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PubMed1992

Electrophysiologic study of dysrhythmias after atrial operations in dogs.

Experiments were conducted with 159 dogs to investigate the mechanism of persistent dysrhythmias clinically encountered after atrial-level operations. Those found after incisions to the internodal pathways (INPs) of the right atrium were analyzed using cardiac mapping in an anesthetized or extracorporeally perfused state. Longitudinal incisions of the posterior INP often allowed inducible sustained atrial flutter, with circus movement of excitation around the right atrium near the tricuspid orfice. Sustained atrial flutter thus produced was modified in cycle length by coexisting division of the middle INP but inhibited by that of the anterior INP. Its incidence increased at chronic stage, with marked cicatricial changes. The disrupted anterior INP markedly prolonged conduction time to the atrioventricular node and A-H interval compared with the other disruptions. Persistent atrioventricular junctional rhythm developed in about 50% of the animals after disruption of all three INPs or anterior and posterior INPs; division of the anterior INP was the common potent factor, although no single blocked INP produced persistent junctional rhythm. Our results support the "summation theory." The incidence of junctional rhythm and hypoxia of the sinoatrial node (flow rate of less than 10 mL.100 g-1.min-1) were markedly enhanced by coexisting blockade of atrial feeding arteries in addition to division of the anterior INP. In conclusion, massive posterior INP disruption is a potent anatomic substrate in producing sustained atrial flutter, middle INP division a modifier, and anterior INP division an inhibitor. Division of the anterior INP is a potent anatomic substrate in producing junctional rhythm, and hypoxia involving the sinoatrial node reacts as its synergic factor.

Animals↗
PubMed1998

Use of adenosine in patients hospitalized in a university medical center.

PURPOSE: Adenosine is a useful agent for the diagnosis and termination of tachycardias. The purpose of this study was to identify the rhythms for which adenosine is prescribed in hospitalized adults and to identify the reasons for its misuse. PATIENTS AND METHODS: Data were collected from the medical records of 100 patients who received intravenous adenosine while hospitalized at a university medical center. The characteristics of the patients, rhythms treated with adenosine, and dosages of adenosine were analyzed. In addition, internal medicine house officers were administered a questionnaire referring to an electrocardiogram of atrial fibrillation with a rapid ventricular response. RESULTS: The arrhythmias for which adenosine was administered consisted of regular, narrow-QRS complex tachycardias in 33% of patients; atrial fibrillation in 32% of patients; regular, wide-QRS complex tachycardias in 23% of patients; atrial flutter in 10% of patients, and multifocal atrial tachycardia in 2% of patients. The mean (+/-SD) number of doses of adenosine given to each patient was 1.6+/-0.8, and the mean dose of adenosine was 7.8+/-2.8 mg. Internal medicine house officers prescribed 70% of the doses of adenosine and were as likely to use it for patients with atrial fibrillation as were surgical house officers. There was a 2% incidence of proarrhythmia, including asystole and polymorphic ventricular tachycardia. Thirty-one percent of the 100 house officers in our survey misdiagnosed a 12-lead electrocardiogram of rapid atrial fibrillation as paroxysmal supraventricular tachycardia, suggesting that adenosine may have been misused for atrial fibrillation because of errors in rhythm diagnosis. Only 5% of those who correctly diagnosed atrial fibrillation also answered that adenosine would be likely to terminate the arrhythmia, suggesting that a misunderstanding that adenosine terminates atrial fibrillation is not a common reason for its misuse. CONCLUSIONS: Approximately 40% of hospitalized adults who are treated with adenosine receive the medication unnecessarily for atrial fibrillation or atrial flutter, and this misuse results in unnecessary expenses and risks of adverse effects. The primary reason that adenosine is misused for atrial fibrillation is the inability to recognize that rhythm on an electrocardiogram. House officers need additional education on the electrocardiographic recognition of atrial fibrillation.

Adenosine↗
PubMed2004

Bipolar radiofrequency to ablate atrial fibrillation in patients undergoing mitral valve surgery.

