SPC365

When imaging is not enough: diagnostic performance of endomyocardial biopsy in cardiac amyloidosis

Session: Sessão de Comunicações Orais 11 – Corações espessos e rígidos: amiloidose cardíaca e companhia
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: Comunicações Orais
FP Number: ---
Authors: Marta Vilela; Diogo Ferreira; João Cravo; Daniel Cazeiro; Sofia Esteves; Inês Araújo; Catarina Silva; 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</strong></span></span></span><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">:</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">The diagnosis of cardiac amyloidosis (CA) has increased in recent years, driven by growing clinical awareness and the recognition of clinical, echocardiographic and electrocardiographic red flags. Non-invasive diagnostic tools, such as bone scintigraphy, have become pivotal in the diagnostic algorithm; however, they can yield inconclusive or false-negative results in a relevant subset of patients. In these cases, endomyocardial biopsy (EMB) remains the gold standard, yet real-world data on its diagnostic yield, safety, and predictors of positivity are limited.</span></span></span></p>

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<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><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">:</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 and safety of EMB in CA and to identify clinical and imaging predictors of biopsy positivity.</span></span></span></p>

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<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 46 patients underwent endomyocardial biopsy for suspected CA (mean age 64 &plusmn; 2 years; 46% male). Among them, 41% were referred due to negative </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 and 59% due to abnormal immunofixation. Amyloid was histologically confirmed in 34 patients (74%): 59% TTR, 21% AL, 15% mixed TTR+AL, and 5% with nonspecific amyloid.</span></span></span></p>

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<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">Compared with biopsy-negative patients, those with positive biopsies showed a trend toward more advanced heart failure symptoms (NYHA III/IV: 15% vs 0%, p=0.10) and significantly higher NT-proBNP levels (3694 [IQR 1051&ndash;12826] vs 872 pg/mL [IQR 155&ndash;3065], p=0.02). ECG findings showed a non-significant trend toward longer PR intervals (181 [172&ndash;196] vs 150 ms [148&ndash;209], p=0.1). Biopsy-positive patients exhibited more pronounced structural remodeling, with greater myocardial wall thickening with higher prevalence of interventricular septum thickness &ge;13 mm (80% vs 42%, p=0.02), increased posterior wall thickness (15&nbsp;&plusmn; 1&nbsp;vs 12&nbsp;&plusmn; 1 mm, p=0.03) and higher indexed LV mass (166 &plusmn; 14 vs 119 &plusmn; 15 g/m&sup2;, p=0.03). In logistic regression analysis, posterior wall thickness emerged as an independent predictor of biopsy positivity, with each 1-mm increase significantly increasing the odds of biopsy positivity (OR 1.3, 95% CI 1.01&ndash;1.6, p=0.046).</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">No significant association was found between</span></span></span><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000">&nbsp;scintigraphy grade and biopsy results. No biopsy-related complications occurred. During a mean follow-up of 24 &plusmn; 3 months, one of the 12 biopsy-negative patients was subsequently diagnosed with AL amyloidosis on extracardiac biopsy. EMB demonstrated 97% sensitivity and 100% specificity, with no false positives and one false negative.</span></span></span></p>

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<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:Calibri,sans-serif"><span style="color:#000000"><strong>Conclusion:</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">Non-invasive imaging plays an essential role in the diagnostic workup of CA and is sufficient in many cases. However, our findings highlight that in patients with high clinical suspicion, particularly those with elevated NT-proBNP and increased myocardial wall thickness, EMB provides excellent diagnostic accuracy and can be safely performed. Therefore, EMB should be considered an integral and safe diagnostic approach when non-invasive methods are inconclusive despite strong clinical suspicion.</span></span></span></p>