A 31 year old male, identified as Lamar “Battlestar” Hoskins was found dead by Emergency Medical Services (EMS) inside a refugee camp, slumped against a stone pillar. Reports indicate that he was a United States Army soldier working with the “New Captain America”. He was recently seen in armed combat with a terrorist organization known as the “Flag Smashers”. The debriefing report by soldiers on the scene stated that the male received a direct punch to the anterior chest in heated conflict by a “super soldier” capable of immense strength. Unfortunately, the man’s death set off international political turmoil after the enraged New Captain America brutally murdered a Flag Smasher in a public square as revenge. As such, you have been tasked to provide a professional opinion on the mechanism of death of this individual.
When asked to expand about the mechanism of injury, witnesses reported that the punch propelled the male at least 5 meters through the air before hitting his back on a stone pillar with enough force to crack it. A cursory primary survey done by the soldier at the scene demonstrated an unresponsive patient with no spontaneous respirations and no palpable carotid pulse. Further exam revealed massive ecchymosis to the anterior chest. Cardiopulmonary resuscitation was not performed on the scene due to active conflict.
Mechanisms of injury and differential diagnosis for blunt cardiac injury
Blunt cardiac injury (BCI) is typically sustained after blunt trauma to the heart or its surrounding structures. While estimates of BCI prevalence vary widely, it is estimated to be present in 20% of blunt thoracic traumas, and up to 76% of severe thoracic injuries.1–3 Given that a significant compressive force is required to overcome the protection of the ribs and sternum, the most common mechanisms of injury are motor vehicle collisions and pedestrians struck by vehicles.4
BCI is commonly seen in the context of multi-system trauma with some involvement of the chest. Prompt recognition and treatment is essential given its high mortality and non-specific symptoms.5 While evaluating for BCI, one must simultaneously evaluate for other life-threatening injuries commonly seen in blunt chest trauma, including but not limited to pulmonary contusion, tension pneumothorax, tracheobronchial injury, acute pericardial tamponade and blunt aortic injury.
Recognition of blunt cardiac injury
BCI should be suspected in all patients presenting with blunt chest trauma, particularly those with a dangerous mechanism (i.e. high-speed MVC and/or multi-system trauma). It is often asymptomatic, or associated with nonspecific signs and symptoms such as hypotension or chest pain that could be confused with other thoracic injuries.6 Recognition of BCI typically stems from prompt identification of its associated complications, many of which may be fatal. These include arrhythmias, cardiogenic shock, myocardial rupture and myocardial infarctions.5
The recognition of BCI remains a clinical challenge because no gold standard exists for diagnosis.5 Current recommendations by the Eastern Association for the Surgery of Trauma (EAST) involve an initial screening ECG as well as troponin to assess for gross conduction abnormalities and myocardial damage. If abnormalities exist, patients should be admitted for continuous telemetry and assessment with a transthoracic echocardiogram; a normal ECG and troponin should make one consider an etiology other than BCI.7 There are no specific ECG changes in BCI, but possible clues may include persistent sinus tachycardia, dysrhythmias or ST segment changes.8 This is further complicated by trying to determine whether these ECG changes preceded, and potentially led to the trauma (e.g., ST elevation suggesting a myocardial infarction) or was a result of BCI. Likewise, findings such as sinus tachycardia may be confounded by various factors during trauma (hypovolemic shock, pain, physiologic stress or even pulmonary embolism). An initial chest radiograph (CXR) done around resuscitation efforts can provide rapid, albeit limited, information in the evaluation of BCI. A CXR might reveal gross injuries or anatomical abnormalities including fractures, hematomas or cardiac enlargements that might point towards a serious underlying injury.9
After initial stabilization of your patient, computed tomography (CT) can be used to identify BCI and other associated injuries in a patient presenting with undifferentiated blunt chest trauma. Multidetector CT scanning provides rapid and accurate visualization of the chest and its structures. It is effective at detecting small pericardial effusions in patients with suspected BCI from more occult sources of bleeding such as atrial bleeds. Likewise, CT scan can be useful in identifying damage to surrounding structures such as traumatic aortic injury or pericardial rupture. However, the use of multidetector CT in the evaluation of BCI is still an area of active debate; it has poor sensitivity when detecting milder cardiac injury such as myocardial contusions.10 Current guidelines for the evaluation of BCI recommend multidetector CT with angiography specifically for the differentiation between BCI and acute myocardial infarction, but acknowledges that it can be used for further evaluation on a case-by-case basis.6The use of dual-energy CT, which has a higher sensitivity for detecting cardiac contusions, is an area of active research beyond the scope of this article.10
Given that there is no unified standard for the evaluation of BCI, in relatively stable patients some physicians may elect to perform transthoracic or transthoracic echocardiography if BCI is strongly suspected despite negative CT imaging.
