Background: A penetrating injury to the "cardiac box" is thought to be predictive of an injury to the heart; however, there is very little evidence available to support this association. This study aims to evaluate the relationship between penetrating trauma to the cardiac box and a clinically significant injury.
Methods: All patients presenting to a Level I trauma center from January 2009 to June 2015 who sustained a penetrating injury isolated to the thorax were retrospectively identified. Patients were categorized according to the location of injury: within or outside the historical cardiac box. Patients with concurrent injuries both inside and outside the cardiac box were excluded. Clinical demographics, injuries, procedures, and outcomes were compared.
Results: During this 7-year period, 330 patients (92% male; median age, 28 years) sustained penetrating injuries isolated to the thorax: 138 (42%) within the cardiac box and 192 (58%) outside the cardiac box. By mechanism, 105 (76%) were stab wounds (SW) and 33 (24%) were gunshot wounds (GSW) inside the cardiac box, and 125 (65%) SW and 67 (35%) GSW outside the cardiac box. The overall rate of thoracotomy or sternotomy (35/138 [25.4%] vs. 15/192 [7.8%], p < 0.001) and the incidence of cardiac injury (18/138 [13%] vs. 5/192 [2.6%], p < 0.001) were significantly higher in patients with penetrating trauma within the cardiac box. This was, however, dependent on mechanism with SW demonstrating a higher incidence of cardiac injury (15/105 [14.3%] vs. 3/125 [2.4%], p = 0.001) and GSW showing no significant difference (3/33 [9.1%] vs. 2/67 [3%], p = 0.328]. There was no difference in overall mortality (9/138 [6.5%] vs. 6/192 [3.1%], p = 0.144).
Conclusion: The role of the cardiac box in the clinical evaluation of a patient with a penetrating injury to the thorax has remained unclear. In this analysis, mechanism is important. Stab wounds to the cardiac box were associated with a higher risk of cardiac injury. However, for GSW, injury to the cardiac box was not associated with a higher incidence of injury. The diagnostic interaction between clinical examination and ultrasound, for the diagnosis of clinically significant cardiac injuries, warrants further investigation.
Level of evidence: Prognostic study, Level IV, Therapeutic V.