Myocardial blood flow and VO2 in conscious lambs with an aortopulmonary shunt

Toorop, G. P.; Hardjowijono, R; Dalinghaus, Michiel; Gerding, A. M.; Koers, Jh; Zijlstra, Wg; Kuipers, Jrg

doi:10.1152/ajpheart.1987.252.4.h681

Cited by 10 publications

(11 citation statements)

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“…The left to right shunt led to significant hemodynamic differences between shunt and control lambs at rest (Table I), differences that were similar to those reported previously from our laboratory (3,24). Aortic systolic pressure in the present study was not significantly lower than in control lambs ( p = 0.07), unlike mean aortic pressure (65 +-1 versus 71 + 2 mmHg, p < 0.01).…”

Section: Resultssupporting

confidence: 89%

“…This effect is accompanied by an increased myocardial oxygen consumption (3), which reflects increased oxidation of substrates to meet the increased ATP demand (4). Often, an increased work load leads not only to increased substrate uptake, but also to a change in the pattern of myocardial substrate utilization (5), as has been shown in hearts with increased afterload (6), contractility (7), and thyroxineinduced volume load (8,9) and during exercise (5,(10)(11)(12).…”

mentioning

confidence: 98%

“…A left to right shunt through a ventricular septa1 defect or ductus arteriosus imposes an increased work load on the heart because of its effect on left ventricular wall stress, external work, contractility, and heart rate (1)(2)(3). This effect is accompanied by an increased myocardial oxygen consumption (3), which reflects increased oxidation of substrates to meet the increased ATP demand (4).…”

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confidence: 99%

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Myocardial Carbohydrate, Ketone, and Fatty Acid Uptake in Conscious Lambs with Aortopulmonary Shunts1

et al. 1992

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ABSTRACT. A left to right shunt increases myocardial work and is often accompanied by increased catecholamine levels. Because both increased myocardial work and increased catecholamine levels may induce increased fatty acid utilization, which could increase resting myocardial oxygen consumption and therefore unfavorably affect coronary reserve, we studied myocardial uptake of glucose, pyruvate, lactate, &OH-butyrate, acetoacetate, FFA, and triglycerides in 12 7-wk-old lambs with aortopulmonary left to right shunts (58 f 2% of left ventricular output, mean f SEM) and in 10 control lambs 2 wk after surgery. Despite the shunt, systemic blood flow in the shunt lambs was maintained at the same level as in the control lambs. This was accomplished by an increased heart rate and stroke volume. Furthermore, the shunt was accompanied by an increased myocardial oxygen consumption in the shunt lambs (834 f 70 versus 528 f 43 pmol 02-mine' -100 g-I; p c 0.05). There were no significant differences in arterial substrate concentrations between the two groups. The same was true for arteriovenous differences across the myocardium, with the exception of lactate, which was substantially higher in shunt than in control lambs (72 f 25 versus 18 f 23 pmol/L; p < 0.05). As a consequence, myocardial lactate uptake in the shunt lambs was increased 15-fold (18 2 6 versus 1 f 2 pmol. min-I. 100 g-I; p c 0.02), whereas uptake of the other substrates merely paralleled the increased myocardial blood flow. Our data demonstrate that myocardial substrate uptake is not substantially different between shunt and control lambs, with the exception of lactate, of which the extraction is 10-fold higher than in control lambs. We speculate that the increased myocardial lactate utilization may reflect an increase of lactate and pyruvate dehydrogenase activities. A left to right shunt through a ventricular septa1 defect or ductus arteriosus imposes an increased work load on the heart because of its effect on left ventricular wall stress, external work, contractility, and heart rate (1-3). This effect is accompanied by an increased myocardial oxygen consumption (3), which reflects increased oxidation of substrates to meet the increased ATP demand (4). Often, an increased work load leads not only to increased substrate uptake, but also to a change in the pattern of myocardial substrate utilization (5), as has been shown in hearts with increased afterload (6), contractility (7), and thyroxineinduced volume load (8, 9) and during exercise (5,(10)(11)(12). Furthermore, catecholamines are often increased in the presence of a substantial left to right shunt (13), and they are also known to affect myocardial metabolism (14,15). Through their effect on myocardial performance, catecholamines stimulate glucose and fatty acid utilization by the myocardium, and, through activation of lipoprotein lipase, they enhance fatty acid utilization (5, [14][15][16].These considerations suggest that a left to right shunt could lead to a change in myocardial substrate metabolism....

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Section: Resultssupporting

confidence: 89%

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confidence: 98%

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confidence: 99%

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Myocardial Carbohydrate, Ketone, and Fatty Acid Uptake in Conscious Lambs with Aortopulmonary Shunts1

et al. 1992

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“…9 The left-to-right shunt was calculated by subtracting systemic blood flow from pulmonary blood flow, whereas the left-to-right shunt fraction was obtained by dividing shunt flow by pulmonary blood flow. The systemic and pulmonary vascular resistances were calculated according to standard equations.…”

Section: Measurements and Calculationsmentioning

confidence: 99%

Effects of nitroprusside on myocardial blood flow and oxygen consumption in conscious lambs with an aortopulmonary left-to-right shunt.

