Internal atrial defibrillation during electrophysiological studies and focal atrial fibrillation ablation procedures.

Induction of sustained AF during electrophysiological studies requires electrical cardioversion to restore sinus rhythm for continuation of the electrophysiological study and mapping procedure. The study included 104 consecutive patients (age 59 +/- 12 years, 74 men), who were in stable sinus rhythm at the beginning of the electrophysiological study, underwent internal atrial defibrillation (IAD) of AF (> 15 minutes) that was induced during electrophysiological study. In 21 patients, AF was regarded to be the clinical problem (group I), and in the remaining 83 patients other arrhythmias represented the primary target of the electrophysiological study (group II). A 7.5 Fr cardioversion catheter (EP Medical) equipped with a distal array was used and placed in the left pulmonary artery and a proximal array of the same size was located along the lateral right atrial wall. All patients were successfully cardioverted with a mean energy of 6.2 +/- 4.0 1. In 18 (78%) of 21 group I patients and in 12 (14%) of 81 group II patients, AF recurred 3.7 +/- 3.4 and 2.4 +/- 1.4 times during electrophysiological study, respectively. The IAD shock did not suppress focal activity, thus the mapping of atrial foci responsible for AF could be continued even after several IADs. No IAD related complications occurred during the study. In conclusion, (1) IAD can be safely and successfully performed during electrophysiological study without using narcotic drugs or high electric energies; (2) IAD does not suppress focal activity; and (3) even if AF recurs frequently during the electrophysiological study, IAD can be performed several times without significant time delay.

Electrophysiologic characteristics of paroxysmal and chronic atrial fibrillation in human right atrium.

OBJECTIVES: The aim of the study was to analyze the electrophysiologic characteristics of paroxysmal (PAF) and chronic (CAF) atrial fibrillation (AF) in the human right atrium (RA). BACKGROUND: Differences that exist between PAF and CAF and the mechanisms of self-sustenance of these arrhythmias are incompletely understood. METHODS: A total of 53 patients with PAF (25 patients, mean age 59 +/- 6.1 years, 3 women) and CAF (28 patients, mean age 59 +/- 13 years, 7 women) underwent multisite mapping of the RA during ongoing AF using a 64-electrode basket catheter. Quantitative evaluation and three-dimensional activation patterns were performed using a computerized system. RESULTS: Patients with PAF, as compared with patients with CAF, had significantly longer AF cycle length, shorter time intervals with type III AF throughout the RA and a smaller number of endocardial breakthroughs (mean 51 +/- 19 vs. 104 +/- 40, p < 0.001). The majority of endocardial breakthrough points (88% in PAF patients and 98% in CAF patients) were located in the septal region and coincided anatomically with major interatrial connection routes. Coexistence of re-entrant and apparently focal activation determined maintenance of AF in the RA in PAF, whereas random re-entry was documented more frequently in patients with CAF. In patients with CAF, the duration of arrhythmia (in years) correlated strongly with the percentage of time during which type III AF was observed in the lateral wall of the RA (r = 0.71). CONCLUSIONS: Clinical PAF and CAF, as recorded in the RA, have, at least quantitatively, distinct electrophysiologic features and different mechanisms of maintenance.

Internal low energy cardioversion of atrial fibrillation using a single lead system: comparison of a left and right pulmonary artery catheter approach.

Internal cardioversion (ICV) has been demonstrated as an effective and safe method for restoring sinus rhythm in patients with AF. Recently, a new single lead system with a balloon-guided cardioversion catheter was introduced. ICV was performed after advancing a 7.5 Fr catheter flow-directed into the left or right pulmonary artery (PA, distal array, cathode). The proximal array (anode) was placed at the lateral RA wall. Synchronized shocks (3/3 ms biphasic impulse) were applied using a stepwise protocol (0.5, 3, 6, 9, 12, 15 J) until sinus rhythm was restored or maximum energy (15 J) was reached. Sixty-five patients (mean age 58 +/- 13 years) with acute and chronic AF were included. Sinus rhythm could be restored in 59 (91%) patients. Cardioversion success was 93% in the left PA compared to 86% in right PA. DFTs for the left and right PA approaches were 7.1 +/- 4.0 J and 10.2 +/- 4.0 J, respectively (P < 0.0001). It was significantly higher in patients with an AF history > 7 days (7.2 +/- 4.1 J) than for those with a recent onset of AF (5.6 +/- 4.1 J), P = 0.0012. Shock impedance differed for the left and right PA lead configuration (53 +/- 11 vs 49 +/- 13 omega, P < 0.05). A right PA lead configuration is as effective compared to a left PA catheter approach when performing ICV for AF. ICV with a single lead system is safe and cardioversion success is comparable to other internal and external cardioversion techniques. In combination with hemodynamic monitoring, flow-directed nonfluoroscopic catheter positioning is feasible and may serve as a valuable therapeutic and diagnostic tool in intensive care units.

