Amyloid heart disease, as seen here grossly and on H&E stain, can be part of systemic amyloidosis or isolated to the heart. Senile amyloidosis is due to abnormal folding of transthyretin.

Amyloid deposition can be demonstrated by polarized light (left) or Congo red stain (right).  It can cause a restrictive cardiomyopathy or can involve the conduction system with resultant bradyarrhythmias.

Amyloidosis due to transthyretin (TTR) can be due to either normal sequence TTR or variant sequence TTR, Cardiac amyloidosis (senile cardiac amyloidosis) with onset in the elderly is due to normal sequence TTR. It may be accompanied by involvement of other organs in which case it is referred to as senile systemic amyloidosis. Variant sequence TTR variants are likely to present in teenagers or young adults and are often familial in various ethnic groups including Portuguese (including Brazilians) and Japanese. Organs involved include the heart, kidney, peripheral nerves, and GI tract. Cardiac involvement results in restrictive cardiomyopathy and/or conduction system disturbances.

From the slide collection of the late Dr. Charles Kuhn