Table 2.

Imaging differences between ATTR and AL cardiac amyloidosis

Modality	ATTR amyloidosis	AL amyloidosis
99mTc-labeled phosphate scintigraphy	Strong myocardial uptake (Perugini grade 2–3); high H/CL ratio (≥ 1.5 at 1 h); low false-positive rate when monoclonal protein is excluded	Minimal or absent uptake; Perugini grade 0–1; false positives rare but possible, especially with myocardial injury or concurrent pathologies
PET (18F-florbetapir, 18F-florbetaben, 18F-flutemetamol, 11C-PiB)	Mild to moderate myocardial uptake; variable depending on genotype (ATTRwt vs. ATTRv)	Strong and diffuse myocardial uptake; high sensitivity and specificity; superior to scintigraphy in some AL cases
CMR	Subendocardial or diffuse LGE; very high ECV (> 45–50%); mildly elevated native T1 and T2 values	Global or transmural LGE; elevated native T1 and markedly prolonged T2 (inflammation/edema); increased ECV; less frequent apical sparing pattern
CCT	LIE; increased CT-derived ECV; applicable in TAVR/ablation planning	May show LIE and increased ECV; less validated and less commonly used in AL amyloidosis evaluation

ATTR, transthyretin amyloidosis; AL, light chain amyloidosis; PET, positron emission tomography; CMR, cardiac magnetic resonance; CCT, cardiac computed tomography; H/CL, heart-to-contralateral lung ratio; LGE, late gadolinium enhancement; ECV, extracellular volume; T1/T2, MRI relaxation times; PiB, Pittsburgh Compound B; LIE, late iodine enhancement; CAD, coronary artery disease; PYP, pyrophosphate; ATTRwt, wild-type ATTR; ATTRv, variant (hereditary) ATTR