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Outcome After ICD Implant in Patients With Brugada Syndrome
Study Questions:
What are the clinical outcomes in patients with Brugada syndrome (BrS) who received an implantable cardioverter-defibrillator (ICD)?
Methods:
The MEDLINE database was searched in December 2017 using the terms “Brugada” and “defibrillator.” Articles had to include clinical outcomes of ICD therapy. Heterogeneity, summary estimates, and meta-analysis of outcomes were performed. Forest plots were created on appropriate and inappropriate ICD therapies (shocks and antitachycardia pacing).
Results:
Out of 828 articles, 22 were included for meta-analysis, consisting of 1,539 patients; 82% men. Primary prevention of sudden cardiac death (SCD) was the indication for ICD implantation in 79%. The top three risk factors were a positive electrophysiology (EP) study for ventricular tachyarrhythmia (72%), spontaneous type 1 electrocardiography (ECG) pattern (51%), and syncope (49%). Over a mean follow-up of about 5 years, 277 (18%) had an appropriate ICD therapy at an intervention rate of 3.1 per 100 person-years; and 230 (15%) had inappropriate therapy at an intervention rate of 3.3 per 100 person-years. The cardiac mortality rate was 0.03 per 1,000 person-years and the noncardiac mortality rate was 0.3 per 100 person-years. Complications included a rate of lead malfunction of 1.6 per 100 person-years and of psychological effects at 1.3 per person-years.
Conclusions:
In patients at high risk for ventricular tachyarrhythmias, the ICD appropriately treated patients with BrS at a rate of 3.1 per 100 person-years over 5-year follow-up. The cardiac mortality rate was low at 0.03 per 100 person-years. However, there was a 3.3 per 100 person-year rate of inappropriate shocks and relatively high incidence of associated complications.
Perspective:
BrS is an inherited channelopathy characterized by the coved type I pattern in the precordial ECG leads. BrS is thought to be responsible for up to 20% of all sudden deaths with a structurally normal heart and with a prevalence as high as 1 in 2,000. Episodes are generally vagally mediated and not in the context of exertion. Atrial fibrillation may occur in up to 30% of BrS patients. The majority of patients are male, asymptomatic until index event, and have structurally normal hearts. The ECG pattern may come and go and be unmasked only by certain triggers such as fever. ICD therapy is the best treatment for patients deemed high risk.
This meta-analysis reminds us that the ICD can be of substantial benefit in BrS, but challenges remain in managing these often young and asymptomatic patients; the rate of inappropriate shocks is not insubstantial, and one would think with improved detection and programming over the 14 years between studies that this rate will continue to decrease. Also, only six studies provided information on atrial fibrillation, the commonest source of inappropriate therapy in all ICD patients, and most patients had a single-lead (i.e., no atrial lead) system; with dual-chamber ICDs as well as improved programming, enhanced atrial fibrillation detection might also mitigate inappropriate shock risk.
T-wave oversensing as a cause of potential shocks remains a concern and is a limitation for using the subcutaneous ICD. Limitations of this meta-analysis, as noted by the authors, include variable risk assessment of primary prevention indication (which has also evolved), limited reporting of ICD leads used, and atrial fibrillation prevalence; the EP study was utilized in the majority of patients, but its role remains controversial; also, ICD shocks are not a surrogate for sudden death. Hence, the ICD is indeed the best option for asymptomatic patients at the highest risk of a cardiac arrest, but this therapy can come at a cost, emphasizing the importance of a shared decision-making approach.
Clinical Topics: Arrhythmias and Clinical EP, Prevention, Implantable Devices, Genetic Arrhythmic Conditions, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias
Keywords: Arrhythmias, Cardiac, Atrial Fibrillation, Brugada Syndrome, Channelopathies, Death, Sudden, Cardiac, Defibrillators, Implantable, Electrocardiography, Electrophysiology, Outcome Assessment, Health Care, Physical Exertion, Primary Prevention, Risk Factors, Syncope, Tachycardia, Ventricular
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