Background: Advent of non-invasive diagnosis of transthyretin cardiomyopathy (ATTR-CM) using 99m-technetium pyrophosphate scan (99m-Tc PYP) and approval of Tafamidis for ATTR-CM have revolutionized the field. The utility of 99m-Tc PYP scan to quantify disease burden while receiving Tafamidis therapy has been proposed. Here, we report a case that questions the reliability of 99m-Tc PYP scan during Tafamidis therapy.
Case: A 76-year-old man with MGUS and diagnosis of ATTR-CM (based on a positive 99m-Tc PYP scan; Figure 1A) on Tafamidis therapy for 5 months presented to our institution for a second opinion. Due to unavailability of outside images at the time, 99m-Tc PYP scan was repeated and was negative (Figure 1B).
Decision-making: Negative repeat 99mTc-PYP scan after 5 months of Tafamidis therapy and non-specific cardiac MRI findings lead to discontinuation of Tafamidis. During follow up, presence of MGUS, elevated cardiac biomarkers and suspicious musculoskeletal findings lead to an endomyocardial biopsy (EMBx), which confirmed the diagnosis of ATTR-CM. TTR gene testing was negative. Tafamidis therapy was resumed.
Conclusion: In addition to emphasizing routine use of EMBx in suspected cardiac amyloid patients with MGUS, this case underscores the importance of EMBx in case with incongruent non-invasive tests and those requiring confirmation of the diagnosis while on Tafamidis therapy.

**Background:** Advent of non-invasive diagnosis of transthyretin cardiomyopathy (ATTR-CM) using 99m-technetium pyrophosphate scan (99m-Tc PYP) and approval of Tafamidis for ATTR-CM have revolutionized the field. The utility of 99m-Tc PYP scan to quantify disease burden while receiving Tafamidis therapy has been proposed. Here, we report a case that questions the reliability of 99m-Tc PYP scan during Tafamidis therapy.
**Case:** A 76-year-old man with MGUS and diagnosis of ATTR-CM (based on a positive 99m-Tc PYP scan; Figure 1A) on Tafamidis therapy for 5 months presented to our institution for a second opinion. Due to unavailability of outside images at the time, 99m-Tc PYP scan was repeated and was negative (Figure 1B).
**Decision-making:** Negative repeat 99mTc-PYP scan after 5 months of Tafamidis therapy and non-specific cardiac MRI findings lead to discontinuation of Tafamidis. During follow up, presence of MGUS, elevated cardiac biomarkers and suspicious musculoskeletal findings lead to an endomyocardial biopsy (EMBx), which confirmed the diagnosis of ATTR-CM. TTR gene testing was negative. Tafamidis therapy was resumed.
**Conclusion:** In addition to emphasizing routine use of EMBx in suspected cardiac amyloid patients with MGUS, this case underscores the importance of EMBx in case with incongruent non-invasive tests and those requiring confirmation of the diagnosis while on Tafamidis therapy.

False Negatives and Final Verdicts: A Complex Journey to Transthyretin Amyloid Cardiomyopathy Diagnosis

This course will explore basic and cutting-edge imaging techniques to improve patient care and hone individual skills in performance and interpretation of echocardiography, nuclear cardiology, cardiac computed tomography, and cardiovascular magnetic resonance imaging. Days will reinforce how cardiovascular imaging may improve comprehension in ischemic heart disease, structural heart disease, cardiomyopathies, and heart failure. Experts will utilize novel techniques to reinforce key topics including taped interventional cases and a strong emphasis on case presentations.