Blunt Cardiac Injury

Article Author:
Shridevi Singh
Article Editor:
Lambros Angus
Updated:
11/14/2018 7:22:12 AM
PubMed Link:
Blunt Cardiac Injury

Introduction

Cardiac contusion is a misnomer that is used to reflect injury to the heart after blunt chest trauma.[1]. Histologically, it was characterized by a contused myocardium, hemorrhagic infiltrate, localized necrosis, and edema. Because of the term's ambiguity in describing a spectrum of myocardial injuries secondary to blunt trauma, "cardiac contusion" is now termed "blunt cardiac injury" (BCI). This is the term trauma experts agree is more appropriate since it encompasses the various types of cardiac injuries seen after blunt chest trauma.[2][3] BCI Injuries can range from clinically silent, transient arrhythmias to fatal cardiac rupture.[4]. Significant BCI usually occurs from high-impact trauma from motor vehicle accidents (50%), pedestrian struck by motor vehicles (35%), motorcycle crashes (9%), and falls from significant heights (6%).[5][6][7]. Diagnosing BCI can be challenging as there is no accepted gold standard diagnostic testing. The injury can be even more complicated in a patient with multiple traumas. The reported incidence of cardiac injury following blunt chest trauma is in the range of 8% to 76%; this reflects the lack of standardized diagnostic criteria.[7] 

In essence, myocardial tissue damage is the only way that BCI can be confirmed, either at surgery or autopsy.[8] In the vast majority of cases, however, this option is not available, and the clinical and diagnostic tools available in our armamentarium are variable and nonspecific. More importantly, in the absence of severe arrhythmia and hemodynamic instability, the significance of BCI becomes more questionable despite the results of noninvasive studies.[5][9] In the setting of blunt trauma, a high, clinical suspicion for BCI is warranted, and if suspicion is high enough, patients should be monitored for adverse sequelae since there are no pathognomonic clinical signs or symptoms that correlate with the risk of cardiac complications.[5][10][11]. Indeed, it is the sequelae of BCI that is of importance and not necessarily its label.

Etiology

Blunt cardiac injury (BCI) from blunt chest trauma is most commonly due to motor vehicle collisions (50%), with 20% of all motor vehicle collision deaths involving blunt chest trauma.[2] Other mechanisms such as falls, blast injuries, assault, and other blunt mechanisms also play a role.[1] The mechanism and magnitude of force determine the cardiac injury that is sustained. The heart sits in the thorax where it is caged in by the sternum, ribs, and spine; therefore, a significant amount of force is needed to result in  BCI. Nevertheless, there can be a direct impact to the chest, resulting in compression of the heart between the sternum and spine. In the setting of a deceleration injury, the heart can tear from its attachments as it hits the bony thoracic cage. Most often, these types of injuries are not survivable, with the patients not even make it to the hospital. Although BCI has been associated with multiple other injuries, such as thoracic aorta, lung, rib, or sternal fractures and spinal injuries, none of those injuries are specific enough to be highly suggestive of BCI.[6] Associated injuries only raise the index of suspicion for the provider who should be alerted to the possibility of BCI,  but they are not pathognomonic and, most often, are not indicative of BCI.

Epidemiology

The incidence of blunt cardiac injury (BCI) has a broad range (8% to 76%)[7] because of the lack of a clear, accepted diagnostic criteria, lack of consensus on the definition, and the inconsistency of nomenclature that makes it difficult to quantify the incidence. Diagnosis can be based on symptoms that are not necessarily related to BCI while some BCI complications, like arrhythmias, can be due to pre-existing heart conditions-particularly in the elderly population. Diagnostic criteria, like elevated troponins,  can also be due to trauma unrelated to the chest.[12] In the United States, trauma is the 4th leading cause of death. The American Association for the Surgery of Trauma (AAST) developed the AAST Cardiac Injury Scale that applies to blunt and penetrating cardiac injuries to use when quantifying cardiac injuries. (see Table) Note: When using the table, advance one grade for multiple penetrating wounds to a single chamber or multiple chamber involvement.

