Effect of initial muscle length on V max  in isotonic contraction of cardiac muscle

Donald, TC; Unnoppetchara, K; Peterson, D. W.; Hefner, LL

doi:10.1152/ajplegacy.1972.223.2.262

Cited by 29 publications

(20 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In our experiments, V max has been calculated according to the Voigt model, since by this procedure V max seems to be most suited to assessment of cardiac contractility (33). But one has soon come to know that V max is not completely independent of preload changes: neither in the intact heart (11,33) nor in the papillary muscle (6,13,14,30,31,32). But one has soon come to know that V max is not completely independent of preload changes: neither in the intact heart (11,33) nor in the papillary muscle (6,13,14,30,31,32).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Preload dependence of dP/dt max, VCE max and calculated V max compared to the inotropic sensitivity of these indices of cardiac contractility

Schmidt

Hoppe

1978

Basic Res Cardiol

View full text Add to dashboard Cite

In five canine heart-lung preparations the preload dependence of dP/dt max, V max, VCE max and (dP/dt:P-EDP + C) max was related to the inotropic sensitivity of these indices. V max and (dP/dt:P-EDP + C) max are less affected by preload changes than dP/dt max and therefore should be more suitable for inotropic measurements. But even if the preload changes caused by inotropic interventions are not taken into account, V max shows the same inotropic sensitivity as dP/dt max when the contractile state is reduced and an even lower sensitivity when the contractile state is enhanced. The sensitivity of (dP/dt:P-EDP + C) max, however, is much lower over the whole range of tested inotropic states. If enddiastolic pressure is kept constant during inotropic interventions, dP/dt max is a much more sensitive inotropic index than V max. VCE max usually shows a negative correlation to the diastolic filling of the heart. In the improved inotropic state this correlation can become positive, thus making it impossible to evaluate the influence of the preload dependence on the result. None of the tested parameters shows a higher inotropic sensitivity than dP/dt max, though the preload dependence of dP/dt max is more evident. Therefore, none of these more complicated parameters has any advantage over the simple measure dP/dt max for evaluation of acute changes in contractility.

show abstract

Section: Discussionmentioning

confidence: 99%

“…However, the preload dependence of V max is less pronounced than that of dP/dt max ( fig. The use of V max is futher limited by tile difficult extrapolation of the presure velocity curve (6,15,33). Therefore, V max does indeed seem to be more appropriate than dP/dt max.…”

Section: Discussionmentioning

confidence: 99%

Preload dependence of dP/dt max, VCE max and calculated V max compared to the inotropic sensitivity of these indices of cardiac contractility

Schmidt

Hoppe

1978

Basic Res Cardiol

View full text Add to dashboard Cite

show abstract

“…The m e c h a n o g r a m (1) was registered u n d e r a low e x t r a c e l l u l a r Ca*+-concentration of 1.1 m-mole/1 and at the force o p t i m u m . W h e n we d o u b l e d the Ca++-concentration a n d at the same time released the p r e p a r a t i o n to a muscle l e n g t h of 9 3 % of L,,,~,~, the r e s u l t was m e c h a n o g r a m (2). Both m e c h a n o g r a m s are characterized by i d e n t i c a l rising phases.…”

Section: Resultsmentioning

confidence: 95%

“…According to these the maximum unloaded shortening velocity -referred to in the further course as the apparent Vm~t.~-value -varies with the preload as well as with the Ca+ § The preload dependency was also proven, for example, by Edman (3), Noble (7) or Donald (2), and the variation with the Ca++-concentration by Brutsaert (1). In view of this an inevitable question arises which, surprisingly enough, has not as yet been explicitly handled in literature, let alone answered; i.e.…”

mentioning

confidence: 81%

The effect of preload and Ca++-ions on the time-course of the isometric force and on the force-velocity relation: Is Vmax dependent on the number of activated cross-bridges?

Gülch

1977

Basic Res Cardiol

View full text Add to dashboard Cite

The maximum shortening velocity of the isolated, externally unloaded papillary muscle of cats, as can be obtained by quick-releases in the initial phase of isometric contractions, is clearly dependent on the Ca++-concentration of the bath solution as well as on the preload: In the range of 0.55 m-mole/1 to 4.4 m-mole/1 a doubling of the Ca++-concentration induces a mean increase of 23% in Vmax; in a range of muscle length assumed to be of physiological relevance, a rise in the extension of 10% of Lmax results in a mean augmentation of 20% in Vmax. In order to reveal possible differences in the effect of calcium and various degrees of filament overlap, firstly, isometric mechanograms were measured under low Ca++-concentration at the muscle length of Lmax. By correspondingly lowering the muscle extension under increased Ca++-concentration the reproduction of almost the entire rising phase of these isometric mechanograms was obtained. Both these experimental conditions result in congruent force-velocity relations and consequently in identical values for Vmax. It must therefore be concluded that there exists an inner relationship between the initial time-course of the isometric force and the force-velocity relations measured during this period. The interpretation of this fact involves weighing the hypothesis of an inner frictional force dependent on velocity against that of a maximum shortening velocity dependent on the number of activated cross-bridges. The resultant consequences for the estimation of the contractile qualities of the myocardium are discussed.

show abstract

“…Such an approach has been valuable, although doubts have been expressed as to the accuracy of estimates of contractility by these methods, particularly in the intact heart (Donald, Unnoppetchara, Peterson & Hefner, 1972;Noble, 1972;Pollack, 1970). In addition, it is not clear that, given evidence of a reduction in myocardial contractility, one can estimate with any precision the degree of impairment of the cardiac output reserve, since factors other than contractility contribute to overall cardiac performance (Braunwald, 1971).…”

Section: Discussionmentioning

confidence: 99%

Quantitative assessment of cardiac pump performance.

Bishop¹,

Horwitz²

1977

The Journal of Physiology

View full text Add to dashboard Cite

SUMMARY1. A means of quantitating left ventricular performance in the conscious dog is presented. Changes in heart rate, stroke volume and cardiac output during elevation of left atrial pressure by acute volume expansion were measured in the conscious dog.2. The changes in heart rate and stroke volume could be described by y = ym-(ym-yi)e-a', where yi and ym are the initial and maximum values of the variable and p is the change in mean left atrial pressure. 3. Because cardiac output is a derived variable (stroke volume x heart rate) its response is described by a multiple exponential relationship. 4. For a given initial heart rate and inotropic state, the stroke volume response is determined by the Frank-Starling mechanism and the pressurevolume characteristics of the myocardium.

show abstract

Effect of initial muscle length on V max in isotonic contraction of cardiac muscle

Cited by 29 publications

References 0 publications

Preload dependence of dP/dt max, VCE max and calculated V max compared to the inotropic sensitivity of these indices of cardiac contractility

Preload dependence of dP/dt max, VCE max and calculated V max compared to the inotropic sensitivity of these indices of cardiac contractility

The effect of preload and Ca++-ions on the time-course of the isometric force and on the force-velocity relation: Is Vmax dependent on the number of activated cross-bridges?

Quantitative assessment of cardiac pump performance.

Contact Info

Product

Resources

About