Effects of bigeminies and paired-pulse stimulation on oxygen consumption in dog left ventricle.

Studies were carried out in order to determine the factors influencing myocardial 201T1 uptake. A total of 158 patients was examined with regard to both 201T1 uptake and the assessment of left ventricular and coronary function (e. g. quantitative ventriculography, coronary arteriography, coronary blood flow measurements). Moreover, 42 animal experiments (closed chest cat) were performed. The results demonstrate that:1) 201T1 uptake in the normal and hypertrophied human heart is linearly correlated with the muscle mass of the left ventricle (LVMM);2) 201T1 uptake is enhanced in the inner (subendocardial) layer and is decreased in the outer (subepicardial) layer of the left ventricular wall. The 201T1 uptake of the right ventricle is 40% lower in comparison to the left ventricle;3) the basic correlation between 201T1 uptake and LVMM is influenced by alterations of both myocardial flow and myocardial oxygen consumption; and4) inotropic interventions (isoproterenol, calcium, norepinephrine) as well as coronary dilatation (dipyridamole) may considerably augment 201T1 uptake in accordance with changes in myocardial oxygen consumption and/or myocardial flow.It is concluded that myocardial 201T1 uptake is determined by multiple factors. The major determinants have been shown to include (i) muscle mass, (ii) myocardial flow and (iii) myocardial oxygen consumption. The clinical data obtained from patient groups with normal ventricular function, with coronary artery disease, with left ventricular wall motion abnormalities and with different degree of left ventricular hypertrophy are correlated with quantitated myocardial 201T1 uptake.

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Force-time integral decreases with ejection despite constant oxygen consumption and pressure-volume area in dog left ventricle.

Circulation Research ◽

10.1161/01.res.60.6.797 ◽

1987 ◽

Vol 60 (6) ◽

pp. 797-803 ◽

Cited By ~ 25

Author(s):

H Suga ◽

Y Goto ◽

T Nozawa ◽

Y Yasumura ◽

S Futaki ◽

...

Keyword(s):

Oxygen Consumption ◽

Left Ventricle ◽

Time Integral ◽

Force Time ◽

Force Time Integral

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Paired-pulse stimulation of an electric-hydraulic pump used to replace the mammalian heart

Cleveland Clinic Journal of Medicine ◽

10.3949/ccjm.35.1.41 ◽

1968 ◽

Vol 35 (1) ◽

pp. 41-47

Author(s):

S. D. Moulopoulos ◽

M. J. Crosby ◽

Y. Nose ◽

W. J. Kolff

Keyword(s):

Hydraulic Pump ◽

Paired Pulse ◽

Mammalian Heart ◽

Pulse Stimulation ◽

Stimulation Of

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External mechanical work during relaxation period does not affect myocardial oxygen consumption

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1991.261.6.h1778 ◽

1991 ◽

Vol 261 (6) ◽

pp. H1778-H1784 ◽

Cited By ~ 4

Author(s):

K. Hata ◽

Y. Goto ◽

H. Suga

Keyword(s):

Oxygen Consumption ◽

Left Ventricle ◽

Potential Energy ◽

Myocardial Oxygen Consumption ◽

Mechanical Work ◽

Relaxation Period ◽

End Diastolic Volume ◽

The Cross

We assessed the effect of external mechanical work (EW) during the relaxation period (RP) on myocardial oxygen consumption (VO2) and clarified the energetic significance of the potential energy (PE) portion of the pressure-volume area (PVA) in the cross-circulated dog left ventricle. We changed the course of the relaxation segment of the pressure-volume (P-V) trajectory by increasing or decreasing EW within a given PVA without changing the end-diastolic volume (EDV) and the systolic segment of the P-V trajectory while measuring VO2. Thus the ventricle underwent ejection or filling during RP. Although the percent fraction of EW in PVA (%EW/PVA) was markedly increased from 32 +/- 12 (SD) to 93 +/- 3% in ejecting contractions (8 hearts) and from 0 to 93 +/- 5% in isovolumic contractions (3 hearts), these marked changes in %EW/PVA did not significantly affect VO2. Moreover, the VO2-PVA data during these procedures fell on the reference VO2-PVA relation line obtained by changing EDV and PVA of isovolumic contractions. We conclude that EW during RP at a constant PVA does not affect VO2 and part of PE can be converted into EW in an energetically equivalent manner.

