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Myocardial Fibrosis Predicts Appropriate Device Therapy in Patients With Implantable Cardioverter-Defibrillators for Primary Prevention of Sudden Cardiac Death
Study Questions:
Are patients with cardiomyopathy who do not have myocardial fibrosis by magnetic resonance imaging (MRI) at low risk of ventricular tachycardia (VT)/ventricular fibrillation (VF)?
Methods:
MRI was performed in 103 patients (mean age 54 years) with a cardiomyopathy (ischemic in 42 and nonischemic in 61) before implantation of an implantable cardioverter-defibrillator (ICD) for primary prevention of sudden cardiac death (SCD). Fibrosis was identified by late gadolinium enhancement (LGE). The ICDs were interrogated for stored events and device therapies at regular intervals during a median follow-up of 19 months.
Results:
LGE was present in all patients with ischemic cardiomyopathy and in 31/61 patients with nonischemic cardiomyopathy. An appropriate ICD therapy for VT/VF was delivered in 14% of patients with ischemic cardiomyopathy, 29% of patients with nonischemic cardiomyopathy and LGE, and 0% of patients with nonischemic cardiomyopathy and no LGE. The significantly lower risk of an ICD therapy in the latter group was independent of ejection fraction and antiarrhythmic medication use.
Conclusions:
In patients with nonischemic cardiomyopathy who meet criteria for implantation of an ICD for primary prevention of SCD, the absence of fibrosis by LGE predicts a low risk of VT/VF.
Perspective:
The results support a mechanistic link between myocardial fibrosis and VT/VF. But because other studies have shown that appropriate ICD events can occur in patients without evidence of fibrosis by LGE, ICDs should not be withheld based on the results of MRI in otherwise appropriate candidates. As is the case with other risk stratifiers such as microvolt T-wave alternans, a negative result on MRI does not guarantee freedom from malignant ventricular arrhythmias.
Keywords: Follow-Up Studies, Cardiomyopathies, Ventricular Fibrillation, Heart Failure, Magnetic Resonance Imaging, Defibrillators, Implantable
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