Restriction cardiomyopathy / diagnostic algorithm of cardiac amyloidosis
If bone marrow examination is indicated, an increase in plasma cells is observed in AL amyloidosis, which in some cases may be associated with multiple myeloma. Examination of subcutaneous fat may also be indicated, where amyloid deposition is present in almost half of all patients, however, with very different yields for different types of amyloidosis.  The definitive diagnosis of amyloidosis is based on the evaluation of a biopsy specimen, in the case of cardiac involvement it is a specimen from an endomyocardial biopsy. Immunohistochemical methods determine a specific type of amyloidosis, which is important for the specific treatment of a given type of amyloidosis.   However, false positive and false negative results may occur.  In addition to immunohistochemical methods, mass spectrometry with very high sensitivity and specificity is therefore used for the typing of amyloidosis.  In the diagnosis of TTR (transthyretin) amyloidosis, genetic testing is also used to distinguish between familial and senile TTR amyloidosis. 
In AL amyloidosis, low voltage in the limb ducts (despite hypertrophy of the ventricular septum due to the deposition of amyloid, which is deposited extracellularly) is very often present on the ECG, and quite specifically for amyloidosis, and there is often an image of anterior wall infarction (Q wave in V1-V3) and AV block I. degree.  Echocardiography usually reveals a normal to small size of the left ventricle, hypertrophy of the left and right ventricular walls (primarily of the interventricular septum), and increased myocardial echogenicity. An increase in left ventricular filling pressures is also detected, and the longitudinal systolic function of the left ventricle is typically severely affected (even with a normal ventricular ejection fraction). Magnetic resonance imaging of the heart is also used in diagnostics, when the thickening of the walls of both ventricles with normal ventricle size is classically present. Diffuse subendocardial late gadolinium enhancement (LGE) also occurs. Both findings are relatively typical for amyloidosis. 
TTR amyloidosis is characterized by progressive biventricular heart failure. Unlike AL amyloidosis, TTR amyloidosis often has normal voltage (which, of course, may not always be the case), nonspecific conduction disturbances, ST-T segment changes  and atrial fibrillation (up to 50 % of cases).  There is also a higher incidence of LBBB (left bundle branch blocked) and higher grade AV blocks. The echocardiographic picture of TTR amyloidosis is similar to that of AL amyloidosis.