What are the safest and easiest extra-cardiac biopsy sites for the diagnosis of wild-type transthyretin cardiac amyloidosis? Confirmation of the diagnosis by biopsy of the pectoralis muscle during pacemaker insertion

Since 2016, wild-type transthyretin cardiac amyloidosis (ATTRwt-CA) has been diagnosed without biopsy; however, biopsy is still required in some cases to detect deposition of amyloid transthyretin (ATTR).Biopsies to confirm ATTR deposition should be performed at sites where technetium-99m-labelled pyrophosphate uptake indicates deposition.The pectoralis major has a high rate of technetium-99m-labelled pyrophosphate uptake and biopsy of this muscle, which can be performed when creating a permanent pacemaker pocket, may be useful for confirming ATTR deposition in patients with suspected ATTRwt-CA.