Current pacemaker and defibrillator therapy.

BACKGROUND: Pacemakers have been available for 50 years, and implantable cardiac defibrillators for 25. Clear indications for each have been established on the basis of data from randomized clinical trials (RCTs). METHODS: This review article is the product of a collaborative effort by a cardiologist and a cardiac surgeon. The authors arrived at a consensus through a selective review of the literature, with special attention to randomized controlled trials and registry data. RESULTS: Atrioventricular (AV) block only rarely necessitates permanent pacemaker stimulation after inferior myocardial infarction, of which it is a rare (12% to 20%) and often transient accompaniment. AV block is more common, however, in anterior wall infarction (frequency ca. 5%), and often necessitates permanent pacemaker therapy in such cases. Pacemaker complications are rare; they include oversensing (the detection of impulse noise) (0.7%), undersensing (the failure to detect impulses) (3.8%), electrode fractures (3.8%), isolation defects (3.4%), perforation (<1%), dislocation (<1%), and infection (<1% to 12%). Many RCTs have confirmed that defibrillators are effective in the prevention of sudden cardiac death (SCD): they lower the risk of SCD by 20% to 30% in primary prevention and by 20% to 40% in secondary prevention. Cardiac resynchronization therapy improves the clinical manifestations and outcome of patients with congestive heart failure, with a relative risk reduction (RR) of 20% to 40%, even among patients in NYHA classes I and II (RR ca. 40%). Implantable defibrillators only rarely cause problems or complications in either the short or the long term. Emotional disturbances, including anxiety, are a rare side effect, occurring in less than 1% of cases. CONCLUSION: Pacemakers and implantable defibrillators are well-established electrotherapeutic devices that are highly effective and have only rare complications.

The natural history of asymptomatic ventricular pre-excitation a long-term prospective follow-up study of 184 asymptomatic children.

OBJECTIVES: The aim of this study was to describe the natural history of asymptomatic ventricular pre-excitation in children and to determine predictors of potentially life-threatening arrhythmic events. BACKGROUND: Sudden death can be the first clinical manifestation in asymptomatic children with ventricular pre-excitation, but reduction of its incidence by prophylactic ablation requires the identification of subjects at high risk. METHODS: Between 1995 and 2005 we prospectively collected clinical and electrophysiologic data from 184 children (66% male; median age 10 years; range 8 to 12 years) with asymptomatic ventricular pre-excitation on the electrocardiogram. After electrophysiologic testing, subjects were followed as outpatients taking no medications. The primary end point of the study was the occurrence of arrhythmic events. Predictors of potentially life-threatening arrhythmias were analyzed. RESULTS: Over a median follow-up of 57 months (min/max 32/90 months) after electrophysiologic testing, 133 children (mean age 10 years; range 8 to 12 years) did not experience arrhythmic events, remaining totally asymptomatic, while 51 children had within 20 months (min/max 8/60 months) a first arrhythmic event, which was potentially life-threatening in 19 of them (mean age 10 years; range 10 to 14 years). Life-threatening tachyarrhythmias resulted in cardiac arrest (3 patients), syncope (3 patients), atypical symptoms (8 patients), or minimal symptoms (5 patients). Univariate analysis identified tachyarrhythmia inducibility (p < 0.001), anterograde refractory period of accessory pathways (APERP)

Prevention of fatal arrhythmias in high-risk subjects by fish oil n-3 fatty acid intake.

BACKGROUND: The long-chain n-3 fatty acids in fish have been demonstrated to have antiarrhythmic properties in experimental models and to prevent sudden cardiac death in a randomized trial of post-myocardial infarction patients. Therefore, we hypothesized that these n-3 fatty acids might prevent potentially fatal ventricular arrhythmias in high-risk patients. METHODS AND RESULTS: Four hundred two patients with implanted cardioverter/defibrillators (ICDs) were randomly assigned to double-blind treatment with either a fish oil or an olive oil daily supplement for 12 months. The primary end point, time to first ICD event for ventricular tachycardia or fibrillation (VT or VF) confirmed by stored electrograms or death from any cause, was analyzed by intention to treat. Secondary analyses were performed for "probable" ventricular arrhythmias, "on-treatment" analyses for all subjects who had taken any of their oil supplements, and "on-treatment" analyses only of those subjects who were on treatment for at least 11 months. Compliance with double-blind treatment was similar in the 2 groups; however, the noncompliance rate was high (35% of all enrollees). In the primary analysis, assignment to treatment with the fish oil supplement showed a trend toward a prolonged time to the first ICD event (VT or VF) or of death from any cause (risk reduction of 28%; P=0.057). When therapies for probable episodes of VT or VF were included, the risk reduction became significant at 31%; P=0.033. For those who stayed on protocol for at least 11 months, the antiarrhythmic benefit of fish oil was improved for those with confirmed events (risk reduction of 38%; P=0.034). CONCLUSIONS: Although significance was not achieved for the primary end point, this study provides evidence that for individuals at high risk of fatal ventricular arrhythmias, regular daily ingestion of fish oil fatty acids may significantly reduce potentially fatal ventricular arrhythmias.

Multifocal atrial tachycardia as a prognostic indicator in patients with severe chronic obstructive pulmonary disease requiring mechanical ventilation.

The records of 121 patients admitted to the Medical Intensive Care Unit (MICU) of Chang Gung Memorial Hospital with severe chronic obstructive pulmonary disease (COPD) requiring mechanical ventilation were reviewed retrospectively. Eighty-seven percent (20/23) of the patients with multifocal atrial tachycardia (MAT) expired during their ICU admission in contrast to 23.5% (23/98) of those without MAT. The only differences between these two groups were incidence of cor pulmonale, and right axis deviation, right bundle branch block, pulmonale P in electrocardiogram. MAT might be considered as a grave prognostic sign in patients with COPD severe enough to require mechanical ventilation.