Dissociation between coronary sinus and left atrial conduction in patients with atrial fibrillation and flutter.

INTRODUCTION: Coronary sinus (CS) recordings are routinely used during electrophysiologic studies for various supraventricular and ventricular arrhythmias with the understanding that they represent left atrial (LA) activity. However, the behavior of CS electrical activity during atrial arrhythmias has not drawn any special attention beyond standard considerations. METHODS AND RESULTS: The study population consisted of 9 patients (3 women; mean age 59 +/- 11 years) with atrial fibrillation (AF) and atrial flutter (AFL) who developed dissociation of conduction between the CS and posterior LA during spontaneous AF and AFL. In all patients, the LA and the CS were mapped using a 64-electrode basket catheter and a multipolar electrode catheter, respectively. The right atrium (RA) was mapped simultaneously using a 24-polar electrode catheter (7 patients) or a 64-electrode basket catheter (2 patients). Eight patients showed stable double potentials in CS recordings during AF (9 episodes) and AFL (3 episodes). During ongoing arrhythmias, the first row of potentials maintained a constant relationship with the RA activity, whereas the second row of potentials was discordant with the posterior wall of the LA in 7 patients and concordant in 2 patients. In 1 patient with counterclockwise AFL, CS activation was isolated from the posterior wall of the RA until it reached the distal portion of the CS, after which it entered the lateral region of the LA. In 1 patient, a macroreentrant LA tachycardia involving CS muscle was observed. Rapid atrial pacing from the proximal CS and extrastimuli produced longitudinal dissociation of CS activation in all patients. CONCLUSION: Conduction between the CS and posterior LA can be dissociated during spontaneous atrial arrhythmias and provocative proximal CS pacing.

Noncontact mapping-guided ablation of atrial flutter and enhanced-density mapping of the inferior vena caval-tricuspid annulus isthmus.

Three-dimensional visualization of cardiac activation has become important in providing further insights into pathophysiological mechanisms of arrhythmias and to increase the efficacy of catheter ablation. The noncontact mapping enables a single beat analysis in a reconstructed geometry of the cardiac chamber. The aim of the study was to describe three-dimensional activation patterns and inferior vena caval-tricuspid annulus (IVC-TA) isthmus conduction characteristics in patients with atrial flutter and the noncontact guidance of the radiofrequency ablation of this arrhythmia. In 34 patients with atrial flutter, the noncontact probe was deployed in the RA. The global three-dimensional activation and the isthmus conduction (enhanced density mapping) were delineated during ongoing a trial flutter and paced rhythms. Ablation was performed nonfluoroscopically based on reconstructed anatomy and conduction patterns. Noncontact mapping was compared and validated with conventional multielectrode technique. IVC-TA isthmus ablation was completed successfully in 33 (97%) of 34 patients. In one patient a lower loop reentry around the inferior vena cava was depicted as a mechanism of atrial flutter. In another patient with positive flutter waves in inferior leads, an activation pattern typical of counterclockwise flutter was demonstrated in propagation maps. During a follow-up of 15.9 +/- 5.9 months, two atrial flutter recurrences occurred (5.8%). A gap of the resumed conduction through the IVC-TA isthmus was delineated as a mechanism of recurrence and ablated with one and three radiofrequency applications. Noncontact mapping allows construction of the global activation patterns in typical and atypical atrial flutter. It enables the nonfluoroscopic guidance of atrial flutter ablation and a comprehensive evaluation of the ablation results.

Acute electrophysiologic effects and antifibrillatory actions of the long linear lesions in the right atrium in a sheep model.

