Maximal myocardial blood flow is enhanced by chronic hypoxemia in late gestation fetal sheep

1992 ◽  
Vol 263 (4) ◽  
pp. H1327-H1329 ◽  
Author(s):  
M. D. Reller ◽  
M. J. Morton ◽  
G. D. Giraud ◽  
D. E. Wu ◽  
K. L. Thornburg
Keyword(s):  
Blood Flow ◽  
Myocardial Blood Flow ◽  
Left Ventricular ◽  
Late Gestation ◽  
Ventricular Free Wall ◽  
Free Wall ◽  
Fetal Sheep ◽  
Arterial Pco2 ◽  
Arterial Concentration ◽  
Arterial Po2

The measurement of maximal myocardial blood flow gives information about the total cross-sectional area of the coronary resistance vessels. During a continuous left atrial infusion of adenosine (60 micrograms.kg-1.min-1), maximal myocardial blood flow was measured in 4 fetuses hypoxemic for a minimum of 5-8 days (pH = 7.33 +/- 0.01, arterial PCO2 = 49.8 +/- 4.2 Torr, arterial PO2 = 16.1 +/- 1.3 Torr, and arterial concentration of O2 = 5.3 +/- 1.2 ml/dl). These data were compared with an identically instrumented group of normoxemic fetuses (n = 7) following the same study protocol (pH = 7.38 +/- 0.02, arterial PCO2 = 43.1 +/- 3.8 Torr, arterial PO2 = 19.8 +/- 2.0 Torr, and arterial concentration of O2 = 7.9 +/- 1.0 ml/dl) (P < 0.05). At comparable arterial pressures, the maximal myocardial flow (ml.min-1.100 g tissue-1) for hypoxemic vs. normoxemic fetuses was 974 +/- 273 and 630 +/- 181 for the total myocardium, 986 +/- 367 and 602 +/- 192 for the left ventricular free wall, 1,025 +/- 346 and 614 +/- 178 for the septum, and 1,231 +/- 274 and 757 +/- 269 for the right ventricular free wall, respectively (P < 0.01). These data suggest that hypoxemia in the fetus can significantly alter the coronary vascular bed, which, if confirmed, would represent an important adaptation in the developing fetus.

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

1987 ◽  
Vol 252 (4) ◽  
pp. H681-H686 ◽  
Author(s):  
G. P. Toorop ◽  
R. Hardjowijono ◽  
M. Dalinghaus ◽  
A. M. Gerding ◽  
J. H. Koers ◽  
...  
Keyword(s):  
Blood Flow ◽  
Myocardial Blood Flow ◽  
Left Ventricular ◽  
Ventricular Free Wall ◽  
Heart Weight ◽  
Rate Pressure Product ◽  
Free Wall ◽  
Left Ventricular Free Wall ◽  
Work Index ◽  
Correct Estimation

We measured myocardial blood flow (QLVFW) and O2 consumption of the left ventricular free wall (VO2, LVFW) in 13 chronically instrumented, 7-wk-old lambs with an aortopulmonary left-to-right shunt (S) and in 10 control lambs without a shunt (C). The measured VO2, LVFW was compared with the calculated values obtained by two predictive indexes, the rate-pressure product (RPP) and the pressure-work index (PWI). Measured VO2, LVFW in S lambs was significantly higher than in C lambs [983 +/- 104 (SE) vs. 475 +/- 57 mumol X min-1 X 100 g LV-1, P less than 0.001]. This was achieved by the significantly higher QLVFW (294 +/- 33 vs. 145 +/- 15 ml X min-1 X 100 g LV-1, P less than 0.002), since the arteriovenous O2 difference across the left ventricular free wall was similar in both groups of lambs. Total coronary blood flow per unit body mass in S lambs was higher than in C lambs (14.1 +/- 1.5 vs. 5.6 +/- 0.6 ml X min-1 X kg-1, P less than 0.001), not only because of the increased VO2, LVFW per unit muscle mass, but also because of the increased total heart weight (102.4 +/- 6.4 vs. 81.2 +/- 4.9 g, P less than 0.02). Correct estimation of VO2, LVFW by means of the RPP and the PWI was only possible in C lambs. In S lambs the estimated values were significantly lower than the measured ones.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional myocardial blood flow and oxygen delivery in fetal, newborn, and adult sheep

1982 ◽  
Vol 243 (5) ◽  
pp. H729-H731 ◽  
Author(s):  
D. J. Fisher ◽  
M. A. Heymann ◽  
A. M. Rudolph
Keyword(s):  
Blood Flow ◽  
Myocardial Blood Flow ◽  
Right Ventricular ◽  
Oxygen Delivery ◽  
Left Ventricular ◽  
Ventricular Free Wall ◽  
Regional Myocardial Blood Flow ◽  
Free Wall ◽  
Right Ventricular Free Wall ◽  
The Right

