Postinfarct enzyme elevation in coronary sinus blood

Abstract

The diagnosis of myocardial infarction in the postoperative period is difficult in the absence of significant electrocardiographic changes. The advent of direct coronary artery surgery has been associated with a relatively high incidence of postoperative myocardial infarction. In order to detect myocardial necrosis better, it was proposed that sampling of blood from the coronary sinus would identify a higher level of serum enzymes [serum glutamic—oxaloacetic transaminase (SGOT), lactic dehydrogenase (LDH), heat-stable LDH, and creatinine phosphokinase (CPK)] associated with myocardial damage than would sampling of peripheral blood and that the elevation would appear sooner after injury. Thirty-two dogs were studied to test this hypothesis. In half of the animals, myocardial infarction was induced by injection of mercury into the circumflex coronary artery. The other half received saline injections into the coronary artery. All dogs underwent simultaneous serial sampling of coronary sinus and peripheral venous blood. Variations in the amount of surgical manipulation and in the time intervals between sampling were carried out. No significant pattern of enzyme elevation could be detected which differentiated the surgical animals sustaining infarction from the control animals, other than that established by the heat-stable (HS) fraction of LDH. However, all too frequently in the clinical setting, the HS-LDH levels cannot be utilized due to hemolysis and variation of LDH levels with each surgical procedure. The levels of enzymes in coronary sinus blood did not differ significantly from those in peripheral venous blood in any group of animals with myocardial infarction. In summary, these experiments demonstrated no statistically significant difference in enzyme levels in coronary sinus versus peripheral venous blood following myocardial infarction in the dog. Surgical procedures obscured the enzymatic picture of infarction. Patterns suggesting infarction associated with surgery could be distinguished but definite criteria could not be established. It is suggested that further investigations be carried out to decide definitively if the cardiac lymph is the major site of drainage of enzymes following myocardial necrosis.