ECG findings in cardiac amyloidosis include low voltage in as many as 70% of cases and a pseudoinfarct pattern in as many as 75% of cases.[5,6] Binding of amyloid fibrils to His-Purkinje cells can lead to sudden cardiac death secondary to atrioventricular block and ventricular dysrhythmias. Echocardiography typically reveals thickening of the ventricular septal and free walls, normal or reduced ventricular cavity size, dilated atria, and a normal or slightly reduced ejection fraction; however, cardiac output is significantly reduced.
Atrial septal thickening with granular, sparkling myocardium is highly specific for differentiating cardiac amyloidosis from other causes of left ventricular hypertrophy. Of note, sarcoidosis and hemochromatosis can also present similarly, with normal or low-voltage ECG findings and thickened ventricle walls. Coronary angiography findings are usually normal; amyloid deposition involving the epicardial vessels may be rarely seen.
The definitive diagnosis of amyloidosis usually requires tissue biopsy. Fine-needle aspiration of abdominal fat is a simple procedure that is positive in > 70% of patients with amyloidosis.[9,10] Biopsies can also be obtained from the minor salivary glands, gingiva, rectum, and skin. Rarely, obtaining tissue from an affected organ may be necessary. In some cases of isolated cardiac involvement, percutaneous endomyocardial biopsy of the right ventricle or interventricular septum may be required.
Other methods of diagnosis include bone marrow biopsy to look for a monoclonal population of plasma cells (either kappa or lambda) or immunofixation electrophoresis to look for monoclonal light chain in the urine or serum (which is more sensitive than conventional electrophoresis). Another, more sensitive method is FLC assay, which detects circulating FLCs of both the kappa and lambda types. This assay can also be used for following the progression of the disease and the response to treatment. A combination of an abnormal kappa-to-lambda ratio and a positive serum immunofixation can identify 99% of patients with amyloidosis.
The median survival in systemic amyloidosis is only 1-2 years; patients with symptomatic heart involvement have a median survival of only 6 months. An elevated N-terminal pro-brain natriuretic peptide level, an elevated cardiac troponin level, a high circulating level of free light chains, and increasing wall thickness all portend a poor prognosis. The thickness of the ventricular septum in diastole is a predictor of survival, with survival ranging from 2.4 years in patients with normal wall thickness to 0.4 year in those with increased wall thickness.
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