ISSN:0268-4705    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

After more than 20 years of clinical use, programmed electrical stimulation for induction of cardiac arrhythmias remains an important clinical and research tool. The procedure continues to undergo refinement but is not without controversy regarding its accuracy in predicting drug efficacy as determined by serial testing for suppression of ventricular tachyarrhythmias. Recent work has streamlined technical aspects of the procedure itself and promises to improve the selection of patients likely to benefit from such studies. Despite these advances, however, recent publications from the Electrophysiologic Study Versus Electrocardiographic Monitoring trial raise fundamental questions about the ability of any current strategy to predict the efficacy of antiarrhythmic drugs for the prevention of ventricular arrhythmias.

ISSN:0268-4705    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Pharmacological therapy of cardiac arrhythmias continues to evolve, with an increasing shift from class I to class III compounds and β-blockers. This is engendered by increasing concern that class I antiarrhythmic drugs might adversely affect mortality in patients with significant structural heart disease. The focus now is on complex molecules such as amiodarone and sotalol, as well as D-sotalol and structurally diverse newer class III agents (such as dofetilide, MK-499, ibutilide, almokalant, and MS-551 among many others), which act only by increasing the time course of myocardial repolarization. In the development of newer drugs, the main endpoint in clinical trials is also beginning to shift to mortality from surrogate endpoints such as those determined by Holter monitoring and programmed electrical stimulation. The advent of implantable devices allows the performance of clinical trials with a mortality endpoint in patients with manifest ventricular tachycardia and fibrillation while providing an alternative mode of therapy for these arrhythmias. In the case of manifest ventricular tachycardia and fibrillation and aborted sudden death, adequately designed, controlled trials can now be undertaken by the use of implantable devices. In such trials, implantable cardioverter-defibrillators may serve in lieu of the placebo arm of a randomized trial. Trials involving a comparison of implantable cardioverter-defibrillators and best medical therapy (for the present, amiodarone and sotalol) are currently in progress. To what extent the newer class III agents will meet the requirements of an ideal antifibrillatory agent that reduces mortality in patients with structural heart disease remains a continuing investigative challenge.

ISSN:0268-4705    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

The use of implantable defibrillation systems in patients with cardiac arrest has resulted in lower mortality than expected from studies of similar patients not receiving defibrillators. Nonthoracotomy lead systems have led to a decrease in operative mortality and lowered the cost of defibrif lator implantation, but these systems have a higher energy requirement for defibrillation than do epicardial ones. The recent introduction of single-lead systems and bipolar defibrillation pulses has simplified nonthoracotomy defibrillator implantation and improved defibrillation efficiency. A prototype unipolar, single-lead pectoral implant defibrillation system is described that may significantly improve the reliability, safety, and cost effectiveness of nonthoracotomy defibrillators. This and other improved nonthoracotomy systems may expand the indications for defibrillator implantation to prophylactic use in high-risk patients who have not yet experienced life-threatening ventricular arrhythmias.

ISSN:0268-4705    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0268-4705    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

A resurgence of interest in atrial fibrillation has led to research in several avenues. Observations on the behavior of the atrium during atrial fibrillation demonstrate that electrical activity is not entirely random and that sinus node activity persists despite surrounding fibrillation. Anticoagulation therapy for chronic atrial fibrillation is now accepted as optimal treatment, but randomized trials have excluded the majority of patients screened and the risk-benefit ratio of therapy in the average patient therefore remains unclear. This is being addressed in comparative trials of warfarin and aspirin and in an analysis of risk factors for stroke derived from a major trial. Assessment of the efficacy of therapy for the control of ventricular rate in atrial fibrillation has underscored the slow action of digoxin and raised the issue of suboptimal dosing. With the recognition that improvement of exercise capacity following cardioversion may be postponed for weeks, several studies have evaluated serial changes in ventricular function and shown that in some patients sinus rhythm is associated with an improved ejection fraction. Transesophageal echocardiography is an area of intense interest for the identification of patients at high risk of thromboembolism following cardioversion, and the significance of left atrial spontaneous echo contrast as well as the left atrial appendage contractile function are being investigated. Finally, new methods of arrhythmia termination are being evaluated and developed, and surgical approaches to atrial fibrillation are being expanded and refined.

ISSN:0268-4705    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Catheter ablation techniques using radiofrequency current have become an accepted form of treatment for a variety of supraventricular tachycardias. The results are excellent in patients with preexcitation syndromes and as the complication rate is low, catheter ablation has become the first line of treatment for these disorders. In atrioventricular nodal reentry, a selective ablation of the fast or slow pathway is feasible. Ablation of the slow pathway guided by electrophysiologic markers appears to be safer with the use of a very low number of radiofrequency applications. Experience with atrial tachycardia remains limited but developments appear promising. Lastly, atrial flutter has become a growing indication for catheter ablation techniques using anatomical approaches. A high success rate can be achieved initially, but the technique is limited by a 20% recurrence rate and the late occurrence of atrial fibrillation.

ISSN:0268-4705    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Neurally mediated episodes of hypotension and bradycardia (neurocardiogenic syncope) are a common cause of recurrent syncope. Clinically, these episodes may present as an isolated event with an identifiable stimulus, or manifest as a syndrome of recurrent idiopathic syncopal events. The technique of head-upright tilt table testing has emerged as a safe and effective modality to identify individuals with this disorder. The use of isoproterenol as an adjunct/to tilt table testing is widely employed although controversial. Whereas the mechanism of neurally mediated syncope is incompletely understood, effective therapies are available. Multiple pharmacologic agents, either alone or in combination, have proven effective in preventing recurrent episodes. The role of cardiac pacing as therapy for a subgroup of patients who manifest severe bradycardia or asystole remains controversial as well. Additional study is necessary to further define the mechanism of neurally mediated syncope, provide new therapeutic strategies, and perhaps provide alternative diagnostic techniques.

ISSN:0268-4705    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

This article reviews recent studies, chapters, and review articles describing advances in cardiac pacing. Initially we discuss expanding and controversial pacing indications, including neurocardiogenic syncope and hypertrophic as well as dilated cardiomyopathies. Recent contributions to the understanding of factors influencing pacing mode selection are then discussed, including survival and atrial fibrillation in the various modes, the hemodynamic importance of atrioventricular synchrony and adaptive atrioventricular intervals, the importance of rate adaptation, the development of pacemaker syndrome, pacemaker response to the development of atrial arrhythmias, and special pacing modes such as VDD and AAIR. Finally, recent advances in rate-adaptive sensors and algorithms are reviewed, including preliminary results with dual sensors.

ISSN:0268-4705    

出版商:OVID    

年代:1994

数据来源: OVID

ISSN:0268-4705    

出版商:OVID    

年代:1994

数据来源: OVID