Concordance between quantitative and semi-quantitative analysis of Tc-99m-pyrophosphate scintigraphy for the diagnosis of transthyretin cardiac amyloidosis in patients with HFpEF

Abstract

Background Transthyretin (TTR) cardiac amyloidosis (CA) is an underdiagnosed cause of heart failure with preserved ejection fraction (HFpEF). Cardiac scintigraphy with 99mTechnetium-pyrophosphate (99mTc-PYP) is referred as a simple, non-invasive and reliable method in the diagnosis of TTR-CA. American Society of Nuclear Cardiology Practice Points recommends two interpretative approaches: the quantitative heart-to-contralateral lung ratio (H/CL) at 1 hour or the semi-quantitative visual assessment at 3 hours after radiotracer injection. Purpose In this study, we evaluated the concordance between semi-quantitative and quantitative approaches in the diagnosis of TTR CA in patients with HFpEF. Methods This single-center, prospective study included 78 patients who had a diagnosis of HFpEF according to 2016 ESC HF guidelines. 99mTc-PYP cardiac scintigraphy was performed in 43 patients who have ≥2 red flags for TTR-CA including left ventricular hypertrophy (LVH) (wall thickness ≥12 mm), biventricular hypertrophy, sparkling pattern, reduction in longitudinal strain with apical sparing, thickening of the interatrial septum (>6mm), low-voltage, pseudo infarct pattern or atrioventricular block on ECG. In the absence of monoclonal protein in the serum and urine, Grade 2 to 3 myocardial uptake in semi-quantitative analysis at 3 hours or a H/CL ratio of ≥1.5 in quantitative analysis at 1 hour post injection of 99mTc-PYP is considered positive for TTR-CA. Grade 2–3 uptake with a H/CL ratio ≥1.5 or Grade 0–1 uptake with a H/CL ratio <1.5 were considered as concordant results. Grade 2–3 uptake with a H/CL ratio <1.5 or Grade 0–1 uptake with a H/CL ratio ≥1.5 were considered as discordant results. Results Mean age of study population was 68.26±9.97 years. 17 (39.5%) of 43 patients who underwent 99mTc-PYP cardiac scintigraphy showed a Grade 2 or 3 cardiac uptake and in these patients with Grade 2–3 uptake, 11 patients (65%) had a H/CL ratio ≥1.5 (concordant results) and 6 patients (35%) had a H/CL ratio <1.5 (discordant results). 26 (60.5%) of 43 patients showed Grade 0–1 cardiac uptake. All patients (100%) with Grade 0–1 uptake had a H/CL ratio <1.5 and therefore, showed concordant results. Overall, 37 (86%) patients had concordant and 6 (14%) patients had discordant results (Table 1). Conclusion The results of this study showed that although there was a high agreement between semi-quantitative and quantitative analysis of 99mTc-PYP cardiac scintigraphy, 14% of patients have discordant results and need further workup to confirm TTR-CA in patients with HFpEF. FUNDunding Acknowledgement Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Pfizer independent grant.