The use of PYP scan for evaluation of ATTR cardiac amyloidosis at a tertiary medical centre.

ABSTRACT

Cardiac transthyretin amyloidosis (ATTR) is an often underdiagnosed disease that can lead to significant morbidity and mortality for patients. In recent years, technetium-99m pyrophosphate scintigraphy (PYP) imaging has become a standard of care diagnostic tool to help clinicians identify this disease. With newly emerging therapies for ATTR cardiomyopathy, it is critical to identify patients who are eligible for therapy as early as possible. At our institution, we sought to describe the frequency of PYP scanning and how it has impacted the management of a patient suspected to have amyloid cardiomyopathy. Between 1 January 2017 and 31 December 2020, we identified 273 patients who completed PYP scanning for evaluation of cardiac amyloidosis at Tufts Medical Center, a tertiary care centre. We reviewed pertinent clinical data for all study subjects. A PYP scan was considered positive when the heart to contralateral lung ratio was greater than or equal to 1.5, with a visual grade of 2 or 3, and confirmation with single-photon emission computerised tomography (SPECT) imaging. In total there were 55 positive, 202 negative, and 16 equivocal PYP scans. Endomyocardial biopsies were rarely performed following PYP results. Of the seven patients with a positive PYP scan who underwent biopsy, five were positive for ATTR amyloid; of the patients with a negative scan who were biopsied, none were positive for ATTR amyloidosis and two were positive for amyloid light-chain (AL) amyloidosis. The biomarkers troponin I, B-type naturietic peptide (BNP), and N-terminal pro-BNP (NT-proBNP), as well as the interventricular septal end-diastolic thickness (IVSd) seen on echocardiogram, were all found to be statistically higher in the PYP positive cohort than in the PYP negative cohort using Mann-Whitney U statistical analysis. In total, 27 out of the 55 patients with a positive PYP scan underwent therapy specific for cardiac amyloid. In conclusion, this study reinforces the clinical significance of the PYP scan in the diagnosis and management of cardiac amyloidosis. A positive scan allowed physicians to implement early amyloid-directed treatment while a negative scan encouraged physicians to pursue an alternative diagnosis.