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PubMedDate not supplied

New antiarrhythmic drugs in pediatric use: amiodarone.

Amiodarone, a class III antiarrhythmic agent, prolongs action potential duration and refractoriness of all cardiac structures. The drug is more rapidly metabolized in pediatric patients than in adults, but its kinetics are still unique compared with other drugs. Due to the unusual pharmacokinetic characteristics of amiodarone, treatment has to be started by administering loading doses, and there is a significant delay both in the achievement of the full anti-arrhythmic effect and in the development of side effects. Amiodarone is a highly effective agent in pediatric patients with automatic and reentrant supraventricular tachycardia as well as in refractory atrial flutter. Efficacy in ventricular tachycardia has been shown to be variable depending on the underlying anatomical substrate. The incidence of side effects is lower than that observed in adult studies with similar duration of therapy but their incidence is still significant. Amiodarone treatment is associated with a significant risk of proarrhythmic effects, requiring hospitalization of the patient during the loading period.

Amiodarone↗
PubMed2002

Catheter ablation for cardiac arrhythmias.

The clinical introduction of catheter ablation in 1981 revolutionized the treatment of cardiac arrhythmias. Implementation of radiofrequency as an alternative energy source, with the advantages of higher selectivity and less collateral damage, provided an expansion of catheter ablation therapy. Today the majority of arrhythmias can potentially be cured with catheter ablation therapy. The safety and efficacy of catheter ablation for treatment of AV nodal reentrant tachycardia, accessory pathway arrhythmias, focal atrial tachycardia, atrial flutter and idiopathic ventricular tachycardia, is well established. Catheter ablation for treatment of atrial fibrillation and ventricular tachycardia secondary to structural heart disease, remains an area of active research. In this article we will review the current state of knowledge about the technique, indications, and results of catheter ablation for the treatment of cardiac arrhythmias.

Animals↗
PubMed1992

[Effects of bonnecor on transmembrane potentials of cardiomyocytes of the ventricular contractile myocardium of the intact heart and ventricular fibrillation].

The microelectrode technique has shown that bonnecor given in a dose of as many as 2 mg/kg increases the action potential amplitude, but when its dose is increased up to 3 mg/kg, the agent decreases the action potential amplitude of ventricular cardiomyocytes in the guinea-pig, the resting potential remaining steady. Administration of bonnecor prevents ventricular fibrillation after aconitine application and provokes ventricular fibrillation and flutter when the focus of ectopic automatism is formed.

Animals↗
PubMed1994

Innovations in pulse generators and lead systems: balancing complexity with clinical benefit and long-term results.

Technologic development of implantable cardioverter defibrillators (ICDs) is now in an exponential growth phase, and many new concepts are being examined. Major innovations have occurred in pulse generators and in lead systems. This may increase ICD use for primary and secondary prevention of sudden cardiac death. Pulse generators now include hybrid pacemaker-defibrillators. Clinical data suggest a need for demand pacing in primary and secondary prevention applications, with antitachycardia pacing being most valuable in the latter group. Atrial leads will allow dual chamber sensing, pacing, and defibrillation. Low energy cardioversion with biphasic shocks can enhance shock efficacy in rapid monomorphic ventricular tachycardia and flutter. Modifications of lead design, biphasic shock waveforms, and optimal thoracic electrode location in axillary or pectoral regions will permit lower energy defibrillation and smaller pulse generators with lower maximum energy outputs of < or = 25 joules. Dual chamber sensing will improve detection of atrial flutter or fibrillation. Minimum data storage requirements for tachycardia events in ICDs still need to be defined. Intracardiac electrogram analysis is still in evolution, and better analytic methods are awaited. Lead system development is likely to support generic pacing and defibrillation catheter electrodes for atrial and ventricular application. Advances in thoracic electrode design are in progress, and a variety of intercostal electrodes are being tested. Improvements in lead design with further impact on defibrillation energy requirements have the potential to permit generator miniaturization. Significant technologic improvements in ICD devices are imminent and should improve clinical results, patient safety, and quality of life.

Algorithms↗
PubMed1996

[Pharmacologic maintenance of sinusal rhythm and/or control of the ventricular response in patients with atrial fibrillation or flutter].

