Cardiovascular magnetic resonance in cardiac amyloidosis

Background - Cardiac amyloidosis can be diagnostically challenging. Cardiovascular magnetic resonance (CMR) can assess abnormal myocardial interstitium. Methods and Results - Late gadolinium enhancement CMR was performed in 30 patients with cardiac amyloidosis. In 22 of these, myocardial gadolinium kinetics with T-1 mapping was compared with that in 16 hypertensive controls. One patient had CMR and autopsy only. Subendocardial T-1 in amyloid patients was shorter than in controls (at 4 minutes: 427 +/- 73 versus 579 +/- 75 ms; P < 0.01), was shorter than subepicardium T-1 for the first 8 minutes ( P <= 0.01), and was correlated with markers of increased myocardial amyloid load, as follows: left ventricular (LV) mass (r = - 0.51, P = 0.013); wall thickness ( r = - 0.54 to - 0.63, P < 0.04); interatrial septal thickness ( r = - 0.52, P = 0.001); and diastolic function ( r = - 0.42, P = 0.025). Global subendocardial late gadolinium enhancement was found in 20 amyloid patients (69%); these patients had greater LV mass (126 +/- 30 versus 93 +/- 25 g/m(2); P = 0.009) than unenhanced patients. Histological quantification showed substantial interstitial expansion with amyloid (30.5%) but only minor fibrosis (1.3%). Amyloid was dominantly subendocardial (42%) compared with midwall (29%) and subepicardium (18%). There was 97% concordance in diagnosis of cardiac amyloid by combining the presence of late gadolinium enhancement and an optimized T-1 threshold (191 ms at 4 minutes) between myocardium and blood. Conclusions - In cardiac amyloidosis, CMR shows a characteristic pattern of global subendocardial late enhancement coupled with abnormal myocardial and blood-pool gadolinium kinetics. The findings agree with the transmural histological distribution of amyloid protein and the cardiac amyloid load and may prove to have value in diagnosis and treatment follow-up.