Effects of nitroglycerin, adenosine, noradrenaline, and isoproterenol on the myocardial oxygen tension

The effects of adenosine, nitroglycerin, noradrenaline, and isoproterenol on the myocardial oxygen tension were studied. The oxygen tension was measured by a polarographic method. Adenosine and nitroglycerin (intravenous and intracoronary injections) did not produce a beneficial effect on the normal myocardium. Intravenous administration of noradrenaline produced an increase in subendocardial oxygen tension, while intravenous administration of isoproterenol decreased subendocardial oxygen tension. However, intracoronary administration of catecholamines increased myocardial oxygen tension. These results suggest that in the absence of systemic hemodynamic changes, catecholamines produce a beneficial effect on the normal myocardium, but administration of adenosine and nitroglycerin (intravenous and intracoronary injections) have no beneficial effect. The effects of several physiological parameters on the myocardial oxygen tension were studied. Pacing with a higher rate resulted in a decrease in subendocardial oxygen tension. When the perfusion pressure was lowered, subendocardial oxygen tension was decreased. When the perfusion pressure was raised, subendocardial oxygen tension was increased.