Physiologic loading of isolated heart muscle

Sulman, David; Bing, O.; Mark, Roger G.; Burns, Stephen K.

doi:10.1016/s0006-291x(74)80280-9

Cited by 26 publications

(10 citation statements)

References 3 publications

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“…Pressure-dimension points did not encounter the fully relaxed line at any point during diastole in 15 beats in 5 hearts during rapid pacing (Fig. 4) at rates from 170 to 200/min and after In studies of isolated muscle it has only been recently recognized that the classic afterloaded muscle is not physiologically sequenced during relaxation (13). Recent studies have attempted to "physiologically load" isolated cardiac muscle such that isometric relaxation precedes isotonic lengthening (13,14).…”

Section: Resultsmentioning

confidence: 99%

“…4) at rates from 170 to 200/min and after In studies of isolated muscle it has only been recently recognized that the classic afterloaded muscle is not physiologically sequenced during relaxation (13). Recent studies have attempted to "physiologically load" isolated cardiac muscle such that isometric relaxation precedes isotonic lengthening (13,14). These studies have concentrated on the time-course of tension fall during the isometric phase and have placed little emphasis on the time-course of isotonic lengthening or effects of lengthening during the period of tension fall.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Evidence of Incomplete Left Ventricular Relaxation in the Dog

Weisfeldt¹,

Frederiksen²,

Yin³

et al. 1978

J. Clin. Invest.

142

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A B S T R A C T Although it has been proposed that incomplete relaxation explains certain increases in left ventricular end diastolic pressure relative to volume, there has been no clear demonstration that incomplete relaxation occurs in the intact working ventricle. To identify incomplete relaxation, left ventricular pressure-dimension relationships were studied in 10 canine right heart bypass preparations during ventricular pacing. The fully relaxed, exponential diastolic pressuredimension line for each ventricle was first determined from pressure and dimension values at the end of prolonged diastoles after interruption of pacing. For 167 beats during pacing under widely varying hemodynamic conditions, diastolic pressure-dimension values encountered this line defining the fully relaxed state during the filling period indicating that relaxation was complete before end diastole. The time constant for isovolumic exponential pressure fall (T) was determined for all beats. For this exponential function, if no diastolic filling occurred, 97% of pressure fall would be complete by 3.5 T after maximal negative dPldt. For the 167 beats the fully relaxed pressure-dimension line was always encountered before 3.5 T.With very rapid pacing rates (170-200 beats/min) and(or) with pharmacologic prolongation of relaxation, incomplete relaxation occurred as evidenced by the fact that the line defining the fully relaxed state was never reached during diastole (n = 15). This evidence of incomplete relaxation occurred only when the subsequent

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Evidence of Incomplete Left Ventricular Relaxation in the Dog

Weisfeldt¹,

Frederiksen²,

Yin³

et al. 1978

J. Clin. Invest.

142

View full text Add to dashboard Cite

show abstract

“…Calcium and ACS resulted in no significant change in T. These studies suggest that T is sensitive to the activity of the active cardiac-relaxing system. Sulman et al (10) studied relaxation in isolated cardiac muscle utilizing 'physiological loading." This system allows isometric relaxation to occur at peak shortening before isotonic relaxation.…”

Section: Discussionmentioning

confidence: 99%

“…Studies of afterloaded isotonic contractions in isolated papillary muscle suggest that the level of total systolic load may be of importance (9). But, as pointed out by Sulman et al (10), such afterloaded isotonic muscles undergo isotonic lengthening before the isometric phase of relaxation. This is opposite in sequence to that of the intact heart, where isovolumic relaxation occurs before ventricular filling.…”

Section: Introductionmentioning

confidence: 97%

Hemodynamic determinants of the time-course of fall in canine left ventricular pressure.

Weiss¹,

Frederiksen

Weisfeldt³

1976

J. Clin. Invest.

1,022

503

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A B S T R A C T The hemodynamic determinants of the time-course of fall in isovolumic left ventricular pressure were assessed in isolated canine left ventricular preparations. Pressure fall was studied in isovolumic beats or during prolonged isovolumic diastole after ejection. Pressure fall from the time of maximum negative dP/dt was found to be exponential during isovolumic relaxation for isovolumic and ejecting beats (r > 0.98) and was therefore characterized by a time constant, T.Higher heart rates shortened T slightly from 52.6 ±4.5 ms at 110/min to 48.2±6.0 ms at 160/min (P < 0.01, ) = 8): Higher ventricular volumes under isovolumic conditions resulted in higher peak left ventricular pressure but no significant change in T. T did shorten from 67.1+5.0 ms in isovolumic beats to 45.8+ 2.9 ms in the ejecting beats (P < 0.001, n = 14). In the ejecting beats, peak systolic pressure was lower, and end-systolic volume smaller. To differentiate the effects of sy-stolic shortening during ejection from those of lower systolic pressure and smaller end-systolic volume, beats with large end-diastolic volumes were compared -to beats with smaller end-diastolic volumes. The beats with smaller end-diastolic volumes exhibited less shortening but similar end-systolic volumes and peak systolic pressure. T again shortened to a greater extent in the beats with greater systolic shortening.Calcium chloride and acetylstrophanthidin resulted in no significant change in T, but norepinephrine, which accelerates active relaxation, resulted in a significant shortening of T (65.6±13.4 vs. 46.3+7.0 ms, P < 0.02).

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“…After this period, muscles were gradually stretched to the peak of the active tension (AT) versus length curve (L max , defined as the muscle length resulting in peak AT) and equilibrated for an additional 15 minutes while performing physiologically sequenced contractions. 17 Isometric contraction parameters were determined, which included resting tension (RT, g/mm 2 ), active tension (AT, g/mm 2 , defined as peak isometric tension minus resting tension), peak rate of isometric tension development (peakϩdT/dt, g ⅐ mm Ϫ2 ⅐ s Ϫ1 ), electromechanical delay (EMD, ms; defined as the time from stimulation to the onset of tension development), time to peak tension (TPT, ms, defined as the time from the onset of tension development to the time of peak tension), maximum rate of tension decline (ϪdT/dt, g ⅐ mm Ϫ2 ⅐ s…”

Section: Isolated Muscle Performancementioning

confidence: 99%

Direct Effects of Colchicine on Myocardial Function

et al. 1999

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Abstract-The aging spontaneously hypertensive rat (SHR) is a model in which the transition from chronic stable left ventricular hypertrophy to overt heart failure can be observed. Although the mechanisms for impaired function in hypertrophied and failing cardiac muscle from the SHR have been studied, none accounts fully for the myocardial contractile abnormalities. The cardiac cytoskeleton has been implicated as a possible cause for myocardial dysfunction.If an increase in microtubules contributes to dysfunction, then myocardial microtubule disruption by colchicine should promote an improvement in cardiac performance. We studied the active and passive properties of isolated left ventricular papillary muscles from 18-to 24-month-old SHR with evidence of heart failure (SHR-F, nϭ6), age-matched SHR without heart failure (SHR-NF, nϭ6), and age-matched normotensive Wistar-Kyoto rats (WKY, nϭ5). Mechanical parameters were analyzed before and up to 90 minutes after the addition of colchicine (10 Ϫ5 , 10 Ϫ4 , and 10

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Physiologic loading of isolated heart muscle

Cited by 26 publications

References 3 publications

Evidence of Incomplete Left Ventricular Relaxation in the Dog

Evidence of Incomplete Left Ventricular Relaxation in the Dog

Hemodynamic determinants of the time-course of fall in canine left ventricular pressure.

Direct Effects of Colchicine on Myocardial Function

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