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CMR-Based Differentiation of AL and ATTR Amyloidosis
Study Questions:
Can cardiac magnetic resonance (CMR) differentiate between cardiac light chain amyloid (AL) and transthyretin-related amyloidosis (ATTR)?
Methods:
The study retrospectively examined a cohort of 97 patients with histologically confirmed systemic amyloidosis referred to a specialized center with prior CMR for suspected cardiac amyloidosis performed at 46 centers. Previously performed CMR images were compared between 46 patients with cardiac AL amyloidosis and 51 patients with ATTR to identify differences in cardiac morphology and late gadolinium enhancement (LGE).
Results:
Between patients with AL amyloidosis and ATTR, there were significant differences in mean left ventricular (LV) end-diastolic (114 ± 31 vs. 131 ± 39 ml, p = 0.02) and end-systolic volumes (43 ± 20 vs. 59 ± 28 ml, p = 0.001), median LV mass (167 vs. 228 g, p < 0.001), mean septal thickness (14 ± 2 vs. 18 ± 2 mm, p < 0.001), and right ventricular (RV) free wall thickness (6 ± 2 vs. 8 ± 2 mm, p < 0.001). LV LGE was observed in almost all patients, with significant differences between AL amyloidosis and ATTR in regard to presence of RV LGE (72% vs. 100%, p < 0.001), and patterns of LGE including the presence of any transmural LGE (37% vs. 90%, p < 0.001). Using a derived LGE scoring system incorporated into a multivariable model with age and wall thickness, the model was able to identify ATTR with a sensitivity and specificity of 87% and 96%. Median survival was significantly different between patients with AL amyloidosis and ATTR (18 vs. 45 months, p = 0.007).
Conclusions:
The authors concluded that CMR is able to distinguish between AL amyloidosis and ATTR with good diagnostic accuracy.
Perspective:
Rapid identification of specific cardiac amyloidosis types is critical given differences in prognosis and treatment, and this manuscript identified marked differences in cardiac morphology and patterns of LGE between the two main subtypes of cardiac amyloidosis. Using a derived scoring system, CMR was able to accurately distinguish between AL amyloidosis and ATTR. One strength of this study was the good observed diagnostic accuracy despite the use of real-world CMR scans from multiple nonspecialized centers. These findings suggest that CMR may play an important role in differentiating and identifying cardiac amyloidosis.
Keywords: Gadolinium, Amyloid Neuropathies, Familial, Magnetic Resonance Spectroscopy
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