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Excitation of lumbar motoneurons by the medial longitudinal fasciculus in the in vitro brain stem spinal cord preparation of the neonatal rat

Journal of Neurophysiology ◽

10.1152/jn.1993.70.6.2241 ◽

1993 ◽

Vol 70 (6) ◽

pp. 2241-2250 ◽

Cited By ~ 26

Author(s):

M. K. Floeter ◽

A. Lev-Tov

Keyword(s):

Spinal Cord ◽

Brain Stem ◽

Short Latency ◽

Medial Longitudinal Fasciculus ◽

Paired Pulse ◽

Long Latency ◽

The Brain ◽

Pulse Stimulation ◽

Stimulation Of

1. The excitation of lumbar motoneurons by reticulospinal axons traveling in the medial longitudinal fasciculus (MLF) was investigated in the newborn rat using intracellular recordings from lumbar motoneurons in an in vitro preparation of the brain stem and spinal cord. The tracer DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine) was introduced into the MLF of 6-day-old littermate rats that had been fixed with paraformaldehyde to evaluate the anatomic extent of this developing pathway. 2. Fibers labeled from the MLF by DiI were present in the cervical ventral and lateral white matter and a smaller number of labeled fibers extended to the lumbar enlargement. Patches of sparse terminal labeling were seen in the lumbar ventral gray. 3. In the in vitro preparation of the brain stem and spinal cord, MLF stimulation excited motoneurons through long-latency pathways in most motoneurons and through both short-(< 40 ms) and long-latency connections in 16 of 40 motoneurons studied. Short- and longer-latency components of the excitatory response were evaluated using mephenesin to reduce activity in polysynaptic pathways. 4. Paired-pulse stimulation of the MLF revealed a modest temporal facilitation of the short-latency excitatory postsynaptic potential (EPSP) at short interstimulus intervals (20–200 ms). Trains of stimulation at longer interstimulus intervals (1–30 s) resulted in a depression of EPSP amplitude. The time course of the synaptic depression was compared with that found in EPSPs resulting from paired-pulse stimulation of the dorsal root and found to be comparable. 5. The short-latency MLF EPSP was reversibly blocked by 6-cyano-7-nitroquinoxaline (CNQX), an antagonist of non-N-methyl-D-aspartate glutamate receptors, with a small CNQX-resistant component. Longer-latency components of the MLF EPSP were also blocked by CNQX, and some late components of the PSP were sensitive to strychnine. MLF activation of multiple polysynaptic pathways in the spinal cord is discussed.

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Myoglobin function in the isolated fluorocarbon-perfused dog heart

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1978.234.5.h567 ◽

1978 ◽

Vol 234 (5) ◽

pp. H567-H572 ◽

Cited By ~ 1

Author(s):

R. P. Cole ◽

B. A. Wittenberg ◽

P. R. Caldwell

Keyword(s):

Oxygen Consumption ◽

Left Ventricle ◽

Mechanical Performance ◽

Left Ventricular Pressure ◽

Dry Weight ◽

Left Ventricular ◽

Facilitated Diffusion ◽

Dog Heart ◽

Before And After ◽

Ringer’S Lactate

An isolated dog heart preparation perfused with hemoglobin-free fluorocarbon suspension has been developed to study the role of myoglobin in myocardial function. The coronary vasculature was perfused at constant flow, with oxygen consumption determined from arteriovenous PO2 differences. Muscle function was assessed by measurement of pressures generated in a latex balloon placed in the left ventricle. The perfusate consisted of 20% perfluorotributylamine and 80% Ringer's lactate with 16 mM glucose. Steady-state oxygen consumption decreased from 0.30 to 0.11 ml/min per gram dry weight left ventricle, as perfusate PO2 decreased from 690 to 150 mmHg. Left ventricular pressure generation and oxygen consumption were determined before and after addition of 8 mM sodium nitrite, which changed functional ferrous myoglobin to high-spin ferric myoglobin. Over the range of perfusate PO2 studied, nitrite addition did not alter mechanical performance or myocardial oxygen consumption. These data suggest that those conditions necessary for substantial myoglobin-facilitated diffusion of oxygen in the myocardium are not present in the isolated fluorocarbon-perfused dog heart.

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