Diagnostic and prognostic value of 99mTc-pyrophosphate SPECT/CT in patients with transthyretin amyloid cardiomyopathy

This study evaluated the diagnostic and prognostic values of Technetium- 99m pyrophosphate (99mTc-PYP) scintigraphy using single-photon emission computed tomography/ computed tomography (SPECT/CT) in patients with transthyretin amyloid cardiomyopathy (ATTR-CM). Among 206 consecutive patients with suspected cardiac amyloidosis who underwent 99mTc-PYP scintigraphy using SPECT/CT and had no evidence of monoclonal protein, 20 patients were diagnosed with ATTR-CM based on SPECT/CT interpretation, whereas183 had no diagnostic findings on SPECT/CT interpretation. We calculated 99mTc-PYP activity in the volume of interest (VOI) for the myocardium and upper aorta for the blood pool as a reference. The heart-to-blood ratio (HBR) was calculated by dividing the mean activity in the VOI of the myocardium by that in the VOI of the upper aorta. Receiver-operating-characteristic (ROC) analysis was used to assess the diagnostic value of the Perugini grade, HBR, and heart-to-contralateral ratio (H/CL). A multivariate Cox model was used to assess whether the parameters, including HBR, were associated with all-cause mortality, cardiac death, and hospitalization for heart failure. By ROC analysis, HBR had the most diagnostic value (HBR area under the curve AUC: 0.997, 95% confidence interval CI 0.990–1.000 vs. H/CL AUC: 0.9617, 95% CI 0.942–0.981 vs. Perugini grade AUC: 0.918, 95% CI 0.891–0.945). During a mean follow-up period of 531 days, 38 major adverse cardiac events occurred. Multivariable Cox models showed that HBR was the most significant prognostic factor (hazard ratio 2.715, 95% CI 1.185–6.221, p = 0.018). This study demonstrated that HBR calculated by 99mTc-PYP scintigraphy using SPECT/CT could have potential diagnostic and prognostic value in patients with ATTR-CM.