The short and long‐term characteristics and outcomes of patients with grade 1 myocardial uptake on cardiac scintigraphy

AIMS: This study aimed to characterize the final diagnosis and prognosis of patients with grade 1 myocardial scintigraphy uptake, which is an unequivocal result for the diagnosis of transthyretin cardiac amyloidosis (ATTR‐CA) requiring further invasive investigation with tissue biopsy. METHODS AND RESULTS: We retrospectively compared the clinical and imaging parameters of patients suspected for ATTR‐CA (based on clinical and echocardiographic parameters) with grade 1 vs. grades 2/3 technetium pyrophosphate uptake on cardiac scintigraphy. Prospectively, grade 1 patients underwent re‐evaluation for ATTR‐CA at long term. Of the 132 ATTR‐CA suspected patients, 89 (67%) were diagnosed as grade 1 and 43 (33%) as grades 2/3 uptake. Grade 1 vs. grades 2/3 patients were younger and female predominant with lower biomarker levels and left ventricular mass. Based on available imaging and pathology findings, only 6 out of the 89 patients with grade 1 uptake (7%) were finally diagnosed with light‐chain cardiac amyloidosis, whereas no patient was diagnosed with ATTR‐CA. At 2 [interquartile range (IQR) 0.75, 3.25] years of follow‐up, the survival of patients with grade 1 vs. grades 2/3 uptake was significantly better [hazard ratio 0.271 (95% confidence interval 0.130 to 0.563, P = 0.0005)]. Prospectively, 30 patients with grade 1 uptake were re‐evaluated at a median follow‐up of 3.2 (IQR 2.2, 3.9) years. Their New York Heart Association class, biomarker levels, and echocardiography findings remained stable. No patient (0/25) demonstrated grades 2/3 uptake at repeated long‐term scintigraphy. CONCLUSIONS: Patients with suspected ATTR‐CA and a grade 1 scintigraphy uptake demonstrate a stable clinical, laboratory, imaging, and scintigraphy phenotype along with a benign survival profile at long‐term follow‐up. Larger studies should define the optimal evaluation strategy in this population.