Clinical Predictors of Positive Tc-99m Pyrophosphate Scan in Patients Hospitalized for Decompensated Heart Failure

659 Objectives: Understanding the characteristics of patients with a final diagnosis of transthyretin amyloid cardiomyopathy (ATTR-CA) may help optimally triage patients for Tc-99m pyrophosphate (PYP) scanning. The study was aimed to investigate the prevalence as well as the clinical features along with the electrocardiographic and echocardiographic characteristics of patients with ATTR-CA, who were referred for PYP scan after being hospitalized for decompensated heart failure. Methods: We included all the patients who were referred for PYP scan after heart failure-related hospitalization at our center between 06/2015 and 06/2019. ATTR-CA was diagnosed by positive PYP scan and negative serum studies for AL amyloidosis; gene testing results were used to differentiate between wild-type ATTR-CA and hereditary ATTR-CA. The transthoracic echocardiogram and electrocardiogram were included which were performed around the time of PYP scan. The echocardiographic measurements were based on the American Society of Echocardiography guidelines. The medical history was obtained through chart review. Results: Of the 155 patients who underwent PYP scan, 45 (29%) were PYP +ve. All PYP +ve patients were wild-type ATTR-CA. In the PYP negative group, 8 patients (7.2%) had eventual diagnosis of AL amyloidosis. Compared to the PYP -ve group, the PYP +ve group had similar age (mean 79.5 vs 78.1 years, p=0.9), BMI (28.2 kg/m2 vs 30.1 kg/m2, p=0.7) and a higher prevalence of bilateral carpal tunnel syndrome (62% vs 15%, p<0.01). PYP +ve patients had higher prevalence of low QRS voltage (47% vs 7%, p<0.01), left anterior fascicular block (LAFB) (27% vs 9%, p<0.01), first-degree atrioventricular block (AVB) (29% vs 11%, p=0.01) and atrial fibrillation (85% vs 41%, p< 0.01). PYP +ve patients also had lower left atrial volume index (LAVI) (43 mL/m2 vs 59 mL/m2, p=0.001), greater left ventricular septal thickness (1.67cm vs 1.5cm, p=0.01), increased posterior wall thickness (1.5cm vs 1.3cm, p=0.02) and worse mean diastology (2.6±0.5 vs 1.7± 0.8, p< 0.001). There was no difference in ejection fraction (51% vs 50%, p=0.7) or pulmonary arterial systolic pressure (39 mmHg vs 37.5 mmHg, p=0.9). Conclusions: At our center, almost one-third of the hospitalized patients who were clinically suspected to have cardiac amyloidosis had a final diagnosis of wild-type ATTR-CA. A history of carpal tunnel syndrome, ECG findings of low QRS voltage, AVB and LAFB, and echocardiographic features of left ventricular hypertrophy and high-grade diastolic dysfunction were prevalent in wild-type ATTR-CA.