Diagnostic Performance of Abnormal Nulling on Cardiac Magnetic Resonance Imaging Look Locker Inversion Time Sequence in Differentiating Cardiac Amyloidosis Types

PURPOSE: To evaluate the diagnostic utility of the Look Locker inversion time (TI) sequence on cardiac magnetic resonance imaging in patients with suspected cardiac amyloidosis and to evaluate whether there are differences in the nulling pattern between amyloid types. MATERIALS AND METHODS: A total of 144 patients with suspected cardiac amyloidosis who had undergone cardiac magnetic resonance imaging were included in this retrospective study. Sixty-four had cardiac amyloidosis (62.1±9.2 y, 70.3% male, 68.8% had light chain amyloid [AL], 18.8% had familial transthyretin amyloid caused by mutant genes [ATTRm], and 12.5% had wild-type transthyretin amyloid [ATTRwt]) and 80 did not have cardiac amyloidosis (61.3±13.3 y, 58.8% male). Time to myocardial and blood pool nulling on the Look Locker TI sequence was classified as normal if blood pool nulled before myocardium or abnormal if blood pool nulling was coincident with or after myocardial nulling. RESULTS: The nulling pattern was abnormal in 26 patients with cardiac amyloidosis compared with none of the patients without cardiac amyloidosis (40.6% vs. 0.0%, P<0.0001). Abnormal nulling had 40.6% sensitivity and 100% specificity for cardiac amyloidosis (area under the receiver operating characteristic curve: 0.703, 95% confidence interval: 0.642-0.764). All patients with cardiac amyloidosis with an abnormal nulling pattern demonstrated late gadolinium enhancement. Among patients with cardiac amyloidosis, there was no significant difference in abnormal nulling between AL, ATTRm, and ATTRwt amyloid types (31.8%, 58.3%, 62.5%, respectively, P=0.10). CONCLUSIONS: An abnormal nulling pattern on the Look Locker TI sequence is highly specific for cardiac amyloidosis when present. However, abnormal nulling is a late finding with low sensitivity and does not differentiate between amyloid types.