An Experimental Study on Intercoronary Reflexes

Sudden complete occlusion of a major coronary artery (left circumflex or right coronary artery) was produced in anesthetized dogs. The effect on arterial inflow, venous outflow and O « saturation of coronary venous blood from the nonischemic left ventricle was studied. The usual response to occlusion of the left circumflex artery was an increase in flow in the left anterior descending artery and in outflow from the great cardiac vein. The O 2 saturation of venous blood from the nonischemic muscle decreased. These changes did not occur following occlusion of the right coronary artery. It was not possible to measure tissue pressure accurately to relate this measurement to flow changes. Observations on coronary sinus flow and O 2 saturation were also made following occlusion of the left circumflex artery and retrograde flow collection from it. These observations plus the changes in anterior descending inflow and great cardiac vein outflow with coronary occlusion suggest that these changes are more likely due to alterations in O 2 consumption of the nonischemic muscle rather than to changes in flow through interarterial or non-interarterial collateral vessels.

Section: Discussionsupporting

confidence: 93%

“…ADDITIONAL KEY WORDS coronary reflex myocardial pressure cardiac metabolism anesthetized dogs venous oxygen collateral circulation • Several investigators have reported that occlusion of a major branch of a coronary artery results in an increased flow in adjacent coronary arteries (1)(2)(3)(4)(5)(6). The mechanism of this response is not known.…”

mentioning

confidence: 99%

Coronary Inflow and Outflow Responses to Coronary Artery Occlusion

Driscol

Eckstein

1967

“…It has been frequently reported that occlusion of a major branch of the canine left coronary artery results in an increased blood flow through the remaining arteries (21)(22)(23)(24)(25)(26). Venous outflow from the great cardiac vein is increased after ligation of the left anterior descending coronary artery, whereas oxygen saturation of venous blood from nonischemic muscle declines (26).…”

Section: Discussionmentioning

confidence: 99%

Expansion of extracellular space in the nonischemic zone of the infarcted heart and concomitant changes in tissue electrolyte contents in the rat.

Polimeni¹,

Al‐Sadir²

1975

The alterations in electrolyte content that occur in an infarcted zone of the heart have also been reported to occur in a similar manner, although to a far less degree, in the distant, apparently normal zones of the heart. These alterations in the nonischemic myocardium have usually been tabulated without comment, presumably because their magnitudes approach values of statistical dispersion. Our measurements of electrolyte content in the normal zone of the infarcted rat heart confirmed that all of the electrolyte contents were slightly modified. There was a rise in sodium, calcium, and chloride and a decline in potassium and magnesium. In addition, the extracellular space ([14C]sucrose) in this zone was elevated by nearly 15%. We have postulated a mechanism for this elevation based on an increase in the net filtration rate through myocardial capillaries. The expansion of the extracellular space can account for all of the electrolyte changes in the normal zone with the exception of the alteration in calcium. Therefore, there is no basis for assuming that these myocardial alterations reflect general movements of electrolytes down their electrochemical gradients. We suggest that the increment in the nominal concentration of cellular calcium is related to a compensatory mechanism that allows the reduced mass of functional myocardium to contract more vigorously.

“…This is usually attributed to a vasoconstrictor reflex which may be blocked in various ways. However, most recent reports have demonstrated an increase in flow in vessels adjacent to an occluded artery (4)(5)(6)(7)(8)(9)(10)(11)(12). These studies range from acute experiments on anesthetized animals subjected to major surgery to elegant chronic studies of conscious, trained animals with gradually induced coronary obstruction (15).…”

Section: Rees Reddingmentioning

confidence: 99%

“…Some previous studies indicated a reduction in flow, but more often an increase was found, particularly when blood pressure was kept constant. When pressure was allowed to change, flow elsewhere in the heart was usually reduced or unaltered (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15).…”

mentioning

confidence: 99%

Experimental Myocardial Infarction in the Dog

Rees

Redding

1969

Control measurements of myocardial blood flow were made in intact dogs by a method of 133 Xe clearance, using a catheter positioned radiographically in the circumflex artery. Acute myocardial infarction was then caused by tying the anterior descending artery. A small catheter was inserted distally beyond the obstructed artery into the infarct, and another proximally toward the anterior ventricular artery supplying adjacent left ventricular muscle. Their ends were brought out as the chest was closed. 133 Xe in solution was injected serially over 4 hours to determine myocardial blood flow within the infarct, in adjacent muscle, and in more distant muscle supplied by the circumflex artery. Myocardial blood flow in the circumflex artery usually fell as a result of infarction. A constant finding was that adjacent flow exceeded the more distant flow by 6% up to 43% (mean 20%) regardless of either spontaneous or induced changes in blood pressure. The difference was not related to the collateral flow rate and was abolished by dipyridamole. Perfusion of muscle adjacent to the infarct was less homogenous than that of more distant muscle.In the normal dog rates of myocardial blood flow in the distribution of the circumflex and anterior descending branches of the left coronary artery were the same, contrasting with lower rates for the right. * In arbitrary units from ratio of mean systemic blood pressure to k. f Number of determinations in parentheses. | Mean ± SD; in parentheses, percent of flow in distribution of circumflex artery.Circ. = circumflex artery. Desc. = anterior descending artery. Right = right coronary artery.