UNLABELLED: Linear lesions (LL) represent an option for curing of atrial fibrillation (AF) with ablation techniques. METHODS AND RESULTS: In 11 sheep (w. 72+/-16 kg), LL were created with radiofrequency ablation in the lateral, posterior and septal walls of the right atrium (RA). AF was induced before and after LL with burst pacing. Mapping of the AF was performed with a 64-electrode basket catheter deployed in the RA. Quantitative analysis was performed with a custom-made software program. LL were confirmed histologically 7 to 10 days after the procedure. LL were transmural in 78% of their length. Stimulation thresholds and right atrial activation times were increased after LL compared to preablation values. Effective refractory periods of the RA were prolonged significantly in 7 out of 12 regions after generation of LL. Conduction velocities in the RA segments between LL were reduced in lateral, posterior and septal walls. During paced rhythms double potentials were recorded in all animals. AF could be induced in all animals of this model despite the presence of LL in the RA. AF episodes were significantly more regular after LL throughout the RA due to a significant reduction of the number of the wave fronts in the RA. During AF episodes, in the presence of LL, the RA was driven by wave fronts of left atrial origin entering the right side of the septum through interatrial connections. CONCLUSIONS: 1) LL profoundly affect electrophysiologic parameters of RA. 2) In the presence of LL, AF manifest a higher degree of regularity as compared to preablation episodes. 3) Dissociation between wave fronts of left atrial origin entering the RA through the interatrial connections is an important mechanism of the antifibrillatory action of the septal LL.

Left atrial fibrillation with regular right atrial activation and a single left-to-right electrical interatrial connection: multisite mapping of dissimilar atrial rhythms.

We report two patients who had isolated atrial fibrillation in the left atrium and regular activation of the entire right atrium. Mapping of the arrhythmia was performed using a 64-electrode basket catheter that was inserted intravenously and deployed in the right and left atria. Both patients manifested a single, stable interatrial electrical connection conducting in a left-to-right direction, consistent with Bachmann's bundle location. The right and left sides of the interatrial septum were activated discordantly, each reflecting activation characteristics of the respective atria. A filtering effect at the level of interatrial septum was demonstrated by calculating the fibrillation intervals on both sides of the operative interatrial connection. It was concluded that differences in activation of the left and right surfaces of the interatrial septum and preferential use and the filtering effect of the interatrial connections play a significant role in explaining the differences in activation patterns of the left and right atria in patients with atrial fibrillation.

Noncontact mapping-guided catheter ablation of atrial fibrillation associated with left atrial ectopy.

We report the use of a novel noncontact mapping system used to perform left atrial mapping and to guide radiofrequency ablation in two patients, each with atrial fibrillation (AF) triggered by left atrial ectopy. A noncontact multielectrode probe and ablation catheter were advanced into the left atrium through a transseptal puncture or a patent foramen ovale. Isopotential mapping delineated the focal origin at the ostium of the right lower pulmonary vein in one patient and close to the ostium of the left upper pulmonary vein in the other patient. The ablation catheter was guided to the target sites using a locator signal. The foci were ablated successfully in both patients. No recurrences of AF were observed during follow-up at 4 and 6 months, respectively.

The recording of monophasic action potentials with fractal-coated iridium electrodes in humans.

The present study was designed to evaluate the feasibility of the recording of monophasic action potentials (MAP) with fractal-coated iridium electrodes in a clinical setting. In 18 patients who underwent an electrophysiological study for various arrhythmias, we performed MAP recordings with both 1.3-mm2 and 6-mm2 tip surface area fractal-coated iridium and standard silver--silver chloride (Ag/AgCl) electrodes in the high right atrium and two ventricular positions. Amplitude and MAP duration at 90%, 50%, and 25% of repolarization were calculated during steady-state pacing at 600, 500, and 400 ms cycle lengths with extrastimuli application. Morphology comparisons of MAP signals recorded with both types of electrodes were performed by regression analysis using 5% of the repolarization segments of the MAP trajectory. Differences between MAP duration at 90%, 50%, and 25% of repolarization recorded with fractal-coated and Ag/AgCl electrodes were statistically insignificant. Amplitude values recorded with 6-mm2 tip electrodes were significantly smaller than those recorded with Ag/AgCl electrodes for all comparisons. During steady-state pacing, the correlation coefficients between Ag/AgCl and fractal-coated 1.3-mm2 and 6-mm2 tip electrodes were within the range of 0.93-0.999 and 0.87-0.999, respectively. The correlation of MAP amplitude and duration at 90%, 50%, and 25% of repolarization following the extrastimulus S2, recorded with both types of electrodes, was significantly weaker for right atrial recordings (r value range 0.78-0.92) as compared to ventricular recordings (r value range 0.92-0.99). The MAP sensing features of fractal-coated iridium and Ag/AgCl electrodes are comparable. The best results for recording of MAPs with fractal-coated electrodes can be achieved with small surface area tip electrodes.

