The Evaluation of Relative Left Ventricular Wall Thickness on Echocardiography for the Diagnosis of ATTR Cardiac Amyloidosis

Background: The number of patients with transthyretin amyloid cardiomyopathy (ATTR-CM) has been increasing recently, and the early diagnosis and treatment of it are important. 99mTc pyrophosphate scintigraphy (99mTc-PYP) plays a key role in the early diagnosis of ATTR-CM. In patients who underwent 99mTc-PYP, the early diagnosis of ATTR-CM by echocardiography was evaluated, focusing on left ventricular myocardial form and left ventricular wall thickness. Methods: The present study was conducted on 144 patients who underwent 99mTc-PYP between February 2020 and March 2024. A comparison was made between the 99mTc-PYP positive (P) and negative (N) groups, and significant factors were subjected to multivariate analysis. Results: 17 of 144 patients were positive (14.9%), and 15 patients were diagnosed with ATTR-CM by myocardial or skin (fat) biopsy. Other positive patients were also clinically considered to have ATTR-CM based on findings such as poor cardiac function and cerebral hemorrhage. 99mTc-PYP positive had a significantly larger CTR (60.3% in the P group vs. 53.9% in the N group, p = 0.007) and a larger left atrial diameter (42.8 mm in the P group vs. 40.0 mm in the N group, p = 0.047). On the other hand, the mean LV wall thickness was significantly thicker (15.7 mm in the P group vs. 12.8 mm in the N group, p < 0.001); however the LV end-diastolic diameter was smaller (41.9 mm in the P group vs. 48.4 mm in the P group, p < 0.001). The LV mass was similar in both groups, thus the relative left ventricular wall thickness (RWT), which indicates relative wall thickening, was significantly higher in the P group (0.85 in the P group vs. 0.52 mm in the N group, p < 0.001). The receiver operating characteristic curve of RWT for assessing 99mTc-PYP positivity had a cut-off value of 0.717 (area under the curve 0.862, 95%CI 0.763–0.961). Conclusions: The evaluation of wall thickness and RWT on echocardiography is important for diagnosing ATTR-CM.