Plotting the End-Systolic Pressure Volume Relationship
(slope of the ESPVR) to assess Myocardial Contractility
E.S.Prakash, MBBS, MD
Division of Basic Medical Sciences,
Mercer University School of Medicine
http://medicine.mercer.edu
prakash_es@mercer.edu
http://esprakash.wordpress.com
License
(2011):
• The intent is to briefly clarify how the End-Systolic Pressure
Volume Relationship (ESPVR) is obtained.
• In experimental situations, the slope of the ESPVR line
provides an index of the the effect of an intervention of
interest on myocardial contractility, when it may not be
possible to control both afterload and preload.
P-V Loops showing the effect of an intervention on the slope of the “End-systolic Pressure Volume Relationship (ESPVR)”,
an index of Myocardial Contractility
X-axis: Left ventricular volume (ml); Y-axis: left ventricular pressure (mm Hg)
Forgive the simplicity in the ejecting limb of the P-V loops – they are simplified to straight lines here;
you know LVP hits its high around mid-ejection.
ESPVR generated by joining end-systolic points in 3
different P-V loops after an intervention whose effect on
contractility is of interest
‘Control’ ESPVR Slope
(contractility) generated by
joining end-systolic points in 3
different P-V loops in variably
loaded beats, and the
experimenter does not change
factors known to affect
contractility considerably.
Which ESPVR – blue or black - represents better myocardial contractility?
• Assess contractility in the baseline (‘control’) state by joining the endsystolic points of P-V loops from multiple cycles. It is OK if these beats
are variably loaded (differing EDV and ESV). This line called ESPVR
may intercept the x-axis or the Y-axis or even zero.
• Assess contractility after the intervention of interest (say, stimulating
sympathetic nerves or administration of a drug or occlusion of
coronary artery etc), by joining the end-systolic points of P-V loops
from multiple cycles.
• The ESPVR line that is steeper with respect to the x-axis represents
better contractility.
• Does contractility change under standard (control) conditions from
beat to beat?
• It may but it has been shown that such changes are of a much lesser
magnitude than with interventions that are clinically significant
(example, coronary artery occlusion, beta-adrenergic agonists etc)
Kass DA and Maughan WL (1988) . From E-max to pressure volume relations: a broader view
http://circ.ahajournals.org/content/77/6/1203.long accessed 1 Oct 2011
P-V Loops showing the effect of an intervention on the slope of the “End-systolic Pressure Volume Relationship (ESPVR)”,
an index of Myocardial Contractility
X-axis: Left ventricular volume (ml); Y-axis: left ventricular pressure (mm Hg)
Forgive the simplicity in the ejecting limb of the P-V loops – they are simplified to straight lines here;
you know LVP hits its high around mid-ejection.
‘Control’ (Baseline)
ESPVR Slope
ESPVR after an intervention of
interest
When you have such a figure and
the slopes are labeled ESPVR
lines, then one can assume that
the lines have been obtained
following the procedure described
in the previous 2 slides.
Which ESPVR – blue or black - represents better myocardial contractility?
Figure below: Y-axis represents Left Ventricular Pressure.
Compare myocardial contractility in the 3 P-V loops below.
Contractility in
GRAY better than BROWN
better than BLUE
All beats were identically
preloaded (same end-diastolic
volume). So is the afterload.
Under such conditions, higher
the stroke volume or ejection
fraction, better the contractility.
One does not need slopes of
ESPVRs here to tell this.
0
60
120
Left ventricular volume (ml)
The slope of the ESPVR is one of the better
indices of myocardial contractility. But there are
caveats.
The following 2 references provide detailed
treatment of this concept:
Sagawa K et al. End-Systolic Pressure/Volume Ratio: A new index of
myocardial contractility. American Journal of Cardiology 1977; 40: 748753 http://www.smjr.org/files/cards/sagawa%20%20am%20j%20cardiol.pdf
Kass DA and Maughan WL . From E-max to pressure volume relations: a
broader view. Circulation 1988
http://circ.ahajournals.org/content/77/6/1203.long accessed 1 Oct 2011