We measured and calculated their product, regional myocardial oxygen delivery, in unanesthetized, previously instrumented fetal, newborn, and adult sheep. In the fetus, blood flow and oxygen delivery were greater to the right ventricular free wall than to the left ventricular free wall. In the left ventricular free wall oxygen delivery increased significantly after birth and later decreased to a level in the adult that was similar to that of the fetus. There was a progressive decrease in oxygen delivery to the right ventricular free wall during the developmental period that we studied. Although the inner-to-outer blood flow ratio was significantly lower for the left and right ventricular free walls of the fetuses as compared with the newborns and adults, the ratio was greater than one in all three groups for both of the ventricular free walls. These data demonstrate that the changes that occur in the circulation after birth are associated with significant alterations in right and left ventricular myocardial blood flow and oxygen delivery, which most likely reflect changes in regional myocardial metabolic demands. In addition, there are further significant changes in regional myocardial blood flow during the transition from the newborn to adult hemodynamics.

Increased in blood flow to ischemic myocardium caused by a new dopamine analog

1978 ◽  
Vol 235 (2) ◽  
pp. H118-H130
Author(s):  
J. N. Diana ◽  
B. C. Brenton ◽  
J. P. Long ◽  
J. G. Cannon ◽  
M. H. Laughlin ◽  
...  
Keyword(s):  
Blood Flow ◽  
Venous Pressure ◽  
Left Ventricular ◽  
Control Flow ◽  
Ventricular Free Wall ◽  
Normal Myocardium ◽  
Free Wall ◽  
Oxygen Utilization ◽  
Right Ventricular Free Wall ◽  
Coronary Vasodilator

In the anesthetized, open-chest dog, intravenous infusion 8– 13 microgram . kg-1. min-1) of a new dopamine analog 5,6-dihydroxy-2-methylaminotetralin hydrobromide (M-8) demonstrated potent coronary vasodilator properties. Blood flow to normal myocardium was increased an average of 53% above control flow values and this was associated with a decrease in coronary vascular resistance of 50%. The increase in blood flow was distributed uniformly to all portions of the myocardium (left ventricular free wall, right ventricular free wall, and septum). Subendocardial/subepicardial (endo/epi) flow ratios of the left ventricle, right ventricle, and septum were not significantly changed from control. In dog hearts subjected to acute, sudden occlusion of portions of the left anterior branch of the left coronary artery, M-8 produced a 93% increase in flow to the whole heart over postocclusion flow values. Flow to tissues of the heart made ischemic by the occlusive procedure in creased by an average of 94% during M-8 administration despite the fact that the occlusive ligatures remained in place. The vasodilation produced by M-8 was accompanied by a 22–24% increase in myocardial capillary surface area available for exchange of lipid-insoluble substances, fructose and sucrose. Hemodynamic changes associated with M-8 include a transient decrease in aortic pressure, but no change in heart rate, left ventricular (dP/dt)/P, or central venous pressure. Propranolol blocked the vasodilator activity of M-8. It was concluded that M-8 is a beta2-adrenergic receptor agonist having potent coronary vasodilator properties which also has the ability to open preexisting collateral blood flow channels and provide nutritive flow to ischemic, marginally ischemic, and normal myocardium. The cardiovascular actions of M-8 increase blood flow and oxygen delivery to the myocardium while decreasing the work and oxygen utilization by the heart, suggesting that it may have important antianginal characteristics.

Rapid-freezing transmural cardiac biopsy drill

1981 ◽  
Vol 240 (1) ◽  
pp. H126-H132 ◽  
Author(s):  
J. R. Allard ◽  
R. L. Conhaim ◽  
G. J. Vlahakes ◽  
M. J. O'Neill ◽  
J. I. Hoffman
Keyword(s):  
Stainless Steel ◽  
Blood Flow ◽  
Myocardial Blood Flow ◽  
Cardiac Cycle ◽  
Left Ventricular ◽  
Rapid Freezing ◽  
Free Wall ◽  
Left Ventricular Free Wall ◽  
Biopsy Site ◽  
Air Turbine

We have built a transmural cardiac biopsy drill that uses an air turbine (10,000 rpm) to turn a stainless steel bore of either 2.0 or 4.5 mm diam. Vacuum draws the cut biopsies through the drill into isopentane chilled to -150 degrees C with liquid nitrogen. The steel bores cut through the beating canine left ventricular free wall in 0.14 +/- 0.04 (SD) permitting sampling in discrete portions of the cardiac cycle. Small and large biopsies traverse the drill in 0.48 +/- 0.19 and 0.15 +/- 0.04 s, respectively. Large biopsies freeze in 1.46 +/- 0.73 s, whereas small biopsies are calculated to freeze in 0.28 s. Average biopsy weights are 34 +/- 14 and 180 +/- 71 mg. Left ventricular myocardial blood flow measured with radionuclide-labeled microspheres showed that muscle plugs sutured into wound sites of 4.5-mm-diam biopsies cause a 30% reduction in myocardial blood flow within 0.5 cm of the biopsy site. Light microscopy shows normal cardiac muscle with little damage from drill rotation.

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