"Loss of Bone Signal" on 99m Tc-Labeled Pyrophosphate Scintigraphy in a Patient With Wild-Type Transthyretin Amyloidosis.

ABSTRACT: 99m Tc-3,3-diphosphono-1,2-propanedicarboxylic acid (DPD) scintigraphy and 99m Tc-pyrophosphate (PYP) scintigraphy are highly sensitive modalities for imaging both myocardial and extracardiac amyloid transthyretin in patients with wild-type transthyretin (ATTRwt) amyloidosis. "Loss of bone signal" on planar imaging of 99m Tc-DPD scintigraphy, in which the tracer uptake in bone is obscured by marked tracer uptake in the overlying skeletal muscles, is reported. However, this phenomenon has not yet been documented on 99m Tc-PYP scintigraphy. We describe an 89-year-old woman with ATTRwt amyloidosis in whom "loss of bone signal" together with marked tracer uptake into the skeletal muscles was clearly demonstrated on 99m Tc-PYP scan.

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

BACKGROUND: Technetium-99m-pyrophosphate (99mTc-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. OBJECTIVE: This study aimed to assess the safety and efficacy of 99mTc-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. METHODS: Patients with suspected ATTR-CA in whom myocardial tracer uptake was detected on chest- and abdomen-centered images of 99mTc-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. RESULTS: All 18 consecutive patients (mean age, 86.3 years ± 6.5; 61.1% male) enrolled in the study showed 99mTc-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. CONCLUSION: In wild-type ATTR-CA, 99mTc-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.

A Gluteus Medius Muscle Biopsy to Confirm Amyloid Transthyretin Deposition in Wild-type Transthyretin Cardiac Amyloidosis: A Report of Two Cases.

In patients with wild-type transthyretin cardiac amyloidosis (ATTRwt-CA), the uptake of the tracer on technetium-99m-labeled pyrophosphate (99mTc-PYP) scintigraphy, which indicates amyloid transthyretin (ATTR) per se, is often observed in skeletal muscles, such as the abdominal oblique and gluteal muscles. Among extracardiac biopsies for confirming ATTR deposition in ATTRwt-CA, a 99mTc-PYP imaging-based computed tomography (CT)-guided core needle biopsy of the internal oblique muscle has relatively high sensitivity. In some patients, the 99mTc-PYP uptake is more pronounced in the gluteal muscles than in oblique muscles. We herein report two cases of ATTRwt-CA in which a CT-guided biopsy of the gluteus medius muscle with 99mTc-PYP uptake confirmed the presence of ATTR deposits.

99mTc-Pyrophosphate Scintigraphy Can Image Tracer Uptake in Skeletal Trunk Muscles of Transthyretin Cardiac Amyloidosis.

PURPOSE: 99mTc-pyrophosphate (99mTc-PYP) uptake in the skeletal muscles is minimal in patients with transthyretin cardiac amyloidosis (ATTR-CA) when assessed qualitatively and quantitatively. We previously demonstrated moderate- to high-grade 99mTc-PYP uptake in the subcutaneous abdominal fat of some patients with ATTR-CA and showed that this abnormal finding could reflect the regional amyloid burden of this tissue. We aimed to investigate the frequency of 99mTc-PYP uptake in skeletal trunk muscles of patients with ATTR-CA. METHODS: Chest- and abdomen-centered 99mTc-PYP scintigraphy images were obtained 2 hours after IV injections of the tracer (20 mCi) in 36 patients with ATTR-CA. The frequency of 99mTc-PYP uptake in the following 11 skeletal trunk muscles was investigated: pectoralis major, deltoid, subscapularis, infraspinatus, trapezius, latissimus dorsi, erector spinae, psoas major, abdominal oblique, rectus abdominis, and the gluteus muscles. RESULTS: Ten of the 11 muscles were involved in patients with the highest number of 99mTc-PYP uptake in the skeletal trunk muscles examined, whereas no muscle was involved in a patient with the least uptake. The muscle with the highest rate of 99mTc-PYP uptake, observed in 34 of 36 patients (94.4%), was the abdominal oblique. No tracer uptake was observed in the psoas major. The frequency of radiotracer uptake in the remaining examined muscles was between those of abdominal oblique and psoas major muscles. CONCLUSIONS: Radiotracer uptake was often detectable in some skeletal trunk muscles of ATTR-CA, although the muscles of patients examined and the skeletal trunk muscles of 1 patient showed heterogeneity in the uptake of 99mTc-PYP.