Implantable cardioverter defibrillators in patients with cardiac amyloidosis

Background: Cardiac amyloidosis (CA) is associated with increased risk of sudden cardiac arrest. Although ICD therapy improves survival in patients with cardiomyopathy due to other etiologies, the benefit of ICD therapy in patients with CA is unclear in large part due to limited data on the precise mechanism of sudden cardiac arrest and selection of patients with cardiac amyloidosis for ICD therapy.

Objective: The objective was to determine the benefit of ICD therapy in cardiac amyloidosis.

Methods: We reviewed all ICD implant indications, procedures, and therapies, of CA patients evaluated at Mayo Clinic between 2000 and 2009.

Results: A total of 53 patients with CA (33 AL, 10 senile, 9 familial, and 1 AA) who underwent ICD implantation were included. Indication for ICD implantation was for primary prevention of sudden cardiac arrest in 41 (77%) patients and secondary prevention in 12 (23%) patients. The rate of appropriate ICD shocks was 32% in the first year and was observed almost exclusively in AL amyloidosis patients, occurring in 15 patients (12 AL amyloidosis, 2 senile, 1 AA). Appropriate ICD shocks were more frequent in patients with prior sudden cardiac arrest or sustained ventricular arrhythmias (secondary prevention indication), and less frequent in patients who presented with decreased ejection fraction or syncope.

Conclusions: A high rate of appropriate ICD shocks was observed especially in patients with AL-type amyloidosis. However, appropriate ICD therapy did not translate into overall survival benefit, suggesting that selection of patients with CA who might be candidates for ICD is imprecise.