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    • Involvement of the ventricular myocardium

    2019-05-20

    Involvement of the ventricular myocardium can lead to delayed conduction or anatomical obstacles that are labile to ventricular tachyarrhythmia. Arrhythmias are independently predictive of sudden cardiac death (SCD) [9]. SCD is common in patients with cardiac AL amyloidosis, and prophylactic implantable cardioverter-defibrillators (ICDs) have been suggested as an option to reduce this risk [10,11]. However, pulseless electrical activity (PEA) appears to be 1 significant cause of SCD in these patients, probably because the mechanical properties of an amyloid heart are markedly injured due to abundant harmful protein deposition, intracardiac ischemia, and norepinephrine reuptake inhibitor of cardiac myocytes [12].
    Discussion The standard treatment of patients with primary AL amyloidosis who are not candidates for hematopoietic cell transplantation generally consists of chemotherapy, including a combination of melphalan and prednisone [5,13]. Especially in AL amyloidosis, chemotherapy may have curative or partial effects on this disease concerning stabilization or improvement of symptoms. In contrast, some patients cannot survive sufficiently long to receive adequate cyclical chemotherapy. Moreover, rapid high-dose chemotherapy is often associated with a risk of treatment-related mortality [5,13]. Cardiac involvement is the predominant manifestation of this disease, and patients with AL amyloidosis suffer progressive cardiomyopathy and SCD. Exertional syncope, which is a sign of severe restrictive cardiomyopathy and is associated with a high mortality several months after the initial event, often results in SCD [6]. The incidence of SCD in AL amyloidosis is only 10–30% [14,15]. In addition, the causes of SCD are reported not only to be ventricular tachyarrhythmia but also PEA [12]. There is a high prevalence of bradyarrhythmia in cardiac amyloidosis, and there are no alternatives to pacemaker implantation for those patients. In contrast, regardless of the low incidence of ventricular arrhythmia, ICD implantation was selected for preventing SCD as previously reported [16,17]. Therefore, it is difficult to decide when to perform an ICD implantation. Some anecdotal reports of ICD therapy in patients with cardiac amyloidosis are available [10,11]. However, Kristen et al. reported 19 cases with cardiac amyloidosis, and these patients died as a result of PEA and other diagnoses not amenable to ICD therapy [16]. In particular, Kristen et al. reported that there was significant difference in the progression of the left ventricular wall thickness and the low-voltage pattern in the electrocardiogram between non-survivors and survivors. They concluded that better methods for selecting patients with arrhythmia-associated SCD are required to elucidate the efficacy of ICD therapy in AL amyloidosis. All of our 4 cases had a low-voltage pattern in the electrocardiogram. Three of the 4 cases had a left ventricular wall thickness (the exception was case 1). All of the 3 patients who underwent chemotherapy were not responsive to the therapy. Two of the 3 patients with an ICD received shocks for ventricular tachyarrhythmias early on; however, these patients soon died due to PEA or severe heart failure. In Case 2, the patient had no episode of ventricular tachyarrhythmias after his ICD implantation. Soon after the implantation, ventricular tachyarrhythmias were documented. ICD implantation and related shock delivery may be labile to ventricular tachyarrhythmias and may deteriorate the clinical course and the disease progression. Recently, ICD shocks have been shown to impair cardiac function, leading to heart failure and worsening prognosis by inducing an electrical storm of ventricular tachyarrhythmias. This is 1 potential reason that ICD implantation therapy may lead to early-stage SCD instead of prolonging the patient\'s survival. The second patient with an implanted ICD had SCD; however, unfortunately, the exact cause of his sudden death could not be determined by examining the logs stored in his ICD device. In Case 4, a wide QRS tachycardia was not detected in the pacemaker. As noted above, it was remarkable that the amplitude of the R wave voltages in the pacemaker decreased gradually. A low amplitude of intracardiac potential may be an indicator of myocardial impairment.