Reassessing the cardiac box: A comprehensive evaluation of the relationship between thoracic gunshot wounds and cardiac injury.

BACKGROUND:High-energy missiles can cause cardiac injury regardless of entrance site. This study assesses the adequacy of the anatomic borders of the current "cardiac box" to predict cardiac injury. METHODS:Retrospective autopsy review was performed to identify patients with penetrating torso gunshot wounds (GSWs) 2011 to 2013. Using a circumferential grid system around the thorax, logistic regression analysis was performed to detect differences in rates of cardiac injury from entrance/exit wounds in the "cardiac box" versus the same for entrance/exit wounds outside the box. Analysis was repeated to identify regions to compare risk of cardiac injury between the current cardiac box and other regions of the thorax. RESULTS:Over the study period, 263 patients (89% men; mean age, 34 years; median injuries/person, 2) sustained 735 wounds (80% GSWs), and 239 patients with 620 GSWs were identified for study. Of these, 95 (34%) injured the heart. Of the 257 GSWs entering the cardiac box, 31% caused cardiac injury, whereas 21% GSWs outside the cardiac box (n = 67) penetrated the heart, suggesting that the current "cardiac box" is a poor predictor of cardiac injury relative to the thoracic non-"cardiac box" regions (relative risk [RR], 0.96; p = 0.82). The regions from the anterior to posterior midline of the left thorax provided the highest positive predictive value (41%) with high sensitivity (90%) while minimizing false-positives, making this region the most statistically significant discriminator of cardiac injury (RR, 2.9; p = 0.01). CONCLUSION:For GSWs, the current cardiac box is inadequate to discriminate whether a GSW will cause a cardiac injury. As expected, entrance wounds nearest to the heart are the most likely to result in cardiac injury, but, from a clinical standpoint, it is best to think outside the "box" for GSWs to the thorax. LEVEL OF EVIDENCE:Therapeutic/care management, level IV.