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

## TL;DR

This study shows that patients with negative 99mTc-DPD scans have high mortality, similar to those with ATTR-CM, highlighting a need for further research into this group.

## Contribution

The study reveals that non-ATTR-CM patients have mortality rates comparable to ATTR-CM, suggesting a need for better characterization and treatment strategies.

## Key findings

- Nearly half of patients referred for 99mTc-DPD scintigraphy were diagnosed with ATTR-CM.
- Non-ATTR-CM patients had similar 5-year mortality rates as those with ATTR-CM.
- There was no significant survival difference between ATTRwt-CM and non-ATTR-CM patients.

## Abstract

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.

The authors aimed to characterize changes in the referral pattern for 99mTc-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.

Retrospective cohort study of all-comers referred for 99mTc-DPD scintigraphy to the Midlands Amyloidosis Service over 15 years.

Of 528 patients referred for 99mTc-DPD scintigraphy, 477 underwent echocardiography suggestive for ATTR-CM and were included in the study. A heightened demand for 99mTc-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.

There is strikingly high mortality among patients with negative 99mTc-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.