IJCS | Volume 32, Nº2, March/April 2019

179 Ribeiro et al. CMR and amyloidosis Int J Cardiovasc Sci. 2019;32(2)177-189 Review Article myocardial thickening increases the suspicion of cardiac amyloidosis. One hypothesis of voltage decrease is related with amyloid infiltration, which would cause a decrease in cardiac muscle cells. Atrioventricular block, atrial flutter and ventricular tachycardia have been also reported in these patients. 9,14,17,18 Echocardiography When c a r d i a c amy l o i do s i s i s suspe c t ed , echocardiography is usually the first imaging test ordered by the physician. The use of two-dimensional speckle tracking technique has been used to detect subclinical or initial changes of the disease, which may help in the treatment of the patients. 19 At initial stages, diagnosis of amyloidosis may be confounded with parietal hypertrophy, as in hypertrophic cardiomyopathy. However, characteristic findings are more frequently seen at more advanced stages of the disease and are observer-dependent. Common findings include increased ventricular parietal thickness, frequently involving the right ventricle, decreased ejection fraction 20,21 and thickening of valve and interatrial septum. Echocardiography may show wall thickening, especially basal, with high birefringence in the apical area (apical sparing) of the amyloid deposits, in addition to involvement of valves and papillary muscles. 18 Cardiac biomarkers Immunoglobulin light chain amyloidosis is commonly associated with increased levels of troponin and BNP and N-terminal pro-B-type natriuretic peptide (NT-proBNP), which is not observed in transthyretin amyloidosis. This is important for patients with some renal dysfunction, since natriuretic peptides require renal excretion. Increased NT-proBNP in patients with systemic amyloidosis is predictive of cardiac disease. 22 More recently, high-sensitivity troponin has been used as a marker of morbidity and mortality. 23 At diagnosis, measurements of natriuretic peptide and troponin are used for risk stratification of patients. Scintigraphy Scintigraphy is performed with intravenous injection of iodine-123 (123I) for locating amyloid deposit in different organs, including liver, kidney, spleen, adrenal glands, and bones. Thus, this is not an adequate technique for cardiac evaluation in amyloidosis. 24 On the other hand, the use of other markers – 99mTechnetium labelled 3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc- DPD) – has been suggested to specifically locate cardiac amyloid in transthyretin amyloidosis and considered the gold standard for the diagnosis of this condition. 25-28 Cardiac magnetic resonance CMR has been widely used as the gold standard for the assessment of myocardial function and characterization of myocardial tissue. The technique is more precise than echocardiography, allowing the detection of earlier changes. 4 CMR without contrast can also be used to provide a precise quantification of amyloid infiltration associated with morphological changes (left ventricular hypertrophy, decreased chamber size and atrial dilation). The method can be used for patients with contraindication to contrast, such as patients with renal failure, using the T1 mapping technique. 15,29 ACMR test for evaluation of diseases characterized by abnormal protein deposit, such as amyloidosis, should have an average duration of 35 minutes. Although routine sequences are cine and delayed enhancement, we believe that, when T1 mapping technique is available, it should be chosen for routine use. Other techniques such as anatomy, perfusion and flow techniques may be included or not in amyloidosis protocol depending on patients’ clinical status and information obtained from the addition of these sequences to the test. Cine MR In the analysis of ventricular, segmental and total activity, gradient-recalled echo (GRE) and balanced steady-state free precession (SSFP) imaging is the most used sequence. The sequence is added to the electrocardiographic tracings by segmented K-space technique, eliminating motion artifacts. 30 Segmented K-space GRE sequences allow acquisition of many frames during the cardiac cycle in a dissection plane. Presentation of the frames in sequence allows dynamic, motion visualization of the heart during cardiac cycle, due to real-time interpolation of the R-R interval in the ECG. Strengths of the technique include optimal temporal resolution, the clear definition of endocardial and epicardial borders and acquisition of bright-blood cine images. Also, images can be obtained in any geometric plan. 31