Pathophysiology and Natural History Myocardial Blood Flow

Coronary sinus flow (CSF) was measured in seven patients with normal coronary arteries (group A) during intracoronary injections of 6 ml arterial blood, 6 ml blood from the coronary sinus, 3 and 6 ml isotonic saline, 3 and 6 ml hypertonic glucose, and 6 ml of a contrast agent (sodium metrizoate). In 10 patients with coronary artery disease (group B), CSF was measured after administration of 6 ml isotonic saline, 6 ml sodium metrizoate, and 6 ml of another contrast medium (iohexol). In group A, arterial blood did not affect CSF, while coronary sinus blood induced a 33% increase. After 6 ml isotonic saline, there was a 35% increase in flow and after hypertonic glucose an increase of 70%. Metrizoate induced a rise in flow of 109%. In group B, the increase in CSF after intracoronary injection of saline, metrizoate, and iohexol was 30%, 83%, and 67%, respectively. Blood from the coronary sinus, in contrast to arterial blood, induced a marked rise in peak flow, suggesting a role for reactive hyperemia secondary to myocardial hypoxia in this response. A similar mechanism might have been operative after injection of isotonic saline, as well as after the hyperosmolar contrast agents. However, additional mechanisms mediated by the high osmotic pressure of these substances, such as induction of the Bezold-Jarisch reflex, which will induce coronary vasodilation, may have played a role. Finally, when hyperosmolar agents are used, the possibility of some direct vasodilating properties of the agents cannot be excluded. Circulation 72, No. 2, 287-291, 1985. AN INTRACORONARY INJECTION of a substance will in most cases lead to a change in coronary blood flow. Factors other than the pharmacologic properties of the injectate can affect the flow response. Such factors include the chemical composition and physical properties of the compound, such as its hyperosmolality and oxygen content. When contrast media are injected in a coronary artery, there is a marked increase in flow that is dependent on the hyperosmolality but not on the iodine content of the agent.' The actual mechanisms of the increase in flow are not well known. The present study was conducted to try to evaluate factors influencing the flow response to intracoronary injections. Various amounts of different substances were therefore injected into the left coronary arteries of 17 patients during continuous measurement of coronary sinus blood flow (CSF). From the Division of Cardiology, Department of Medicine 1, and Department of Radiology I, Sahlgrenska Hospital, S-413 45 Goteborg, Sweden. Address for correspondence: Dr. Hakan Emanuelsson, Division of Cardiology, Department of Medicine l, Sahlgrenska Hospital, S-4 13 45 Goteborg, Sweden. Received Nov. 26, 1984; revision accepted April 18, 1985. Vol. 72, No. 2, August 1985 Material and methods Patients. Seventeen patients who had been admitted to the hospital for coronary angiographic examination due to anginalike chest pain were investigated. Seven patients (group A) had angiographically normal coronary arteries. Two were women and five men, and their median age was 57 years (range 39 to 62). Group B consisted of 10 patients, all of whom proved to have significant coronary artery disease with narrowing of at least one vessel of more than 70%. There were two female and eight male patients in this group and their median age 57 years (range 48 to 62). No cardiac medication was given for 12 hr before the study. Informed consent was obtained from each patient and the Hospital Ethics Committee approved the study. Catheterization. A Judkins catheter was used to engage the ostium of the left coronary artery of each patient. A thermodilution pacing catheter (Wilton-Webster Lab.) was positiond in the coronary sinus. The position of the catheter was confirmed by injection of radiopaque dye and was adjusted during flow measurement until there was a stable baseline flow curve. With a bolus injection of 10 ml of isotonic saline in the right atrium during temperature recording in the coronary sinus, the presence of reflux as a source of measurement error2 could be detected and was eliminated when necessary by changing the position of the catheter. Measurements. The CSF was determined with the continuous-infusion thermodilution method.3 Isotonic saline solution at room temperature was infused into the coronary sinus at a rate of 44 ml/min by infusion pump. Blood oxygen saturation was determined by a photometric method4 and the erythrocyte volume fraction (EVF) was estimated after 10 min centrifugation of 287 by gest on A ril 3, 2017 http://ciajournals.org/ D ow nladed from