Atrial fibrillation is the most common cardiac arrhythmia and is usually responsible for symptoms requiring some treatment. Antiarrhythmic drugs are the first choice therapy, but their potential risks are significant. This together with their limited efficacy restricts their use. Antiarrhythmic drug use should be tailored; mainly according to the underlying heart disease. When reversion to sinus rhythm is not eligible, the adequate control of ventricular rate and the reduction of embolic risk are the therapeutic goals. Atrial flutter shows different behaviour regarding the very limited efficacy of antiarrhythmic drugs for reversion to and maintenance in sinus rhythm.

Anti-Arrhythmia Agents↗
PubMed2004

Wolff-Parkinson-White syndrome: essentials for the primary care nurse practitioner.

PURPOSE: To provide nurse practitioners with a basic understanding of the pathophysiology, clinical characteristics, diagnostic methods, and management of Wolff-Parkinson-White (WPW) syndrome. DATA SOURCES: Selected research and clinical articles. CONCLUSIONS: WPW syndrome is the most common form of ventricular preexcitation. The ventricular myocardium is activated earlier than expected by an accessory conduction pathway that allows a direct electrical connection between the atria and ventricles. Although many patients remain asymptomatic throughout their lives, approximately half of the patients with WPW syndrome experience symptoms secondary to tachyarrhythmias, such as paroxysmal supraventricular tachycardia, atrial fibrillation, atrial flutter, and, rarely, ventricular fibrillation and sudden death. Symptoms include palpitations, dizziness, syncope, and dyspnea. Diagnosis is usually made by electrocardiogram findings, but further testing may be warranted to confirm the diagnosis. IMPLICATIONS FOR PRACTICE: A thorough patient history and physical examination can aid the practitioner in identifying patients who may have WPW syndrome. With appropriate referral, treatment, and patient education, patients with WPW syndrome can expect to have a normal life expectancy and good quality of life.

Cardiac Pacing, Artificial↗
PubMed1994

Sensitivity and specificity of a dual-chamber arrhythmia recognition algorithm for implantable devices.

Present ventricular rate-based arrhythmia detection algorithms lack specificity. Using a training set of 109 endocardial electrogram recordings, a sensitive and specific dual-chamber arrhythmia recognition algorithm has been developed. The algorithm uses atrial and ventricular rates, irregularity, degree of beat-to-beat similarity, and measure of electrogram complex distinctiveness to arrive at a diagnostic conclusion. A test set of 121 endocardial electrogram recordings obtained during provocative electrophysiology studies was then used for blinded validation of the algorithm. In normal rhythm, 1:1 tachycardia, atrial tachycardia, atrial flutter, atrial fibrillation, ventricular tachycardia, and ventricular fibrillation, the percentages of sensitivity/specificity were, respectively, 100/99, 100/99, 80/99, 89/98, 91/97, 92/100, and 100/98. Although ventricular rate alone can usually distinguish normal rhythm, ventricular tachycardia, and ventricular fibrillation, it is confounded by atrial arrhythmias and 1:1 tachycardias. When tested on a database, a ventricular rate-only algorithm resulted in sensitivity/specificity of 100/65, 90/78, and 100/99%, respectively, for these three rhythms. Therefore, the dual-chamber algorithm based on both temporal and morphologic measures provides better distinction of normal rhythm and ventricular tachycardia than existing methods, without sacrificing sensitivity.

Arrhythmias, Cardiac↗
PubMed1980

Atrial flutter associated with obstructive sleep apnea syndrome. A case report.

An obese 57-year-old man with the obstructive sleep apnea syndrome had partial tracheostomy occlusion and palpitations. Continuous ECG monitoring demonstrated atrial flutter, occasional premature ventricular beats, and a high degree of atrioventricular block during apneic episodes. A 7-s period of ventricular asystole was demonstrated during one such episode. Revision of the tracheostomy produced an improvement in the patient's condition.

Airway Obstruction↗
PubMed1990

Moricizine: a new class I antiarrhythmic.