The spatial dispersion of atrial refractoriness and atrial fibrillation vulnerability.

The local dispersion of conduction and refractoriness has been considered essential for induction of atrial arrhythmias. This study sought to determine whether a difference of refractoriness and vulnerability for induction of atrial fibrillation between trabeculated and smooth as well as high and low right atrium may contribute to initiation of atrial fibrillation in dogs. In 14 healthy mongrel dogs weighing 22.4 +/- 1 kg, closed-chest endocardial programmed stimulation was performed from four distinct right atrial sites. Atrial refractory periods and vulnerability for induction of atrial fibrillation or premature atrial complexes were determined during a basic cycle length of 400 and 300 ms and an increasing pacing current strength. For a pacing cycle length of 300 ms, atrial refractory periods were longer on the smooth, as compared to the trabeculated right atrium (102 +/- 25 vs. 97 +/- 17 ms, p < 0.05), whereas for a pacing cycle length of 400 ms, there was no significant difference. The duration of the vulnerability zone for induction of atrial fibrillation was longer on the smooth right atrium, for a cycle length of both 400 ms (40 +/- 30 vs. 31 +/- 22 ms; p < 0.05) and 300 ms (33 +/- 25 vs. 23 +/- 21 ms; p < 0. 01). When comparing high and low right atrium, refractory periods were longer on the the low right atrium, for a cycle length of both 400 ms (111 +/- 23 vs. 94 +/- 24 ms; p < 0.01) and 300 ms (104 +/- 20 vs. 96 +/- 23 ms; p < 0.01). For a pacing cycle length of 300 ms, the duration of the atrial fibrillation vulnerability zone was longer for the high, as compared to the low right atrium (34 +/- 22 vs. 22 +/- 22, p < 0.01). Seven dogs with easily inducible episodes of atrial fibrillation demonstrated significantly shorter refractory periods as compared to 7 non-vulnerable dogs, regardless of pacing site and current strength. In conclusion, significant differences in refractoriness and vulnerability for induction of atrial fibrillation can be observed in the area of the crista terminalis in healthy dogs. Thus, local anatomic factors may play a role in the initiation of atrial fibrillation.

Use of intracardiac echocardiography during electrophysiologic evaluation and therapy of atrial arrhythmias.

The relationship between endocardial anatomy and the substrate for a variety of atrial arrhythmia mechanisms is being increasingly appreciated. By using intravascular ultrasound imaging systems in the cardiac chambers, direct endocardial visualization can be provided. The advantages include: precise anatomic localization of the ablation catheter tip in relation to important endocardial structures that cannot be visualized with fluoroscopy; the ability to guide ablative procedures partly, or in some instances entirely, by anatomic landmarks; potential reduction in fluoroscopy time; evaluation of stability of catheter tip-tissue contact; confirmation of lesion formation and identification of lesion size and continuity; immediate identification of complications such as clot and pericardial effusion; assistance in the guidance of transseptal puncture; and as a research tool to help in understanding the critical role played by specific endocardial structures in atrial arrhythmogenesis. Presently, intracardiac echocardiography (ICE) is useful as an adjunct in guiding mapping and ablation of focal atrial tachycardia. In our laboratory, it has significant advantage in modification or ablation of sinus node function in patients with inappropriate sinus tachycardia syndrome. Its use in helping to guide ablation of atrial fibrillation remains an exciting, but largely unproved, hypothesis. Better technology will be required if widespread clinical use of ICE is to occur.

Organized activation during atrial fibrillation in man: endocardial and electrocardiographic manifestations.