BACKGROUND: Atrial fibrillation (AF) affects 30% to 50% of patients undergoing mitral valve surgery. The optimum treatment of AF in these patients is unclear. The purpose of this study was to describe initial clinical experience using a bipolar radiofrequency clamp to facilitate AF ablation in patients undergoing mitral valve surgery. METHODS: From November 2001 through March 2003 a bipolar radiofrequency clamp was used to facilitate AF ablation in 108 patients undergoing mitral valve surgery. Preoperative AF was paroxysmal in 25%, persistent in 26%, and permanent in 49% of the patients. All patients underwent bilateral pulmonary vein isolation performed with the bipolar radiofrequency clamp and excision or exclusion of the left atrial appendage. Most patients had connecting lesions between the right and left pulmonary veins and between the left atrial appendage and the left pulmonary veins. Novel statistical methods were used to create a plot of the prevalence of AF versus time after surgery. RESULTS: Mean time required for AF ablation was 17+/-4 minutes (range, 9-28 minutes). All patients left the operating room with sinus rhythm or with atrial or atrioventricular pacing for an underlying nodal rhythm. Perioperative AF was common, affecting 64% of patients. At discharge, 33% of patients were in AF or atrial flutter. By 3 months postoperatively, the predicted prevalence of AF or atrial flutter was 15%. There were no device-related complications. CONCLUSIONS: Bipolar radiofrequency facilitates rapid and safe AF ablation in patients with mitral valve disease. Perioperative AF is common and should be treated aggressively. By 3 months postoperatively, 85% of patients are free of AF or atrial flutter. Continued follow-up is necessary to document late results of this strategy.

Absorptiometry, Photon↗
PubMed1994

Contraction-excitation feedback in atrial reentry: role of velocity of mechanical stretch.

To determine the effects of atrial stretch on atrial flutter, we analyzed variations in atrial flutter cycle length (CL) caused by ventricular contraction in five dogs with artificially induced atrioventricular block. In contrast to absence of variations in CL during sustained ventricular asystole, atrial stretch by ventricular contraction consistently produced phasic variations in CL. The variations were not confined to any specific atrial sites, but depended on the time of ventricular contraction relative to atrial activation phase. The phase-response curve of the variations was closely related to that of the velocity of changes in the atrial pressure with no time lags, but not to that of the atrial pressure itself. Pharmacological denervation did not abolish the variations. Conventional electrophysiological study revealed greater changes in intra-atrial activation time by atrial stretch at a short pacing cycle length than at a longer one, suggestive of changes in repolarization by mechanical stretch. In conclusion, atrial stretch caused by ventricular contraction produces phasic variations in CL, the extent of which depends on the velocity of the mechanical stretch of atrial muscles.

Animals↗
PubMed1985

Autoregressive modeling and power spectral estimate of R-R interval time series in arrhythmic patients.

The signal constituted by the successive R-R intervals in the ECG tracing carries important information about the control mechanisms of heart rate. The present paper describes advanced methods of parameter extraction from the R-R duration time series which use autoregressive (AR) modeling and power spectral estimates applied to patients in the MIT-BIH arrhythmia data base. The described methodologies enhance information which characterize the most common rhythm disturbances (A-V block, bigeminy/trigeminy, atrial and ventricular flutter, atrial fibrillation, etc.). Important applications of such methods are in the area of the pathophysiological comprehension of cardiac rhythm control mechanisms in the research side and the classification of abnormal rhythms as well in the clinical side. A few examples from the data base are illustrated which show interesting properties of signal processing and classification in respect to the more traditional methods.

Arrhythmias, Cardiac↗
PubMed1998

A testing system for implantable cardioverter defibrillators.

Implantable cardioverter defibrillator (ICD) testing during the implantation process is important in order to avoid repeated induction of arrhythmias, which extends the implantation procedure and poses a risk to the patient. Hence, an in vitro testing system has been designed to assist optimal device programming and avoid repetitive inductions. The system includes a high-speed computer with A/D and D/A subsystems. Software has been designed to eliminate repeated arrhythmia induction by real-time capture and storage of the electrogram. Subsequently, the electrogram can be replayed into ICD software simulators at a variety of settings to determine candidate programming parameters. To validate the simulation system, signals were fed directly to an ICD via an attenuator. Output event markers were captured simultaneously with the signal into a digital file to assess the device performance. Four ventricular tachycardia (VT), three supraventricular tachycardia, (SVT), three atrial flutter (AFL), three atrial fibrillation (AF), and ten ventricular fibrillation (VF) passages were used to verify the system. Test settings were 110-160 beats/min for detection rate and 5 seconds for shock delay. The simulator and ICD detected the episodes for all passages at the 110 beats/min setting. For the setting of 160 beats/min, two VTs, two SVTs, three AFLs, and nine VFs were detected by the device, but no Afb triggered a shock. The simulator detection criteria were met by two VTs, two SVTs, three AFLs, ten VFs, and one AF. The mean detection time was 6,869-7,330 ms (110-160 beats/min) for the simulator and 7,840-8,170 ms for device. Comparison of results showed general agreement between simulator and device. Results demonstrated that device behavior at a variety of settings can be elucidated by the simulator for selection of optimal performance. The automated system can also function as a test bed for evaluation of new algorithms during device development and design.