The chemistry, pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage of the Class I antiarrhythmic agent moricizine hydrochloride are reviewed. Moricizine is chemically similar to the phenothiazines but does not appear to block dopaminergic receptors. Its major electrophysiologic actions are a concentration-dependent decrease in maximum rate of phase 0 depolarization; increased rates of phase 2 and 3 repolarization, decreased action potential duration, and decreased effective refractory period. Moricizine causes a dose-related prolongation of the PR interval and of AV nodal, infranodal, and intraventricular conduction times but has little effect on ventricular repolarization. The antiarrhythmic and electrophysiologic effects are not correlated with plasma concentrations of the drug or its metabolites. Moricizine reduces the occurrence of ventricular premature contractions (VPCs), couplets, and nonsustained ventricular tachycardia. It appears to suppress symptomatic nonsustained ventricular tachycardia, sustained ventricular tachycardia, and ventricular fibrillation or flutter. Moricizine appears to be as effective as quinidine and more effective than disopyramide, propranolol, and imipramine but less effective than flecainide and encainide at reducing VPCs. Moricizine continues to be evaluated in the Cardiac Arrhythmia Suppression Trial, which was designed to assess the long-term benefit of arrhythmia suppression in patients with left ventricular dysfunction after myocardial infarction. Moricizine seems to be better tolerated than quinidine, disopyramide, and imipramine and to have less proarrhythmic potential than flecainide or encainide. Noncardiac adverse effects include dizziness, nausea, and headache. Cimetidine appears to decrease moricizine clearance, and decreased theophylline clearance has been reported in subjects given moricizine. The usual adult dosage of moricizine hydrochloride is 600-900 mg/day given in three divided doses; an every-12-hour regimen may be used in some patients. Because of the risk of proarrhythmic effects, indications are limited to treatment of documented life-threatening arrhythmias. Moricizine will compete with other agents as first-line therapy for life-threatening arrhythmias.

Arrhythmias, Cardiac↗
PubMed2003

Review of diagnosis, treatment, and outcome of fetal atrial flutter compared with supraventricular tachycardia.

OBJECTIVE: To review the diagnosis, treatment, and outcome of fetal atrial flutter compared with supraventricular tachycardia. DESIGN: Retrospective review of published reports: 11 papers about fetal tachyarrhythmia published between 1991 and 2002 were selected for review. MAIN OUTCOME MEASURES: All selected studies were analysed for the type of arrhythmia, degree of atrioventricular block in atrial flutter, occurrence of hydrops fetalis, gestational age at diagnosis, first and second line drug treatment, associated cardiac and extracardiac malformations, and mortality of the fetuses. RESULTS: Atrial flutter accounted for 26.2% of all cases of fetal tachyarrhythmias, and supraventricular tachycardia for 73.2%. Hydrops fetalis was reported in 38.6% and 40.5% of fetuses with atrial flutter and supraventricular tachycardia, respectively (NS). Hydropic fetuses with atrial flutter had higher ventricular rates (median 240 beats/min, range 240-300) than non-hydropic fetuses (220 beats/min, range 200-310) (p = 0.02), whereas the atrial rates were not significantly different (median 450 beats/min, range 370-500). Digoxin treatment resulted in a higher conversion rate in non-hydropic fetuses with fetal tachyarrhythmias than in hydropic fetuses (p < 0.001). The overall mortality of atrial flutter was similar to that of supraventricular tachycardia, at 8.0% v 8.9% (p = 0.7). CONCLUSIONS: The prevalence of hydrops fetalis did not differ in fetal atrial flutter and supraventricular tachycardia with 1:1 conduction. There was no difference between the response rate to digoxin in fetus with atrial flutter or supraventricular tachycardia. Mortality was similar in the two types of tachyarrhythmia.

Anti-Arrhythmia Agents↗
PubMed1978

["Torsades de pointe" and reentry induced by anti-arrhythmia agents].

Some anti-arrhythmic agents which have a stabilising effect on the membrane, particularly those belonging to Group I of Vaughan William's classification, are likely to cause rythmic disturbances by a re-entry phenomenon (atrial flutter 1/1, premature ventricular contractions, ventricular tachycardia, "torsades de pointe", even fatal ventricular fibrillation). The quinidines have been the most often condemned due to their effect on the action potential and on the speed of conduction. The fact that these re-entry phenomena are more frequent at therapeutic doses than at high or toxic doses suggests an individual susceptibility and the interaction of various predisposing factors: renal insufficiency, potassium depletion, pre-existing conduction disturbances, potentialsing drugs. In order to prevent these incidents it is advisable not to prescribe such anti-arrhythmic agents for susceptible patients, to control individual tolerance and to watch for the first ECG signs of conduction disturbances or of re-entry, such as premature contraction with fixed coupling. Treatment consists in an electrosystolic stimulus and the possible administration of potassium and bretylium.

