Continuing Education Activity

Cardiac trauma can be categorized as either blunt or penetrating according to the mechanism of injury. Outcomes range from spontaneously-resolving arrhythmias to lethal injury. Those with lethal injuries often succumb quickly, with an estimate that 90 percent of individuals with lethal injuries expire before arriving at a hospital. Of those that make it to the hospital, survival is estimated at between 20 and 75 percent. This activity reviews the evaluation, management, and treatment of cardiac trauma and highlights the role of the interprofessional team in caring for affected patients.

Objectives:

• Review common mechanisms of injury associated with cardiac trauma.
• Explain how to evaluate a patient for cardiac trauma.
• Describe management options for patients with cardiac trauma.
• Outline interprofessional team strategies for enhancing care coordination and communication in order to improve rapid diagnosis and management of cardiac trauma and improve patient outcomes.

Introduction

Cardiac trauma can be grouped by the method of injury as either blunt or penetrating with outcomes ranging from lethal injuries to spontaneously resolving arrhythmias. Those with lethal injuries often succumb quickly with some documenting over 90% of individuals expiring before arriving at a hospital, and only a 20-75% survival rate of those that make it to the hospital.[1]

Etiology

Blunt cardiac trauma is generally caused by a direct impact to the anterior chest, sudden high-speed deceleration, compression of the chest, or a mixture of those.  Motor vehicle accidents are the most common cause and include all three of the mechanisms above.  Individuals struck by motor vehicle falls, crush injuries, and seemingly innocuous trauma such as sports-related (baseball hitting a chest) or animal-related (animal kick) may also cause blunt cardiac injury (BCI).[2]

Penetrating cardiac trauma has been primarily due to stab wounds, with gunshot wounds being the second leading cause. Non-firearm-related blast injuries and impalements are also causes of penetrating cardiac trauma.[3]

Epidemiology

Blunt cardiac injury: BCI may affect anyone, but most often affects males with an average age in the 30s.  Pediatric patients with blunt cardiac injury are also often male, with an average age of 7, and most commonly from motor vehicle accidents. Patients with blunt thoracic trauma have been noted to have as high as a 30% incidence of electrical abnormalities.

Penetrating cardiac injury: Any gender or aged individual may be the victim of a penetrating cardiac injury, but males and those in the 3rd or 4th decade of life are most common.  The right ventricle is most frequently injured, followed by the left ventricle, and then atria or multiple-chamber injuries.[4]

Pathophysiology

Cardiac contusion following blunt chest trauma might result in myocardial necrosis. The myocardial necrosis might ultimately cause cardiac rupture and even sudden cardiac death.[5] Anterior thoracic blunt trauma might result in a bruising caused by a decelerating force. The first thing in the pathophysiological mechanism is the abrupt compression of the heart to the dorsal side of the sternum, which is called a coup. Regarding the total amount of energy absorbed by the rib cage, the thoracic spine can add an additive traumatic effect by hitting the heart at the posterior side, which is called contrecoup. Finally, the distance between the sternum and spine will decrease additionally, resulting in either septal or intracardiac components injuries.[6][7]

Histopathology

Defects in mitochondrial function and structure are significantly prominent in the pathogenesis of multiple myocardial injuries.[8] Multi-focal subepithelial contusions of ventricles might be evident. Several experimental studies have investigated the presence of morphological changes in the myocardium following cardiac concussion.[9]Blunt trauma might cause myocardial infarction. In that case, associated time-sensitive histopathological changes are predicted. In the first few minutes following the myocardial infarction, the increased distance of the cross stripe in the infarcted zone is notable.[9] Later, in the first thirty minutes, swelling of the mitochondria is significant. Myocyte edema, glycogen loss, and decreased myoglobin stainability in the immunohistochemistry staining are predictable in the second thirty minutes. First hyalinised myocytes are visible two to three hours following the myocardial infarct. However, first agglutinated sarcoplasmic tubes are predictable after three to four hours. Primary evidence of necrosis and extended necrosis zone is visible in the first four to seven hours and after 18 hours post-infarction.[10][11]

History and Physical

The history of events for patients with a cardiac injury is often straightforward, detailing some mechanism injuring the chest or back. However, some individuals may give alternative stories due to potential legal ramifications or altered mentation.  A subset of patients may also be unconscious or without a pulse with the only information available from first responders.

