Atrial fibrillation: epidemiology, mechanisms and management.

The incidence of AF, the most common sustained arrhythmia in clinical practice, increases with age and coronary artery disease, hypertension and valvular heart disease are common underlying substrates; however, occasionally, AF may occur without any underlying heart disease. The most widely accepted theory of its mechanism is Moe's multiple wavelet hypothesis, although recent studies are helping to shed light on other mechanisms, including the focal origin of AF in some patients. Most patients experience palpitations, but fatigue, dyspnoea, and dizziness may also occur. Therapy includes prevention of thromboembolism, control of rate, and restoration and maintenance of sinus rhythm. The risks and benefits of each treatment modality need to be assessed according to each patient's circumstances. Unlike other arrhythmias, there is still no highly successful therapy for treating AF. However, significant advances are being made using non-pharmacological approaches to either prevent or cure this troublesome arrhythmia.

Ventricular arrhythmias, electrophysiologic studies, and devices.

Because of the high incidence of heart disease in the elderly, ventricular tachyarrhythmias are not infrequent. Determining the nature and extent of the underlying heart disease and identifying precipitating causes is required prior to instituting long-term therapy. Recent studies suggest that for hemodynamically unstable ventricular tachyarrhythmias, mortality is lower with the implantable cardioverter-defibrillator compared with pharmacologic therapy. This benefit is likely to be more modest in the elderly because of competing cardiac and noncardiac causes of death. For similar reasons, the favorable results reported with the prophylactic use of the implantable cardioverter-defibrillator are likely to be attenuated in the elderly.

Catheter ablation in supraventricular tachycardia.

The evolution of catheter ablation for the treatment of supraventricular tachycardias represents a major advance in the management of cardiac arrhythmias. Excellent results in the majority of patients undergoing the procedure, together with a low rate of early complications and a brief hospitalization, make catheter ablation a highly cost-effective permanent cure. At present, however, its place in relation to alternate therapies in the management of supraventricular tachycardias has not been clearly established owing to unresolved risk-benefit issues. Continuing technical advances will likely enable catheter ablation to be successfully applied to a broader range of cardiac arrhythmias.

Role of implantable cardioverter defibrillator therapy in the management of high-risk patients.

Cardiovascular mortality from ventricular tachycardia (VT) and ventricular fibrillation (VF) continues to be a major health problem. Several therapeutic approaches are now available to treat patients with known VT/VF. Among the various therapeutic options are antiarrhythmic drugs, catheter or surgical ablation of VT focus, and implantable cardioverter defibrillator (ICD). The overall 2-year cardiovascular mortality is significantly reduced by ICD therapy. The ICD is particularly useful in patients with 1) no inducible but clinical VT/VF, 2) drug refractory VT/VF, and 3) VT/VF in association with left ventricular ejection fraction of less than or equal to 30%. Significant improvements in ICD therapy have already been made; these improvements include tiered antitachycardia therapy, antibradycardia pacing, lower defibrillation threshold, and longer life of generator. Further improvements are expected, including nonthoracotomy approach to defibrillation, pectoral implant, and dual chamber sensing. It is likely that with all of the advances in ICD therapy its acceptance as a therapeutic option will increase.