Algorithms↗
PubMed1997

Ventricular fibrillation and sudden death after radiofrequency catheter ablation of the atrioventricular junction.

Two hundred thirty-five patients underwent RF catheter ablation of AV conduction for symptomatic drug refractory AF (84%), atrial flutter (9%), and atrial tachycardia (7%). In the first 100 patients, postablation pacing was not prospectively set at any specific rate and was always < or = 70 beats/min. In the next 135 patients, postablation pacing was prospectively set at 90 beats/min for 1-3 months. Six of the first 100 patients (6%) had VF or sudden death after the RF procedure and none (0%) of the next 135 patients did (P < 0.05). One of the six patients had recurrent VF 4 days after the ablation. Five patients were successfully resuscitated and one patient died. There were no statistically significant differences between patients with and without (aborted) sudden death or between the first 100 and the next 135 patients with respect to age, sex, underlying heart disease, EF, number of RF applications, or left-or right-sided approach of the procedure. VF mostly occurred during episodes of slow ventricular escape rhythms or during slow ventricular pacing. We conclude that malignant ventricular arrhythmias and sudden death are possible complications of RF ablation of the AV function. The mechanism of these complications could have a bradycardia dependent nature and it seems that the occurrence of malignant arrhythmias can be prevented by temporarily pacing the heart at relatively fast rates immediately after ablation.

Aged↗
PubMed2006

Mechanisms of atrial tachyarrhythmias following surgical atrial fibrillation ablation.

INTRODUCTION: Typical and atypical atrial flutters (AFLs) and atrial tachycardias (ATs) have been reported in patients with prior surgical atrial fibrillation ablation. The underlying mechanisms for this group of atrial tachyarrhythmias have not been well characterized and the efficacy of catheter ablation in their treatment is unknown. METHODS AND RESULTS: Twenty patients (6 females) with a surface ECG diagnosis of AFL or AT following surgical atrial fibrillation ablation underwent 26 electrophysiology studies. Patients manifesting sustained, organized, and beat-by-beat reproducible atrial electrical activity underwent complete right and left atrial catheter mapping and catheter ablation. One patient had no inducible tachyarrhythmia, while 5 patients had nonmappable arrhythmias. Nineteen of the 31 potentially mappable atrial tachyarrhythmias were completely characterized in 14 patients. The underlying mechanisms were macro-reentrant left AFL (n = 9), focal left AT (n = 3), typical right AFL (n = 6), and atypical right AFL (n = 1). Of the 19 completely characterized atrial arrhythmias, catheter ablation was performed for 18, and the procedure was successful for 13 of these. After a mean follow-up of 15 +/- 10 months, 15 of 20 patients (75%) were in sinus rhythm including 10 of 13 patients (77%) with AT/flutter ablation. Ten patients, including 6 following ablation, were maintaining sinus rhythm without antiarrhythmic medications. CONCLUSIONS: Patients with an ECG diagnosis of AFL or AT following surgical atrial fibrillation ablation may have multiple tachycardia mechanisms with the right or left atrium as the site of origin. Many of these rhythms may resolve with further maturation of surgical atrial fibrillation ablation (SAFA) lesions or be treatable with antiarrhythmic medication. However, persistent tachyarrhythmias can often be treated successfully with catheter mapping and ablation.

Atrial Fibrillation↗
PubMed2001

Temporary transvenous atrial pacing in horses: threshold determination.

The purpose of this study was to perform temporary atrial pacing and to determine the atrial strength-duration (S-D) curve which displays the minimal pulse intensity necessary to achieve atrial capture. In 7 horses, atrial pacing was applied using a temporary pacing catheter and a pacemaker as electrical pulse generator. Using the stimulus reduction method, 3 approaches for atrial threshold determination were used. With the fixed pulse width method, at several pulse widths, the corresponding minimal amplitudes to achieve capture were determined, describing an S-D curve. With the fixed amplitude method, the corresponding threshold pulse widths were determined at several fixed amplitudes. The third method proved to be the best and was a combination of both aforementioned methods to determine 2 points of the S-D curve. From these 2 points the whole S-D curve was calculated using a mathematical equation. Temporary pacing can be used to terminate atrial flutter, to induce atrial arrhythmias or to obtain more information about the electrophysiological properties of the heart, such as the atrial refractory period, atrial vulnerability and atrioventricular conduction.

Animals↗
PubMed1984

The use of intravenous disopyramide for the conversion of supraventricular tachyarrhythmias.

