Impact of Tafamidis on [^99mTc]Tc-pyrophosphate Scintigraphy in Ala97Ser Hereditary Transthyretin amyloid cardiomyopathy: significant initial reduction with stable Long-Term effects.

Abstract

Tafamidis has shown potential in slowing disease progression in patients with transthyretin amyloid cardiomyopathy (ATTR-CM). This study aimed to evaluate serial changes on [^99mTc]Tc-pyrophosphate (PYP) scintigraphy during tafamidis treatment for hereditary ATTR-CM. We retrospectively analyzed a prospectively collected cohort of Ala97Ser (A97S) hereditary ATTR-CM patients treated with tafamidis (61 mg/day) and a control group comprising A97S hereditary ATTR-CM patients who had not received disease-modifying medications. The tafamidis group was further divided into two cohorts: cohort A received [^99mTc]Tc-PYP SPECT/CT scans at baseline, 1 year, and 2 years; cohort B at baseline, 2 years, and 3 years. Visual score, planar heart to contralateral lung (H/CL) ratio, and volumetric heart to lung (H/L) ratio were measured. Nineteen patients were enrolled in the tafamidis group and nine in the control group. After 2 years of follow-up, a significant decrease in volumetric H/L ratio (3.86 ± 0.91 to 3.01 ± 0.19, p < 0.001) was noted in the tafamidis group, while there was no significant change in the control group. When evaluated over time, a significant decrease in volumetric H/L ratio was observed during the first year of tafamidis treatment (3.75 ± 0.37 to 2.82 ± 0.15, p = 0.004), followed by stable [^99mTc]Tc-PYP uptake in the subsequent two years (2.82 ± 0.15 to 2.83 ± 0.18, p = 0.934 and 3.20 ± 0.14 to 3.09 ± 0.16, p = 0.404, respectively). A significant reduction in [^99mTc]Tc-PYP uptake was observed in hereditary ATTR-CM patients after tafamidis treatment, particularly within the first year. While the effect appeared to be sustained, stable [^99mTc]Tc-PYP uptake without further significant reductions was observed in the subsequent years.