Adrenergic beta-Antagonists↗
PubMed1992

The use of implantable sensors for the control of pacemaker mediated tachycardias: a comparative evaluation between minute ventilation sensing and acceleration sensing dual chamber rate adaptive pacemakers.

The role of implantable sensors to control pacemaker mediated tachycardias was investigated in 16 patients with two different dual chamber rate adaptive (DDDR) pacemakers, which sensed eiter minute ventilation (DDDR-Meta, nine patients) or body acceleration (Relay, seven patients). Successive atrial sensed events beyond a programmable rate occurring in the absence of detection of exercise by the sensors were considered to represent retrograde conduction or atrial arrhythmias, and the pacemakers responded by either a mode shift from DDDR to ventricular rate adaptive (VVIR) pacing (DDDR-Meta) or by tracking at an interim rate, the so-called conditional ventricular tracking limit (CVTL, Relay). In the unipolar atrial sensing mode, myopotential sensing (MPI) and external chest wall stimulations (CWS) at 250 beats/min were induced to be preferentially sensed by the atrial channel to simulate the conditions of atrial arrhythmias. In the DDD mode, these maneuvers resulted in ventricular responses of 88 +/- 3 beats/min and 110 +/- 3 beats/min for MPI and CWS, respectively. The pacing rate was significantly reduced in the DDDR mode with the sensors correctly detecting and responding to the sensed abnormal atrial signals (68 +/- 5 beats/min during MPI and 71 +/- 5 beats/min during CWS, P less than 0.005 compared with the corresponding DDD rate). One patient with a Relay pacemaker developed spontaneous atrial flutter and the ventricular tracking responses were 140 and 85 beats/min in the DDD and DDDR pacing modes, respectively. Thus MPI and CWS are useful bedside testing methods to assess pacemaker response during atrial arrhythmias. The use of implantable sensors to judge the appropriateness of atrial rate is a new approach to the management of pacemaker mediated tachycardias.

Adult↗
PubMed1992

[Modification of atrio-ventricular conduction in treatment of supraventricular reentry tachycardia. (preliminary results)].

Intracardiac defibrillation to produce complete heart block is a modern and effective method for treatment of refractory supraventricular arrhythmias. The main drawback of this technique is the necessity of implantation of permanent pacemaker. There is however a growing interest in modification of atrio-ventricular (A-V) conduction to prevent arrhythmias without producing complete heart block. A new energy source used for this purpose is the radiofrequency (RF) current. Preliminary clinical results of modification of antegrade conduction in 5 patients with recurrent supraventricular arrhythmias are presented. HAT 100 (Dr Osypka GmbH, Germany) a high frequency generator was used for modification. Electrophysiological studies showed slow/fast type of junctional reentry tachycardia in 4 patients and paroxysmal atrial flutter with rapid ventricular response in 1. Since RF current produces much smaller and more discrete lesion, the precise localization of the active electrode was of primary importance. We manipulated the catheter, used for modification, in AV region until a relatively large atrial potential with only barely visible His bundle deflection was obtained. During reentry tachycardia the place of the earliest retrograde atrial depolarization was searched for. Current and voltage were monitored during the modification procedure. It was possible to titrate the HF energy to achieve the desired effect changing the power and the time of current application. The modification was repeated several times since PQ and AH interval increased > 50%. No prolongation of HV was noted. The modification was effective in all patients and allowed to avoid the induction of reentry despite the persistence of 1:1 AV conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2003

Prolonged ventricular asystole, sinus arrest, and paroxysmal atrial flutter-fibrillation: an uncommon presentation of vasovagal syncope.

We described a 55-year-old woman with recurrent syncope, complete atrioventricular (AV) block, sparsely scattered idioventricular beats lasting for 56 seconds, and long sinus arrest recorded during the syncopal episode. Paroxysmal atrial flutter-fibrillation was also presented during Holter electrocardiograph (ECG) monitoring without clinical symptom. During tilt test, atrial flutter with variable AV block was induced and the patient suddenly passed out. The vasovagal syncope was successfully treated with a DDD permanent pacemaker with a rate drop response algorithm. Vasovagal syncope with concomitant ventricular asystole and sinus arrest is rare. Aggressive management with permanent pacemaker is strongly advocated in malignant vasovagal syncope.

