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[Rhythm disorders and infarction]
1Departement für Innere Medizin, Universitätsspital, Zürich.
Insights
Ventricular arrhythmias, including ventricular tachycardia and fibrillation, are a leading cause of cardiac death after myocardial infarction. Risk stratification and targeted therapies improve outcomes for affected patients.
Area of Science:
- Cardiology
- Electrophysiology
- Internal Medicine
Context:
- Ventricular arrhythmias are a significant complication following myocardial infarction (MI).
- These arrhythmias are a primary cause of sudden cardiac death in both acute and late stages post-MI.
- Risk factors include impaired left ventricular function and electrical instability.
Purpose:
- To summarize the causes, risk factors, and management strategies for ventricular arrhythmias after myocardial infarction.
- To highlight the prognostic implications and therapeutic options for patients experiencing sustained ventricular tachycardia and fibrillation.
Summary:
- Ventricular arrhythmias, such as ventricular tachycardia (VT) and ventricular fibrillation (VF), are common and life-threatening complications of myocardial infarction.
- Key risk factors for sudden cardiac death include reduced left ventricular function, electrical instability (e.g., complex ventricular premature beats, late potentials), bundle branch block, and ventricular aneurysm.
- While beta-blockers aid secondary prevention, most antiarrhythmic drugs are not recommended for asymptomatic patients due to proarrhythmic risks; amiodarone is an exception.
- Prognosis for sustained VT/VF is poor, but outcomes can improve with tailored antiarrhythmic therapy, surgical interventions, or cardioverter-defibrillator implantation.
Impact:
- Identifies critical risk factors for sudden cardiac death post-MI, aiding in patient stratification.
- Clarifies the role and limitations of antiarrhythmic drug therapy, emphasizing the risks of proarrhythmia.
- Underscores the importance of advanced therapies like cardioverter-defibrillators for improving survival in high-risk patients.
Abstract:
Ventricular arrhythmias are a frequent complication of myocardial infarction. In either the acute or the late stage, ventricular tachycardia and ventricular fibrillation represent the most common cause of cardiac death. About 15% of the patients with acute myocardial infarction die before entering the hospital, the majority due to ventricular fibrillation. Another 10 to 15% of the survivors of an acute myocardial infarction die suddenly within the subsequent year, again mostly due to ventricular arrhythmias. Independent risk factors for sudden cardiac death consist of depressed left ventricular function, persistent electrical instability (e.g. repetitive and complex VPB's, documented 'late potentials', inducibility of arrhythmias at programmed electrical stimulation), new onset complete-bundle branch block and large aneurysm of the left anterior ventricular wall. Bradyarrhythmias (i.e. high-degree AV-Block, asystole) are a far less common etiology of sudden cardiac death caused by an ischemic lesion to the conduction system. Betablockers have a well-known benefit in secondary prevention, whereas antiarrhythmic agents (with the exception of amiodarone) are ineffective in asymptomatic patients or may even increase the risk for sudden death due to a proarrhythmic effect (class IC); therefore, the latter are not recommended in asymptomatic patients with documented VPB's and preserved left ventricular function. The prognosis of patients with sustained VT and VF is poor. Their outcome is improved in responders to an individual antiarrhythmic therapy with serial drug testing or with subendocardial resection of localized areas and by implantation of a cardioverter defibrillator.