A Potential Approach to Bridge the Diagnostic Gap and Propose a Referral Pathway for Suspected ATTR-CA Based on Incidental Cardiac Uptake in 99mTc-MDP Bone Scans: A Pilot Descriptive Study.

Background/Objectives: Early diagnosis of cardiac amyloidosis is crucial to improve patient outcomes. Although 99mTc-MDP is less sensitive than other bone-avid tracers for detecting ATTR-CA, it is widely used for routine bone imaging in this region. Incidental cardiac uptake on 99mTc-MDP bone scintigraphy may therefore offer a practical opportunity for identifying suspected ATTR-CA in resource-limited settings. To evaluate incidental cardiac uptake, warranting further evaluation for ATTR-CA on routine 99mTc-MDP bone scans as an incidental flag method for patients who require further evaluation and to propose a referral pathway in resource-limited settings. Methods: A retrospective review of 229 patients was performed. The assessment of myocardial uptake was performed using the Perugini visual score and H/CL ratio analysis. Patients' medical records were reviewed, and available cardiac imaging reports were evaluated for further assessment of cardiac involvement. Results: Nine patients demonstrated a Perugini score = 2; of these, five underwent echocardiography, demonstrating abnormalities that may indicate amyloid involvement. No patient had confirmatory ATTR-CA testing, AL-CA exclusion testing, (CMR), biopsy, or amyloid typing. In patients without prior cardiac disease, echocardiographic abnormalities may potentially represent subclinical disease, such as cardiac amyloidosis, though this requires further confirmation. In patients with HTN or diabetes, the echocardiographic changes may be attributed to the underlying conditions. Echocardiographic characteristics suggestive, but not specific, for cardiac amyloidosis were observed in patients selected based on positive 99mTc-MDP uptake. Conclusions: Incidental cardiac uptake with a Perugini score ≥ 2 can highlight patients for ATTR-CA investigation. These results provide preliminary evidence that incidental 99mTc-MDP cardiac uptake can flag patients who require further evaluation for ATTR-CA and support the implementation of a referral pathway from local evaluation to a specialized center.