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.