ISSN:0268-4705    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Cardiac arrhythmias are a major health threat. Multiplicities, discontinuities, dynamic interactions, and other complexities that exist among the determinants of cardiac excitability should give rise to unpredictably complex behavior, yet electrophysiologic events are unusually sufficiently coordinated to produce predictable outcomes. Theoretical and experimental work is discussed in terms of the electrophysiologic matrix and assisted bifurcations, which show how complex systems can act simply to produce order out of apparent chaos. We propose that altered excitability underlies abnormal impulse propagation and formation. The increased prominence of anisotropy and functional block in reentrant arrhythmias is noted, with emphasis placed on cell-to-cell communication. Important work on the effects of stretch, the autonomic nervous system and central events, triggered automaticity, and both biochemical and metabolic alterations to arrhythmias is reviewed. New methodologies for the study of arrhythmias are also mentioned. Finally, new work is cited relating the importance of nonlinear dynamics to cardiac excitability, impulse propagation, and entrainment.

ISSN:0268-4705    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Pharmacologic control of cardiac arrhythmias is currently undergoing major changes. To a large extent, the change has been initiated by the publication of the results of the Cardiac Arrhythmia Suppression Trial (CAST), which recently showed that preventing ventricular contractions by certain drugs that block myocardial conduction does not necessarily reduce the incidence of sudden death. The mortality is, in fact, increased. A meta-analysis of randomized, controlled clinical trials in such patients has indicated that the so-called class I drugs in general may also increase mortality or may have no effect. In contrast, β-blockers consistently reduce sudden death in the survivors of myocardial infarction. There is also emerging data indicating that agents that homogeneously lengthen the refractory period (class III effects), particularly with associated anti-adrenergic effect, also have the potential to prolong survival in patients with life-threatening ventricular arrhythmias. The overall data suggest that the focus on the drug therapy of arrhythmias may need to shift from class I agents to class III agents with an emphasis on mortality as a point of therapy.

ISSN:0268-4705    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Sixty-seven recent publications in the field of cardiac pacing are reviewed under the headings of underlying mechanisms, temporary pacing, reports of therapy, pacing technology, and complications. The reference list is annotated, and papers considered of particular importance are highlighted. This review offers an appraisal of the recent advances in this highly technologic field, with particular emphasis on clinical problems, and is divided into five sections. The first covers the underlying mechanisms that lead to the need for pacing and the changes in hemodynamics and the neuroendocrine system that pacing imposes. The second examines two aspects of temporary pacing. The third gives a wide view of reports of therapy, and the fourth gives a clinical view of advances in pacing technology. The final section covers complications of pacing therapy.

ISSN:0268-4705    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

In this review, the diagnosis and treatment of various supraventricular tachycardias are discussed. The atrial inhomogeniety and dispersion of refractoriness play as important a role in the genesis of atrial arrhythmias as does anisotropic conduction. Both inhomogeniety of conduction and anisotropy are more marked in the lower part of the right atrium than in its upper parts because of regional differences in the action potential duration. Three models of atrial flutter,ie, sterile pericarditis, surgically induced anatomic obstacle, and atrial dilatation are studied to further elucidate the mechanism of atrial flutter. Although reentry remains the most common mechanism, the mechanisms by which antiarrhythmic agents of different classes terminate atrial flutter may be quite different. Detailed activation mapping and localization of areas of slow conduction provide better insights into the mechanism of supraventricular tachycardias and a higher success yield for ablative procedures. The safety and efficacy of a given antiarrhythmic therapy (pharmacologic or nonpharmacologic) is significantly influenced by the underlying cardiac pathology. The results of trials of newer antiarrhythmic agents (eg, sotalol, propafenone) are presented, as well as the results of antitachycardia pacing and electrode catheter ablation techniques in treating supraventricular tachycardias. In general, both techniques are used for a very selected and well-investigated population of patients. However, more ablative techniques will emerge in the 1990s. Controversy about the role of anticoagulation in atrial fibrillation of nonrheumatic etiology continues; preliminary results of several randomized trials demonstrate that anticoagulation is beneficial. The role of aspirin in reducing thromboembolic complications in lone atrial fibrillation is promising.

ISSN:0268-4705    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Though tachyarrhythmias occur commonly in patients with the Wolff-Parkinson-White syndrome, many patients remain asymptomatic. Recent studies suggest that routine electrophysiologic testing in these individuals is of limited value. However, electrophysiologic testing remains very helpful in the symptomatic patient for predicting arrhythmia recurrence and for determining accessory pathway location and function. Unfortunately, noninvasive tests to predict high-risk WPW patients has not been proven helpful because of their low specificity. A number of recent studies have shown that autonomic function can markedly improve accessory pathway function and even counteract the effect of antiarrhythmic drugs. Given the frequent failure of antiarrhythmic therapy in the WPW syndrome, there has been increasing interest in nonpharmacologic therapies, including high-energy DC shock and radiofrequency catheter ablation of accessory pathways, which may prove to be more cost-effective than surgery.

ISSN:0268-4705    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

This review article investigates the value of late potentials and programmed electrical stimulation of the heart to predict arrhythmic events in the present of heart disease. Special attention is paid to patients with nonischemic ventricular arrhythmias and to patients resuscitated from aborted sudden cardiac death. The efficacy of various antiarrhythmic agents is also described.

ISSN:0268-4705    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Syncope is a common and important clinical problem that occurs in up to 30% of adults and accounts for up to 6% of general hospital admissions. Syncope of cardiovascular origin is particularly important to identify as it is associated with a high risk of sudden cardiac death. A complete history and physical examination may suggest a diagnosis in the majority of patients, but additional evaluation is often required. Electrophysiologic testing is of highest diagnostic yield in patients with structural heart disease. Negative electrophysiology test results are also of importance as they predict a very low incidence of sudden cardiac death during follow-up. Tilt-table testing is a recently developed tool that allows a diagnosis of vasopressor syncope to be established despite an atypical clinical history. Tilt-table testing can also be used to guide therapy.

ISSN:0268-4705    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Catheter ablation is gaining increasing interest for the therapy of symptomatic, sustained arrhythmias of various origins. The scope of this review is to give an overview of the biophysical aspects and major characteristics of some of the most widely used energy sources in catheter ablation,eg,the discharge of conventional defibrillators, modified defibrillators, laser light, and radiofrequency current application. Results from animal studies are considered to explain the basic mechanisms of catheter ablation. The recent achievements with the use of radiofrequency current to modify or ablate cardiac conduction properties are outlined in more detail.

ISSN:0268-4705    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Medically refractory tachyarrhythmias remain a significant clinical problem. The indications for surgical intervention in this challenging patient population continue to expand. Advances in noninvasive detection of patients at risk, as well as expanding electrophysiologic testing, continue to help define patients best served by surgical therapy. Refinements in surgical techniques, including rapid computerized intraoperative arrhythmia mapping, have made operative therapy safer and more effective. This review describes recent observations and advances in surgical therapy for supraventricular and ventricular tachyarrhythmias.

ISSN:0268-4705    

出版商:OVID    

年代:1991

数据来源: OVID