Relaxation of ventricular cardiac muscle.

Brutsaert, Dirk L.; Clerck, Nora M. De; Goethals, M A; Housmans, Philippe R.

doi:10.1113/jphysiol.1978.sp012513

Cited by 129 publications

(70 citation statements)

References 45 publications

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“…18 The effect of late systolic load on LV relaxation has also been the subject of previous studies. Brutsaert et al 19 initiated the concept of load-dependence of relaxation and described acceleration of relaxation and early termination of a twitch contraction in response to late systolic load clamps. This, however, was only observed in isolated cardiac muscle with isotonic-isometric relaxation sequence and isometrically contracting hearts subjected to volume clamps.…”

Section: Discussionmentioning

confidence: 99%

Early and Late Systolic Wall Stress Differentially Relate to Myocardial Contraction and Relaxation in Middle-Aged Adults

et al. 2013

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A fterload is recognized as an important determinant of myocardial function. Experimental animal studies demonstrate that increased afterload impacts diastolic relaxation. [1][2][3][4][5] Furthermore, studies in healthy instrumented dogs showed that, within physiological ranges, increased afterload results in differential responses in relaxation depending on its timing. In anesthetized open-chest dogs, mild-to-moderate increases in early systolic load resulted in unchanged or slightly enhanced relaxation, whereas increases in late systolic load resulted in a slow rate of diastolic ventricular pressure fall. 2,6 This, however, was not observed in conscious dogs subjected to a similar protocol.7 More recently, greater late systolic pressure assessed from a carotid pressure waveform 8 or an invasively measured aortic pressure waveform 9 has been shown to be associated with impaired early diastolic relaxation in humans. These studies implicate the loading sequence as a potential mechanistic determinant of diastolic relaxation.Whereas analyses of central arterial pressure and pressureflow relations are highly informative regarding arterial properties and ventricular-arterial interactions, they do not describe the time-varying mechanical load (stress) on the myocardium, which is determined by complex interactions between myocardial contractile elements, instantaneous leftventricular (LV) geometry and the time-varying hydraulic Abstract-Experimental studies implicate late systolic load as a determinant of impaired left-ventricular relaxation. We aimed to assess the relationship between the myocardial loading sequence and left-ventricular contraction and relaxation.

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Section: Discussionmentioning

confidence: 99%

Early and Late Systolic Wall Stress Differentially Relate to Myocardial Contraction and Relaxation in Middle-Aged Adults

et al. 2013

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“…This phenomenon plausibly corresponds with a depressed force-length relation in cardiac muscle (18,33). It is interesting to note that Edman and Nilsson (33) found that in cardiac muscle, after constant velocity shortening contraction, force is decreased to an amount related to the shortening velocity.…”

Section: Co T a + Ementioning

confidence: 92%

“…This phenomenon is not accounted for by pure elastance-resistance models. On the cellular (59), as well as on the muscular (16,18,33,73) level, it has long been known that the capability to redevelop force after fiber shortening, is negatively affected. The present study, however, indicates that it is the shortening itself, rather than the state of having shortened that is associated with deactivation.…”

Section: System Identificationmentioning

confidence: 99%

The step response of left ventricular pressure to ejection flow: A system oriented approach

Boom

Wijkstra

1992

Ann Biomed Eng

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“…In mammalian ventricular muscle, comparative analysis of the time course of a series of afterloaded isotonic contractions against various loads up to full isometric twitch, proved that early deactivation occurred when the muscle was allowed to shorten against a load, resulting in a load-induced premature isometric relaxation (Brutsaert et al, 1978b). Figure 1 shows the length and force traces of an atrial strip that went through a similar course of Results are expressed as mean ± SE.…”

Section: Mammalian Atrial Strips Afterloaded Contractionsmentioning

confidence: 92%

Relaxation properties of mammalian atrial muscle.

Couttenye¹,

Clerck²,

Goethals³

et al. 1981

Circulation Research

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SUMMARYThe properties of relaxation, in particular the sensitivity of relaxation to load, were analyzed in isolated intact atrial muscle and in manually dissected, detergent-treated cellular preparations from cat, dog, and rat atria. Force and length traces under increasing afterloads and following load clamps were obtained using an electromagnetic lever-force transducer system for the intact muscles and a capacitance transducer system for the cellular preparations. In both types of preparations, the time course of relaxation was hardly affected by the load or by alterations in load (load clamps), unlike intact mammalian ventricular muscle. This load independence of relaxation, which was hardly influenced by variations of initial muscle length, resembled relaxation in intact frog ventricular muscle and in detergent-treated mammalian ventricular single cells. As relaxation of these ventricular preparations with poorly developed (frog) or absent (detergent-treated single cells) calcium-sequestering systems was shown to be governed by the dissipation of activation, these results suggest a similar control mechanism for relaxation in mammalian atrial muscle. Furthermore, load independence of relaxation of mammalian atrial muscle in late diastole may promote optimal filling of the ventricle. Circ Res 48: 352-356, 1981ALTHOUGH the contractile properties of the contraction phase of mammalian atrial muscle have been well studied and compared with the contractile performance of ventricular muscle (Fabiato and Fabiato, 1972;Tarr et al., 1979;Urthaler et al., 1975), its properties during the relaxation phase are less well understood. Because of the unquestionable contribution of atrial contraction to the pump function of the ventricle, and because of the significant differences between the contractile properties of atrial and ventricular muscles (Blinks and KochWeser, 1963;Koch-Weser and Blinks, 1963), we have analyzed, in the present study, the mechanical behavior of mammalian atrial muscle during relaxation and in particular, its sensitivity to load or load alterations and its possible role in the functioning of the heart. Two kinds of preparation were used: (1) intact atrial muscle strips from cat and dog and (2) single atrial cells of rat, obtained by manual dissection after treatment with detergent to destroy the membranous systems. MethodsAtrial muscle strips were dissected from cat (n = 9) and dog (n = 2). The basic characteristics of these preparations are summarized in Table 1.Long thin strips of longitudinally oriented bundles of muscle fibers were cut from the free left atrial wall. The muscle strips were mounted vertically, the lower end being held by a force transducer (compliance, 0.3 |iim/mN; resonant frequency in aqueous solution, 250 Hz) and the upper end being tied (7.0 braided thread, Deknatel, Surgical Tevdek, Code 103-T) to an electromagnetic lever system (compliance 0.2 jum/mN, equivalent moving mass 155 mg, step response 3 msec). The current through the coil of the electromagnet determined the load on...

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Relaxation of ventricular cardiac muscle.

Cited by 129 publications

References 45 publications

Early and Late Systolic Wall Stress Differentially Relate to Myocardial Contraction and Relaxation in Middle-Aged Adults

Early and Late Systolic Wall Stress Differentially Relate to Myocardial Contraction and Relaxation in Middle-Aged Adults

The step response of left ventricular pressure to ejection flow: A system oriented approach

Relaxation properties of mammalian atrial muscle.

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