Blunt cardiac injury: is this diagnosis necessary?

The diagnosis of blunt cardiac injury in traumatized patients is problematic and the implications of such a diagnosis are not clear. Although cardiac selective creatine kinase (CK-MB) assays and electrocardiograms (EKG) are the most widely available laboratory investigations, they often correlate poorly with diagnoses made on clinical grounds, or by other laboratory methods. We therefore retrospectively studied the Montreal General Hospital experience with 342 consecutive blunt trauma patients admitted to our surgical intensive care/trauma unit. Using clinical criteria, cardiac injury was diagnosed in 44 patients (13%). Twenty-seven of these patients (61%) developed arrythmias or cardiogenic hypotension, half of which required treatment. Heart injuries contributed to six of the 12 deaths in this group. Many of the patients maintained normal CK-MB levels and/or had normal admission EKG's despite the clinical diagnosis of cardiac injury. However, using our criteria for CK-MB positivity, there was a strong correlation between CK-MB elevation and the development of cardiac complications, and very high CK-MB levels (greater than 200 mu/L) were associated with a 100% incidence of such complications. Focusing on patients who developed cardiac complications serious enough to require treatment, we found combined CK-MB/EKG positivity in all cases (100% sensitivity). This method also provided a negative predictive value of 100%. We conclude that although blunt cardiac injury is an important source of morbidity and mortality its 'diagnosis' is not the issue. Rather, it is more important to recognize which of these clinically identified 'high-risk' patients will actually develop cardiac complications. We feel our approach will enable clinicians to do this.