Pathophysiology

Blunt cardiac injury (BCI) most commonly occurs from motor vehicle accidents, followed by falls and crush injuries. Six potential mechanisms have been suggested for BCI: direct, indirect, bidirectional, deceleration, blast, crush, concussive, or combined[1][2]. Direct impact to the chest is considered the most common mechanism, and cardiac injury is most likely when the ventricles are maximally distended at the end of diastole.[5] Indirect cause is due to an increase in preload by way of abdominal or extremity veins that results in a sudden increase in the intracardiac pressure, thereby making the heart susceptible to rupture.[5] Bidirectional forces result in compression of the heart between the spine and sternum.[5] Deceleration mechanisms allow the heart to move freely, resulting in valvular, myocardial, coronary artery tears, or laceration.[1][5]

The cardiac chamber injury distribution reflects the position of the heart in the chest where the right ventricle and right atrium are more anterior compared to the left ventricle and left atrium.[5][13]

The most common cardiac injuries from blunt trauma resulting in death are often due to one or more cardiac chamber rupture (64%), venous-atrial confluence tears (33%), or coronary artery tear or dissection.[6]

Of note, commotio cordis is sudden death due to cardiac arrest from BCI in the absence of preexisting disease and with no morphological injury to the heart at autopsy. It is usually seen in the young, male athlete. The thought process is that the impact occurs during ventricular repolarization and sets the heart to ventricular fibrillation.[2][6]

Most patients who survive BCI due to blunt trauma have less severe injuries that range from structural injuries to electrical and conduction disturbances.[6] An intramural hematoma is one such structural injury that, for the most part, has a benign clinical course that resolves in 4 to 12 weeks. It can cause premature ventricular contraction (PVC) and transient bundle branch block (BBB). Another common structural injury is papillary muscle rupture that can lead to regurgitation of the valves and require valve repair or salvage.[6] On clinical exam, septal injuries can present with a murmur or arrhythmias on echocardiogram (ECG). The course of this injury begins with contusion followed by necrosis and then delayed rupture. Hence, early diagnosis is important as it can be treatable if discovered.[5][6]. Dysrhythmias are fairly common in BCI and, most commonly, are evident by sinus tachycardia on ECG followed by premature atrial or ventricular contractions, atrial fibrillation, and BBBs.[2][6] The most common cardiac abnormality seen in BCI is tachycardia; however, most ECG changes have been noted to be clinically irrelevant.[6] That finding does not relinquish the importance of monitoring these patients closely because most trauma patients will exhibit tachycardia on initial assessment, and ECG with persistent tachycardia is more suggestive of BCI rather than the transient tachycardia seen in the patient who is polytraumatized. The provider should also realize, however, that tachycardia in the trauma patient should raise greater suspicion of ongoing bleeding than BCI. Once bleeding is ruled out, BCI becomes more probable in the differential diagnosis.

History and Physical

It is important to first identify the trauma patient with blunt chest injury by the mechanism of force. For instance, patients involved in an MVC should be queried on whether there was a steering wheel impact. Furthermore, 54% of patients with a history of a fall greater than 20 feet had BCI.[6]

The most common complaint is chest pain or shortness of breath.[1][2], but some may report palpitations or even present with typical angina symptoms.[2][14] It is also important to assess for cardiac risk factors such as a history of myocardial infarction, cardiovascular disease, and/or comorbidities. Medication assessment is important, especially in the patient taking cardiac drugs which can alter the patient presentation such as beta blockers and calcium channel blockers (which can mask tachycardia).

The physical exam should be thorough. Patients can present with cardiac tamponade, and suspicion should be high for jugular venous distention and hypotension. The focused assessment with sonography for trauma (FAST exam)  will help in the assessment for pericardial fluid and cardiac tamponade. Tachypnea, irregular lung sounds, chest wall tenderness, chest abrasion or ecchymosis, rib or sternal fractures, and seatbelt sign across the chest are some of the physical findings that should raise suspicion for BCI[10] although they are non-specific.[1][2][10][14] Furthermore, patients with severe BCI are more likely to have other significant traumatic injuries that can mask some of the physical effects of BCI.[10][14]

Evaluation

No consensus has been established to diagnose blunt cardiac injuries. In 2012, the Eastern Association of Trauma (EAST) published BCI practice guidelines that supported obtaining an ECG in all patients with suspected BCI.[5][6] Patients with abnormal findings should be admitted for continuous cardiac monitoring; however, a normal ECG does not entirely exclude BCI as it has been reported that a significant number of patients with an initial normal ECG were noted to have a cardiac injury 24 hours later, measured by laboratory results of elevated cardiac troponin I (cTnI) levels.[2][5] Nevertheless, patients with a normal ECG in conjunction with normal levels of cTnI can be safely discharged home.[2][5][6] Furthermore, it should be noted that a normal ECG and cTnI levels do not rule out all BCI as some may have a delayed presentation (e.g., septal injury). Following an abnormal ECG and cTnI level, an echocardiography is usually obtained to further characterize the injury. Computerized tomography (CT) and magnetic resonance imaging (MRI) do not play a role in the initial diagnostic evaluation of BCI; however, these modalities can be complementary or useful in the patient with symptoms without a clear clinical etiology and can be considered on a case-by-case basis.[2][5]

