Coronary Arteriovenous Oxygen Difference Research Articles

Coronary hemodynamics and myocardial oxygen metabolism during oxygen breathing in patients with and without coronary artery disease.

Oxygen in high concentration (arterial pO 2 over 400 mm Hg), administered for 7-10 minutes to six subjects with normal coronary arteries and nine subjects with coronary artery disease caused the following significant changes: The heart rate and cardiac index decreased in both groups. The mean arterial pressure increased in the coronary group. The coronary sinus blood flow fell from 158 ± 11 (mean ± sem ) to 131 ± 13 in the noncoronary and from 151 ± 14 to 138 ± 14 ml/min in the coronary group, due to an increase in coronary resistance. The coronary sinus oxygen tension increased from 19 ± 1 to 22 ± 1 in the noncoronary and from 19 ± 1 to 24 ± 1 mm Hg in the coronary group. The coronary arteriovenous oxygen difference decreased from 13.2 ± 0.6 to 12.5 ± 0.6 ml/100 ml in the coronary group. Left ventricular oxygen consumption fell from 21.5 ± 2.1 to 18.2 ± 2.4 in the noncoronary and from 19.9 ± 2.0 to 16.7 ± 1.7 ml/min in the coronary group. Myocardial lactate extraction increased from 40 ± 9 to 60 ± 4 and from 4 ± 6 to 28 ± 3%, respectively. In four patients with severe coronary artery disease, oxygen breathing reverted myocardial lactate production to extraction. It would appear that oxygen breathing might be beneficial in myocardial ischemia by increasing coronary arterial oxygen tension and reducing myocardial oxygen consumption.

Cardiovascular Effects of Carotid Sinus Nerve Stimulation in Resting Man

The carotid sinus nerves were selectively stimulated in three patients and observations were made in basal state before and 15 minutes after the onset of continuous stimulation. The myocardial oxygen consumption decreased from 5.5 ± 0.6 to 4.8 ± 0.5 ml/min/100 gm, and the coronary blood flow from 48 ± 6 to 43 ± 6 ml/min/100 gm (mean ± SE). The coronary arteriovenous oxygen difference remained the same in two and narrowed in one patient who also showed a decrease in the coronary venous lactate:pyruvate ratio during stimulation. The lactate and pyruvate removal continued in all patients. The stimulation lowered the cardiac output from 3.0 ± 0.2 to 2.6 ± 0.2 L/min/M2, and raised the systemic arteriovenous oxygen difference from 5.0 ± 0.3 to 5.7 ± 0.4 ml/100 ml. The total body oxygen consumption remained the same. The brachial artery mean pressure diminished from 103 ± 7 to 88 ± 6 mm Hg. The heart rate was not significantly different.

The effects of inhalation of 100 per cent oxygen on myocardial lactate metabolism in coronary heart disease

Hemodynamic changes occurred after administration of 100 per cent oxygen to subjects with normal coronary arteries and to patients with coronary artery disease as demonstrated by coronary arteriograms. Cardiac index decreased but mean arterial pressure and peripheral vascular resistance increased slightly. Left ventricular work was decreased in normal subjects and in patients with less than 50 per cent narrowing of the coronary vessels; it remained unchanged in patients with significant coronary artery disease. On the other hand, the arterial oxygen content and coronary arteriovenous oxygen difference were significantly increased during inhalation of oxygen. In patients with significant coronary artery disease, especially in the presence of severe triple vessel disease, abnormal lactate changes were produced or accentuated during the administration of oxygen. The significance of these changes are discussed. Further studies are needed to assess the indications for oxygen therapy in coronary heart disease.

EFFECT OF CORONARY VASODILATOR DRUGS ON RETROGRADE FLOW IN AREAS OF CHRONIC MYOCARDIAL ISCHEMIA.

The effects of two coronary vasodilator drugs, nitroglycerin and dipyridamole, on the coronary collateral flow were studied in twelve dogs with chronic myocardial ischemia and in five normal dogs, by means of the retrograde flow technique. In the ischemic dogs with well developed collateral circulation, both drugs caused a reduction in systemic blood pressure. Dipyridamole caused a significant reduction in both the retrograde flow and peripheral coronary pressure as well. Nitroglycerin, by contrast, did not cause a significant reduction in either retrograde flow or peripheral coronary pressure in spite of a greater fall in mean arterial pressure. When arterial pressure was held constant artificially, nitroglycerin caused a large increase of retrograde flow in chronic "ischemic" dogs while dipyridamole did not. In normal dogs these differences between the two drugs were not observed. Both drugs caused a reduction of retrograde flow and peripheral coronary pressure which paralleled the reduction in systemic pressure. In both ischemic and normal dogs, dipyridamole caused a reduction in the coronary arteriovenous oxygen difference. Nitroglycerin did not change this value. Reported differences between these two drugs, together with these observations, suggest that nitroglycerin may have an action which is to be seen only in the presence of well developed collateral circulation; this is to increase flow through collateral channels without significantly altering total coronary artery flow. Dipyridamole does not seem to alter collateral flow but does increase total coronary flow. The site of action of these two drugs in the coronary vascular tree must thus be different.

The acute effect of alcohol on the circulation and on the oxygen metabolism of the heart

Alcohol, in an average dose of 58 mg per kilogram per minute, was infused during 20 minutes into 10 anesthetized dogs. Cardiac output and the external work of the heart decreased, with no change in arterial blood pressure. Coronary sinus outflow increased as a result of a fall in coronary vascular resistance. There was no change in either coronary arteriovenous oxygen difference or myocardial oxygen extraction. Oxygen consumption, however, increased in the myocardium. The results are discussed in terms of the effect of alcohol on the pain of angina pectoris.

