Significance of regional myocardial 99mTc-PYP uptake on clinical outcomes in wild-type transthyretin amyloid cardiomyopathy.

To investigate the prognostic significance of regional myocardial technetium-99m-pyrophosphate (99mTc-PYP) uptake distribution in patient with transthyretin amyloid cardiomyopathy (ATTR-CM). This single-center retrospective cohort study included patients diagnosed with wild-type ATTR-CM (ATTRwt) at the Hamamatsu University School of Medicine between August 2019 and May 2024. Regional 99mTc-PYP uptake was assessed using polar mapping across nine left (LV) and right (RV) ventricular segments. A total of 33 patients were analyzed with a median follow-up duration of 372 (range, 189–597) days. During the follow-up period, 17 patients experienced composite cardiovascular events (CCEs). Increased 99mTc-PYP uptake in both LV and RV segments was associated with a higher incidence of CCEs. The area under the curve (AUC) for predicting CCEs was 0.711 for National Amyloidosis Centre (NAC) staging alone, which increased to 0.824 and 0.809 when combined with the RV uptake score or RV basal free wall (RVBF) uptake ratio, respectively. The net reclassification improvement (NRI) for both parameters added to NAC staging was 0.669 (95% confidence interval [CI]: 0.027–1.312, p = 0.041). Similarly, the AUC for echocardiography-derived LV-global longitudinal strain (LV-GLS) alone was 0.743, which improved to 0.787 with the RV uptake score and 0.798 with the RVBF uptake ratio. Corresponding NRI values were 0.669 (95% CI: 0.027–1.312, p = 0.041) and 0.794 (95% CI: 0.172–1.416, p = 0.012). Incorporating the RV uptake score or RVBF uptake ratio significantly enhanced the predictive accuracy of outcome models based on NAC staging or LV-GLS in patients with ATTRwt.