Agreement between different non-invasive methods of ventricular elastance assessment for the monitoring of ventricular–arterial coupling in intensive care

Ventricular–arterial coupling is calculated as the arterial elastance to end systolic elastance ratio (E_A/Ees). Although the gold standard is invasive pressure volume loop analysis, Chen method is the clinical reference non-invasive method for estimating end systolic elastance (Ees). Several simplified methods calculate Ees from the end systolic pressure to volume ratio (ESP/ESV). The objective of the present study was to determine whether ESP/ESV simplification can be used instead of the Chen formula to measure ventricular–arterial coupling and to monitor changes following therapeutic intervention. In this retrospective, single-center study, 3 non-invasive E_A/Ees calculation methods were applied to 86 cardiac ICU patients. The Chen method was used as the reference method. Ees was also calculated according to method 1: Ees₁ = 0.9 × SAP/ESV and method 2: Ees₂= E_A/(1/LVEF) − 1. E_A was estimated as 0.9 × SAP/SV (mmHg ml⁻¹). After simplification: E_A/Ees1 = E_A/Ees2 = (1/LVEF) − 1, with the stroke volume estimated as the product of the aortic velocity–time integral (VTIAo) and the aortic area or as the difference between the end diastolic volume (EDV) and the ESV. All patients received fluid infusion, norepinephrine, or dobutamine. At baseline, the concordance correlation coefficient with E_A/Ees_Chen was 0.13 [− 0.07; 0.31] for E_A/Ees₁ and 0.32 [0.19; 0.44] for E_A/Ees₂. Bias and limit of agreement were 0.28 [− 0.02; 0.36] and [− 5.8; 2.6] for E_A/Ees₁ and of 0.44 [0.31; 0.53] and [− 3.2; 2.6] for E_A/Ees₂. When used to follow variations in E_A/Ees following therapeutic interventions, only 65% (for E_A/Ees₁) and 70% (for E_A/Ees₂) of measures followed the same trend as E_A/Ees_Chen. Our results do not support the use of ESP/ESV based method as substitute for Chen method to measure and assess changes in ventriculo–arterial coupling (E_A/Ees) in cardiac intensive care patients. Further investigations are needed to establish the most reliable non-invasive method.