Time to Reframe Ejection Fraction in Light of New Pathophysiological Insights Into Heart Failure

Assessing clinical and biomarker characteristics to optimize the benefits of sacubitril/valsartan in heart failure

Of the various medical therapies for heart failure (HF), sacubitril/valsartan is a first-in-class angiotensin receptor-neprilysin inhibitor that combines sacubitril, a pro-drug that is further metabolized to the neprilysin inhibitor sacubitrilat, and the angiotensin II type 1 receptor blocker valsartan. Inhibition of neprilysin and blockade of the angiotensin II type 1 receptor with sacubitril/valsartan increases vasoactive peptide levels, increasing vasodilation, natriuresis, and diuresis. Left ventricular ejection fraction (LVEF) is widely used to classify HF, to assist with clinical decision-making, for patient selection in HF clinical trials, and to optimize the benefits of sacubitril/valsartan in HF. However, as HF is a complex syndrome that occurs on a continuum of overlapping and changing phenotypes, patient classification based solely on LVEF becomes problematic. LVEF measurement can be imprecise, have low reproducibility, and often changes over time. LVEF may not accurately reflect inherent disease heterogeneity and complexity, and the addition of alternate criteria to LVEF may improve phenotyping of HF and help guide treatment choices. Sacubitril/valsartan may work, in part, by mechanisms that are not directly related to the LVEF. For example, this drug may exert antifibrotic and neurohumoral modulatory effects through inhibition or activation of several signaling pathways. In this review, we discuss markers of cardiac remodeling, fibrosis, systemic inflammation; activation of neurohormonal pathways, including the natriuretic system and the sympathetic nervous system; the presence of comorbidities; patient characteristics; hemodynamics; and HF signs and symptoms that may all be used to (1) better understand the mechanisms of action of sacubitril/valsartan and (2) help to identify subsets of patients who might benefit from treatment, regardless of LVEF.

Hemodynamic Profiles of Shock in Patients With COVID-19

Patients with serious COVID infections develop shock frequently. To characterize the hemodynamic profile of this cohort, 156 patients with COVID pneumonia and shock requiring vasopressors had interpretable echocardiography with measurement of ejection fraction (EF) by Simpson's rule and stroke volume (SV) by Doppler. RV systolic pressure (RVSP) was estimated from the tricuspid regurgitation peak velocity. Patients were divided into groups with low or preserved EF (EF_L or EF_P, cutoff ≤45%), and low or normal cardiac index (CI_L or CI_N, cutoff ≤2.2 L/min/m²). Mean age was 67 ± 12.0, EF 59.5 ± 12.9, and CI 2.40 ± 0.86. A minority of patients had depressed EF (EF_LCI_L, n = 15, EF_LCI_N, n = 8); of those with preserved EF, less than half had low CI (EF_PCI_L, n = 55, EF_PCI_N, n = 73). Overall hospital mortality was 73%. Mortality was highest in the EF_LCI_L group (87%), but the difference between groups was not significant (p = 0.68 by ANOVA). High PEEP correlated with low CI in the EF_PCI_L group (r = 0.44, p = 0.04). In conclusion, this study reports the prevalence of shock characterized by EF and CI in patients with COVID-19. COVID-induced shock had a cardiogenic profile (EF_LCI_L) in 9.6% of patients, reflecting the impact of COVID-19 on myocardial function. Low CI despite preservation of EF and the correlation with PEEP suggests underfilling of the LV in this subset; these patients might benefit from additional volume. Hemodynamic assessment of COVID patients with shock with definition of subgroups may allow therapy to be tailored to the underlying causes of the hemodynamic abnormalities.