Abstract Body (Do not enter title and authors here): Background:
Tafamidis has been shown to improve outcomes in patients with transthyretin cardiac amyloidosis (ATTR-CM). However, 41% of patients experience clinical deterioration despite treatment, which is associated with poor prognosis. Therefore, identifying Tafamidis responders early on may improve patient management and outcomes.

Objective:
To evaluate whether pre-treatment imaging and biomarker parameters can predict response to Tafamidis in patients with wild-type ATTR-CM using serial PiB PET imaging as a surrogate for treatment response.

Methods:
Twenty-five patients with wild-type ATTR-CM were prospectively enrolled and underwent PiB PET, cardiac MRI, echocardiography and laboratory testing (high-sensitivity troponin I, NT-proBNP and eGFR) prior to the initiation of Tafamidis treatment. PiB PET consisted of a 30-minute dynamic acquisition following intravenous injection. The retention index (RI) was calculated by dividing the mean myocardial PiB activity between 15 and 25 minutes by the arterial input function integral over 0 and 20 minutes. SUV images were derived from summed data between 10 and 20 minutes. Correlations were assessed between baseline parameters and changes in RI and SUV after one year of Tafamidis therapy.

Results:
Baseline RI (r = 0.58, p < 0.005), interventricular septal thickness (r = 0.49, p < 0.05) and LV mass index (r = 0.52, p < 0.01) showed significant positive correlations with percent RI change over one year. However, baseline levels of high-sensitivity troponin I, NT-proBNP and eGFR did not significantly correlate with changes in RI or SUV. However, the percentage change in high-sensitivity troponin I correlated with SUV change (r = 0.54, p < 0.05), while changes in NT-proBNP correlated with changes in left atrial volume index (LAVI) (r = 0.60, p < 0.01) and patient age (r = 0.41, p < 0.05).

Conclusion:
Higher baseline PiB uptake and greater left ventricular (LV) hypertrophy may predict an increase in amyloid burden despite Tafamidis therapy. Pre-treatment PiB PET scanning could be a useful method of identifying patients with wild-type ATTR-CM who will respond to tafamidis therapy.