The usefulness of serum troponin levels in evaluating cardiac injury

The diagnosis and clinical significance of blunt cardiac injury remains con troversial. Cardiac troponin I is not found in skeletal muscle and has a hi gh sensitivity for myocardial ischemia or injury. We hypothesized that norm al troponin levels 4 to 6 hours postinjury would effectively exclude the di agnosis of cardiac contusion. A prospective evaluation of all blunt trauma patients older than 16 and admitted with the possible diagnosis of blunt ca rdiac injury was undertaken. Patients in whom this diagnosis was considered had an electrocardiogram (EKG) on admission, serum troponin, CPK and isoen zymes 4 to 6 hours postinjury, and admission with overnight telemetry. Othe r laboratory data and radiographic imaging was obtained as indicated. Seven ty-two patients met criteria for entry into the study. Data was incomplete or inaccurately obtained on six patients, and they were excluded. Forty pat ients had normal troponins and normal EKG's on admission and were discharge d the following day without any untoward effect. Sixteen patients were admi tted with abnormal EKGs. All of these 16 patients had normal troponins 4 to 6 hours after their injury. They all did well and were discharged the foll owing day. Ten patients had elevated troponins 4 to 6 hours after injury. O ne died two days later from refractory cardiogenic shock. Another was noted to have severely depressed left ventricular function by echocardiography. The other eight patients sustained no cardiac sequelae and were discharged once recovered from injuries. In the hemodynamically stable patient a norma l troponin 4 to 6 hours after injury excludes clinically significant blunt cardiac injury. This holds true whether the admission EKG is normal or no,. An elevated troponin does not definitively diagnose a clinically significa nt contusion. However, these patients should be monitored at least for 24 h ours. Patients suspicious for cardiac contusions who have normal troponins and no other serious injuries may be safely discharged to go home from the emergency department.