INTRODUCTION: Atrial fibrillation is not entirely random, but little is known about the spatiotemporal endocardial organization and its surface ECG manifestations. METHODS AND RESULTS: In 16 patients with atrial fibrillation (chronic, n = 14), endocardial mapping of the trabeculated, the posteroseptal smooth right atrium, and the coronary sinus was performed using multipolar catheters. The surface ECG was analyzed by determining "fibrillation wave" (F wave) amplitude, rate, and polarity. During 50 minutes of atrial fibrillation, an organized activation was present 72% +/- 32% of the analyzed time on the trabeculated, 19% +/- 15% on the smooth right atrium (P < 0.01), and 51% +/- 33% along the coronary sinus (P < 0.05). The direction of organized activation was craniocaudal in 72% +/- 16%, caudocranial in 10% +/- 9% (P < 0.01), and indeterminable in 18% +/- 11%. The mean surface F wave amplitude in lead V1 was 0.128 +/- 0.06 mV during 28 seconds of atrial fibrillation with a craniocaudal direction of activation and 0.065 +/- 0.02 mV during a disorganized activation (P < 0.01). A stable relation between surface F waves and organized trabeculated right atrial activation was observed, and the mean F wave cycle length (190 +/- 27 msec) was highly comparable to the simultaneously measured endocardial cycle length (191 +/- 27 msec, correlation coefficient 0.97). F wave polarity in V1 was positive in 12 of 14 patients during craniocaudal and negative in 11 of 14 patients during caudocranial right atrial free-wall activation. CONCLUSION: An organized activation during atrial fibrillation with a predominant craniocaudal direction on the trabeculated right atrium is frequently present and influences the appearance of "coarse" or "fine" atrial fibrillation as well as F wave polarity on the surface ECG.

"Cristal tachycardias": origin of right atrial tachycardias from the crista terminalis identified by intracardiac echocardiography.

OBJECTIVES: We sought to use intracardiac echocardiography (ICE) to identify the anatomic origin of focal right atrial tachycardias and to define their relation with the crista terminalis (CT). BACKGROUND: Previous studies using ICE during mapping of atrial flutter and inappropriate sinus tachycardia have demonstrated an important relation between endocardial anatomy and electrophysiologic events. Recent studies have suggested that right atrial tachycardias may also have a characteristic anatomic distribution. METHODS: Twenty-three consecutive patients with 27 right atrial tachycardias were included in the study. ICE was used to facilitate activation mapping in relation to endocardial structures. A 20-pole catheter was positioned along the CT under ICE guidance. ICE was also used to assist in guiding detailed mapping with the ablation catheter in the right atrium. RESULTS: Of 27 focal right atrial tachycardias, 18 (67%, 95% confidence interval [CI] 46% to 83%) were on the CT (2 high medial, 8 high lateral, 6 mid and 2 low). ICE identified the location of the tip of the ablation catheter in immediate relation to the CT in all 18 cases. The 20-pole mapping catheter together with echocardiographic visualization of the CT provided a guide to the site of tachycardia origin along this structure. Radiofrequency ablation was successful in 26 (96%) of 27 (95% CI 81% to 100%) right atrial tachycardias. CONCLUSIONS: This study demonstrates that approximately two thirds of focal right atrial tachycardias occurring in the absence of structural heart disease will arise along the CT. Recognition of this common distribution may potentially facilitate mapping and ablation of these tachycardias.

Relationship between atrial fibrillation and typical atrial flutter in humans: activation sequence changes during spontaneous conversion.

