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Table 1. Hemodynamic Concepts, Definitions, and Common
Clinical Surrogates
Concept or term Definition Common surrogates
Preload Degree of ventricular stretch at end-
diastole
Gold standard is
EDV; EDP or atrial
pressures commonly
used as surrogates
Aerload Forces opposing ventricular ejection Ea, ESP, SVR, PAR,
TPR
Effective arterial
elastance (Ea)
Total arterial load (pulsatile and
nonpulsatile); LVESP/SV
SBP, SVR
Impedance Ratio of the arterial pressure
waveform to the blood flow waveform
over the entire cardiac cycle; requires
spectral and Fourier analysis
Systemic vascular
resistance (SVR)
Describes resistance without
consideration of pulsatility; (MAP-
RAP)/CO
Contractility Strength of contraction in response to
ventricular load
Ees, EF, δp/δt, SW,
CPO
Pulmonary vascular
resistance (PVR)
Describes resistance without
consideration of pulsatility; (Mean
PAP – mean LAP)/pulmonary flow
Pulmonary arterial
compliance (PAC)
Distensibility of pulmonary artery;
C=δv/δp
Ventricular
diastolic stiffness
Slope of EDPVR (δp/δV) – 1 EDP
Tau Time constant of myocardial
relaxation; represents exponential
decay of ventricular pressure during
isovolumic relaxation
– δp/δt
Ventricular
interdependence
Describes changes in ventricular
volumes and pressures mediated by
common septum with pericardium
intact; examined via comparison of
right-sided vs. le-sided pressures
RAP, RVSP, LAP,
LVSP, SV
Diagnosis
Key Points
➤ Invasive catheter-based assessments performed in the cardiac
catheterization laboratory remain the gold standard for hemodynamic
evaluations of cardiovascular patients.