Loading determinants of relaxation in cat papillary muscle

Goethals, M A; Housmans, P. R.; Brutsaert, Dirk L.

doi:10.1152/ajpheart.1982.242.3.h303

“…The finding of an inverse relation between total load (or minimum length) and maximum isotonic lengthening rate is in agreement with observations of Goethals et al, 22 using cat right-ventricular papillary muscles, and Wiegner et al,'…”

supporting

confidence: 92%

“…Goethals et al 22 demonstrated that maximum isotonic lengthening rate increased when a small external load (late load) was placed on the muscle during isotonic lengthening. In that study, the magnitude of the late load was equal to or less than the preload.…”

mentioning

confidence: 99%

Mechanical determinants of maximum isotonic lengthening rate in rat left ventricular myocardium.

Zile¹,

Gaasch²,

Wiegner³

et al. 1987

Circulation Research

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The effects of changing loading conditions and inotropic state on maximum isotonic lengthening rate ( +dL/dt, muscle lengths/sec) were examined in isolated rat myocardium. Physiologically sequenced contractions were studied in 18 left ventricular papillary muscle preparations (stimulation rate, 12/min). To study the effects of changing loading conditions, only one loading variable (preload, total load, or late load) was changed during each contraction, while the others were held constant. To study the effects of isoproterenol (10~6 M) and temperature (28 vs. 33° C) on maximum isotonic lengthening rate, preload and late load were held constant and +dL/dt was examined at a common total load. When preload was increased from 0. ), +dL/dt rose from 1.6 ± 0.1 muscle lengths/sec at 28° C to 2.4 ± 0.2 muscle lengths/sec at 33° C and 2.05 ±0.1 muscle lengths/sec with isoproterenol. Thus, the load against which the muscle shortens (and/or the length to which it shortens), the magnitude of the late load, and the time at which the late load is applied are independent determinants of maximum isotonic lengthening rate. Under any constant set of loading conditions, both isoproterenol and increased temperature increase the maximum isotonic lengthening rate. A bnormalities of left ventricular (LV) early dia-/ \ stolic chamber filling appear to be sensitive X \ -indicators of myocardial disease 1 " 7 ; chamber filling rate has also been found to be useful in following the natural history and the response to therapy of pathological processes.8 " 14 To understand the effects of disease or pharmacologic therapy on chamber filling rate, it is important to define the specific mechanical and hemodynamic factors that influence the speed of relaxation and filling in the normal heart. Once the mechanical determinants of ventricular filling rate are defined, the effects of the disease process or the effects of pharmacologic treatment on filling rate can be interpreted within the context of changes in these mechanical determinants. In the intact heart, it is difficult to create isolated changes in mechanical variables such as loading conditions. This is true because most interventions cause concomitant changes in LV volume, LV pressure, left atrial pressure, and heart rate, each of which may have an effect on filling rate. Using the isolated muscle preparation, where muscle length and load can be independently and precisely controlled, the effects of isolated changes in loading conditions on isotonic lengthening rate can be studied. In addition, data obtained using this method are not affected by neurohumoral and other factors that might influence relaxation in the intact heart. Accordingly, the purpose of the current study is to define the independent determinants of maximum isotonic lengthening rate using physiologically sequenced isolated papillary muscle preparations. We hypothesize that loading conditions, specifically preload, total load, and late load, are primary mechanical determinants of the maximum isotonic lengthening rate. Ther...

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“…29 A higher lengthening load shifted the relation upward, but a higher calcium concentration had no effect. These findings imply that during diastolic lengthening, normal cardiac muscle behaves like a spring: When the spring is more forcefully compressed during systole or when a heavier load is suspended on the spring, diastolic lengthening velocity is higher.…”

Section: Response By Little and Oh On P 820 From Myocardial Lengthenimentioning

confidence: 90%

“…50 In patients with heart failure, the stage of diastolic dysfunction is a stronger predictor of mortality than EF. 29 A short DT indicates an increased LV operating stiffness, is a hallmark of restrictive filling pattern, and denotes poor prognosis in patients after myocardial infarction, dilated cardiomyopathy, and heart transplantation; in those with hypertrophic cardiomyopathy; and in patients with restrictive cardiomyopathy ( Figure 7). 23 Both pseudonormalized and restricted filling patterns indicate a 4-fold increase in the risk of death in patients with heart failure and coronary artery disease.…”

Section: Prognosismentioning

confidence: 99%

Echocardiographic Evaluation of Diastolic Function Can Be Used to Guide Clinical Care