Classification of BCI
Although there are no established guidelines for classifying BCI, several methods are available which vary in complexity. The most popular severity scale has been published by the American Association for the Surgery of Trauma (AAST). This scale ranges from injury resulting in nonspecific ECG changes (Grade I) to more severe scenarios such as heart failure and coronary artery occlusion (Grade 3+). Although this scale can be useful in certain scenarios, given the heterogeneity of BCI, it is more common to classify it based on the pattern of injury and the areas involved.6
|Grade I||Blunt cardiac injury with minor EKG abnormality (non specific ST of T wave changes, premature atrial or ventricular contractions, or persistent sinus tachycardiaBlunt or penetrating pericardial wound without cardiac injury, tamponade, or cardiac herniation|
|Grade II||Blunt cardiac injury with heart block or ischemic changes without cardiac failurePenetrating tangential cardiac wound, up to but not extending through endocardium, without tamponade|
|Grade III||Blunt cardiac injury with sustained or multifocal ventricular contracationsBlunt or penetrating cardiac injury with septal rupture, pulmonary or tricuspid incompetence, papillary muscle dysfunction, or distal coronary artery occlusion without cardiac failureBlunt pericardial laceration with cardiac herniationBlunt cardiac injury with cardiac failurePenetrating tangential myocardial wound, up to but not through endocardium, with tamponade|
|Grade IV||Blunt or penetrating cardiac injury with septal rupture, pulmonary or tricuspid incompetence, papillary muscle dysfunction, or distal coronary artery occlusion producing cardiac failureBlunt or penetrating cardiac injury with aortic or mitral incompetenceBlunt or penetrating cardiac injury of the right ventricle, right or left atrium|
|Grade V||Blunt or penetrating cardiac injury with proximal coronary artery occlusionBlunt or penetrating left ventricular perforationStellate injuries, less that 50% tissue loss of the right ventricle, right or left atrium|
|Grade VI||Blunt avulsion of the heartPenetrating wound producing more than 50% tissue loss of a chamber|
What caused Battlestar’s death?
In the heat of battle against supersoldiers, Battlestar died from a massive blunt trauma to the anterior thorax, followed by a rapid deceleration when striking his posterior thorax on the pillar. This mechanism and presentation of a blunt traumatic chest injury causing near-instant death points towards three possible causes:
- Myocardial concussion (AKA commotio cordis)
Perhaps the most famous example of complications arising from BCI is commotio cordis, although it is extremely rare (only 190 reported cases as of 2009)11. It is classically seen in young adults in sports such as baseball, hockey or martial arts after an acute, sharp blow to the chest. Although the blow typically lacks the power to cause permanent cardiac injury, in cases of commotio the concussive force strikes the heart at the precise moment to induce a fatal dysrhythmia, such as ventricular fibrillation or asystole. Patients typically lose consciousness suddenly after the event and often perish before reaching the hospital. In patients who suffer from commotio outside of hospital, resuscitation with a defibrillator started within 3 minutes of collapse has a survival rate of 25%; after 3 minutes, this rate drops to 3%.11
Although commotio cordis is a rare diagnosis, management involves following standard Advanced Cardiovascular Life Support (ACLS) guidelines for the corresponding rhythm. In the small proportion of patients that do survive, it is important to rule out any other complications of BCI, such as coronary artery occlusion or myocardial infarction. Following resuscitation, continuous telemetry monitoring for 6-12 hours is recommended, as well as further cardiac workup before returning to play.5
- Myocardial rupture
Myocardial rupture typically results from chest trauma sustained during high-speed MVCs. To the author’s knowledge, no randomized controlled trials have been performed to interrogate the punching power of a super-soldier, but we suspect that the force generated is likely to meet or exceed that which is required to produce such an injury. Myocardial rupture usually causes patients to perish before arriving at hospital, but up to 20% may survive. The pathophysiology of myocardial rupture has multiple proposed mechanisms and is likely multifactorial. Typically, it is thought that myocardial chambers were filled with blood at the time of injury (i.e., ventricles in diastole and atria in late systole) and then subjected to a significant compressive force, resulting in high pressures within the myocardium and resultant rupture of the ventricular walls.5 This force is often seen in so-called “steering wheel injuries”, where an individual in an MVC is thrown forcefully forward, striking their chest on the steering wheel of their vehicle. Given the mechanism of injury typically involves polytrauma, patients will often have associated injuries to the pericardium, valves and papillary muscles, coronary arteries or ascending aorta. Right ventricular rupture is the most common form of myocardial rupture.
