Impact of Increasing Referral for 99mTc-DPD Scintigraphy on Prognosis Across the Phenotypic Spectrum of Restrictive Cardiomyopathy

BACKGROUND: Although bone scintigraphy has been widely accepted as integral to the non-biopsy diagnostic algorithm for transthyretin amyloid cardiomyopathy (ATTR-CM), its prognostic role remains uncertain. OBJECTIVES: Tc-DPD scintigraphy and its influence on the clinical phenotype and prognosis of patients diagnosed with ATTR-CM, and among those individuals in whom ATTR-CM is excluded. METHODS: Tc-DPD scintigraphy to the Midlands Amyloidosis Service over 15 years. RESULTS: Tc-DPD scintigraphy was linked to increasing proportions of referrals from cardiologists over 5-year periods (47% vs 87% vs 96%, P < 0.001). Nearly half of patients (216/477, 45%) were diagnosed with ATTR-CM: 186 had ATTRwt-CM and 30 had ATTRv-CM; the commonest TTR variant was V142I (25/30, 83%). Compared to ATTR-CM, patients with nonamyloid CM (261/477, 55%) were younger and more often female yet with similar 5-year mortality rates (40% vs 31%, P = 0.044). In an age- and sex-adjusted Cox-proportional hazards model, there was no significant difference in survival between patients with ATTRwt-CM and nonamyloid CM (HR 0.99, 95% CI: 0.98-1.38, P = 0.96). There was also no difference in mortality according to Perugini grading. CONCLUSIONS: Tc-DPD scintigraphy, equivalent to that of ATTR-CM. This finding serves as a call for future studies to better characterise this seemingly overlooked cohort, with the aim of developing targeted therapies and improving outcomes.