The physical examination of a patient with potential cardiac trauma should typically follow the primary and secondary survey of Advanced Trauma Life Support (ATLS).  Along with obtaining initial vital signs, and after ensuring the airway and breathing or intact and not compromised, a brief evaluation of circulation and the cardiac system should occur.  Inspection for obvious anterior/lateral chest wounds, auscultation for the presence of muffled heart tones, murmurs, and arrhythmias, and palpation for strength and presence of pulses should be done.  After completing a primary survey, the secondary survey should include further examination for a potential cardiac injury, such as evaluating for distended neck veins and evaluating for signs of trauma to the posterior and lateral torso. While a patient may have stable vital signs and few features to suspect a cardiac injury, findings concerning cardiac trauma include hypotension, tachycardia, arrhythmias, visible trauma, distended neck veins, muffled heart sounds, and other signs of shock.[12]

Evaluation

Evaluating patients with concern for cardiac trauma following physical examination is multi-faceted and varies depending on the nature of the mechanism of injury.  A general trauma evaluation is typical and usually, includes plain films of the chest and a point-of-care ultrasound (POCUS).[13]

Plain films of the chest have limited utility for the diagnosis of BCI but may have some utility in penetrating cardiac trauma. They may demonstrate the presence and approximate location of a foreign body, the presence of a hemothorax, displaced heart, and other non-cardiac thoracic injuries.  Acute cardiac tamponade is unlikely to show significant findings on an initial plain film. 

POCUS is common in emergency departments with a focused assessment with sonography for trauma (FAST) exam done routinely that includes a cardiac view, which can aid in rapidly diagnosing pericardial effusions.  While physical examination such as distended neck veins and abnormal vital signs can be used with POCUS for demonstrating tamponade, the findings of inferior vena cava distension and septal bounce can also be identified on POCUS.  For individuals more proficient with POCUS, or through ordering a formal echocardiography study, other findings such as wall motion and valvular abnormalities may be identified.  If the views are suboptimal and the patient is stable then transesophageal echocardiography may be beneficial and may provide additional information about the great vessels.

Computed Tomography (CT) is also part of the trauma evaluation if the patient is stable enough.  It has a high sensitivity for pericardial or myocardial lacerations, cardiac luxation, and other thoracic injuries, and can help identify the path of a projectile and the location of a foreign body.[14]

Evaluation specific to blunt cardiac trauma is difficult as there are no validated screening criteria for BCI.  An electrocardiogram (ECG), while not standard in the evaluation of the acutely injured patient, is useful in demonstrating the presence of new dysrhythmias, which should make a clinician suspicious of BCI (excluding sinus tachycardia).  A normal ECG alone has a high negative predictive value for BCI.  In addition to an ECG, cardiac enzymes such as cardiac-specific troponins should be considered to add to the routine trauma evaluation.  Troponins can help evaluate for the presence of a myocardial contusion or ischemia secondary to a vessel injury, and also have a high negative predictive value of a blunt cardiac injury.  A normal ECG and troponin within the normal range have been shown to have a near 100% negative predictive value for blunt cardiac injury, though there is a debate about when to perform the troponin, and if serial troponins should be done.[15]

Further evaluation based on the suspected underlying injury may be beneficial such as angiography for those with infarction patterns on ECG, or cardiac magnetic resonance (MR) imaging to help identify the extent of a myocardial contusion.

Penetrating cardiac injury evaluation should be considered for any individual with an open wound to the thorax.  Wounds within the imaginary box defined by the inferior clavicles, inferior costal margins, and mid-clavicular lines are especially concerning.  Echocardiography has been shown to have high sensitivity and specificity for cardiac wounds.  No further workup is needed aside from physical examination and echocardiography, though as mentioned above plain films may help provide approximate location and presence of foreign bodies.

Treatment / Management

Trauma patients should undergo routine ATLS care such as airway, breathing, and cervical spine protection.  Identification of a blunt or penetrating cardiac injury should prompt further specific care.[16]

BCI has many possible patterns, including dysrhythmias, contusions, rupture, valvular injury, and coronary artery injury. Dysrhythmias range from commotio cordis with non-perfusing ventricular fibrillation to stable first-degree atrioventricular blocks. Advanced cardiovascular life support (ACLS) management should be initiated for dysrhythmias, ruling out other traumatic injuries and alternative etiologies of the dysrhythmia.  Any dysrhythmia outside of sinus tachycardia that is presumed new should prompt consideration of further cardiac telemetry monitoring and echocardiography if not already done.  Patients with atrial dysrhythmias have been shown to benefit from treatment, and a beta or calcium channel blocker should be considered for the stable patient.  In the unstable patient, electrical cardioversion may be an option if their instability is suspected secondary to the dysrhythmia.[4][17] 

Myocardial contusions can present with electrical disturbances or may be found only with an elevated troponin. Treatment is supportive and determined by the severity of other findings, such as hypotension or high-grade dysrhythmias. Evaluation of these patients parallels that of patients with myocardial infarctions, with a similar range of outcomes and complications.[7]

Cardiac rupture may be lethal depending on the location and extent of damage to cardiac tissue.  Operative repair is indicated with a sternotomy or thoracotomy and potentially cardiopulmonary bypass. Valvular injuries may be repaired depending on the nature of the damage. Certain cases, such as papillary muscle rupture, may require valve replacement.[18]