et al. 1990

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We studied the effect of vasodilation on regional myocardial blood flow and oxygen consumption of the left ventricular free wall by infusing 10 ,ug/kg/min sodium nitroprusside into 7-week-old conscious lambs with and without aortopulmonary left-to-right shunts. Resting myocardial oxygen consumption in the 13 shunt lambs was significantly higher than in the nine control lambs (989±104 [+ SEMI vs. 432 ±41 ,umol/min/100 g left ventricle). This was achieved by a significantly higher left ventricular myocardial blood flow (294 ±33 vs. 143±16 ml/min/100 g left ventricle) because the arteriovenous oxygen concentration difference across the left ventricular free wall was similar in shunt and control lambs. Infusion of nitroprusside did not significantly change myocardial oxygen consumption and regional myocardial blood flows at 10 and 50 minutes after the onset of the infusion. This occurred despite a substantial drop in aortic and left atrial pressures and stroke volume, which decreases wall stress as well as external work of the left ventricle. Heart rate, however, increased significantly. We postulate that, during infusion of nitroprusside, the potential decrease in myocardial oxygen consumption due to a decrease in wall stress and external work of the left ventricle is neutralized by the consequences of the increased heart rate. In view of this and because of its hemodynamic effects, we do not consider sodium nitroprusside useful in the treatment of circulatory congestion in patients with left-to-right shunts, normal arterial pressures, and normal systemic blood flows. (Circulation 1990;81:319-324 and, therefore, myocardial oxygen consumption through the decreased afterload accompanying dilation of the resistance vessels. The lack of uniformity in experimental data concerning the importance of the above mechanisms and the beneficial effects of vasodilation has prompted us to investigate the hemodynamic changes caused by the infusion of sodium nitroprusside. We infused this commonly used vasodilator45 into chronically instrumented lambs with and without aortopulmonary leftto-right shunts.6 In these studies, it was shown that, in lambs with shunts, sodium nitroprusside decreased the flow through the shunt in the first few minutes after the onset of infusion. The decrease, however, was of a duration too short to consider beneficial. Systemic blood flow hardly changed, whereas heart rate increased substantially. We ascribed this lack of favorable hemodynamic effects to the abrupt pressure decrease induced and to the activation of counteracting mechanisms. On the other hand, we did show that preload decreased during nitroprusside

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“…The surgery was necessary to close the arterial duct, as left to right shunt may have large effects on coronary flow (3,30). Mechanical ventilation and anesthesia might have effects on basal coronary flow and CFR, but data obtained in anesthetized mechanically ventilated children have shown CFR values comparable to values obtained in adults who were not subject to anesthesia (5,10).…”

Section: Discussionmentioning

confidence: 99%

Coronary Flow Reserve in the Newborn Lamb: An Intracoronary Doppler Guide Wire Study

et al. 2004

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Recent studies indicate a severely reduced coronary flow reserve (CFR) in neonates with congenital heart disease. The significance of these studies remains debatable, as the ability of the anatomically normal neonatal heart to increase coronary flow is currently unknown. This study was designed to establish normal values for CFR in newborns after administration of adenosine [pharmacologic CFR (pCFR)] and as induced by acute hypoxemia (reactive CFR). Thirteen mechanically ventilated newborn lambs were studied. Coronary flow velocities were measured in the proximal left anterior descending coronary artery before and after adenosine injection (140 and 280 g/kg i.v.) using an intracoronary 0.014-in Doppler flow-wire. Measurements were made at normal oxygen saturation (SaO 2 ) and during progressive hypoxemia induced by lowering the fraction of inspired oxygen. CFR was defined as the ratio of hyperemic to basal average peak flow velocity. In a hemodynamically stable situation with normal SaO 2 , pCFR was 3.0 Ϯ 0.5. pCFR decreased with increasing hypoxemia. Regression analysis showed a linear relation between SaO 2 and pCFR (R ϭ 0.86, p Ͻ 0.0001). Reactive CFR obtained at severe hypoxemia (SaO 2 Ͻ30%) was 4.2 Ϯ 0.8, and no significant further increase in coronary flow velocity occurred by administration of adenosine. Newborn lambs have a similar capacity to increase coronary flow in response to both pharmacologic and reactive stimuli as older subjects. Administration of adenosine does not reveal the full capacity of the newborn coronary circulation to increase flow, however, as the flow increase caused by severe hypoxemia is significantly more pronounced. Hemodynamic problems in the neonatal period, often related to congenital heart defects, may affect coronary blood flow (1-3). The coronary physiology in newborns has become of greater importance as cardiac surgery for congenital heart defects is increasingly performed in the neonatal period. Coronary flow reserve (CFR) has been found to be useful in evaluating the effects of cardiac disease and pathologic hemodynamic conditions on coronary flow dynamics in adults (4 -6). CFR is defined as the ratio of maximal coronary blood flow, as induced by reactive hyperemia or administration of vasodilators, divided by resting flow (4).Recent studies performed with positron emission tomography (PET) have shown low CFR in neonates and infants with congenital heart disease (1, 7). The significance of these studies remains debatable, as the ability of the anatomically normal neonatal heart to increase coronary flow is currently unknown (1, 7). The objective of this study was to provide normal values for CFR in the normal neonatal heart by administration of adenosine [pharmacologic CFR (pCFR)

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Myocardial blood flow and VO2 in conscious lambs with an aortopulmonary shunt

Cited by 10 publications

References 0 publications

Myocardial Carbohydrate, Ketone, and Fatty Acid Uptake in Conscious Lambs with Aortopulmonary Shunts1

Myocardial Carbohydrate, Ketone, and Fatty Acid Uptake in Conscious Lambs with Aortopulmonary Shunts1

Effects of nitroprusside on myocardial blood flow and oxygen consumption in conscious lambs with an aortopulmonary left-to-right shunt.

Coronary Flow Reserve in the Newborn Lamb: An Intracoronary Doppler Guide Wire Study

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