze atrial activity in the electrocardiogram for such rhythms as atrioventricular dissociated ventricular tachycardia and atrial fibrillation. However, how well the cancellation methods work has never been evaluated by some gold standard. In this study of patients undergoing radiofrequency ablation of the atrioventricular junction, the contribution of imperfect cancellation was evaluated by comparing the "pure" atrial fibrillation (the gold standard) during a brief ventricular asystole to data obtained by a cancellation method during pacing just before and after the asystole. The results were compared by linear regression. The peak frequencies were 4.8-7.3 (6.1 +/- 0.8) Hz for the "pure" and 4.8-6.8 (5.9 +/- 0.7) Hz for the cancelled electrocardiogram segments (R(2) = 0.89) (similar results for median frequency), and the mean short-time Fourier transform peak frequencies were 4.6-7.1 (5.9 +/- 0.8) Hz for the "pure" and 4.7-6.8 (5.9 +/- 0.7) Hz for the cancelled segments (R(2) = 0.96). Further comparison was accomplished using synthesized signals. Based on our study, the cancellation method is reliable for studying atrial fibrillatory wave characteristics. As reported previously, the peak frequency and most power for atrial fibrillation in humans are in the 4-9 Hz band.

Surface ECG vector characteristics of organized and disorganized atrial activity during atrial fibrillation.

BACKGROUND: The aim of this study was to examine atrial organization from vectorcardiograms (VCGs) derived from the surface ECG of atrial fibrillatory waves. METHODS: We retrieved ECGs recorded during ventricular asystole from 22 patients with AF undergoing ablation of the AV junction. The synthesized VCG of each f-wave cycle of each ECG and its plane of best fit, described by azimuth and elevation angles relative to the frontal plane, were computed. RESULTS: Fifteen of the 22 ECGs had at least 30% of the planes in a single 30-degree region of azimuth angles. Of these 15, 12 had the greatest percentage of planes with azimuth angles within 30 degrees of the sagittal plane; two were near the frontal plane; and one near the right anterior oblique plane. CONCLUSIONS: Varying degrees of organization were observed from VCGs of fibrillatory waves with the more organized examples having planes predominately near the sagittal plane.

Atrial flutter vector loops derived from the surface ECG: does the plane of the loop correspond anatomically to the macroreentrant circuit?

We hypothesized that if the right atrial circuit during isthmus dependent atrial flutter provides the dominant contribution to the surface electrocardiogram (ECG), the three-dimensional vector loop of the flutter waves would primarily be in a plane approximately parallel to the tricuspid ring. Twenty vectorcardiograms of isthmus dependent atrial flutter derived from 12-lead ECGs of 19 patients recorded prior to radiofrequency ablation were analyzed. The plane of each loop, described by azimuth and elevation angles relative to the frontal plane, was estimated with two methods: 1) plane of maximum loop area and 2) plane of best fit. The plane of maximum loop of the loops had mean azimuth of -58 +/- 37 degrees. and elevation of 15 +/- 15 degrees. The plane of best fit of the loops had mean azimuth of -50 +/- 46 degrees and elevation of 15 +/- 14 degrees. Thus, clinical implications include the potential to predict atrial flutter mechanisms prior to intracardiac mapping.