When the amyloidosis appears in the heart, it is due to amyloid deposits in the interstitial compartment and the cardiac nervous tissues. This damage shows up clinically as symptoms of heart failure (dyspnoea) and rhythm disorders, most often in the atrium (atrial flutter and atrial fibrillation) and less often in the ventricles.
The extra-cardiac manifestations of this illness are diverse and vary depending on the type of amyloidosis: carpal tunnel syndrome, macroglossia, periorbital haematoma, etc. Neurological damage is mainly found in the autonomic nervous system and the peripheral nerves, with damage to the length dependant fibres. Damage to the peripheral nervous system shows up clinically as sensory problems like paresthesia in the extremities. It is not uncommon for neurological symptoms in the elderly to be wrongly attributed to other neurological causes (diabetic neuropathy, spondylolisthesis, etc.). Electromyograms can detect sub-clinical damage by analysing small fibres and measuring their progression.