Little

¹

,

Oh

²

2009

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For normal cardiac performance, the left ventricle (LV) must be able to eject an adequate stroke volume at arterial pressure (systolic function) and fill without requiring an elevated left atrial (LA) pressure (diastolic function). These systolic and diastolic functions must be adequate to meet the needs of the body both at rest and during stress. Response by Tschöpe and Paulus on p 809Systolic function is conveniently (although not always accurately) measured as the ejection fraction (EF), calculated as stroke volume divided by end-diastolic volume. 1 The LV EF is easily interpreted. The lower limit of normal is Ϸ50%. The lower the EF is, the greater the reduction in systolic function. Diastolic function has been more difficult to evaluate. 2 Traditionally, invasive measures of LV diastolic pressure-volume relations and the rate of LV pressure fall during isovolumetric relaxation have been used. However, these methods are not practical for routine clinical use and do not adequately evaluate all aspects of diastolic filling. 3 Comprehensive echocardiographic evaluation of the dynamics of LV filling using blood pool and tissue Doppler has now progressed so that it provides clinically important information that can be used to direct patient care. We present data that support the use of echocardiographic evaluation of diastolic function to recognize cardiac dysfunction in patients with heart failure, especially those with preserved EF; to guide the management of patients by identifying those with and without elevated left filling pressures regardless of underlying EF; and to determine prognosis in a wide variety of patient populations. LV FillingAlthough the LV end-diastolic pressure-volume relation describes the passive properties of the LV, LV filling is not a passive or slow process. 3 In fact, the peak flow rate across the mitral valve is equal to or greater than the peak flow rate across the aortic valve. Understanding the physiological basis of LV filling provides the basis for the interpretation of the information available from a comprehensive echocardiographic evaluation of LV filling dynamics.During LV ejection, energy is stored as the myocytes are compressed and the elastic elements in the myocardial wall are compressed and twisted. 4 Relaxation of myocardial contraction allows this energy to be released as the elastic elements recoil. This causes LV pressure to fall rapidly during isovolumetric relaxation. Furthermore, for the first 30 to 40 milliseconds after mitral valve opening, relaxation of LV wall tension is normally rapid enough to cause the LV pressure to continue to decline despite an increase in LV volume. 5 This fall in LV pressure produces an early diastolic pressure gradient from the LA that extends to the LV apex (Figure 1). 6 This accelerates blood out of the LA andThe opinions expressed in this article are not necessarily those of the editors or of the American Heart Association.

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“…Almost all patients with heart failure, regardless of EF, have diastolic dysfunction. 29,30 In contrast, a normal eЈ (Ͼ8 cm/s medial or Ͼ10 cm/s lateral) is very unusual in a patient with heart failure (unless the patient has pericardial constriction) and indicates the need to look for other causes of the patient's symptoms. 31 Lam et al 32 found that eЈ was reduced and E/eЈ was increased in patients with heart failure and a normal EF compared with both normal subjects and patients with hypertension without heart failure.…”

Section: Evaluation Of Patients With Heart Failurementioning

confidence: 99%

Doppler Echocardiography Yields Dubious Estimates of Left Ventricular Diastolic Pressures

Tschöpe

¹

,

Paulus

²

2009

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For normal cardiac performance, the left ventricle (LV) must be able to eject an adequate stroke volume at arterial pressure (systolic function) and fill without requiring an elevated left atrial (LA) pressure (diastolic function). These systolic and diastolic functions must be adequate to meet the needs of the body both at rest and during stress. Response by Tschöpe and Paulus on p 809Systolic function is conveniently (although not always accurately) measured as the ejection fraction (EF), calculated as stroke volume divided by end-diastolic volume. 1 The LV EF is easily interpreted. The lower limit of normal is Ϸ50%. The lower the EF is, the greater the reduction in systolic function. Diastolic function has been more difficult to evaluate. 2 Traditionally, invasive measures of LV diastolic pressure-volume relations and the rate of LV pressure fall during isovolumetric relaxation have been used. However, these methods are not practical for routine clinical use and do not adequately evaluate all aspects of diastolic filling. 3 Comprehensive echocardiographic evaluation of the dynamics of LV filling using blood pool and tissue Doppler has now progressed so that it provides clinically important information that can be used to direct patient care. We present data that support the use of echocardiographic evaluation of diastolic function to recognize cardiac dysfunction in patients with heart failure, especially those with preserved EF; to guide the management of patients by identifying those with and without elevated left filling pressures regardless of underlying EF; and to determine prognosis in a wide variety of patient populations. LV FillingAlthough the LV end-diastolic pressure-volume relation describes the passive properties of the LV, LV filling is not a passive or slow process. 3 In fact, the peak flow rate across the mitral valve is equal to or greater than the peak flow rate across the aortic valve. Understanding the physiological basis of LV filling provides the basis for the interpretation of the information available from a comprehensive echocardiographic evaluation of LV filling dynamics.During LV ejection, energy is stored as the myocytes are compressed and the elastic elements in the myocardial wall are compressed and twisted. 4 Relaxation of myocardial contraction allows this energy to be released as the elastic elements recoil. This causes LV pressure to fall rapidly during isovolumetric relaxation. Furthermore, for the first 30 to 40 milliseconds after mitral valve opening, relaxation of LV wall tension is normally rapid enough to cause the LV pressure to continue to decline despite an increase in LV volume. 5 This fall in LV pressure produces an early diastolic pressure gradient from the LA that extends to the LV apex (Figure 1). 6 This accelerates blood out of the LA andThe opinions expressed in this article are not necessarily those of the editors or of the American Heart Association.

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Loading determinants of relaxation in cat papillary muscle

Cited by 13 publications

References 0 publications

Mechanical determinants of maximum isotonic lengthening rate in rat left ventricular myocardium.

Mechanical determinants of maximum isotonic lengthening rate in rat left ventricular myocardium.

Echocardiographic Evaluation of Diastolic Function Can Be Used to Guide Clinical Care

Doppler Echocardiography Yields Dubious Estimates of Left Ventricular Diastolic Pressures

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