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  • 1
    Electronic Resource
    Electronic Resource
    Characteristic dysfunction of stunned myocardium induced by 2,3-butanedione monoxime without ischaemia (2005)
    Oxford, UK : Blackwell Science Pty
    Clinical and experimental pharmacology and physiology 32 (2005), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. In the present study, we tested the hypothesis that, even in the absence of prior ischaemia, 2,3-butanedione monoxime (BDM), an inhibitor of contraction at the actin–myosin level, could produce the postischaemic dysfunction characteristic of stunned myocardium. 2,3-Butanedione monoxime was injected directly into the left anterior descending coronary artery (LAD) before and again after myocardial stunning produced by 15 min occlusion of the LAD followed by 30 min reperfusion.2. Regional myocardial force, segment shortening and regional work were measured in both the LAD-perfused area and the area perfused by the circumflex coronary artery, which served as a control area. Regional dysfunction produced by BDM injection or ischaemia–reperfusion was assessed quantitatively by five parameters: end-diastolic length (EDL), shortening onset delay (delay), systolic bulge (bulge), end-shortening time delay (EST) and tail work ratio (TWR).3. It was found that injection of BDM into the LAD caused dyskinesis similar to that caused by occlusion–reperfusion. Both displayed elevated EDL and marked increases in delay, bulge, EST and TWR; these parameters were significantly higher in the dyskinesis caused by BDM injection. Despite dysfunctional fibre shortening, intracoronary BDM injection did not reduce regional force.4. Thus, BDM can elicit changes similar to those characteristic of postischaemic dysfunction. Because contractility was not impaired, dysfunction was apparently caused by disrupting the association between contractile force and muscle motion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.2005.04292.x
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  • 2
    Electronic Resource
    Electronic Resource
    Hypervolaemia improves global and local function and efficiency in postischaemic myocardium (2001)
    Melbourne, Australia : Blackwell Science Pty
    Clinical and experimental pharmacology and physiology 28 (2001), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. In the present study, we investigated the effects of blood volume on postischaemic function and efficiency. In 14 anaesthetized dogs, following recovery from a period of 15 min occlusion of the left anterior descending coronary artery, the effects of hypervolaemia (HYPER; 15% increased volume produced by fast infusion of Hespan; B Braun Medical, Irvine, CA, USA), normovolaemia (NORMO) and hypovolaemia (HYPO) were studied.2. Although myocardial O2 consumption was not significantly increased by volume (6.37±0.94 vs 6.89±1.1 mL/min per 100 g for HYPO and HYPER, respectively), local work of the stunned myocardium was markedly elevated (8.8±1.7 vs 22.5±3.5 g·mm/ beat, for HYPO and HYPER, respectively; P 〈 0.05). External work of the heart was also significantly improved (71.8±12.7 vs 139.5±16.2 mmHg·L/min for HYPO and HYPER, respectively). These data indicate markedly improved efficiency produced by volume, because work was increased with no change in myocardial O2 consumption.3. Local dysfunction was characterized by several parameters, including systolic bulge, end-diastolic length, delay to onset of shortening, end shortening time delay (EST) and tail work ratio. Hypervolaemia reduced EST compared with hypovolaemia (98.6±18.3 vs 110.7±14.9 msec, respectively; P 〈 0.05) and improved tail work ratio (28.0±7.0 vs 36.0±7.0%, respectively; P 〈 0.05), with no effects on systolic bulge, end-diastolic length and delay to onset of shortening.4. Thus, even in the postischaemic myocardium, increasing work by volume is energetically efficient and is accompanied by partial improvement of local dysfunction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1440-1681.2001.03498.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of heart rate on the relation between global and regional cardiac work and oxygen consumption
    Amsterdam : Elsevier
    Journal of Molecular and Cellular Cardiology 20 (1988), S. III 
    Details
    ISSN: 0022-2828
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0022-2828(88)80039-7
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  • 4
    Electronic Resource
    Electronic Resource
    Studies with EMMA 4 on changes in the intracellular concentration and distribution of calcium in heart muscle of the dog in different steady states
    Amsterdam : Elsevier
    Micron (1969) 5 (1974), S. 11-20 
    Details
    ISSN: 0047-7206
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0047-7206(74)90030-2
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  • 5
    Electronic Resource
    Electronic Resource
    The oxygen wasting effect of isoproterenol is altered by chemical denervation and cardiac hypertrophy (1996)
    Springer
    Basic research in cardiology 91 (1996), S. 308-318 
    Details
    ISSN: 1435-1803
    Keywords: β-adrenergic stimulation ; segment work ; regional blood flow ; regional O2 consumption ; efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We tested the hypothesis that isoproterenol would increase myocardial work and O2 consumption at reduced efficiency and that both left ventricular hypertrophy and chemical sympathectomy would lead to changes in this myocardial efficiency response. Left ventricular hypertrophy was produced by aortic valve plication in 23 puppies. Six months later, sympathetic denervation (6-hydroxydopamine) was produced in 12 hypertrophied and 10 non-hypertrophied dogs, 5 days prior to acute experiments. Ten non-hypertrophied and 11 hypertrophied animals were not denervated. Measurements were made before and during an isoproterenol infusion (0.5 μg/kg/min). Regional myocardial work was calculated as the integrated product of force (miniature transducer) and segment shortening (ultrasonic crystals). Regional O2 consumption was calculated from regional blood flow (microspheres) and regional O2 saturations (microspectrophotometry). In all groups, regional O2 consumption increased with isoproterenol (non-hypertrophied, non-sympathectomized 6.5±0.8 to 20.3±5 ml O2/min/100 g, non-hypertrophied, sympathectomized 5.0±0.7 to 10.0±1.5, hypertrophied, nonsympathectomized 9.8±1.3 to 16.2±2.2, hypertrophied, sympathectomized 6.1±0.5 to 13.3±1.6). Regional segment work also increased in all groups with isoproterenol stimulation (non-hypertrophied, non-sympathectomized 781±73 to 1197±61 g·mm/min, non-hypertrophied, sympathectomized 996±221 to 2118±412, hypertrophied, non-sympathectomized 1031±145 to 3262±753, hypertrophied, sympathectomized 721±116 to 1745±402). In the non-hypertrophied, non-sympathectomized group, efficiency (work/O2 consumption) was significantly decreased from 122±17 to 76±9 g·mm/ml O2/100 g demonstrating an “oxygen wasting” effect. In the hypertrophied, non-sympathectomized group, segment efficiency significantly increased from 94±19 to 250±63. In both sympathectomized groups, efficiency was not altered by isoproterenol. Thus the oxygen wasting effect of β-adrenergic stimulation was reversed by left ventricular hypertrophy and blocked by sympathectomy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00789303
