Amyloidosis is characterized by extracellular deposition of amyloid protein. Amyloid deposit can occurred in various organs including heart, kidney, liver, etc., and cardiac amyloidosis (CA) is refers to the amyloid deposit in heart tissue causing progressive thickening of cardiac walls and restrictive cardiomyopathy. Two main forms of amyloidosis affect heart, AL amyloidosis and amyloid transthyretin (ATTR)-related amyloidosis.
Cardiac manifestations of CA include heart failure and arrhythmias. Rapid and progressive heart failure presented with progressive dyspnea (60%), peripheral edema (81%) and ascites. Atrial fibrillation (10-15%) is most frequent arrhythmia in CA, and conduction abnormality or sudden cardiac death is frequently observed.
CA is suspected from thickened ventricular walls in echocardiography with low voltage in electrocardiogram. Granular sparkling myocardium, dilated both atria with thickened septum, thickened valve and pericardial effusion seen in echocardiography is suggestive of the diagnosis, and marked diastolic dysfunction is shown. Currently, apical sparing pattern using 2-dimensional speckle tracking echocardiography is considered pathognomic finding of CA.
Cardiac magnetic resonance shows diffuse uptake of gadolinium or subendocardial ring-like late gadolinium enhancement. Definitive diagnosis is made by endomyocardial biopsy which shows characteristic extracellular amorphous deposit in hematoxylin and eosin stain and apple-green birefringence when stained with Congo red. Free light chain assay from blood and urine can discriminate AL amyloidosis from other types of amyloidosis, and if AL amyloidosis is suspected, a bone marrow biopsy for detecting plasma cell disorder is needed.
Figure 1. Congo red staining shows a reddish-orange appearance of amyloid protein (A) that exhibits birefringence under polarized light (B). (Modified from Cardiovasc Pathol. 2015; 24(6): 343-50)
Management of cardiovascular complication is important in CA patients. Salt restriction and diuretics is needed for treating fluid retention. Permanent pacemaker can be implanted in patients presenting with conduction disturbance, and antiarrhythmic agent such as amiodarone is used if atrial fibrillation develops. Treatment of underlying amyloidosis is also important to prevent disease progression, and survival of AL amyloidosis is being improved using chemotherapeutic agents or autologous stem cell transplantation. Heart transplantation can be a therapeutic option for patients with advanced heart failure.