The Assessment of Interatrial Septum Thickness by Echocardiography in Wild-type Transthyretin Amyloidosis

Objective Thickening of the interatrial septum (IAS) is one of red flags for cardiac amyloidosis (CA), but the available evidence concerning it is poor. We evaluated the IAS thickness (IAST) using transthoracic echocardiography to determine the criteria for thickening of the IAS for diagnosing wild-type transthyretin cardiac amyloidosis (ATTRwt-CA). Methods We reviewed 60 patients with ATTRwt-CA (mean age: 78.7±5.6 years old, 50 men) and 56 control individuals (mean age: 74.3±6.1 years old, 29 men) with normal echocardiographic findings. We measured the end-diastolic (ED) and end-systolic (ES) IAST in the middle region of the anterior atrial septum in an apical four-chamber view and a subcostal four-chamber view. Results The IAST was significantly greater in patients in the ATTRwt-CA group than in the control group at both sites and phases. In a receiver operating characteristic analysis to discriminate ATTRwt-CA patients from control subjects, the best cutoff value of IAST was 5.2 mm, which was measured at ES in a subcostal four-chamber view, with a sensitivity of 80.0% and specificity of 78.6%. There was no significant correlation between the IAST and disease stage of ATTRwt-CA. Conclusion An IAST ≥5.2 mm measured in a zoomed subcostal four-chamber view at ES might be useful for detecting ATTRwt-CA, regardless of the disease stage of CA.