Cardiac mechanical efficiency as a predictor of in-hospital mortality in patients with cardiogenic shock

Cardiogenic shock (CS) is characterized by critically low cardiac output and impaired myocardial energy transfer to cardiac work. Left-ventricular (LV) cardiac mechanical efficiency (CE), defined as the fraction of total pressure-volume area (PVA) converted to external work (EW), captures how effectively the LV converts energy into stroke work. Because CE integrates load, chamber volumes, and pump performance into a single physiologic construct, it may directly reflect the energy-work mismatch that characterizes CS. The prognostic value of transthoracic echocardiography (TTE)-derived CE for in-hospital outcomes in CS remains uncertain.

To determine whether TTE-derived CE measured within 24 hours of admission predicts in-hospital mortality in patients with CS, and to compare its discriminatory performance with LV ejection fraction (LVEF).

Data from CS patients admitted between 2007 and 2018 were analyzed. First LV end-systolic pressure (LVESP=0.9×systolic blood pressure), stroke volume (SV), and LV end-diastolic pressure (LVEDP, estimated using the Nagueh formula) was estimated. CE was then estimated based on EW (EW=(LVESP×SV)−(SV×LVEDP)), potential energy (PE=0.5×LVESP×LV end-systolic volume) and PVA (EW+PE) as CE=EW/PVA×100. We assessed CE and LVEF by TTE performed within 24 hours of admission. Patients were separated into tertiles of CE: high (>47%), moderate (36% < CE ≤47%), and low (CE ≤36%). The primary endpoint was in-hospital mortality. A key secondary endpoint was cardiac intensive care unit (CICU) mortality. Associations were tested with multivariable logistic regression (pre-specified covariates including LVEF).

A total of 577 patients were included. Median age was 69 (IQR: 59-78) years, 38% were females and 65% had acute coronary syndrome. CICU mortality was 20% and total in-hospital mortality was 29%. Patients with low CE had a lower LVEF compared with patients with moderate or high CE (21% (IQR:19-24%) vs 31% (IQR: 28-33%) and 45% (39-51%) respectively). Median CE was 40.5% (IQR 31.8–51.0%) and was lower for in-hospital deaths (37.1% vs 42.1%, P<0.001). Patients with lower CE exhibited significantly higher CICU (P=0.003) and in-hospital mortality (P<0.001; Figure 1). Patients with CE in the lowest tertile had significantly increased risk of CICU and in-hospital death (Figure 2) compared with moderate or high CE tertiles. In multivariate analysis, every 1% decrease in CE corresponded to an 10% increased risk of CICU death and an 8% increased risk of in-hospital death. When both CE and LVEF were included in the same multivariate model, both were significant predictors of CICU death, while only CE remained a significant predictor of in-hospital death.

In patients with CS, TTE-derived CE measured within 24 hours of admission predicts early risk of death, underscoring the prognostic importance of LV energy-work coupling as a marker of disease severity beyond LVEF measurement.Figure 1:  Figure 2: