Blunt chest trauma commonly results in chest wall injuries, but may also be associated with significant cardiac and great vessel injuries. Blunt trauma to the chest primarily occurs from abrupt deceleration such as in motor vehicle crashes. Because of inertia of motion, the internal organs remain in motion and get compressed between the sternum and the spine, with the abrupt stoppage of the motor vehicle.⁴ The second most common cause of blunt chest trauma is an explosion, in which cardiac injury can be from multiple sources. The primary cause is the blast that creates a pressure wave which can result in tissue disruption and lead to a tear in a major blood vessel.⁵ In addition, penetrating injuries from nearby objects flying from the area of the blast may also cause cardiac injury.

Blunt chest trauma results in five major injuries that occur either in isolation or in conjunction with each other: myocardial contusions, traumatic aortic dissection or tear, flail chest, tracheobronchial disruption, and sternal fractures.⁶ The severity of cardiac injury may range from minor, asymptomatic myocardial concussion to ventricular rupture. Cardiac concussion represents segmental wall-motion abnormality without evidence of myocardial injury in the form of elevated plasma cardiac enzymes.⁷ On the other hand, cardiac contusions represent actual myocardial cell injury, leading to myocardial necrosis and hemorrhage with elevated plasma cardiac biomarkers.⁵ Extensive myocardial contusion with hemopericardium may develop in the absence of external thoracic injuries, and thus appropriate testing should be performed depending on the impact of the injury.⁸ Because the right ventricular free wall is located anteriorly, it is the most common site of ventricular injury with blunt chest trauma. Patients with ventricular free wall rupture present with severe hypotension and rapid diagnosis, and early operative intervention is lifesaving.⁹ Occasionally, relatively minor impact injuries may lead to contained ventricular rupture and ventricular pseudoaneurysm.¹⁰ Atrial rupture occurs less often, with right atrial rupture occurring more frequently than does left atrial rupture because of its relative anterior location.¹¹ Cardiac tamponade due to atrial rupture occurs more slowly than with ventricular rupture because of lower pressures in the atria. Despite the anterior location of the tricuspid and pulmonary valves, the aortic and mitral valves are affected more commonly in trauma because of high mural pressures.¹² Valve rupture as a result of trauma can cause rapid heart failure and is usually manifested with sudden onset of shortness of breath, severe orthopnea, and a murmur (Figure 23.1). Ventricular septal rupture can be associated with myocardial contusion and initially may not cause any symptoms, but present later with heart failure.¹³ A rare complication of blunt cardiac injury is myocardial infarction secondary to coronary artery injury, leading to dissection, laceration, and thrombosis.¹⁴ The left anterior descending artery is the coronary artery most commonly affected vessel because of its anterior location.¹⁵

Pericardial injury and effusion may occur from direct high-energy impact or secondary to a significant increase in intra-abdominal pressure (Figure 23.2). A pericardial tear typically involves either the pleuropericardium or diaphragmatic pericardium. Clark et al. reported that the left pleuropericardium was involved in 50% of cases, followed by diaphragmatic pericardium, right pleuropericardium, and the superior pericardium.¹⁶ Cardiac evisceration or herniation is a serious complication from pericardial rupture, and is associated with a high mortality rate. It can lead to torsion of the great vessels along with strangulation of the heart and impaired cardiac output.¹⁷

Commotio cordis is a fairly low-impact blunt trauma to the chest. This usually occurs in athletes with a projectile object such as a baseball, lacrosse ball, or hockey puck that strikes the chest at a certain time of the cardiac cycle and triggers ventricular fibrillation. It has frequently been noted in males and in individuals without underlying structural heart disease.¹⁸ Even though the injury is a mechanical event, the cause of death is secondary to an electrical event or arrhythmia. The timing of the impact in relation to the cardiac cycle has a direct relation to the generation of ventricular fibrillation. When the impact
happens to fall in the early ventricular repolarization phase, within 20 to 40 ms of the upslope of the T-wave, it can trigger ventricular fibrillation with sudden cardiac arrest and death.¹⁹ The velocity of the projectile also seems to have a relation to the onset of ventricular fibrillation. If the impact is less than 40 miles per hour, there is an increased chance of developing ventricular fibrillation, whereas if the velocity is more than 40 miles per hour, it may cause myocardial contusion instead.²⁰

Over the past several years, the incidence of penetrating cardiac trauma has increased with the rise in stab wounds and gunshot injuries. Penetrating cardiac injury is highly lethal, with mortality rates of about 70% to 80%.²¹ In the past, stab wounds were more common; however, recently, gunshot wounds have been noted to be more frequent—even in the civilian setting—and carry a higher mortality than do stab wounds.²² The right ventricle is the most common site of entry—62% of penetrating cardiac injuries—because of its anterior location. Even though the left ventricle is less affected with penetrating injuries, the mortality is significantly higher at 98%.²³ The two most common causes of death in individuals with penetrating cardiac trauma are hemorrhagic shock (77.5%) and cardiac tamponade (22.5%).²⁴

Thoracic aortic injuries can result from either blunt or penetrating trauma (ie, stab wounds or gunshot injuries). Aortic injuries are more commonly caused by blunt trauma, typically deceleration injuries from a motor vehicle crash or from a fall from height. Most blunt aortic injuries occur because of head-on motor vehicle crash (72%), followed by side impact (24%), and then by rear impact crashes (4%).²⁵ Trauma to the aorta occurs most commonly at the isthmus, approximately 90% of the time.²⁶ This is the portion of the proximal descending thoracic aorta that lies between the origin of the left subclavian artery and the ligamentum arteriosum, which tethers the aorta. With deceleration injuries, shearing forces and luminal compression against this fixed portion of the aorta may lead to a tear and transection of the aorta.²⁶ Blunt trauma to the aorta may also result in aortic laceration that is typically a transverse intimal tear or an aortic transection where the injury traverses through the three layers of the vessel wall. Occasionally, aortic rupture is contained by the adventitia or periaortic tissue leading to an aortic pseudoaneurysm or may cause a hematoma in the wall of the aorta leading to an aortic intramural hematoma.²⁷ Aortic dissection, which is a longitudinal tear in the aortic wall, may also occur secondary to blunt trauma. Penetrating aortic injuries secondary to either a stab wound or a gunshot wound has a very high mortality rate despite contemporary improvement in trauma care in recent years.²⁸