Cardiovascular Magnetic Resonance in Cardiac Amyloidosis

Abstract

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 T₁ mapping was compared with that in 16 hypertensive controls. One patient had CMR and autopsy only. Subendocardial T₁ in amyloid patients was shorter than in controls (at 4 minutes: 427±73 versus 579±75 ms; P1 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, Pr=−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/m²; 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 T₁ 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.