Carbon Monoxide Has Direct Toxicity on the Myocardium Distinct from Effects of Hypoxia in an Ex Vivo Rat Heart Model

Abstract

Carbon monoxide (CO) toxicity causes significant central nervous system and cardiac injury. Although the neurological damage caused by CO toxicity is extensively described, the mechanisms underlying myocardial insult are unclear. The authors used an externally perfused isolated rat heart model to examine the effects of a physiological saline solution (Krebs Henseleit HEPES, KHH) aerated with CO on cardiac function. Fifteen rats were equally divided into three groups: the control group (KHH + 100% O(2)), the nitrogen control group (KHH + 70% O(2), 30% N(2)), and the CO group (KHH + 70% oxygen, 30% CO). Left ventricular peak systolic pressure (LVPsP), end diastolic pressure (LVEdP), and coronary perfusion pressure were measured while the isolated heart was paced and perfused on a modified Langendorf apparatus. Left ventricular generated pressure (LVGP = LVPsP - LVEdP) decreased in the nitrogen control and CO groups compared to the control group. There was higher LVGP in the recovery phase between the nitrogen control group compared to the CO group. Both groups had increased lactic acid levels in the experimental phase. Carbon monoxide with hypoxia and hypoxemic hypoxia both result in similar depression of cardiac function. Hearts poisoned with CO with hypoxia do not recover function to the extent that hearts rendered hypoxic with nitrogen do when perfused with 100% oxygen after the insult. This suggests that CO causes direct myocardial toxicity distinct from the effects of hypoxia.