Objectives: Transthyretin amyloid cardiomyopathy (ATTR-CA) was a rare disease; however, since the approval of tafamidis meglumine, ATTR-CA has been reported in many institutions in Japan. It is effective to start administration of tafamidis meglumine early, and early diagnosis and treatment of ATTR-CA are required. Pyrophosphate scintigraphy (Tc-PYP) is effective for the diagnosis of ATTR-CA. We examined the characteristics of Tc-PYP positive patients at our institution.
Materials and methods: A total of 76 patients who underwent Tc-PYP from February 2020 to December 2022 were investigated. We divided them into Tc-PYP positive and Tc-PYP negative groups, and compared between groups. Evaluated factors were age, gender, medical history, blood examination, chest X-ray, 12-lead ECG and echocardiography.
Results: Nine of the 76 patients were Tc-PYP positive (11.8%), and eight patients were diagnosed with ATTR-CA by myocardial or skin (fat) biopsy. The other positive patient died from a cerebral haemorrhage before biopsy. Cerebral haemorrhage is an amyloid-related disease, and Tc-PYP positive patients were considered ATTR-CA patients. In blood examinations, troponin I levels were significantly higher in the positive group (0.945 in positive group versus 0.077 in the negative group, p<0.001). ECG showed few patients with low voltage in either group (one patient in each group, no difference), and left ventricular hypertrophy was observed more frequently in the negative group (11% in the positive group versus 46% in the negative group, p=0.046). In addition, in the positive group, the left ventricular posterior wall thickness was significantly thickened (15.5 mm in the positive group versus 12.5 mm in the negative group, p=0.003). In contrast, there was no difference in septal wall thickness (16.1 mm in the positive group vs 13.7 mm in the negative group, p=0.084).
Conclusion: ATTR-CA is not uncommon, and Tc-PYP should be performed in cases of heart failure with left ventricular hypertrophy of unknown cause. Tc-PYP may be particularly useful for troponin I-positive patients who have left ventricular hypertrophy (particularly of the posterior wall), however do not show hypertensive changes on ECG.