Abstract 17577: Cardiomyopathy With Positive ATTR Mutation but Negative Tc-PYP Scan: A Conundrum

Abstract

Background: Cardiac amyloidosis (CA) is a Hypertrophic Cardiomyopathy (HCM) mimic. Technetium labeled pyrophosphate (Tc-PYP) scan provides a rapid & non-invasive means for identifying ATTR-type CA with 99% sensitivity and specificity. We present 2 patients who were referred to HCM clinic but were found to have genetic testing positive for hTTR. In both cases, Tc-PYP scan was negative. Case Presentation: Outlined in Figure 1. Discussion: Both cases present a diagnostic and management dilemma. Neither of these two patients can be strictly considered asymptomatic carriers of the ATTR gene as both had phenotypic expression in the form of cardiomyopathy & massive LVH on imaging. Yet, in both Tc-PYP scan was negative. Neither had the ATTR mutations (Phe64Leu and Val30Met) that have reported association with negative Tc-PYP scan. Another possibility is early CA, which maybe rarely associated with negative Tc-PYP scan. Patient 1 refused endomyocardial biopsy, so early CA remains on the differential for her. Patient 2 had a negative endomyocardial biopsy. Her case is unique due to history of liver transplant 20 years prior to presentation making phenotypic CA less likely, but not impossible as there have been prior reports of cardiac disease progressing even after liver transplantation in familial ATTR. She also had tacrolimus exposure, which is known to cause LVH in rare cases. Both patients had hypertension, which could have also contributed to LVH. This case series serves to highlight the importance of maintaining a broad differential diagnosis in patients undergoing evaluation for HFpEF and severe LVH, particularly in cases of positive genetic testing but negative PYP scan for CA. From a management standpoint, it is unclear if early initiation of tafamidis might have a role in preventing cardiomyopathy progression in such patients with diagnostic uncertainty & ongoing concern for early CA.