Effects of protoveratrine on coronary blood flow of the renal hypertensive dog.

In renal hypertension, protoveratrine decreased coronary blood flow, cardiac oxygen consumption, arterial and venous oxygen saturation, coronary arteriovenous oxygen difference, mean arterial blood pressure, cardiac output, cardiac work, cardiac efficiency, cardiac rate, total peripheral resistance, coronary resistance, respiratory rate, and minute volume. The decrease was significant in all functions except coronary blood flow, coronary venous oxygen saturation, and cardiac output. The results of these experiments indicate that in the renal hypertensive animal, a therapeutically beneficial effect was derived from protoveratrine on the circulation by its ability to decrease the work of the heart (lowering the elevated mean arterial pressure) and the coronary vascular resistance while maintaining coronary blood flow and cardiac output within normal levels. The less advantageous effect of protoveratrine on circulation resulted from its respiratory inhibiting effect which reduced the arterial blood oxygen saturation. Although a small decline in coronary venous oxygen saturation was noted, the coronary flow and oxygen delivery in face of the reduced arterial oxygen saturation was apparently adequate to maintain a normal cardiac activity.

Aorto-inferior vena caval fistula of neoplastic origin. Hemodynamic and coronary blood flow studies.

A case report of a 51-year-old man is presented, who spontaneously developed an aorto-vena caval fistula in the region of a mesenchymal tumor involving both the abdominal aorta and vena cava. The disease was manifested clinically by rapidly progressive and massive leg swelling, prominent abdominal and leg veins, a machinery murmur over the abdomen and in the flanks, and a pulsatile abdominal mass, with signs of cardiac enlargement and a high output state. The fistula was demonstrated preoperatively by translunmbar aortography and closed surgically by resection of the tumor en masse, with a part of the vena caval wall and the distal aorta and proximal common iliac arteries. Vascular continuity was restored by lateral suture of the vena cava and by insertion of a bifurcation graft bridging the defect in the aorta and iliac arteries. The patient has been relieved of all clinical manifestations of the fistula to date, 1 year after operation. Preoperative hemodynamic studies revealed certain alterations characteristic of systemic arteriovenous fistula, including increased pulse pressure, high cardiac output and stroke volume, reduced systemic vascular resistance and arteriovenons oxygen difference, and increased plasnma and circulating blood volumes. Some degree of cardiac failure appeared to be present. Coronary arteriovenous oxygen difference was normal, indicating that the observed increase in coronary blood flow closely paralleled the augmented energy requirement of the heart as reflected by the ventricular oxygen uptake. Reversion to normal of the observed changes in systemic hemodynamics, coronary blood flow, and myocardial metabolism was demonstrated 2 weeks postoperatively.

Effect of changes in blood CO2 level on coronary flow and myocardial O2 consumption.

The effect of hypo- and hypercapnia—induced by changing the respiratory gas mixture—on coronary flow and myocardial oxygen consumption was observed at constant cardiac output and over a broad range of pressure-loads in open-chested, anesthetized dogs. The correlation of cardiac effort (as indexed by the product of heart rate and mean aortic blood pressure) with myocardial oxygen consumption was not altered by increasing or decreasing the arterial CO2 content. Coronary blood flow was observed to be increased relative to the cardiac effort during hypercapnia but not during hypocapnia. The coronary arteriovenous oxygen difference and the percentage of oxygen extracted decreased during hypercapnia pari passu with the increase in venous oxygen content.

Effects of aortic insufficiency on circulatory dynamics of the dog; with special reference to coronary blood flow and cardiac oxygen consumption.

In dogs with chronic aortic insufficiency accompanied by cardiac hypertrophy, the coronary blood flow, cardiac oxygen consumption, coronary arteriovenous oxygen difference, coronary oxygen utilization, systolic pressure and cardiac rate are increased significantly above the normals, while coronary venous oxygen saturation, coronary resistance and diastolic pressure are significantly decreased.

Effect of Catecholamines, l-Epinephrine and l-Norepinephrine on Coronary Flow and Oxygen Metabolism of the Myocardium

The effect of continuously infused intravenous l-epinephrine and l-norepinephrine (0.1–2.5 gamma/kg/min.) was determined in the open-chest, anesthetized dog prepared for measurement of total coronary flow. Coronary blood flow, myocardial oxygen availability and coronary venous oxygen content consistently increased after catecholamine administration despite wide fluctuations, above and below control values, in heart rate and mean aortic pressure at constant cardiac output. Thus, there was a significant decrease in the coronary arteriovenous oxygen difference after catecholamine administration. The increase in coronary flow and decrease in the coronary A-V oxygen difference were seen even when blood pressure and heart rate were lowered. It is concluded that the departure from the usual relationship between coronary flow and myocardial oxygen consumption is attributable to coronary vasodilatation. However, myocardial oxygen consumption is still the primary factor controlling coronary flow during catecholamine action.

The oxygen content of coronary venous blood as affected by anoxia and cytochrome C

1. 1. By means of the bubble flowmeter and the coronary sinus catheterization methods of investigating the coronary circulation of the dog, the “normal” values for the coronary venous oxygen content have been found to be 3 to 6 volumes per cent. 2. 2. When 8 to 10 per cent oxygen mixtures were breathed, the oxygen content of coronary venous blood was reduced to 2 volumes per cent or less. 3. 3. Increases in oxygen uptake by the heart were accomplished primarily by increases in the volume of coronary blood flow. 4. 4. Cytochrome C, when injected intravenously in amounts varying from 3.8 to 12.5 mg. per kilogram of body weight, did not increase the coronary arteriovenous oxygen difference or the oxygen uptake of the heart.