Oxygen Uptake of the Nonworking Left Ventricle

McKeever, William P.; Gregg, Donald E.; Canney, P. C.

doi:10.1161/01.res.6.5.612

Cited by 151 publications

(30 citation statements)

References 19 publications

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“…However, when pressures are lowered in parallel in all branches of the left coronary artery, there will be global left ventricular ischemia, as well. We do not believe that our findings can be explained by the effects of global myocardial ischemia, because the differences between pressure-flow relations described when interarterial pressure gradients were present and were absent were similar in beating hearts and during diastolic arrest; in the latter, ischemia would be minimal or absent because the metabolic demand during cardiac arrest is only about 20% of that in the beating heart (McKeever et al, 1958;Monroe and French, 1960). There is no doubt that ischemia would have occurred at low flows in the beating heart, but even then it could not explain our results.…”

Section: Effects Of Interarterial Pressure Gradientsmentioning

confidence: 71%

Effects of pressure gradients between branches of the left coronary artery on the pressure axis intercept and the shape of steady state circumflex pressure-flow relations in dogs.

Messina¹,

Hanley²,

Uhlig³

et al. 1985

Circulation Research

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SUMMARY. When steady state pressure-flow relations are studied in the circumflex coronary artery, pressure gradients develop between it and other branches of the left coronary artery. To assess the effects of these pressure gradients, we compared the pressure axis intercept and shape of steady state circumflex pressure-flow relations in the presence and absence of gradients after autoregulation was abolished, both in the beating heart and during long diastoles in dogs. We used peripheral coronary pressures and radionuclide-labeled microspheres to assess arterial collateral flow. In the beating heart, interarterial pressure gradients reduced the curvature at low circumflex pressures, and overestimated the mean pressure axis intercept by 7.8 mm Hg (P < 0.05). The results were similar for the pressure-flow relations derived during long diastoles. This overesrimation exaggerates the difference between the pressure axis intercept and coronary sinus pressure. The peripheral coronary pressure and microsphere results indicate that these effects are mediated largely by arterial collateral flow. {Circ Res 56: 11-19, 1985) CORONARY arterial pressure-flow relations have been used to investigate the physical forces that regulate coronary blood flow (Cross et al., 1961;Downey and Kirk, 1975;Bellamy, 1978). The pressure axis intercept of these relations has been interpreted as the downstream pressure opposing forward flow in the coronary circulation; however, this pressure has greatly exceeded the coronary sinus pressure, which traditionally has been assumed to be the downstream pressure. The shape of these relations, found to be linear by some (Dole and Bishop, 1982;Eng et al., 1982) but curvilinear by others (L'Abbate et al., 1980;Klocke et al., 1981), is thought to convey information about the conductance of the coronary circulation. Because of this variability of the pressure axis intercept and the shape of coronary arterial pressure-flow relations, the physiological significance of both remains uncertain.One factor that might account for this variability is the specific coronary artery in which the pressureflow relation is obtained. In our laboratory, we have consistently found that the pressure axis intercept of a steady state circumflex pressure-flow relation (Verrier et al., 1980;Vlahakes et al., 1982) is much higher than that in a steady state left main coronary arterial pressure-flow relation (Rouleau et al., 1979;Uhlig et al., 1984). A possible explanation for the higher pressure axis intercept of the circumflex pressure-flow relation may be that when circumflex pressure is selectively lowered below that in the other branches of the left coronary artery, interarterial pressure gradients occur and are accompanied by collateral flow that is not measured by the upstream flow transducer. This error in measurement could underestimate total circumflex flow and thus overestimate the pressure axis intercept. Whether these pressure gradients also affect the shape of a circumflex pressure-flow relation is unknown.To assess...

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Section: Effects Of Interarterial Pressure Gradientsmentioning

confidence: 71%

Effects of pressure gradients between branches of the left coronary artery on the pressure axis intercept and the shape of steady state circumflex pressure-flow relations in dogs.

Messina¹,

Hanley²,

Uhlig³

et al. 1985

Circulation Research

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“…The myocardial basal metabolism may be constant even if heart rate is changed, because it has been shown not to be influenced so much even by large dose of catecholamines (Klocke et al 1965). In this experiment, 2 ml/100gHW/min (McKeever et al 1958;Van Citters et al 1957) was subtracted from MVO2/min as oxygen consumption for myocardial basal metabolism. As stated above, left ventricular systolic peak pressure (LVSP) and Vmax were highly significantly correlated with the corrected MVO2, and left ventricular end-diastolic volume (LVEDV) was correlated at a borderline significance.…”

Section: Discussionmentioning

confidence: 96%

Effects of Heart Rate on Ventricular Performance, Myocardial Contractile State and Coronary Circulation

Ikeda

1974

Tohoku J. Exp. Med.

