Original-clinicalProphylactic implantation of cardioverter-defibrillator in patients with severe cardiac amyloidosis and high risk for sudden cardiac death
Introduction
Amyloidosis is a rare disorder of protein conformation and metabolism that results in tissue deposition of insoluble fibrils. Increased amyloid tissue deposition causes organ dysfunction and finally death. Usually, systemic amyloid deposits are formed by immunoglobulin light-chains (light-chain amyloidosis) and may involve various organs.1 Cardiac involvement occurs in approximately 60% of patients with light-chain amyloidosis2 and is by far the most relevant factor for the poor prognosis of patients. High-dose melphalan chemotherapy and autologous stem cell transplantation represent a potentially curative treatment of light-chain amyloidosis, resulting in complete remission in approximately 60% of patients.3, 4 However, treatment-related mortality is exceptionally high in patients with advanced cardiac involvement.5, 6, 7, 8 Without therapy, patient survival is approximately 6 months.9
Approximately two thirds of patients with cardiac amyloidosis die of “sudden” types of death.10 In patients with light-chain amyloidosis, ventricular rhythm disturbances (ventricular extra beats Lown grade IVa or higher) are common and prognostically relevant.11 Syncope is an independent risk factor for sudden cardiac death (SCD).12
Implantable cardioverter-defibrillator (ICD) therapy theoretically could be a treatment option for high-risk patients with light-chain amyloidosis because ICD placement has been proved to be the treatment of choice in patients with ischemic and dilated cardiomyopathies.13, 14, 15 To date, only anecdotal reports of ICD therapy in patients with cardiac amyloidosis are available.16, 17
The aim of the present study was to evaluate the impact of ICD treatment on the prognosis of selected patients with histologically proven cardiac light-chain amyloidosis and at least one risk factor for SCD.11, 12, 18
Section snippets
Study population
Nineteen patients with light-chain amyloidosis and histologically proven cardiac involvement diagnosed at a university tertiary referral center between March 2003 and December 2006 received an ICD because of potentially high risk for SCD.
Diagnosis of amyloidosis was made by Congo red staining of any biopsy. The type of light-chain amyloidosis was confirmed by immunohistochemical staining.19 Further organ involvement was defined according to the guidelines of amyloidosis diagnostics.20 All
Results
At the time of ICD placement, 4 (21%) patients had a history of syncope, 10 (53%) had ventricular extra beats (Lown grade IVa or higher), and 5 (26%) had both risk factors for SCD. Also present were low-voltage pattern (n = 12 [63%]), interventricular septum ≥15 mm (n = 17 [89%]), markedly impaired left ventricular ejection fraction ≤45% (n = 5 [26%]), cardiac troponin T level ≥0.03 μg/L (n = 9 [47%]), N-terminal pro-brain natriuretic peptide (NT-proBNP) level ≥3,500 ng/L (n = 12 [63%]), and
Discussion
The present study attempted to elucidate the impact of ICD placement on mortality in patients with cardiac amyloidosis. The data indicate that (1) mortality in patients with cardiac light-chain amyloidosis is mainly due to electromechanical dissociation that is not amenable to ICD treatment, (2) ICD treatment successfully terminated sustained ventricular arrhythmias in individual patients, (3) the percentage of ventricular pacing was very low, and (4) patients who died due to electromechanical
Conclusion
Cardiac light-chain amyloidosis carries a critical prognosis, with infrequent occurrence of sustained ventricular arrhythmias amenable to ICD treatment. Based on the results of this study with small sample size, prophylactic ICD placement cannot be generally recommended. Nevertheless, select patients might benefit from ICD therapy; therefore, larger randomized studies are needed to further elucidate the impact of prophylactic ICD placement in patients with cardiac amyloidosis. Novel selection
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