Atrial Fibrillation↗
PubMed1983

The induction of atrial flutter and fibrillation and the termination of atrial flutter by esophageal pacing.

In patients with Wolff-Parkinson-White syndrome (WPW), it is important to assess the ventricular response during atrial flutter or fibrillation since conduction across the accessory pathway during these atrial rhythms may cause hemodynamic impairment or life-threatening ventricular arrhythmias. We have recently reported the effective use of an esophageal electrode in pacing the atrium. In this study we prospectively assessed the ability to induce atrial flutter and fibrillation by esophageal pacing in 23 patients with WPW or other electrophysiological abnormalities. An esophageal bipolar electrode with 29 mm interelectrode distance was positioned in the esophagus to record the most rapid and largest esophageal electrogram (mean distance of 36.6 +/- 2.9 cm (SD) from the nares). Pacing was performed at cycle lengths of 40-340 ms (mean 166 +/- 72), pulse durations of 7.0-9.9 ms, and currents of 10-25 mA. Atrial flutter alone was induced in 6 patients, fibrillation alone in 11 patients, and both arrhythmias in 5 patients. In one patient neither flutter nor fibrillation was induced by esophageal pacing, and fibrillation was induced only with difficulty using intracavitary pacing. Of the 11 patients with flutter, the arrhythmia was terminated in 8 by esophageal pacing at cycle lengths of 160-220 ms (mean 176 +/- 18 ms). All patients tolerated the procedure well with only mild to moderate discomfort. Therefore, esophageal pacing appears to offer an effective, well tolerated method of initiating atrial fibrillation and flutter and terminating atrial flutter and offers a potentially useful noninvasive method of following patients serially.

Adolescent↗
PubMedDate not supplied

Atrial fibrillation and flutter with left bundle branch block aberration referred as ventricular tachycardia.

Five patients were referred for electrophysiologic evaluation of nonsustained or sustained ventricular tachycardia. In each patient, the clinical rhythm disturbance was reproduced and identified as atrial fibrillation or flutter with left bundle branch block aberrancy. All five patients demonstrated enhanced or accelerated atrioventricular conduction through the normal atrioventricular nodal-His Purkinje pathway. This rapid conduction created an electrophysiologic substrate suitable to the preferential development of this less common form of aberration. Four of five patients responded well (ventricular rate control or reversion to sinus rhythm) to verapamil therapy. Electrocardiographic criteria for differentiating supraventricular tachycardia with aberration from ventricular tachycardia exist. Nevertheless, misdiagnosis of wide complex tachycardia remains common. Electrophysiologic testing plays an important role in correctly identifying these rhythms, assessing long-term prognosis, and choosing effective therapy.

Adult↗
PubMed2000

Three-dimensional catheter positioning during radiofrequency ablation in patients: first application of a real-time position management system.

INTRODUCTION: Precise localization of target sites for radiofrequency catheter ablation (RFCA) of arrhythmias is hampered by the relative inaccuracy of X-ray localization procedures. This study evaluated the efficacy of a three-dimensional (3D) real-time position management system in guiding RFCA procedures in patients. METHODS AND RESULTS: Patients (n = 30, age 59+/-20 years) referred for ablation of either atrial flutter (n = 10), ventricular tachycardia (n = 15), or accessory pathways (n = 5) were studied. The real-time position management system uses ultrasound ranging techniques to track the position of an ablation catheter relative to two multitransducer reference catheters, positioned in the right atrium or coronary sinus and the right ventricle. Each catheter contains three or four ultrasound transducers. The distance between the transducer(s) is determined by calculating the time necessary for an ultrasound pulse to reach other transducers, assuming the speed of sound in blood is 1,550 m/sec. The proximal His bundle was marked at the beginning and the end of the procedure as an electrical landmark to verify reproducibility. After identification of target sites, the position of each lesion created with the ablation catheter was marked. Successful ablation was achieved in 94% of the patients. The distance between the location of the proximal His bundle as marked at the beginning and at the end of the procedure was 2.0+/-1.2 mm (range 1.5 to 3.5). CONCLUSION: The new 3D real-time position management system facilitated RFCA procedures as it allowed accurate and reproducible 3D tracking of the mapping and ablation catheter.

Adult↗