Diagnostic value of papillary muscle hypertrophy and mitral valve thickness to discriminate cardiac amyloidosis and Fabry disease

Background: Cardiac amyloidosis (CA) and Fabry disease (FD) cause myocardial damage but may also affect the valvular and subvalvular apparatus. We aimed to evaluate the diagnostic accuracy of new echocardiographic indices including mitral valve thickness and papillary muscle (PM) hypertrophy to differentiate CA and FD. Methods: In patients with confirmed CA and FD, a detailed assessment of valvular function, mitral valve leaflet thickness and PM area as well as PM left ventricular area ratio (PM/LV-ratio) was performed in offline analyses. Receiver operating characteristic curve analyses were conducted to determine the diagnostic accuracy of mitral valve thickness, PM hypertrophy, and PM/LV-ratio to distinguish CA from FD. Results: We retrospectively analyzed a cohort of 129 patients (FD n = 49, CA n = 80). CA patients showed significantly more thickened mitral valve leaflets (4.1 +/- 1.3 mm vs. 2.9 +/- 1.1 mm, p < 0.001) and a higher PM area [4.0 (3.1-4.6) mm(2) vs. 2.8 (2.1-4.6) mm(2), p = 0.009] with a comparable PM/LV-ratio in both groups. Mitral valve thickness showed the highest diagnostic accuracy to discriminate CA [AUC 0.77 (95% CI 0.67-0.87)]. The prevalence of aortic, tricuspid, and pulmonary valve regurgitation was significantly higher in CA (aortic regurgitation >= II degrees 13% vs. 4%, tricuspid regurgitation >= II degrees 19% vs. 8%, p < 0.001). Conclusion: Our results suggest that the assessment of mitral valve thickness may be a new useful echocardiographic parameter to differentiate CA and FD, whereas papillary muscle hypertrophy and PM/LV-ratio showed a limited diagnostic performance to discriminate CA.