Conventional and afterload-adjusted measurements of left ventricular ejection fraction and velocity-time integral in assessing septic cardiomyopathy; a prospective longitudinal study

Abstract Background: The role of echocardiography in septic shock is still problematic, since depressed cardiac afterload may overestimate left ventricular (LV) systolic performance and mask septic cardiomyopathy (SC). We hypothesized that afterload-adjusted LV ejection fraction (LVEF) and LV outflow tract velocity-time integral (VTI) values for given systemic vascular resistances (SVR) could provide novel insights into recognizing and stratifying the severity of SC.Methods: In this observational, one-center study, 14 mechanically-ventilated septic-shock patients having a PiCCO system in place for hemodynamic monitoring were prospectively included. Echocardiographic and PiCCO longitudinal examinations (71 pairs overall) were performed simultaneously at the onset of septic shock and every 12 hours for 60 hours overall. Results: VTI-derived stroke volume (SV) and cardiac output (CO) were significantly correlated with PiCCO measurements (r≥0.993, both P<0.001). LVEF and VTI showed linear and exponential inverse correlation to SVR (R2=0.183;0.507, P<0.001;<0.001), respectively. The equations LVEF=86.168-0.011*SVR and VTI=41.23*e(-0.0005*SVR) were found to provide “predicted” values for given SVR. Measured to predicted (for given SVR) LVEF ratios (afterload-adjusted LVEF) defined the severity of SC (mild≥90%, 80%≤moderate<90% and severe<80%). Mortality in severe, moderate and mild SC was 25%, 0%, and 60%, respectively (P=0.108). Moderate SC was distinguished from severe SC by markedly higher LVEF, LV end-diastolic volume, VTI, SV, CO but significantly lower SVR (all P<0.05). LVEF and VTI decreased over-time in mild SC, LVEF decreased in moderate SC, while LVEF and VTI increased over-time in severe SC (P≤0.038). LVEF and VTI demonstrated significant performance in identifying severe SC [cut-off<61.5%, area under the curve (AUC)=1±0.0, sensitivity/specificity=100/100, P<0.001; cut-off<17.9cm, AUC=0.882±0.042, sensitivity/specificity=80/77, P<0.001, respectively], while VTI in identifying SVR<800dynes.sec.cm-5 and SVR>1500dynes.sec.cm-5 (cut-off>21.6cm, AUC=0.889±0.049, sensitivity/specificity=83/79, P<0.001; cut-off<16.8, AUC=0.0.857±0.082, sensitivity/specificity=83/86, P=0.002, respectively).Conclusions: Our study may suggest that LVEF and VTI assessment and adjustment to corresponding SVR may provide valuable insights for the comprehension of SC phenotypes, underlying vasoplegia and cardiac output fluctuations in septic shock. Clinical Trial Registration: Non-applicable