Abstract
Background/Objectives: Cardiac amyloidosis (CA) is associated with amyloid infiltration of the extra-cardiac tissue, which may occur in the early stages of the disease. This study evaluates the diagnostic utility of thoracic fat pad biopsy obtained during a pacemaker or ICD implantation as an alternative to the standard diagnostic criteria for systemic amyloidosis. Methods: This exploratory, retrospective study included 27 patients with suspected or diagnosed CA who underwent pacemaker or defibrillator therapy. Results: Of these, 16 patients were confirmed to have CA (15 with technetium-labeled bisphosphonate bone scintigraphy and 1 with protein electrophoresis and echocardiographic findings) while 11 were confirmed to be CA-negative. The thoracic fat pad biopsy demonstrated a specificity of 100% but a sensitivity of only 31%. Among patients with transthyretin (ATTR)-CA, the sensitivity remained similarly low, at 27%. These results are consistent with prior findings on abdominal fat pad biopsy in ATTR-CA, highlighting the limited diagnostic yield of this method. Conclusions: Thoracic fat pad biopsy cannot be recommended as a standard diagnostic tool for CA, particularly in ATTR-CA, due to its poor sensitivity. However, in AL (amyloid light-chain) amyloidosis, this minimally invasive procedure may aid diagnosis without additional invasive interventions.