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Electrophysiology studies in patients with dilated cardiomyopathies
Henry H Hsia1, Francis E Marchlinski
1Electrophysiology Service, Cardiovascular Division, University of Pennsylvania Health System, Philadelphia, Pennsylvania, USA. henry.hsia@uphs.upenn.edu
Insights
Dilated cardiomyopathy can cause ventricular tachycardia (VT) through scar-related reentry or other mechanisms. Electrophysiology studies have limited prognostic value, but identifying specific causes like Chagas
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Electrophysiology
Background:
- Dilated cardiomyopathy (DCM) presents with diverse arrhythmia substrates and variable responses to programmed stimulation.
- Sustained monomorphic ventricular tachycardia (VT) in DCM is often linked to scar-related reentry, similar to coronary artery disease.
- VT in DCM can be refractory to pharmacologic therapy and is associated with myocardial fibrosis and anisotropic conduction.
Purpose of the Study:
- To explore the mechanisms of ventricular arrhythmias in dilated cardiomyopathy.
- To evaluate the role of electrophysiology studies in guiding therapy and determining prognosis in DCM patients.
- To investigate the utility of identifying specific etiologies like sarcoidosis or Chagas' cardiomyopathy.
Main Methods:
- Programmed electrical stimulation during electrophysiology studies.
- Analysis of arrhythmia induction, characteristics, and response to therapy.
- Correlation of electrophysiological findings with myocardial fibrosis and clinical outcomes.
Main Results:
- Majority of sustained monomorphic VT in DCM is due to scar-related reentry, often inducible and pharmacologically refractory.
- Arrhythmia inducibility and suppression do not reliably predict clinical outcome or prognosis in DCM.
- Non-reentrant mechanisms like focal automaticity and bundle branch reentry VT are also observed.
Conclusions:
- Electrophysiology studies have limited utility in predicting prognosis or guiding therapy for VT in DCM.
- Specific etiologies such as sarcoidosis and Chagas' cardiomyopathy should be considered in unexplained DCM with VT.
- Catheter ablation of bundle branches is an effective treatment for bundle branch reentry VT in DCM.
Abstract:
Dilated cardiomyopathy is a diverse group of heart diseases with variable arrhythmia substrates. The response to programmed stimulation is dependent on spontaneous arrhythmia presentation. In patients with dilated cardiomyopathy, the majority of sustained monomorphic VT is caused by a scar-related reentrant mechanism, similar to that of coronary artery disease. The arrhythmia is uniformly inducible and is often refractory to pharmacologic therapy. Sustained VT is associated with more extensive myocardial fibrosis and non-uniform anisotropy, involving both the endocardium and epicardium, compared to those without sustained reentry. The response to programmed stimulation is more variable in patients presenting with nonsustained arrhythmia, cardiac arrest or syncope. Inducibility of monomorphic VT is much lower compared to those with ischemic heart disease. Other non-reentrant mechanism, such as focal automaticity, can also be observed in patients with monomorphic VT, in the absence of myocardial scar or evidence of slow conduction. The utility of electrophysiology studies to determine prognosis and to guide therapy remains limited in this patient population. The clinical outcome does not correlate with arrhythmia inducibility, and suppression of induced arrhythmia does not predict a good prognosis. The diagnosis of sarcoidosis or Chagas' cardiomyopathy should be considered in patients with dilated cardiomyopathy of unknown etiology, particularly in those with marked regional wall motion abnormalities and inducible VT. Epicardial reentrant circuits may be more prevalent in these cardiomyopathies, especially in those with VT related to chronic Chagas' disease. Although bundle branch reentry VT is a common finding in patients with dilated cardiomyopathy, it can occur in cardiomyopathy of any type and may coexist with other myocardial reentrant VT. It often has a typical bundle branch block QRS pattern during VT and is associated with His-Purkinje conduction delay. Evidence of macroreentry involving the bundle branches can usually be demonstrated, and catheter ablation of the bundle branches provides an effective and specific treatment.