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of dopamine on regional myocardial function and oxygen consumption in experimental left ventricular hypertrophy (1991)
    Springer
    Basic research in cardiology 86 (1991), S. 449-460 
    Details
    ISSN: 1435-1803
    Keywords: Myocardial O2 balance ; microspectrophotometry ; regionalblood flow ; dogs ; functional reserve
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We investigated the hypothesis that the capacity of left ventricular myocardium to respond to an inotropic challenge by dopamine would be diminished in left ventricular hypertrophy induced by plication of the aortic valve. Seven mongrel dogs (LVH group) aged 6–8 weeks and weighing 4–6 kg, were subjected to preliminary surgery in which the noncoronary sinus of Valsalva was plicated. Six months later these animals, as well as a control group of dogs, were subjected to acute experiments in which the effect of dopamine (7.5 and 15 μg/kg/min) on regional and global myocardial function and oxygen consumption was studied. Myocardial segment length was measured with ultrasonic dimension transducers, and left ventricular and aortic blood pressures were recorded from catheter-tip transducers. Regional coronary blood flow was determined with radioactive microspheres, and regional oxygen saturation in small arteries and veins was measured using microspectrophotometry. Regional myocardial O2 consumption was calculated from these parameters. Heart weights were significantly elevated in the LVH group, and a pressure gradient of about 25 mm Hg was observed across the aortic valve. In both groups, dopamine infusion produced a dose-dependent increase in heart rate, left ventricular pressure, and LV dP/dtmax. Prior to dopamine infusion, percent shortening per beat was greater in the LVH group (13.97 ± 1.2 %) than in the control group (9.49 ± 1.07 %). Although the maximum speed of segment shortening was elevated by dopamine in both groups, percent shortening was not elevated in the LVH group. Stimulation by the high dose of dopamine produced a threefold elevation in regional coronary blood flow in both groups. Oxygen extraction was unchanged; the proportion of small veins with low O2 saturation was not elevated in LVH hearts, even during dopamine stimulation. Regional myocardial O2 consumption was elevated by dopamine (15 μg/kg/min) to about the same extent in both the control and LVH groups (19.1 ± 2.3 and 17.5 ± 2.3 ml O2/min/100 g) respectively. It is concluded that, in dogs with six months of aortic stenosis, dopamine does not exhaust functional reserve and the relationship between O2 supply and consumption is not significantly impaired.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02190713
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  • 7
    Electronic Resource
    Electronic Resource
    Regional asynchrony of segmental contraction may explain the “oxygen consumption paradox” in stunned myocardium (1994)
    Springer
    Basic research in cardiology 89 (1994), S. 149-162 
    Details
    ISSN: 1435-1803
    Keywords: Myocardial ischemia ; coronary reperfusion ; stunned myocardium ; postischemic dysfunction ; oxygen consumption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Despite apparently depressed function, stunned myocardium maintains oxygen consumption and has the capacity to increase contractility with inotropic stimulation. We hypothesized that during stunning, O2 demand is maintained because regional segment work is performed, but is asynchronous with global left ventricular contraction, and that inotropic stimulation would restore regional work and synchrony. Thirteen open-chest anesthetized dogs were subjected to three left anterior descending (LAD) coronary artery occlusions (10 min) and reperfusions (15 min) to produce regional myocardial stunning. Segment shortening and force development were measured independently and simultaneously in the LAD (experimental) region and circumflex (control) regions. Regional myocardial work was calculated as the integrated product of instantaneous force and shortening, during two periods: 1) over the entire cardiac cycle (Positive Work), and 2) limited to the systolic portion of the cardiac cycle (Systolic Work). Regional myocardial O2 consumption (MVO2) was calculated from regional blood flow (radiolabeled microspheres) and O2 saturation data (microspectrophotometry). Occlusion of the LAD produced a delay in onset of segment shortening in the ischemic region, but not in regional force development. A time delay of 67–81 ms persisted through the three stages of occlusions and reperfusion. Systolic regional work was depressed to a greater extent (924±182 to 149±118 g*mm*min−1) than total positive regional work (1437±337 to 857±174 g*mm*min−1). Regional subepicardial MVO2 in the stunned region was not different than in the control region (7.3±1.5 vs. 6.9±1.4 ml O2*min−1*100 g−1). Local infusion of isoproterenol reversed the delay in regional shortening from 73±7 to 21±8 ms, thereby augmenting systolic work (298%) more than positive work (60%), without a significant increase in MVO2 (7.3±1.5 to 10.5±3.2 ml O2*min−1*100 g−1). It is concluded that myocardial stunning decreases regional systolic work due to regional mechanical asynchrony, while MVO2 is used supported total positive work which was not significantly reduced. Isoproterenol restores regional work by restoring synchrony, without greatly affecting regional MVO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00788734
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