SPC365

99mTC-DPD Bone Scintigraphy in ATTR-CM: Are We Missing Patients?

Session: Sessão de Posters 08 - Amiloidose cardíaca por transtirretina: diagnóstico e reconhecimento da doença
Speaker: Marta Vilela

Congress: CPC 2026
Topic: F. Valvular, Myocardial, Pericardial, Pulmonary, Congenital Heart Disease
Theme: 17. Myocardial Disease
Subtheme: 17.3 Myocardial Disease – Diagnostic Methods
Session Type: Posters Eletrónicos
FP Number: ---
Authors: Marta Vilela; João Cravo; Daniel Cazeiro; Diogo Ferreira; Sofia Esteves; João Fernandes Pedro; Inês Araújo; Catarina Campos; Isabel Conceição; Fausto Pinto; Dulce Brito; João Agostinho

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000"><strong>Introduction:&nbsp;</strong></span></span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000"><sup>99m</sup></span></span></span><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">TC-DPD scintigraphy is widely regarded as the standard non-invasive imaging technique for diagnosing transthyretin cardiac amyloidosis (ATTR-CM). However, its diagnostic performance across the full phenotypic spectrum of ATTR-CM remains incompletely validated. Reduced sensitivity has been reported, particularly in early-stage hereditary forms. In these scenarios, reliance solely on scintigraphy may delay diagnosis and treatment, making endomyocardial biopsy (EMB) essential for accurate diagnosis.</span></span></span></p>

<p>&nbsp;</p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000"><strong>Aim:</strong></span></span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">To evaluate the diagnostic performance of </span></span></span><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000"><sup>99m</sup></span></span></span><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">TC-DPD scintigraphy&nbsp;ATTR-CM and to identify clinical and imaging predictors of non-diagnostic scintigraphy.</span></span></span></p>

<p style="text-align:justify">&nbsp;</p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000"><strong>Methods:</strong></span></span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">We conducted a single-center retrospective study of patients diagnosed with ATTR-CM between 2022 and 2024. Scintigraphy was negative when the Perugini score was 0 or 1. All patients with negative scans subsequently underwent EMB for diagnostic confirmation. TTR genotyping was performed in all patients using next-generation sequencing.</span></span></span></p>

<p>&nbsp;</p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000"><strong>Results:</strong></span></span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">A total of 100 patients with confirmed ATTR-CM were included (51% hATTR-CM; 49% wtATTR-CM). Overall, 90% presented a positive </span></span></span><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">scintigraphy at diagnosis. Patients with negative scans were significantly younger (60 &plusmn; 5 vs 77 &plusmn; 1 years; p=0.009), and all had hATTR-CM.&nbsp;The sensitivity of <sup>99m</sup>TC-DPD scintigraphy was 100% in wtATTR-CM and 77% in hATTR-CM, including 77% in V30M and 100% in non-V30M variants. Those with negative scans showed a trend towards lower symptom (NYHA III/IV: 0 vs 25 [28%]; p=0.06) and required less diuretic therapy (20% vs 53%; p=0.046).</span></span></span></p>

<p>&nbsp;</p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">Echocardiographic evaluation at diagnosis showed significantly lower interventricular septal (IVS) thickness in patients with negative</span></span></span><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">&nbsp;scintigraphy (13 &plusmn; 0.5 vs 16&nbsp;&plusmn; 0.5 mm; p=0.001) and a trend toward lower sPAP (26 [IQR 17&ndash;34] vs 33 [IQR 26&ndash;39] mmHg; p=0.08). Biomarker levels were also lower: NT-proBNP (280 [IQR 104&ndash;379] vs 1136 [IQR 521&ndash;2924] pg/mL; p=0.001) and troponin (14 [IQR 10&ndash;29] vs 38 [IQR 19&ndash;56] ng/L; p=0.02). All patients with negative scintigraphy underwent EMB, which confirmed amyloid deposition.&nbsp;In multivariable logistic regression, IVS&nbsp;&le;13 mm was independently associated with a negative scintigraphy result, conferring a seven-fold greater likelihood of a negative scan (OR 7; 95% CI 1.3&ndash;36; p=0.03).</span></span></span></p>

<p>&nbsp;</p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000"><strong>Conclusion:&nbsp;</strong></span></span></span></p>

<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000"><sup>99m</sup>TC-DPD scintigraphy&nbsp; demonstrates high diagnostic performance in most patients with ATTR-CM; however, its sensitivity is reduced in younger individuals and in hereditary forms, particularly those with V30M mutation and less advanced structural remodeling. In this subgroup&mdash;especially when IVS is &le;13 mm&mdash;EMB is essential to avoid missed diagnoses and ensure timely initiation of targeted therapy. These findings reinforce the need for a tailored diagnostic approach, integrating clinical suspicion, genotyping&nbsp;and myocardial histology when scintigraphy is non-diagnostic.</span></span></span></p>