Combination of commonly examined parameters is a useful predictor of positive99 mtc-labeled pyrophosphate scintigraphy findings in elderly patients with suspected transthyretin cardiac amyloidosis

Abstract

Background: A recent study revealed a high prevalence of transthyretin (TTR) cardiac amyloidosis (CA) in elderly patients. 99m Tc-labeled pyrophosphate (99 m Tc-PYP) scintigraphy is a remarkably sensitive and specific modality for TTR-CA, but is only available in specialist centres; thus, it is important to raise the pretest probability. The aim of this study was to evaluate the characteristics of patients with99 mTc-PYP positivity and make recommendations about patient selection for99 mTc-PYP scintigraphy. Methods and Results: We examined 181 consecutive patients aged ≥70 years who underwent99 mTc-PYP scintigraphy at Kumamoto University Hospital between January 2012 and December 2018. Logistic regression analyses showed that high-sensitivity cardiac troponin T (hs-cTnT) ≥0.0308 ng/mL, left ventricular posterior wall thickness ≥13.6 mm, and wide QRS (QRS ≥120 ms) were strongly associated with99 mTc-PYP positivity. We developed a new index for predicting99 mTc-PYP positivity by adding 1 point for each of the 3 factors. The99 mTc-PYP positive rate increased by a factor of 4.57 for each 1-point increase (P<0.001). Zero points corresponded to a negative predictive value of 87% and 3 points corresponded to a positive predictive value of 96% for99 mTc-PYP positivity. Conclusions: The combination of biochemical (hs-cTnT), physiological (wide QRS), and structural (left ventricular posterior wall thickness) findings can raise the pretest probability for99 mTc-PYP scintigraphy. It can assist clinicians in determining management strategies for elderly patients with suspected CA.