W J Paulus and D L Brutsaert 1980;46:303-304 doi: 10.1161/01.RES.46.2.303

Comments on "How to quantify pump function of the heart".
W J Paulus and D L Brutsaert
Circ Res. 1980;46:303-304
doi: 10.1161/01.RES.46.2.303
Circulation Research is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
Copyright © 1980 American Heart Association, Inc. All rights reserved.
Print ISSN: 0009-7330. Online ISSN: 1524-4571
The online version of this article, along with updated information and services, is located on the
World Wide Web at:
Permissions: Requests for permissions to reproduce figures, tables, or portions of articles originally published in
Circulation Research can be obtained via RightsLink, a service of the Copyright Clearance Center, not the
Editorial Office. Once the online version of the published article for which permission is being requested is
located, click Request Permissions in the middle column of the Web page under Services. Further information
about this process is available in the Permissions and Rights Question and Answer document.
Reprints: Information about reprints can be found online at:
Subscriptions: Information about subscribing to Circulation Research is online at:
Downloaded from http://circres.ahajournals.org/ by guest on September 22, 2014
Comments on "How to Quantify Pump
Function of the Heart"
In a recent paper by Elzinga and Westerhof
(1979) the contribution of isolated cardiac muscle
mechanics to the evaluation of ventricular performance was considered unrewarding and questionable.
They proposed, instead, that ventricular performance be analyzed in terms of mean ventricular pressure and mean ventricular flow. Such an approach
clearly distinguished changes in inotropism from
changes in end-diastolic volume and showed a remarkable resemblance to roller pump mechanics.
They finally proposed to solve the apparent differences between isolated muscle mechanics and ventricular performance by loading papillary muscles
as if they were part of the ventricular wall. Many of
the controversies in studies of isolated muscle mechanics and ventricular performance can indeed be
ascribed to the nature of the loading, which is
ejection for the ventricle and either isotonic or
isometric contraction for the muscle strip. This view
is not entirely new, however, since it was already
suggested in this journal a few years ago by Abbott
and Gordon (1975) when they proposed to impose
inertial forces on papillary muscle strips. Moreover,
the idea of a loading feedback principle has been
expanded more recently to include vascular impedance (Paulus et al., 1976, 1979). When imposing
these impedance loads on isolated muscle strips,
the hypothetical sets of pressure and flow waves
are similar to the pressure and flow waves that a
ventricle creates when facing the same impedance.
From these observations it is obvious that studies
of papillary muscle reveal valid information on ventricular performance when it is loaded as a ventricular muscle and not as a striated muscle.
Walter J. Paulus
Dirk L. Brutsaert
Department of Physiology
University of Antwerp
Antwerp, Belgium
Abbott BC, Gordon DC (1975) A commentary on muscle mechanics. Circ Res 36: 1-7
Elzinga G, Westerhof N (1979) How to quantify pump function
of the heart. Circ Res 44: 303-308
Paulus WJ, Claes VA, Brutsaert DL (1976) Physiological loading
of isolated mammalian cardiac muscle. Circ Res 39: 42-53
Paulus WJ, Claes VA, Brutsaert DL (1979) Physiological loading
of isolated feline cardiac muscle. Circ Res 44: 491-497
Reply to the Preceding Letter
In the paper by Abbott and Gordon (1975) the
pressure gradient between ventricle and aorta was
emphasized as the driving force to overcome the
inertia of the system. However, we think that the
temp 3 S 7 ° C
FIGURE 1 A thin (375 fim diameter) trabecular muscle,
loaded "physiologically," was stimulated at 120 beats/
minute. A different isotonic load was introduced every
15 contractions (beating) to avoid the gradually developing influence of the load on muscle behaviour (Parmley et al., 1969). Left: a number of superimposed contractions as a function of time. Right: The same contractions
displayed in an x-y diagram. Two identical "physiologically" loaded contractions are shown in the figure, one
before and one at the end of the experiment, to show the
stability of the preparation.
three factors they claim to be responsible for this
difference in pressure do not constitute an important part of the total arterial load. The approach
followed by Paulus et al. (1979), who loaded papillary muscles with an R-C-R network (Westerhof,
1968), provides a more direct solution when one
wants to study isolated muscle in a way analogous
to the whole heart.
In such studies not only the loading of the muscles is important but also the type of experiments
performed. An example of one of the experiments
we had in mind when we stated in our part of the
controversy (Elzinga and Westerhof, 1979) "... i.e.
to study isolated heart muscle as if it were part of
the ventricular wall," is given in Figure 1. In this
figure are shown force and length obtained from a
number of contractions of a thin trabecular muscle,
isolated from an adult cat, recorded as a function of
time (left) and displayed in an x-y diagram (right).
The experiment was designed to resemble closely
the normal cardiac contraction with respect to: the
stimulation frequency (2 Hz), the temperature (±
37°C), the contraction pattern (isometric contraction followed by shortening and subsequently isometric relaxation followed by lengthening), and the
load (one of the contractions is loaded "physiologically").
This is just one example of a number of experiments which would be needed to use the muscle
experiments as a building block to understand cardiac pump function. Other questions are for instance: Is the same pump function graph obtained
with all sorts of loads or only with loads within the
limited range of configurations as tested in our
cardiac studies (Elzinga and Westerhof, 1973,1979)?
What property of muscle or heart is responsible for
the clear cut difference in the alteration of the
pump function graph resulting from a change in
Downloaded from http://circres.ahajournals.org/ by guest on September 22, 2014
end-diastolic volume and from a change in inotropic
state? Is the end-systolic force-length relationship
independent of the length at which the contraction
These and similar questions need to be answered
before we will be able to use isolated muscle experiments towards the understanding of cardiac pump
Gijs Elzinga, M.D. Ph.D.
Nicolaas Westerhof, Ph.D.
Physiological Laboratory
Free University
Van der Boechorststraat 7
Amsterdam, The Netherlands
VOL. 46, No. 2, FEBRUARY
Abbott BC, Gordon DG (1975) A commentary on muscle mechanics. Circ Res 36: 1-7
Elzinga G, Westerhof N (1973) Pressures and flow generated by
the left ventricle against different impedances. Circ Res 32:
Elzinga G, Westerhof N (1979) How to quantify pump function
of the heart. The value of variables derived from measurements on isolated muscle. Circ Res 44: 303-308
Parmley WW, Brutsaert DL, Sonnenblick EH (1969) Effects of
altered loading on contractile events in isolated cat papillary
muscle. Circ Res 24: 521-532
Paulus WJ, Claes VA, Brutsaert DL (1979) Physiological loading
of isolated feline cardiac muscle. The interaction between
muscle contraction and vascular impedance in the production
of pressure and flow waves. Circ Res 44: 491—497
Westerhof N (1968) Analog studies of human systemic arterial
hemodynamics. Ph.D. thesis, Philadelphia, University of
Downloaded from http://circres.ahajournals.org/ by guest on September 22, 2014