Influence of carbon monoxide (CO) on the early course of acute myocardial infarction.

OBJECTIVE

To clarify the influence of an elevated carboxyhemoglobin (COHb) blood level on the course of acute myocardial infarction and to evaluate the administration of supplemental oxygen on the COHb level and the incidence of complications.

DESIGN

Prospective clinical study with randomized, unblinded intervention.

SETTING

Coronary Care Unit of a university hospital.

PATIENTS

78 consecutive patients with acute myocardial infarction. Excluded were patients with severe dyspnea, pulmonary edema or any other medical indication for supplemental oxygen therapy.

INTERVENTIONS

Randomized therapy with 41/min oxygen in 35 patients.

MEASUREMENTS AND RESULTS

COHb was measured at admission and 4 h later. The incidence of serious arrhythmias and the maximal creatine kinase (CK) values were recorded. In patients with initial COHb > or = 5%, there were significantly more arrhythmias and significantly higher maximal CK values than in those with normal COHb admission (89 vs 33%, p < 0.001; and 1897 +/- 1602 u/l vs 960 +/- 1097 u/l, p=0.05). This effect was seen only in patients with Q-wave infarction, not in those with non-Q-wave infarction. Supplemental oxygen had no effect on the incidence of arrhythmias.

CONCLUSIONS

We conclude that myocardial infarction patients with acute Q-wave infarction and increased COHb levels at admission suffer a more severe course of the disease. This outcome was not influenced by oxygen therapy. Whether this finding indicates a casual relationship and whether higher oxygen concentrations would favorably alter the course of acute myocardial infarction remains to be determined.