Additive diagnostic value of thoracic SPECT/CT imaging in perugini grade 1 patients who underwent bone scintigraphy

Left ventricular (LV) myocardial uptake of ^99mTechnetium-labeled tracers is assessed to diagnose transthyretin amyloid cardiomyopathy (ATTR-CM). The degree of uptake is visually graded using planar images utilising the Perugini score. Today, non-invasive diagnosis of ATTR-CM is broadly established in practice; however, in patients with mild tracer uptake (Perugini grade 1), no definite diagnosis can be made without endomyocardial biopsy.

Within the scope of a prospective cardiac amyloidosis registry at the Medical University of Vienna, all patients who underwent bone scintigraphy graded as Perugini grade 1 with additional SPECT/CT imaging performed between September 2014 and May 2025 were retrospectively analysed.

41 patients (70.8 years, IQR: 64.9-78.8, 41.5% female) were included. The majority (n = 32, 78.0%) of scans were ordered for a suspicion of ATTR-CM. On SPECT/CT images, true LV tracer uptake was confirmed in 4 (9.8%) patients, and 1 (2.4%) patient presented with focal myocardial uptake. In all other patients, tracer uptake was not within the myocardial tissue but rather blood-pool uptake. In follow-up [^99mTc]-DPD scintigraphy, myocardial tracer uptake eventually progressed to Perugini grade 2 in 3 patients who previously demonstrated mild LV myocardial tracer uptake. In contrast, those with diffuse LV uptake did not show any signs of progression in follow-up SPECT/CT imaging.

SPECT/CT is mandatory in patients with mild mediastinal tracer uptake interpreted as Perugini grade 1. Among patients with Perugini grade 1 and confirmed [^99mTc]-DPD LV uptake on SPECT/CT images, progression to Perugini grade 2 was observed in all individuals who underwent nuclear medicine imaging follow-up.