A comparison of mathematical models of left ventricular contractility derived from aortic blood flow velocity and acceleration: Application to the esophageal doppler monitor

The use of the oesophageal Doppler in perioperative medicine: new opportunities in research and clinical practice

The oesophageal Doppler (OD) is a minimally invasive haemodynamic monitor used in the surgical theatre and the ICU. Using the OD, goal-directed therapy (GDT) has been shown to reduce perioperative complications in high-risk surgical patients. However, most GDT protocols currently in use are limited to stroke volume optimisation. In the present manuscript, we examine the conceptual models behind new OD-based measurements. These would provide the clinician with a comprehensive view of haemodynamic pathophysiology; including pre-load, contractility, and afterload. Specifically, volume status could be estimated using mean systemic filling pressure (MSFP), the pressure to which all intravascular pressures equilibrate during asystole. Using the OD, MSFP could be readily estimated by simultaneous measurements of aortic blood flow and arterial pressure with sequential manoeuvres of increasing airway pressure. This would result in subsequent reductions in cardiac output and arterial pressure and would allow for a linear extrapolation of a static MSFP value to a "zero flow" state. In addition, we also demonstrate that EF is proportional to mean blood flow velocity measured in the descending thoracic aorta with the OD. Furthermore, OD-derived indexes of blood flow velocity and acceleration, as well as force and kinetic energy, can be derived and used for continuous assessment of cardiac contractility at the bedside. Using OD-derived parameters, the different components of afterload: inertia, resistance and elastance, could also be individually determined. The integration of these additional haemodynamic parameters could assist the clinician in optimising and individualising haemodynamic performance in unstable patients.

Hemodynamic determinants and ventriculo-arterial coupling are sex-associated in heart failure patients

End-systolic volume (ESV) and end-diastolic volume (EDV) are key parameters in the analysis of left ventricular (LV) function, and the study of cardiac remodeling. The volume regulation graph (VRG) relates these fundamental determinants, and permits convenient stratification for clinically relevant covariates. This contribution analyzes sex-associated differences in hemodynamic parameters for 197 heart failure (HF) patients, evaluated by biplane ventriculography, in combination with arterial pressure. We calculated LV parameters such as stroke volume (SV), cardiac output (CO), ESV, EDV, ejection fraction (EF), end-systolic elastance (Emax), besides arterial parameters: effective arterial elastance (Ea), elastance ratio (the coupling index k), peripheral resistance (Rs), pulse pressure (PP), and arterial compliance (C), all normalized for body surface area when appropriate. Average values for heart rate, SV, CO, Ea, C, Rs are similar between the sexes, as are the VRG regression lines. However, ESV and EDV are significantly (P<;0.034 and P<;0.016, respectively) smaller in women (N=67), whereas EF, Emax, mean arterial pressure, PP, and k are higher (P<;0.008 or less). We conclude that the various sex-associated differences observed in these HF patients are striking, and thus require due attention when evaluating the clinical status of HF patients. Formulation of distinct cut-off values for male and female patients with HF seems warranted, when considering specific HF phenotypes.