Cardiac Enzyme Evidence of Cardiac Injury in Patients Intubated for Respiratory Failure

Abstract

Introduction

Patients who develop acute respiratory failure (ARF) experience multiple patho-physiologic events that can produce cardiac injury in the immediate postintubation period. Although myocardial infarction is stated to be a complication of respiratory failure, no patient series confirm this impression or describe the importance of cardiac injury in this clinical setting.

Methods

We prospectively evaluated 81 patients over 45 years old who required intubation and mechanical ventilation for ARF to determine the incidence of cardiac enzyme evidence of cardiac injury related to the initiation of mechanical ventilation, the association of elevated cardiac enzymes with clinical outcome, the clinical features that predicted the occurrence of elevated cardiac enzymes, and the cost-effectiveness of different diagnostic strategies.

Results

We observed that 11 of 81 patients [14%, 95% confidence interval (CI), 6–21%] had enzyme evidence of cardiac injury of whom two demonstrated new Q waves. No patient developed clinically apparent events attrib-utable to a myocardial infarction, and enzyme elevation did not correspond to mortality. A logistic model identified patients for cardiac enzyme screening by the presence of a postintubation heart rate > 140 beats/min or a history of coronary artery disease. The model had a diagnostic accuracy of 67% (95% CI, 56-77%), sensitivity of 91% (95% CI, 59-100%), specificity of 63% (95% CI, 51-74%), positive predictive value of 28% (95% CI, 14-45%), and negative predictive value of 98% (95% CI, 88-100%).

Conclusion

Selection of patients with noncardiac respiratory fail-ure for cardiac enzyme evaluation by the presence of postintubation heart rate > 140 beats/min or a history of coronary artery disease is more cost-effective than screening all intubated patients.