Tafamidis treatment in ATTR-CM patients significantly reduced the heart-to-contralateral (H/CL) ratio by 0.33 (p=0.0039) after ~24 months, indicating treatment response.
Does 99mTc-pyrophosphate scintigraphy H/CL ratio decrease in response to tafamidis treatment in patients with ATTR-CM?
99mTc-pyrophosphate scintigraphy H/CL ratio may serve as a sensitive imaging biomarker to monitor therapeutic response to tafamidis in ATTR-CM, even when conventional echo and blood biomarkers remain unchanged.
Absolute Event Rate: 0% vs 0%
Abstract Background & Purpose Clinical trials have shown that a transthyretin stabilizer (tafamidis) improves the prognosis of transthyretin amyloidosis cardiomyopathy (ATTR-CM) in terms of hospitalization and long-term mortality. However, the lack of clear indicators of therapeutic efficacy remains an unresolved problem. We aimed to verify the usefulness of 99mTc-pyrophosphate (PYP) bone imaging scintigraphy to monitor response to tafamidis treatment in parallel with conventional cardiac electrocardiogram/echo parameters and blood biomarker changes. Methods We analyzed 10 ATTR-CM patients (9 wild-type, 1 variant) who underwent pyrophosphate scintigraphy before and after initiation of tafamidis treatment. Heart to contralateral (H/CL) ratio was calculated as the fraction of mean heart region-of-interest (ROI) counts to mean contralateral chest ROI counts by a single blinded expert. We also analyzed changes in electrocardiogram (QRS width) and echocardiogram parameters (left ventricular ejection fraction: LVEF, global longitudinal strain: GLS, LV mass index: LVMI) and blood biomarkers (NT-ProBNP, Troponin T). Results After a mean of 24 months of treatment (interquartile range 14.5-22.2 months), echocardiographic and blood marker indices showed no significant changes, while the H/CL ratio decreased in all patients (mean reduction: 0.33, interquartile range 0.17-0.33, p=0.0039 by paired t-test) with a logarithmic trend depending on the duration of treatment (H/CL reduction = 0.3691xln(duration)-0.781, Figure 1 & 2). One case in which the H/CL ratio hardly decreased showed a significant increase in QRS width even during the treatment period (Figure 3). Conclusion Tafamidis treatment in ATTR-CM patients results in a significant reduction in the H/CL ratio in our cohort, which was not associated with a significant improvement in conventional echocardiographic parameters and blood biomarkers. The poor reduction in H/CL ratio with prolonged treatment may indicate myocardial disease progression even with tafamidis therapy. These results indicate the potential usefulness of this index in assessing treatment response and identifying responders.Methods & Figure 1 Figure 2 and Figure 3
Saito et al. (Sat,) reported a other. Tafamidis treatment in ATTR-CM patients significantly reduced the heart-to-contralateral (H/CL) ratio by 0.33 (p=0.0039) after ~24 months, indicating treatment response.
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