The aim of this section is to discuss the advantages and shortcomings of clinical signs, imaging modalities, and other diagnostic procedures in evaluating cardiac, great vessel, and hilar injuries. It must be emphasized again that emergent thoracotomy should not be delayed by diagnostic procedures in hemodynamically unstable patients and especially patients “in extremis.” A simple and direct algorithm was developed by Mattox in 2000 and remains applicable today (Fig. 12.1).

Any patient with a penetrating mechanism, specifically a projectile, is at risk of a cardiac injury with subsequent cardiac tamponade or hemorrhage [2, 9, 12]. Traditionally, trauma surgeons have been taught to expect a cardiac injury when an exterior wound was located in “the box” (Fig. 12.2). However, with current military and civilian ballistics, cardiac injury can occur from any entry point into the body. The earliest signs of hemorrhage are due to sympathetic nervous system surge with increases in heart rate, respiratory rate, and peripheral vascular resistance, i.e., narrowed pulse pressure. On exam, these patients will have pallor, agitation, or anxiety [11–13]. If blood is collecting in the pericardium rather than being drained either externally or into the thoracic cavity, a cardiac tamponade can occur. Awake patients early in tamponade physiology will not be comfortable in the supine position as this compromises their venous return and right heart cardiac output. Many of the classical signs of tamponade or Beck’s triad, i.e., muffled heart sounds, distension of jugular veins, and hypotension will often be absent or difficult to observe in the trauma bay [12]. Frequently trauma patients early in the tamponade physiology may not present with any symptoms of cardiac injury and yet later succumb to cardiac tamponade or exsanguinating wounds. In fact, an increased mortality from cardiac trauma has been reported in large case series when the exterior wound was located away rather than inside the precordium, possibly due to a lower-level of suspicion and attention from the clinical team [9].

Evaluation of the trauma patient and specifically the unstable patient occurs best with a regimented approach. Blunt injury to the pericardium can be evaluated in the same manner as penetrating. Portable chest radiographs remain the best initial film to assess the thorax for injury and ballistic vector. The FAST exam or ultrasound is the trauma surgeon’s best friend in evaluating for internal bleeding [14]. All unstable blunt trauma patients once the initial ABC’s of trauma are complete require a FAST exam [14, 15]. Patients with penetrating thoracic trauma require a focused cardiac ultrasound to evaluate for pericardial effusion [16, 17].

The FAST is specific and sensitive for intra-abdominal and cardiac injuries with a sensitivity for intra-abdominal fluid of 81–88 %, 99 % specificity, and 97 % accuracy and sensitivity of pericardial fluid approaching 100 % [14–16]. The ultrasound can also evaluate pneumo- and hemothorax with excellent sensitivity assuming the patient does not have subcutaneous emphysema [16, 18]. If the patient is stable and the penetrating mechanism crosses the mediastinum without evidence of cardiac injury on ultrasound, then these patients require evaluation of their mediastinum for injuries. Multi-detector CTA of the chest provides excellent evaluation of the superior mediastinal vascular structures [19]. In addition, these images will assist with surgical planning, incision choice, and evaluation of other injuries. If concern remains regarding middle mediastinal injury, then the subxiphoid pericardial window should be considered the gold standard for detecting blood in the pericardium [8, 12]. For the most part penetrating cardiac and great vessel injuries will be diagnosed by either exsanguinating hemorrhage, ultrasound of the pericardium, CTA or angiography of the chest, or subxiphoid window.

Video-assisted thoracic surgery (VATS) is being introduced to evaluate hemodynamically stable patients for intrapericardial injuries [20]. We recommend a modified VATS approach, using only partial pulmonary deflation, and limiting the deflation to a few respiratory cycles, as well as reserving this diagnostic approach for the completely stable patients as not all patients will tolerate the periprocedural reduction in pulmonary capacity. This approach could be combined with an otherwise indicated chest tube placement. Unstable patients should be evaluated by TTE or TEE at the bedside or in the operating theater for the detection of complex cardiac injuries such as cardiac wall and septal defects, valvular insufficiency, or injuries to the pulmonary artery and vein [20]. For stable patients, a chest X-ray and 12-lead ECG should be obtained to screen patients suspected of myocardial ischemia or contusion, conduction abnormalities, or arrhythmias that may be present in BCI [2, 21]. Biomarkers of myocardial cell damage are generally not used to estimate the seriousness of injury as they can be either normal or elevated in the presence of significant cardiac injury [3]. However in blunt trauma, the combination of a normal ECG, normal chest X-ray, and normal levels of troponin I has a very high negative predictive value [22, 23].