BACKGROUND: A transitional rhythm precedes the spontaneous onset of atrial flutter in an animal model, but few data are available in man. METHODS AND RESULTS: In 10 patients, 16 episodes of atrial fibrillation (166+/-236 seconds) converting into atrial flutter during electrophysiological evaluation were analyzed. A 20-pole catheter was used for mapping the right atrial free wall. Preceding the conversion was a characteristic sequence of events: (1) a gradual increase in atrial fibrillation cycle length (150+/-25 ms after onset, 166+/-28 ms before conversion, P<.01); (2) an electrically silent period (267+/-45 ms); (3) "organized atrial fibrillation" (cycle length, 184+/-24 ms) with the same right atrial free wall activation direction as during atrial flutter; (4) another delay on the lateral right atrium (283+/-52 ms); and (5) typical atrial flutter (cycle length, 245+/-38 ms). The coronary sinus generally had a different rate than the right atrial free wall until the beat that initiated flutter, when right atrium and coronary sinus were activated in sequence. During 1313 seconds of fibrillation, there were 171 episodes of "organized atrial fibrillation." An additional activation delay at least 30 ms longer than the mean organized atrial fibrillation cycle length was sensitive (100%) and specific (99%) for impending organization into atrial flutter. During organized atrial fibrillation, right atrial free wall activation was craniocaudal in 70% and caudocranial in 30%, which may explain why counterclockwise flutter is a more common clinical rhythm than clockwise flutter. Atrial flutter never degenerated into fibrillation, even after adenosine infusion. CONCLUSIONS: Anatomic barriers, along with statistical properties of conduction and refractoriness during atrial fibrillation, may explain the remarkably stereotypical pattern of endocardial activation during the initiation of atrial flutter via fibrillation and the rarity of degeneration of flutter to fibrillation once it stabilizes.

Use of intracardiac echocardiography in interventional electrophysiology.

Intracardiac echocardiography is emerging as a potentially useful tool during RF ablation procedures. There are a number of potential benefits of direct endocardial visualization during RF ablation including: (1) precise anatomical localization of the ablation catheter tip in relation to important endocardial structures, which cannot be visualized with fluoroscopy; (2) reduction in fluoroscopy time; (3) evaluation of catheter tip tissue contact; (4) confirmation of lesion formation and identification of lesion size and continuity; (5) immediate identification of complications; and (6) as a research tool to help in understanding the critical role played by specific endocardial structures in arrhythmogenesis. This article will review existing data and speculate as to possible future roles for intracardiac echocardiography in interventional electrophysiology.

Potential role of 'hybrid therapy' for atrial fibrillation.

Atrial fibrillation is the most common sustained arrhythmia in clinical practice. Several new non-pharmacological technologies are emerging which may offer hope for effective therapy and quality of life improvement of patients with atrial fibrillation. While both catheter-based atrial segmentation and implanted atrial defibrillators have the potential to revolutionize the treatment of patients with atrial fibrillation, both are also associated with the potential for significant limitations. Catheter ablation with the goal of curing atrial fibrillation may be a lengthy procedure and if left atrial lesions are required there is the potential for complications. As regards implanted atrial defibrillators an important question is whether many patients will tolerate the discomfort associated with energy levels required to restore sinus rhythm. The concept of 'hybrid therapy' is that in a given patient a combination of modalities might be used so as to achieve a synergistic effect, with each technology improving the efficacy of the other. For example, the presence of a more 'organized' pattern of fibrillation implies a lower defibrillation threshold. Data in a canine model of atrial fibrillation suggests that linear lesions in the right atrium alone may organize the atrial fibrillation in both atria and in so doing lower the atrial defibrillation threshold. Hybrid therapy may also employ drugs and pacing in combination with ablative lesions and an implanted atrial defibrillator.

Regional entrainment of atrial fibrillation in man.

INTRODUCTION: The feasibility of entrainment of macroreentrant atrial arrhythmias such as atrial flutter is well documented. Recently, it has been shown that regional entrainment of atrial fibrillation is feasible in dogs. METHODS AND RESULTS: Three patients with chronic atrial fibrillation underwent electrophysiologic evaluation with attempted entrainment of atrial fibrillation prior to successful endocardial atrial defibrillation. A 16-pole catheter was positioned in the trabeculated right atrium, and in two patients a multipolar catheter was positioned along the septum. In addition, two large surface area defibrillation catheters were placed, one in the lateral right atrium and one in the coronary sinus. Regional entrainment was attempted in the right atrium and from the catheter in the coronary sinus. Entrainment was achieved in the right atrium in all three patients over a cycle length range of 28, 17, and 13 msec, respectively, and over a radius of atrial tissue of at least 2.8 cm. Regional entrainment was demonstrated from the coronary sinus in one patient during simultaneous right atrial entrainment. Termination of atrial fibrillation during entrainment was not observed. CONCLUSION: Regional entrainment of chronic atrial fibrillation is feasible in humans.