A study of the efficacy of intravenous disopyramide in the conversion of supraventricular tachyarrhythmias to sinus rhythm was undertaken in a group of 23 patients with a variety of cardiological diagnoses. An intravenous bolus (2 mg/kg) followed, where appropriate, by an infusion (0.4 mg/kg) resulted in an overall conversion rate of 63% (43% in atrial fibrillation, 50% in atrial flutter, 89% in atrial tachycardias). Serious cardiotoxic side effects occurred in 15%. The study shows that such a regime is useful in a selected group of patients provided certain precautions are observed.

Adolescent↗
PubMed1982

[Atrial fibrillation and flutter in children].

Flutter and atrial fibrillation are extremely rare in children. Their aetiology and pathogenesis vary from one case to another. The clinical picture may be influenced by a number of factors (age, duration of the arrhythmia, ventricular frequency), while the natural history is often related to the presence or otherwise of associated cardiopathies. There is no standard treatment. Digitalis with or without other antiarrhythmic drugs is often employed as the drug of choice, though its place may be taken by ayodarone or verapamil.

Anti-Arrhythmia Agents↗
PubMed1980

Double pacemaker implantation.

A demand-type pacemaker and an inductive radiofrequency atrial pacemaker were implanted in four patients presenting with sick sinus syndrome, bradycardia-tachycardia syndrome, Wolff-Parkinson-White syndrome, atrial flutter, and paroxysmal atrial tachycardia, and in one patient having ventricular tachycardia with ectopic ventricular beats. Our follow-up of these patients showed that double implantation is feasible and effective in controlling different types of arrhythmia occurring in the same patient.

Aged↗
PubMed1993

Pathophysiology of atrial fibrillation: current aspects.

The existence of independent wandering wavelets as the basis for fibrillation was postulated by Moe and coworkers in their multiple wavelet theory and was later confirmed in both animal and human atria. The process of initiation of fibrillation however is less clear but probably depends on a) an increase in inhomogeneity in conduction and b) a decrease in the length of the excitation wave. Recently a method has been introduced to quantify inhomogeneity in conduction in isolated rabbit atria. Already during slow basic rhythm, inhomogeneties based on structural inhomogeneities could be identified. Premature activation increased conduction inhomogeneities in the neighborhood of the premature stimuli while rapid pacing induced the highest degree of inhomogeneity throughout the myocardium. The role of the second prerequisite for atrial fibrillation, the length of the excitation wave, has also recently been studied in chronic instrumented conscious dogs. Conduction velocities, refractory periods and wavelengths were measured during the administration of a variety of drugs and correlated with the induction of atrial arrhythmias. The predictive power of the wavelength was much higher than for refractory period or conduction velocity alone. Upon gradual reduction of the wavelength, first rapid repetitive responses, then atrial flutter, and finally atrial fibrillation was observed. In summary, at least two factors are of importance for the initiation of atrial fibrillation: inhomogeneity in conduction and a short excitation wave. Other factors, such as abnormalities in atrial structure and function will certainly modify the contribution of these factors to an extent that remains to be investigated.

Animals↗
PubMed1994

[Value of cibenzoline in the preventive treatment of recurrent atrial arrhythmia].

Cibenzoline is a Vaughan-Williams class I anti-arrhythmic with properties intermediate between subclasses IA and IC which limit the incidence of proarrhythmic effects. These specific properties of the drug facilitate the prescription of cibenzoline in cardiology, particularly for the prevention of recurrent atrial arrhythmia: fibrillation, flutter, atrial tachycardia. This study demonstrates that cibenzoline is effective in these indications, since only 23% of the patients had relapsed after 6 months. This efficacy, combined with the good tolerance of the treatment, makes it possible to recommend the prescription of cibenzoline as a first-line treatment for the prevention of atrial arrhythmia. It represents an effective and safe option.

Adrenergic beta-Antagonists↗
PubMed1987

Adenosine: a clinical experience and comparison with verapamil for the termination of supraventricular tachycardias.