Figure 1. Axial contrast-enhanced CT of a patient with hemopericardium (arrows) following traumatic myocardial rupture.
Myocardial rupture is an acutely life-threatening condition. Patients usually present following severe trauma and usually perish before arriving to ED; those that do survive can be very unstable upon presentation. They typically will have complications of rupture including cardiac tamponade and/or severe intrathoracic hemorrhage. If there is an associated pericardial tear and lung injury, auscultation may reveal a harsh, “splashing” murmur known as a bruit de moulin, caused by pneumopericardium. Prompt recognition and immediate treatment of myocardial rupture and acute tamponade is essential for patient survival. Once tamponade is confirmed by an experienced ultrasonographer during FAST and cardiac rupture is suspected, it is appropriate to proceed with an ED thoracotomy in acutely unstable patients who are peri-arrest. Prognosis for traumatic myocardial rupture is extremely poor. The mortality rate is in the vicinity of 76-89%, with only half of patients having vital signs upon arrival to hospital, and most perishing in the field.12
- Blunt Thoracic Aortic Injury
Battlestar could have also died from a blunt thoracic aortic injury. Although usually caused by a sudden deceleration in an MVC, an abrupt backwards acceleration from a super-soldier punch may have replicated a similar mechanism of injury. Aortic injuries range from intimal tears to pseudoaneurysms to frank rupture that results in lethal hemorrhage. The pathophysiology may vary depending on the affected segment of aorta. In the ascending aorta, the compressive force caused by blunt trauma leads to a sudden increase in pressure, potentially inducing rupture. Given that the descending thoracic aorta is a fixed structure, a rapid deceleration may produce a shearing force resulting in significant injury to the structure.5 The vast majority of blunt thoracic aortic injuries are to the descending aorta, and have a better prognosis; when the ascending aorta is involved, there should be a strong suspicion of associated cardiac injuries.
Figure 2. Axial chest computerized tomography demonstrating aortic tear with intimal flap (arrow).
Like in the case of myocardial rupture, prompt recognition and treatment of aortic injury is key to patient survival. This is often challenging, however, as trauma patients will likely present with other distracting injuries. Likewise, symptoms of blunt thoracic aortic injury are generally nonspecific and difficult to identify, and often only confirmed once the patient has been sufficiently stabilized for CT scanning. While the most common symptom is retrosternal or interscapular pain, this is present in only 25% of patients, and is also found in numerous other traumatic injuries. Other uncommon symptoms include stridor, hoarseness and dyspnea. A notable sign is reflex hypertension, caused by stretching of the aortic isthmus. Although nonsensitive and nonspecific, patients may also present with signs of a precordial/posterior interscapular harsh systolic murmur, a pulsatile neck mass, or significant drainage from a chest tube placed for hemothorax (>750mL). When blunt thoracic aortic injury is suspected, a chest CT should be ordered as soon as the patient is stable enough for scanning. Once an aortic injury is identified, it should be assumed to have a high risk of rupture and should be repaired surgically or endovascularly as soon as the patient is stable enough to tolerate the OR. Prognosis for blunt thoracic aortic injury is significantly influenced by its prompt recognition and initiation of appropriate care by prehospital emergency medical professionals. 60-90% of patients with blunt thoracic aortic injury die on the scene or within several hours of arrival to a hospital.5
- Blunt cardiac injury should be considered in any trauma patient with signs of injury to the thorax.
- Signs and symptoms of blunt cardiac injury will vary based on the pathology. A non-specific presentation does not rule out a life-threatening condition!
- Many pathologies resulting from cardiac injury require prompt recognition and intervention for survival. Ancillary testing including FAST, ECG, troponin and a high degree of clinical suspicion are your friend!
What do you think the etiology of Battlestar’s death was? Comment below or reach out on Twitter to @WeAreCanadiEM.
Copy-edited by @jamievanderende.
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