Preservation of Circumferential and Radial Left Ventricular Function as a Mitigating Mechanism for Impaired Longitudinal Strain in Early Cardiac Amyloidosis

Abstract

In patients with cardiac amyloidosis (CA), left ventricular ejection fraction (LVEF) is frequently preserved, despite commonly reduced global longitudinal strain (GLS). We hypothesized that nonlongitudinal contraction may initially serve as a mitigating mechanism to maintain cardiac output and studied the relationship between global circumferential (GCS) and radial (GRS) strain with LVEF and extracellular volume (ECV), a marker of amyloid burden. Patients with CA who underwent cardiac magnetic resonance (CMR; n=140, 70.7±11.5years, 66% male) or echocardiography (n=67, 71±13years, 66% male) and normal controls (CMR, n=20; echocardiography, n=45) were retrospectively identified, and GCS, GLS, and GRS were quantified using feature-tracking CMR or speckle-tracking echocardiography and compared between CA patients with preserved and reduced LVEF (CAHFpEF, CAHFrEF) and controls. The prevalence of impaired strain (magnitudes <2.5th percentile of the controls) was compared between CAHFpEF and CAHFrEF and between ECV quartiles. While echocardiography-derived GLS was impaired in both CAHFpEF (-13.4%±3.1%, P<.003) and CAHFrEF (-9.1%±3.2%, P<.003), compared with controls (-20.8%±2.4%), GCS was more impaired in CAHFrEF compared with both controls (-15.6%±5.0% vs -32.3%±3.3%, P<.003) and CAHFpEF (-30.4%±5.7%, P<.003) and did not differ between CAHFpEF and controls (P=.24). The prevalence of abnormal CMR-derived GCS (P<.0001) and GRS (P<.0001) but not GLS (P=.054) varied significantly across ECV quartiles. Among CA patients with preserved LVEF, preserved GCS and GRS, despite near-universally impaired GLS, may be explained by an initial predominantly subendocardial involvement, where mostly longitudinal fibers are located. If confirmed in future studies, these findings may facilitate identification of patients with early stages of CA, when treatments may be most effective.