The efficacy and side-effects of adenosine for treatment of supraventricular arrhythmias were compared to verapamil therapy in patients presenting to the emergency room. Clinical variables and the time interval from the initiation of treatment to the termination of the supraventricular tachycardia, as well as the time from the initial effective dose of medication to the termination of supraventricular tachycardia were compared for adenosine and verapamil. Adenosine was given to a total of 44 patients, 16 patients in the electrophysiology laboratory, and 28 patients in the emergency room for evaluation and termination of their tachycardia. In the electrophysiology laboratory, 7 patients had AV node reentry, 5 had Wolff-Parkinson-White syndrome, 2 of whom had atrial flutter and fibrillation but no bypass tract reentry, 1 had concealed bypass tract reentry, 1 had Lown-Ganong-Levine syndrome, 1 had intraatrial reentry, and 1 had an automatic atrial tachycardia. Twenty-five patients received adenosine in the emergency room and 3 patients in the hospital for 31 episodes of supraventricular arrhythmias. In the emergency room, 11 patients had supraventricular tachycardia due to AV node reentry, 3 had Wolff-Parkinson-White syndrome, 6 had atrial flutter or intra-atrial re-entry, 2 had ventricular tachycardia, and 3 had sinus tachycardia. In the hospital, 2 patients had atrial flutter and one had sinus tachycardia. The group of 14 patients with supraventricular tachycardia due to Wolff-Parkinson-White syndrome or AV node reentry presenting in the emergency room were compared in a retrospective manner to the patients treated with standard verapamil therapy with respect to time from initiation of therapy to termination of supraventricular tachycardia and time from effective dose of medication to the termination of supraventricular tachycardia, as well as side-effects. There was no significant difference between the two groups with respect to clinical variables. Adenosine converted 18 of 18 episodes of supraventricular tachycardia in 14 patients 24.6 +/- 9.6 seconds from the administration of the effective dose (0.104 +/- 0.024 mg/kg) and a mean of 4.4 +/- 2.0 minutes from the initiation of therapy. Verapamil converted 29 of 32 episodes of supraventricular tachycardia in 20 patients, 10.9 +/- 7 minutes from the administration of the effective dose, and a mean of 16.8 +/- 20 minutes from the initiation of therapy using a mean of 8.4 +/- 3.4 mg of IV verapamil.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine↗
PubMed1990

Antiarrhythmic activity and unbound concentrations of disopyramide enantiomers in patients.

Six patients with reproducible inducible atrial flutter randomly received, in double-blinded fashion, 77 mg of S(+)-disopyramide and R(-)-disopyramide over 20 min by intravenous infusion on two occasions separated by at least 24 h. The S(+) enantiomer prevented the inducibility of atrial flutter in five of the six patients; atrial flutter was inducible following R(-) enantiomer administration in all six patients (p less than 0.05). The mean (+/- SD) antiarrhythmic unbound serum concentration range of S(+)-disopyramide was 0.55 +/- 0.31-0.90 +/- 0.81 mg/L. The binding of disopyramide was stereoselective: the mean unbound fractions of S(+)- and R(-)-disopyramide were 0.207 +/- 0.119 and 0.338 +/- 0.214 (p less than 0.05). Binding of the individual enantiomers in some patients was markedly concentration dependent. The data suggest that the antiarrhythmic activity associated with racemic disopyramide resides in the S(+) enantiomer.

Anti-Arrhythmia Agents↗
PubMed2000

Automatic atrial tachyarrhythmia detection from intracardiac electrograms.

BACKGROUND: Automatic atrial tachyarrhythmia recognition is crucial in order to allow a correct switching-mode function of dual-chamber pacemakers and to avoid inappropriate shocks of ventricular implantable cardioverter-defibrillators. In this paper we considered three algorithms suitable for implantable devices. The first was based on the atrial cycle length; the others analyze different morphologic characteristics of atrial signals. METHODS: Intracardiac bipolar electrogram recordings were obtained from the high right atrium during electrophysiological study. Twenty patients were considered, some of them presenting with different types of cardiac rhythm at different intervals of the study. Cardiac rhythms were divided into three groups: sinus rhythm consisting of 2,196 s obtained from 12 subjects, atrial fibrillation consisting of 771 s obtained from 7 subjects, and atrial flutter consisting of 1,793 s obtained from 7 subjects. The automatic detection was performed on each electrogram segment lasting 1 or 4 s. Atrial segments were separated into two subgroups: the first for the training of the algorithm and the second for testing and validation of results. We considered two types of statistical analysis: comparison between pairs of rhythm (paired classification), and classification among the three different groups (direct classification). RESULTS: The combination of the cycle length algorithm with a morphological method achieved the best performance for both statistical analyses. Paired classification resulted in the following: atrial fibrillation vs sinus rhythm was detected with no error; atrial flutter vs sinus rhythm with a total accuracy of 99.3% (sensitivity 99.4%, specificity 99.2%); atrial fibrillation vs atrial flutter with a total accuracy of 99.1% (sensitivity 98.5%, specificity 99.4%). The total accuracy achieved for the direct classification was 98.6% (average sensitivity 98.5%, specificity 98.8%). CONCLUSIONS: Our results support the association of algorithms for future enhancement of atrial tachyarrhythmia detection in dual-chamber devices, thanks to the limited computational effort.

Algorithms↗