Treatment / Management

Patients with abnormal ECG and/or cTnI levels should be admitted for cardiac monitoring for 24 to 48 hours because life-threatening arrhythmias or cardiac failure will most likely present during this time.[2][14] Patients can be admitted to the intensive care unit or placed under telemetry, depending on concurrent injuries, type of ECG change, and the grade of hemodynamic imbalance. It is not necessary to admit all sternal fractures with a normal ECG to rule out BCI. The most prevalent of the BCIs are the subset of patients with isolated abnormal ECG and/or cTnI elevations which usually has a benign course with the rare occurrence of long-term functional impairment.[1]   

Management of dysrhythmias should be approached and treated as in the non-BCI patient. Replete electrolytes accordingly, avoid hypoxia and acidosis, and utilize antidysrhythmics and any additional intervention or defibrillation if clinically indicated. Although rare with isolated BCI, the occasional patient may present with complete heart block, necessitating a pacemaker. ST segment elevations can be due to either a contused heart or traumatic myocardial infarction, necessitating coronary angiography.[2]

Patients with severe clinical or imaged structural cardiac injury require emergent cardiology evaluation for further management. Temporizing measures such as resuscitation, inotropes, or vasopressors may be indicated in the interim based on the specific clinical findings and associated injuries. A patient presenting with high suspicion for cardiac tamponade, most frequently seen in cardiac rupture, will benefit from surgical intervention as an emergency.[1][2] Cardiothoracic intervention is required and time is of the essence in the majority of those cases. Refractory cardiogenic shock can benefit from intra-aortic balloon pump (IABP) to help increase coronary blood flow, allowing the stunned heart to recover in days or weeks.[1]

Prognosis

Prognosis in blunt cardiac injury (BCI) is highly dependent on the specified injury and its association with concomitant injuries and a history of previous cardiac disease or injuries.[14] The patient with isolated BCI that is presented by way of an abnormal ECG or cTnI level has a more favorable outcome than the patient who is hemodynamically compromised with cardiac structural injury one who has an associated high trauma injury score.[6][14] Given that the former represents the largest pool of BCI patients, BCI can be presumed to have a favorable prognosis overall.

Complications

Overall, complications from blunt cardiac trauma are rare.[6][14] Acute complications from severe cardiac injury usually necessitate immediate management, and those that survive may have long-term complications related to their specific injury. Most BCI patients, do not have long-term sequelae, but a few, late complications have been reported, including delayed cardiac rupture, complete atrioventricular block, heart failure, pericardial effusion, and constrictive pericarditis.[6] Therefore, good practice entails reevaluating these patients in 3 to 6 months.[6]

Enhancing Healthcare Team Outcomes

A multidisciplinary approach to blunt cardiac injury

The diagnosis of blunt cardiac injury (BCI) remains challenging due to its variable presentation and the range of myocardial injuries that are encountered. Further limitations are due to the lack of consensus, diagnostic criteria, and gold standard diagnostic tests. However, the crucial factor in caring for these patients is to have a high suspicion for injury in patients with suspected blunt chest trauma and polytrauma. ECG and cTnI levels can be used as screening tools and followed by admission and echocardiography for any resultant abnormalities with the understanding that BCI can take up to 48 hours to manifest. A consensus among interprofessional should be employed to identify BCI based on the specific injury.

Given that the vast majority of cases diagnosed as BCI are inconsequential, the true significance of such diagnosis remains controversial since there are no long-term follow up studies available to asses long-term outcome. Lastly, since most patients diagnosed with BCI develop no adverse clinical effect, the cost of the current practice of admitting such patients simply to obtain a diagnosis is questionable and studied in a healthcare system already strained financially. Indeed, those suspected of BCI who are hemodynamically stable with no lethal arrhythmia should perhaps have a short period of observation. Further consensus and research among providers are warranted to define the management and long-term significance of BCI better.



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      Contributed by the American Association for the Surgery of Trauma (AAST) 2012