Technetium-99m-pyrophosphate imaging-based computed tomography-guided core-needle biopsy of internal oblique muscle in wild-type transthyretin cardiac amyloidosis

BackgroundTechnetium-99m-pyrophosphate (Tc-99m-PYP) uptake in the internal oblique muscle (IOM), which is often observed in patients with wild-type transthyretin cardiac amyloidosis (ATTR-CA), indicates amyloid transthyretin (ATTR) deposition.ObjectiveThis study aimed to assess the safety and efficacy of Tc-99m-PYP imaging-based computed tomography (CT)-guided core-needle biopsy of the IOM as a new extracardiac screening biopsy for confirming the presence of ATTR deposits.MethodsPatients with suspected ATTR-CA in whom myocardial tracer uptake was detected on chest- and abdomen-centered images of Tc-99m-PYP scintigraphy underwent CT-guided core-needle biopsy at the site with the highest tracer uptake in the IOM between September 2021 and November 2022.ResultsAll 18 consecutive patients (mean age, 86.3 years & PLUSMN; 6.5; 61.1% male) enrolled in the study showed Tc-99m-PYP uptake into the IOM. Adequate tissue samples were obtained from all patients except one without serious complications. Immunohistochemical analysis confirmed ATTR deposits in 16/18 (88.9%) patients. In the remaining two patients, ATTR deposits were observed via endomyocardial biopsy. All patients were diagnosed with wild-type ATTR-CA based on transthyretin gene sequence testing results.ConclusionIn wild-type ATTR-CA, Tc-99m-PYP imaging-based CT-guided core-needle biopsy of the IOM could be used as an extracardiac screening biopsy to confirm the presence of ATTR deposits.