Authors' Reply

Abstract

At most centers, echocardiography is the primary diagnostic method for patients with heart failure symptoms. Thus, comprehensive echocardiographic assessment of myocardial anatomy and function is of paramount importance to guide the diagnostic pathway and for risk stratification. It is well recognized that cardiac amyloidosis (CA) is severely underdiagnosed, and traditional echocardiographic parameters fall short as diagnostic tools in patients with left ventricular (LV) hypertrophy. With the advances in speckle-tracking imaging, we now have useful tools to raise the suspicion of underlying CA and to provide prognostic information. However, the optimal strain parameters and surveillance strategies are debatable and the topic of several ongoing investigations. We read with interest the comments from Pagourelias et al. These investigators have conducted several important studies regarding the use of speckle-tracking imaging in CA populations. Pagourelias et al.1Pagourelias E.D. Mirea O. Duchenne J. Van Cleemput J. Delforge M. Bogaert J. et al.Echo parameters for differential diagnosis in cardiac amyloidosis: a head-to-head comparison of deformation and nondeformation parameters.Circ Cardiovasc Imaging. 2017; 10: e005588Crossref PubMed Scopus (142) Google Scholar elegantly demonstrated that the ejection fraction–to–strain ratio (EFSR) was superior to other parameters to differentiate patients with CA (n = 40) from those with hypertrophic cardiomyopathy (n = 40) and those with hypertension-induced LV hypertrophy (n = 20). Even though the study population was of intermediate size and the results require external validation, the idea of combining LV ejection fraction (LVEF) and LV global longitudinal strain (GLS) is interesting. LVEF is determined mainly by the radial function and circumferential function,2Stokke T.M. Hasselberg N.E. Smedsrud M.K. Sarvari S.I. Haugaa K.H. Smiseth O.A. et al.Geometry as a confounder when assessing ventricular systolic function: comparison between ejection fraction and strain.J Am Coll Cardiol. 2017; 70: 942-954Crossref PubMed Scopus (254) Google Scholar whereas LV GLS is determined mainly by long-axis function. The combined model therefore reflects the ratio of radial to longitudinal function, which could add to the apical-to-basal strain ratio derived from LV GLS assessment. However, in our opinion, the clinical utility of EFSR is limited by potentially significant interobserver variation. Even though the coefficient of variation for LV GLS is low, there is significant interobserver variation for LVEF. Furthermore, LVEF is highly angle and loading dependent, which reduces the clinical value of prospective surveillance. We therefore argue that EFSR may not prove to be as robust and clinical useful as LV GLS and LV myocardial work index (MWI). We appreciate the suggestions of Pagourelias et al. to evaluate LV circumferential strain and torsion during exercise and to provide information on a potential epicardial-to-endocardial strain gradient. As also demonstrated in the comments of Pagourelias et al., patchy distribution of circumferential late gadolinium enhancement is often seen in the endocardium in early stages of CA, but in advanced stages, late gadolinium enhancement is often transmural.3Dungu J.N. Valencia O. Pinney J.H. Gibbs S.D. Rowczenio D. Gilbertson J.A. et al.CMR-based differentiation of AL and ATTR cardiac amyloidosis.JACC Cardiovasc Imaging. 2014; 7: 133-142Crossref PubMed Scopus (202) Google Scholar However, during exercise, we obtained images at each exercise step but only from the three apical projections in order to preserve the acoustic window and to reduce angle differences from step to step. Furthermore, cardiac magnetic imaging was not conducted in our study. Thus, we cannot correlate our findings of reduced LV MWI and increased apical-to-basal work ratio to the presence of endocardial or transmural extracellular amyloid deposits or a potential epicardial-to-endocardial gradient. We used echocardiographically derived LV mass as a surrogate marker of amyloid deposits. When adjusted for LV mass, the differences in LV MWI between patients with CA and control subjects were more pronounced. LV MWI and the apical-to-basal work ratio was significantly associated with symptoms and functional capacity in patients with CA and may be used as a simple supplement to LV GLS assessment. Left Ventricular Pressure Strain–Derived Myocardial Work at Rest and during Exercise in Patients with Cardiac AmyloidosisJournal of the American Society of EchocardiographyVol. 33Issue 10PreviewIn a recent paper, Clemmensen et al.1 have applied left ventricular pressure strain–derived myocardial work (LVMW) indices in a cohort of cardiac amyloidosis (CA) patients and healthy controls, both at rest and during semisupine exercise.1 The authors report that CA patients have significantly lower rest longitudinal strain (LS) along with lower LVMW and myocardial work efficiency compared with controls. In addition, during exercise, they present a lower improvement of LVMW mainly driven by apical regions and a significantly reduced energy exploitation (based on LS evaluation). Full-Text PDF