Infiltration of Conduction Tissue Is a Major Cause of Electrical Instability in Cardiac Amyloidosis

Authors: Andrea Frustaci, Romina Verardo, Matteo Antonio Russo, Marina Caldarulo, Maria Alfarano, Nicola Galea, Fabio Miraldi, Cristina Chimenti

Cardiac amyloidosis (CA) is an infiltrative heart muscle disease characterized by interstitial myocardial deposition and polymerization into 10 nm-wide fibrils of amyloidogenic proteins, including antibodies’ light chains, serum amyloid A, transthyretin and apolipoprotein A1–A2 [1,2,3].
Βeta-pleated organization confers to amyloid fibrils specific physic-chemical properties such as uptake of Congo Red stain and birefringence to polarized light that are used for its histologic recognition.
The accumulation of amyloid fibrils in the myocardium results in progressive thickening and stiffness of the cardiac wall with increasing compromise of diastolic and, finally, of systolic function. The decline in QRS voltages is commonly seen as the consequence of low amyloid conductivity, as well as the result of progressive cardiomyocyte loss.
The involvement of cardiac conduction tissue (CT) is poorly investigated in CA because of the difficulty to obtain in-life histological sections of CT, although the occurrence of severe brady-arrhythmias requiring pacemaker implantation and/or ventricular tachy-arrhythmias resulting in sudden death is frequently registered [4,5,6,7].
We experienced the possibility, particularly in patients with thickened hearts, of including CT sections in endomyocardial biopsies obtained from the left ventricular septum [7,8,9,10]. In the following study, the pathology of CT affected by various forms of CA is reported.

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