Circulation: Cardiovascular Imaging | 2021
Left Atrial Coupling Index and Its Prognostic Value in Heart Failure With Reduced Ejection Fraction.
Abstract
It is well known that the left atrium (LA) has an important role in the pathophysiology of heart failure (HF). LA function has been divided into 3 phases: (1) the reservoir phase, during which the LA fills with blood while the left ventricle (LV) contracts (LV systole); (2) the conduit phase, during which the mitral valve opens and the LA empties passively into the LV; and (3) the booster pump phase, which corresponds to LA contraction (LA systole) and active emptying into the LV.1 In patients with heart failure with reduced ejection fraction (HFrEF), as the severity of disease worsens with a progressive impairment of LV relaxation and compliance, LA pressure increases, which can lead to LA remodeling, fibrosis, and dysfunction. In addition, myocardial pathological processes that lead to LV dysfunction can also directly affect the LA wall. Prior studies demonstrate that in patients with heart failure, LA enlargement and poor LA function, assessed via phasic volume changes or strain-based measurements of reservoir, conduit, and booster pump function, are associated with worse survival in HF.2 In this issue of Circulation: Cardiovascular Imaging, Benfari et al3 report on a large study assessing a novel echocardiographic parameter (named the left atrial volumetric/mechanical coupling index, LACI) and its association with mortality in patients with HFrEF. The authors retrospectively identified 4196 patients with HFrEF who were in sinus rhythm and underwent a transthoracic echocardiographic examination at the Mayo Clinic between 2007 and 2011. They quantified the LA volume index and a’ velocity at the medial mitral annulus by tissue Doppler, and LACI was computed as LA volume index/a’ velocity at the medial mitral annulus by tissue Doppler. Using spline modeling, the authors found that mortality with medical management over a median follow-up of ≈4 years increased linearly with increasing LACI, identifying a value of 6 as the cutoff above which patients experienced excess mortality when compared with the average mortality of the cohort. Therefore, increased LACI was subsequently defined as ≥6 and a low LACI as <6. A high LACI, due to increased LA volume index or reduced a’ velocity at the medial mitral annulus by tissue Doppler, was independently associated with increased severity of functional mitral regurgitation (FMR), lower EF, higher E/e’, high LV mass, larger LV cavity diameter, worse renal function, more severe heart failure symptoms, higher pulmonary artery systolic pressures, worse right ventricular dysfunction, and higher degrees of tricuspid regurgitation. High LACI was significantly associated with increased mortality with medical management, even after adjustment with several clinical variables, and this relationship was independent of FMR severity. Finally, the strong association of high LACI and mortality was highly consistent in various subgroup analyses, including all FMR grades. Overall, the authors found that a high LACI is independently associated © 2021 American Heart Association, Inc. Circulation: Cardiovascular Imaging