Coronary artery lacerations or bleeding should be managed operatively to control the involved artery and coronary bypass.  In cases where non-bleeding coronary artery injuries are suspected, angiography with management based on findings is generally indicated, such as with stenting or medical management.[19]

Using a Foley to close a cardiac wound temporarily allows for rapid transfusion of blood products. There are multiple acceptable means of temporarily closing a cardiac wound during an emergency thoracotomy, including Foley placement, digital pressure, sutures, or staples.  Each is acceptable, but only the placement of a Foley can provide a route for rapid resuscitation while also closing the wound.[19]

Cardiac wounds may lead to exsanguination if nothing is done to temporize while waiting for definitive repair. Lacerations can be controlled initially with digital pressure, vascular clamp (atrial wounds), or the insertion of a Foley followed by inflation of the balloon and light traction.  Blood products may be able to be transfused through the Foley, in addition to helping temporize a cardiac wound. Cardiac laceration repair can be done using 3-0 polypropylene (Prolene) sutures, typically in running, horizontal mattress, or purse stitch.  Pledgets or pieces of the pericardium are often used to distribute tension when repairing ventricular wounds.[20]

Penetrating cardiac trauma is more straightforward in management, with operative management ultimately required.  If the patient is unstable, a pericardiocentesis can be performed with a catheter placed for intermittent drainage to help temporarily stabilize the patient. A median sternotomy or thoracotomy is used to obtain the heart with a pericardiotomy done, avoiding the phrenic nerve.  Lacerations can be controlled initially with digital pressure, vascular clamp (atrial wounds*), or the insertion of a Foley followed by inflation of the balloon and light traction.  Blood products may be able to be transfused through the Foley, in addition to helping temporize a cardiac wound.

Cardiac laceration repair can be done using 3-0 polypropylene (Prolene) sutures, typically in running, horizontal mattress, or purse stitch.  Pledgets or pieces of the pericardium are often used to distribute tension when repairing ventricular wounds. Key points to remember while repairing the wound are to ensure taking adequate bites of the myocardium to help avoid tissue tearing, placing ventricular sutures during ventricular contraction to help minimize tearing of the myocardium, and to avoid ligating coronary arteries when repairing cardiac wounds.  Posterior heart lacerations may need to be done with patience as elevating the heart for a continued period of time to visualize, place sutures, and tie sutures, as lifting the heart can cause hypotension and potentially cardiac arrest. Finally, staples have also been used in place of sutures to help close the wound, though they are controversial.[18]

Differential Diagnosis

• Cardiac tamponade

• Cardiogenic pulmonary edema

• Cardiogenic shock

• Hemorrhagic shock

• Mitral regurgitation

• Right ventricular infarction[14]

Prognosis

Penetrating cardiac injuries management has evolved recently, affecting the patients' outcomes significantly. Simple clinical observations are no longer accepted, and diagnostic measures, including focused assessment sonography for trauma (FAST), trans-thoracic echocardiogram, and CT scan, have assisted in more precise diagnostic measures. Collectively, the survival rate of penetrating cardiac traumas improved significantly. However, the mortality rate of penetrating cardiac trauma is still up to 40%.[21]

Complications

Following complications are predicted with cardiac trauma: 1. pericardial effusion, 2. abnormal wall motion, 3. decreased ejection fraction, 4. intramural thrombus, 5. valve injury, 6. cardiac enlargement, 7. conduction abnormality, 8. pseudoaneurysm, 9. aneurysm, and 10. septal defect.[22]

Pearls and Other Issues

Foreign bodies that are visible externally on patient arrival, and suspected to be related to a penetrating cardiac injury, should be left in place temporarily to allow for set-up for operative evaluation and care.  Otherwise, retained foreign bodies should be removed operatively if there is contamination or electrical abnormalities.

Emergency department thoracotomy is controversial due to survival rates ranging from around 1-30% depending on the patient population.  Despite low survival rates, as the alternative is guaranteed death, it is still performed in select situations. Individuals with blunt trauma and loss of vital signs are less likely to survive.  An emergency thoracotomy should be considered for blunt trauma victims with the loss of pulses less than 5-10 minutes (depending on the literature followed), though there have been reports of survivors with up to 15 minutes of loss of pulses.  An emergent thoracotomy should be considered for penetrating trauma victims with the loss of pulses less than 15 minutes, though survivors have again been documented with up to 32 minutes of CPR.

Enhancing Healthcare Team Outcomes

Cardiac trauma is best managed by a mutlidisciplinary team that includes the emergency department physician, trauma surgeon, cardiologist, cardiac surgeon, radiologist, the perfusioniost, cardiac nurses and the intensivist. Cardiac trauma is initially managed according to ATLS protocol. Depending on the type of trauma, one may either observe the patient or the patient may need open heart surgery to repair a defect. The prognosis of these patients depends on age, associated trauma, shock at the time of presentation, availability of a cardiac surgeon and mental status on arrival.[23]