Blunt Cardiac Injury in Thoracic Trauma

Figure 1: Evaluation and management of blunt cardiac injury in hemodynamically stable patients.The recognition of blunt cardiac injury (BCI) remains challenging, in part due to the rarity with which these patients make it to the emergency department (ED). Epidemiologic data indicate that, of the nearly 40,000 trauma-related deaths occurring annually in the United States, approximately 20%-25% are the result of thoracic injuries. Motor vehicle collisions (MVCs) are the leading cause of thoracic trauma; however, other contributing mechanisms include falls from significant heights, sports-related injuries, and assaults. In the prehospital setting, features of an MVC that should increase our suspicion for thoracic injury include extensive vehicle damage, steering-wheel deformity, fatality on scene, prolonged extrication, and ejection.1 By the time patients arrive at the ED, the clinical manifestations of BCI may be subtle or delayed, at times not becoming apparent until several hours into the hospital course. Further complicating this diagnosis is the absence of a universally accepted definition for BCI. Instead, we currently recognize that there is a spectrum of injury, from mild damage to the myocardium that manifests as unexplained tachycardia, all the way to sudden cardiac death. Though BCI can be an elusive diagnosis, its high morbidity and mortality make it an important topic in trauma care. Dr Andrew Petrosoniak is an emergency physician at St. Michael's Hospital and professor at the University of Toronto, where he is a leader in resuscitation with a focus on in-situ simulation for high-stakes trauma scenarios. EM:RAP's Anand Swaminathan sat down with Dr Petrosoniak to discuss the evaluation and management of patients with suspected BCI.2 How to Recognize It The American Association for the Surgery of Trauma (AAST) has developed a grading system to assess the severity of BCI.3 The spectrum of BCI ranges from grade 1, characterized by minor electrocardiogram (ECG) changes (like persistent tachycardia or PVCs) to the most catastrophic grade 6 (which includes avulsion of the heart and is instantly fatal). The patients we may be able to identify in the ED are those who develop heart block (grade 2), sustained multifocal ventricular contractions (grade 3), or are found to have valvular injury (grade 4). With this grading system in mind, what clinical manifestations should make us suspect BCI to enhance early recognition? Key features suggestive of BCI include the presence of: New dysrhythmia New murmur New hypokinesis on cardiac ultrasound Severe chest pain Unexplained hypotension Physical exam findings that may indicate an increased likelihood of intrathoracic injury include: crepitus, ecchymosis of the chest (seatbelt sign), increased work of breathing or paradoxical chest movement, to name a few. It is also important to avoid the common pitfall of assuming that hemodynamic stability and/or lack of external signs of trauma exclude significant thoracic injury.1 Concerning clinical manifestations should prompt further consideration about the underlying cause of BCI, which can be separated into structural or electrical injury. Structural injury may involve damage to the coronary arteries, valvular incompetence, or wall rupture. Electrical injury may include a new bundle branch block, atrial fibrillation, or life-threatening arrhythmias leading to cardiac arrest, as in commotio cordis. How to Work It Up If there are red flags for BCI in your patient's presentation, or your clinical gestalt raises concern, the following algorithm may help direct your next steps. Figure 1 summarizes the critical decision points that can help guide your diagnostic approach in hemodynamically stable patients.ECG is used early in the workup as a screening tool and branch point. In low-risk patients, this initial screening tool may be enough to exclude significant BCI if the ECG is reassuring. However, if patients meet any of the high-risk criteria, consider further testing with cardiac biomarkers, and a discussion with trauma surgery is likely warranted. It is important to highlight that a sternal fracture is not included under the high-risk criteria. While many hospitals may have a protocol to pursue BCI testing in patients with sternal fractures, current evidence suggests that isolated fractures do not place patients at higher risk for BCI. Additionally, the degree of fracture displacement also correlates poorly with myocardial injury. Studies have demonstrated that the small proportion of patients with sternal fractures who were diagnosed with BCI also had additional high-risk thoracic injuries, reinforcing that isolated sternal fractures are unlikely to cause BCI.4,5 While institutional protocols should be adhered to, it is essential to incorporate the evidence when assessing the level of clinical suspicion for BCI. Early research supports the use of cardiac biomarkers in evaluating for BCI focused on troponin I (TnI). However, recent studies have demonstrated that high-sensitivity troponin I (hsTnI) is comparable to TnI in detecting clinically significant BCI. The range of sensitivity in the literature falls between 71% and 100% when combining both ECG and serum troponin.6 The ideal threshold for troponin remains uncertain, as most of the studies have been smaller, single-center research. The study by Becker et al suggested an initial cutoff for hsTnI of 76 ng/L but later found that a cutoff of 40 ng/L improved the sensitivity to nearly 80%.7 Until more concrete data is available, it is wise to follow individual hospital algorithm cutoffs. If the initial troponin is greater than or equal to twice the level of the hospital cutoff, then BCI is likely. It becomes more nuanced when a delta troponin is required. Old data suggest the use of a 4-6-hour delta troponin level. At present, there is no standardized guideline defining a positive delta; therefore, clinicians should adhere to their hospital's specific troponin algorithm. Managing Blunt Cardiac Injury Once the diagnosis of BCI has been made, the management depends on the stability of the patient and the grade of BCI. Higher-grade BCIs will likely be unstable on arrival to the ED, need emergent resuscitation, and surgical intervention with trauma surgery or cardiothoracic surgery. This will all happen rather quickly in collaboration with the trauma team. Hemodynamically stable patients will undergo further evaluation. If identified later to have a lower-grade BCI, they will require a minimum of 24 hours of telemetry and discussion with the trauma team. Most will go on to require a formal echocardiogram and likely a cardiology consultation during their admission. Key Takeaways Not all patients with blunt thoracic trauma or isolated sternal fracture need a workup for BCI, particularly in the absence of high-risk features. If patients meet high-risk criteria and are hemodynamically stable, pursue evaluation for BCI with ECG and troponin. Place patients on telemetry early to assess for new dysrhythmias, as this can develop at any point during their ED course. Maintain BCI on your differential in patients with thoracic trauma to ensure timely recognition and management. Use CorePendium on shift to help guide your clinical management. Download the CoreP app today! Want to hear this audio segment in full? Go to EM:RAP.