Iatrogenic intramuscular hematoma of the oblique muscles as a complication of technetium-99m-labeled pyrophosphate imaging-based computed tomography-guided core-needle biopsy in a patient with wild-type transthyretin cardiac amyloidosis.

Technetium-99m-labeled pyrophosphate imaging-based computed tomography-guided core-needle biopsy of the internal oblique muscle with tracer uptake is a safe and sensitive extracardiac screening biopsy. It can provide histopathological confirmation of the deposition of amyloid transthyretin in patients with wild-type transthyretin cardiac amyloidosis. This case report presents the case of a 73-year-old man receiving triple anti-thrombotic therapy for atrial flutter and coronary stenting who underwent this biopsy to confirm the diagnosis of transthyretin cardiac amyloidosis. The biopsy needle reached the internal oblique muscle via the external oblique muscle between the skin and the target. A type 1 intramuscular hematoma involving these muscles developed subsequently; however, manual compression hemostasis prevented further increase in size. Since this biopsy often targets elderly patients receiving anti-thrombotic therapy who are at high risk of bleeding owing to multimorbidity and polypharmacy, efforts should be made to reduce the frequency of complications, particularly bleeding, which can lead to the development of intramuscular hematoma.