Prevalence and diagnostic value of extra-left ventricle echocardiographic findings in transthyretin-related cardiac amyloidosis

Background: Cardiac amyloidosis (CA) is cardiomyopathy with a hypertrophic phenotype characterised by diffuse deposition of anomalous fibrillar proteins in the extracellular matrix. Objectives: To evaluate the prevalence and diagnostic value of extra left ventricle echocardiographic findings in patients with left ventricular (LV) hypertrophic phenotype and amyloid deposition. Methods: A group of 146 patients with LV thickness ≥15 mm were enrolled: 70 patients who received a definite diagnosis of sarcomeric hypertrophic cardiomyopathy (HCM group) and 76 patients with transthyretin cardiac amyloidosis (CA group). Echocardiographic analysis of crista terminalis (CriT), atrio-ventricular plane (AVP), mitro-aortic lamina (MAL), anterior ascending aortic wall, interatrial septum (IAS), Eustachian valve (EusV) and coumadin ridge (CouR) was performed in all patients, and these structures were compared among the two groups. Results: CA group showed significantly higher dimensions of CriT, IAS, CouR, AVP, MAL and IAS compared to the HCM group. The logistic analysis showed that LV EF, LV septal thickness, CriT presence, CriT area, MAL and IAS were all predictors of CA in univariate analyses. The stepwise multivariate analysis showed independent predictors of CA: CriT area, MAL and LVEF. According to areas under the receiver operating characteristic curves the best cut-off values to determine CA were identified (IAS > 9 mm, MAL > 7 mm, CriT > 9 mm2). Among these 3 independent predictors, IAS > 9 mm had the best specificity (96%) and positive predictive value (93%) in identifying CA. Conclusions: evidence of extra left ventricle sites of amyloid deposition is a frequent finding in CA. In the context of hypertrophic phenocopies, an increased thickness of IAS, and/or CT and/or MAL should suggest a diagnosis of transthyretin CA.