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IKEDA, S. Effects of Heart Rate on Ventricular Performance, Myocardial Contractile State and Coronary Circulation. Tohoku J. exp. Med., 1974, 112 (1), 89-100-Effects of heart rate on ventricular performance, myocardial contractile state and coronary circulation were studied under constant cardiac output in right heart by-passed anesthetized dogs. Myocardial contractile state (Vmax) was elevated as heart rate increased, and this was considered to play an important role in impeding further increase of systolic time ratio which would have occurred unless this elevation had occurred. Myocardial oxygen consumption (MV02) was mainly influenced by heart rate, left ventricular systolic peak pressure and the contractile state of the left ventricle, but neither by stroke volume of the left ventricle nor left ventricular work. After administration of propranolol, the left ventricle was deteriorated at tachycardia more than 210 beats per minute, and Vmax did not rise at such a tachycardia. These results suggest that adrenergic beta-receptor plays an important role in augmenting the contractile state of the left ventricle and in preventing it from being deteriorated at tachycardia. heart rate; myocardial contractility; coronary circulation; myocardial oxygen consumption; propranolol Bowditch (1871) reported a staircase phenomenon in the frog ventricle. That is, when the ventricle was stimulated at a constant rate, the strength of contrac tion reached a plateau, and when it was stimulated at a faster or slower rate, the strength reached a higher or lower plateau, respectively. This phenomenon was demonstrated in mammalian cardiac muscles (Woodworth 1902; Abbott and Mommaerts 1959;Blinks and Koch-Weser 1961;Sonnenblick 1962). The effects of heart rate on the intact pumping ventricle have also been examined, but the conclusions are controversial. Sarnoff et al. (1963 and Covell et al. (1967) concluded that myocardial contractility was increased as heart rate increased, while Noble et al. (1966Noble et al. ( , 1969 reported that it was not altered by changes in heart rate in conscious dogs. On the other hand, it is generally accepted that coronary circulation is influenced greatly by heart rate and ventri cular performance.This experiment was designed to ascertain whether the changes in heart rate varies the myocardial contractile state and which factors contribute to alteration of coronary blood flow and myocardial oxygen consumption. Heart rate was changed by atrial pacing, and the left ventricular pressure, its dp/dt and the total coronary venous return were measured in right heart by-passed dogs. The experiment was also performed after administration of propranolol in order to ascertain whether the activation of beta-receptor mediates the effects of heart rate on myo cardial contractile state, ventricular performance and coronary circulation. METHODEight mongrel dogs of both sexes weighing from 12 to 20 kg were anesthetized with pentobarbital sodium (30 mg/kg) given intravenously. Ventilation was provided by a positive pre...

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“…Previous studies in mature dogs have demonstrated that the major determinants of myocardial oxygen consumption in anesthetized mature dogs are contractility and wall stress, that external cardiac work and basal metabolism are quantitatively less important determinants, and that electrical activation accounts for less than 1 % of myocardial oxygen consumption (3,4,27,28,29). Parmley and Tyberg (30) has estimated that contractility and wall stress each account for 30-40% of total myocardial oxygen consumption in the basal state whereas external cardiac work and basal metabolism each may account for 10-20%.…”

Section: Discussionmentioning

confidence: 99%

β-Adrenergic Influence on Increased Myocardial Oxygen Consumption during Hypoxemia in Awake Newborn Lambs

Fisher

1989

Pediatr Res

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ABSTRACT. The purpose of this investigation was to Abbreviations determine the role of increased P-adrenergic activity in regulating the increase in myocardial oxygen consumption LVEDP, left ventricular and diastolic pressure that occurs during hypoxemia in unanesthetized newborn dP/dt, first derivative of left ventricular pressure lambs. Through a left thoracotomy, fluid-filled catheters LV, left ventricle were placed in the ascending aorta, coronary sinus and left atrium, a pressure transducer was introduced into the left ventricle, and pacing wires were sutured onto the left atrium. The lambs were studied 3 d later by making Acute hypoxemia has important effects on the developing intermittent m a~~r e m e n t s of aortic and coronary sinus myocardium. We have demonstrated previously that myocardial blood oxygen saturations and Hb concentrations, left ven-oxygen consumption increased by 30-40% during moderate tricular myocardial blood flow, cardiac output, heart rate, hypoxemia (Fio2 = 0.08-0.10) in unanesthetized newborn lambs left atrial and aortic blood Pressures, the nmximal first (1). To understand the underlying mechanism, we reasoned that derivative of left ventricular pressure, aortic and coronary hypoxemia also has been associated with P-adrenergically mesinus blood oxygen contents, the arteriovenous difference diated increases in several of the hemodynamic determinants of of oxygen across the left ventricular myocardium, myocar-myocardial oxygen consumption. Thus, we postulated that indial oxygen consumption, and external cardiac work (aortic creased 0-adrenergic activity would be an important regulator of mean blood Pressure times cardiac output). In nine lambs the increase in myocardial oxygen consumption that occurs with an intact P-adrenergic nervous system (group I), the during hypoxemia (2-7). above measurements were made during a control period Previous studies have demonstrated that myocardial oxygen and during hypoxemia (Fioz = 0.08-0.10) with sponta-consumption increased during hypoxemia in @-adrenergically neous tachycardia. In another group of 12 lambs (group blocked anesthetized newborn lambs and mature dogs (8, 9). 2), the measurements were made during a control period, However, all of these experimental animals were studied under after P-blockade (1.5 mg/kg intravenous propranolol) with the influence of @-blockade. Thus, there is no information using pacing at the control heart rate, during hypoxemia with the same experimental preparation with and without @-blockade pacing at the control heart rate, and during hypoxemia that would permit a quantitative estimation of the role of the Pwith pacing-induced tachycardia. In the group 2 lambs, P-adrenergically mediated augmentation of cardiovascular funcblockade completely inhibited the increase in heart rate, tion on the increase in myocardial oxygen consumption during maximal first derivative of left ventricular pressure, cardiac hypoxemia. Furthermore, the previous studies were performed output and cardiac work that ~~c~r r e d during hypo...

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Oxygen Uptake of the Nonworking Left Ventricle

Cited by 151 publications

References 19 publications

Effects of pressure gradients between branches of the left coronary artery on the pressure axis intercept and the shape of steady state circumflex pressure-flow relations in dogs.

Effects of pressure gradients between branches of the left coronary artery on the pressure axis intercept and the shape of steady state circumflex pressure-flow relations in dogs.

Effects of Heart Rate on Ventricular Performance, Myocardial Contractile State and Coronary Circulation

β-Adrenergic Influence on Increased Myocardial Oxygen Consumption during Hypoxemia in Awake Newborn Lambs

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