The diagnostic yield of non-invasive testing features in cardiac amyloidosis

Cardiac amyloidosis (CA) is a progressive disease in which amyloid fibrils infiltrate the heart muscle. This study aimed to identify features from cardiac biomarkers, electrocardiography (ECG), and echocardiography that may distinguish between transthyretin amyloidosis (ATTR) scintigraphy-positive and negative patients.

Seventy-eight consecutive patients, median age 69 years (range 34-81), with suspected CA, negative serum free light chains, and negative serum and urine protein electrophoresis with immunofixation, referred to cardiac scintigraphy between 2021 and 2024, were retrospectively enrolled. Cardiac uptake was assessed by Perugini grades. Troponin T, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and various ECG and echocardiographic features were compared between ATTR scintigraphy-positive and negative participants using the t-test, Mann-Whitney U-test, and χ2-test as appropriate. Multivariable stepwise logistic regression created the prediction model for ATTR-positive scintigraphy. The significance level was 0.05.

Scintigraphy was ATTR-positive in 24 participants (30.77%). The variables significantly connected with ATTR-positive testing were atrial fibrillation (p = 0.010), first- or second-degree atrioventricular block (p = 0.041), left ventricle (LV) end-diastolic dimension (p = 0.018), LV global longitudinal strain (GLS) (p = 0.040), a restrictive transmitral inflow pattern (p = 0.025), LV posterior wall thickness (p < 0.001), interventricular septum (IVS) thickness (p < 0.001), QRS voltages (p < 0.001), the pseudo- infarct pattern (p < 0.001), and relative apical sparing of the GLS ratio (p < 0.001). The latter four were incorporated into the prediction model for ATTR-positive scintigraphy.

ECG and echocardiography remain the essential diagnostic procedures that raise the suspicion of CA and trigger further diagnostics. Low QRS voltages, the pseudo-infarct pattern, IVS thickness, and relative apical sparing of the GLS ratio are sensitive predictors of ATTR-positive scintigraphy findings.