Cardiac amyloidosis beyond Perugini. Can diphosphonate scan tell you more?

Abstract Introduction Cardiac transthyretin amyloidosis is a restrictive cardiomyopathy that poses a diagnostic challenge due to its rarity and overlapping clinical symptoms with other diseases. While 99mTcTc-diphosphonate has proven to be sensitive for detecting ATTR, there remains a gap in understanding the correlation between the intensity of cardiac uptake and disease severity. Purpose The aim of this study is to investigate whether there is a correlation between the intensity grade and specific clinical and analytical parameters in patients with ATTR amyloidosis. Methods A single-tertiary center observational, retrospective, and longitudinal study was conducted, encompassing patients aged ≥ 18 years who underwent bone scintigraphy with 99mTcTc-DPD or 99mTcTc-HMDP from 2020 to 2021. Inclusion criteria involved patients witha Perugini score of ≥2. Exclusion criteria were applied to individuals lacking follow-up information. Planar anterior images of the chest were reprocessed to assess the maximum and average uptake within regions of interest, encompassing both the heart and the contralateral thoracic region. Clinical, analytical, and imaging data were extracted from available digital records. Statistical analyses using single and multiple linear regression were conducted using R software. Results 33 patients met the inclusion criteria (85% men, average age: 79 ± 10 years old). Sixteen patients were classified as grade 2, while 17 were classified as grade 3 on the Perugini amyloidosis scale. The radiopharmaceutical used was 99mTcTc-HMDP in 25 patients. The main referring specialties were internal medicine (55%) and cardiology (30%). One patient was referred for bone metastasis, and amyloidosis was an incidental finding. Twenty nine patients had hypertension, 21 had atrial fibrillation, 18 were dyslipidemic, 14 had aortic stenosis, 13 had diabetes mellitus, 6 had chronic kidney disease, and 5 had obstructive airway disease. All patients exhibited left ventricular hypertrophy on echocardiography, the average ejection fraction was 50 ± 12 (58% with preserved ejection fraction), septal thickness of 15.87 ± 2.26 mm and relative myocardial wall thickness was 0.60 ± 0.16 mm. Several patients had degenerative articular disease (11 hip prosthesis, 3 carpal tunnel syndrome surgeries, 3 vertebral surgeries). There were statistically significant associations between an older age and a higher ratio of average counts and the presence of aortic stenosis and a higher ratio of maximum counts. No other correlation was found for other ATTR manifestations (neurological, muscular or cardiac). Conclusion Higher intensity of 99mTcTc-diphosphonate uptake ratios in ATTR seem to be correlated with aortic stenosis and older age.