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De Gaspari et al. Vessel Plus 2022;6:57 https://dx.doi.org/10.20517/2574-1209.2022.05 Page 9 of 13

medin. Lactadherin is expressed by several kinds of cells including vascular smooth muscle cells, and the
amyloid deposits are commonly located in the aortic tunica media [74-76] . This form is called AMed
[77]
amyloidosis and has been demonstrated to also occur in some arterial vessels other than the aorta .
However, the clinical relevance is not clear yet, and no casual relation between aortic amyloid and
hypertension or aneurysms has been observed.

Valves
Many works describe the histological involvement by amyloid buildups in cardiac valves, particularly in
aortic valves affected by dystrophic calcification causing stenosis [78-82] . This deposition appears to be linked
to the native degenerative pathology of the valve itself and the high hemodynamical stress . However, only
[81]
limited demonstrations of amyloid fibrils in the valvular tissue by immunohistochemistry or electron
microscopy exist, and they generally exclude the presence of the common AL and TTR deposits, suggesting
a different subtype for this phenomenon [83,84] .

Conduction system
Typical ECG abnormalities in CA such as atrioventricular block or left anterior hemiblock prompted the
detailed study of the conduction system in autopsy cases. Contrasting results were found by different
authors on the localization of amyloid deposits in the specialized conduction tissue [38,67,85,86] . Most often, the
sinus node, the atrioventricular node, the bundle of His, and its major branches appeared to be spared from
amyloid infiltration at histological analysis. The most creditable explanation for the discordance between
ECG abnormalities and amyloid sparing was given by the presence of fibrosis found in the sinoatrial and
atrioventricular node, in contrast to the non-CA control group [67,86] .

Pericardium
Pericardial involvement in CA is usually referred to as the presence of pericardial effusion in cases of
congestive heart failure and a critical role in the prognosis . However, histological demonstrations of
[87]
pericardial infiltration by amyloid are scarce. When examined in the context of the autopsy series,
pericardial infiltration is present in about 50% of the patients affected by CA [38,40] . In addition, a single
intriguing report of isolated pericardial infiltration in AL-CA has been described but is surely an
exception .
[88]

CONCLUSION
CA is an underestimated cause of heart failure, usually with preserved ejection fraction and restrictive
hemodynamics. The role of the pathologist is not only to provide a definitive diagnosis of CA through EMB
but also to help in providing precise amyloid typing since this information is essential for prognostic and
therapeutic purposes.

DECLARATIONS
Authors’ contributions
Draft the manuscript: De Gaspari M
Complete and revise the paper: Finato N, Basso C

Availability of data and materials
Not applicable.