Commotio Cordis – Pathophysiology, Causes and Prevention

What is Commotio Cordis?

Commotio cordis can happen to a person with a normal heart and occurs when a blunt trauma to a person’s chest often while playing sports leads to cardiac arrest where their heart stops pumping blood. Commotio cordis typically occurs in children and adolescents. The impact needs to be forceful and occur at a very particular moment in the heart’s electrical cycle. When this happens, the normally well-organized electrical signals that control the heart become chaotic. The uncoordinated electrical pulses cause the heart, and in particular the large blood-pumping chambers called the ventricles, to twitch and spasm in what is known as ventricular fibrillation, a type of heart arrhythmia.

When a heart is in ventricular fibrillation, it is no longer able to pump blood throughout a person’s body, and their organs begin to suffer damage due to lack of oxygen. Heart attacks, abnormal heart or artery structure, and many other issues can lead to ventricular arrhythmia. Regardless of the cause, if a person’s heart stops beating, the result can be deadly.

Pathophysiology of Commotio Cordis

Commotio Cordis is a diagnosis of exclusion. Commotio Cordis is a primary arrhythmic event that occurs when the mechanical energy generated by a blow is confined to a small area of the precordium (generally over the left ventricle) and profoundly alters the electrical stability of the myocardium, resulting in ventricular fibrillation. In most instances (58%), the patient is struck on the chest by a projectile, commonly pitched, thrown, or batted, and the speed of the projectile is estimated to be 30-50mph on impact. The impact occurs within a specific 10-30 millisecond portion of the cardiac cycle. This period occurs in the ascending phase of the T wave, when the ventricular myocardium is repolarizing, during the transition from systole to diastole (relaxation). This small window of vulnerability makes commotio cordis a very rare event.

Commotio Cordis Epidemiology

Approximately 10 to 20 cases are added to the Commotio Cordis Registry yearly. Until the late 1990s, commotio cordis was only rarely reported. It is thought that this increase in the number of cases is not due to an increase in incidence but rather to a greater awareness based on the 1995 New England Journal of Medicine report on commotio cordis. Many more cases of commotio cordis are now recognized as such. Indeed, what was thought to be a uniquely North American phenomenon is increasingly being reported in countries outside the United States.

Commotio cordis primarily affects young individuals, generally in adolescence. In the Registry, the mean age is 15 years; there have been very few commotio cordis victims over the age of 20 years. It traditionally has been thought that the stiffening of the chest wall contributes to this decrease in incidence in older individuals; however, this decreased incidence in those over 20 years of age is likely also influenced by the reduced ball-related sports participation by older individuals. Victims are overwhelmingly male. A partial explanation for the overwhelming predominance of males is that they populate the majority of sports in which commotio occurs, but it appears unlikely that the 95% predilection for males reflects a 95% incidence of chest wall impact in sports and activities of daily living.

It is suspected that there may also be some gender-related biological susceptibility to chest wall impact induced sudden cardiac death. Indeed, other arrhythmic conditions demonstrate a gender predilection for arrhythmia, including females with long-QT syndrome and males with Brugada syndrome. Genetic differences in ion channels between the sexes or biological modification of these channels by sex hormones may be involved in the male susceptibility to commotio cordis.

Causes

Commotio cordis can occur if you get a 90-degree hit from a baseball or another small, hard sports object on the left side of your chest, right over your heart.

On the left side of your chest, your heart is located. A baseball, lacrosse ball, or hockey puck coming straight towards your chest at 40 or 50 mph, for instance, could cause commotio cordis.

Symptoms of Commotio Cordis

Symptoms can include:

  • A sudden collapse, with stumbling for a few seconds beforehand
  • Unresponsiveness
  • Not breathing
  • No pulse
  • No heartbeat
  • Bluish or purple skin (cyanosis) due to a lack of oxygen
  • Seizures
  • Bruising or injury to the chest

Common risk factors of Commotio Cordis

Commotio cordis happens most often to people who:

  • Play sports, especially those involving a baseball or another hard object (commonly a lacrosse ball, softball or hockey puck)
  • Are younger than age 20 (average age of around 15)
  • Are male or assigned male at birth (AMAB)

Complications of commotio cordis

The serious complications, include:

Cardiac arrest – Cardiac arrest is a life-threatening condition that occurs when the heart suddenly stops pumping blood to the body.

Heart damage – Heart damage can occur if the heart is unable to pump effectively after the arrhythmia.

Brain damage – Brain damage can occur if the brain does not receive enough oxygenated blood during the arrhythmia.

Diagnosis

During resuscitation, rhythm strip analysis may help guide interventions. Point-of-care ultrasound may be useful to exclude concomitant injuries like pneumothorax or pericardial effusion/tamponade.

Radiography has essentially no role in the management of commotio cordis, but may be important to identify concomitant serious injuries like a sternal fracture.

The American Heart Association and the American College of Cardiology provide a strong recommendation based on moderate quality evidence that after resuscitation, patients with commotio cordis should undergo “a comprehensive evaluation for underlying cardiac pathology and susceptibility to arrhythmias”.

An electrocardiogram (ECG) may reveal evidence of myocardial injury, but it may be difficult to distinguish whether it occurred primarily, or secondary to the cardiac arrest. Troponin and echocardiogram may be useful to determine the presence of myocardial contusion. An echocardiogram may also help identify if there are other underlying structural abnormalities. Stress testing or cardiac catheterization may be considered to evaluate for coronary artery disease, as appropriate. Pharmacological testing for Brugada syndrome and long-QT syndrome should also be considered.

Treatment

Initial efforts should focus on resuscitation from cardiac arrest due to ventricular fibrillation. This includes closed chest compressions and early defibrillation. If the arrest is prolonged, it may be prudent to provide rescue ventilation and/or medications to improve coronary perfusion pressure (e.g., epinephrine).

For an isolated blunt cardiac injury resulting in dysrhythmia, stabilization of the electrical activity may be the only necessary intervention. After resuscitation, appropriate post-cardiac arrest care should be implemented.

It may be appropriate to consider other forms of traumatic arrest, depending on the clinical scenario. These may include tension pneumothorax, cardiac or coronary laceration or tamponade, traumatic valvular injury, pulmonary laceration or great vessel injury, hemorrhagic shock, etc., or extrathoracic injuries, depending on the mechanism of injury.

Prevention of Commotio Cordis

It may be impossible to prevent injuries to the chest in sports or in other circumstances, such as car accidents. However, there are steps that can be taken to reduce complications from commotio cordis, including loss of life.

Some important steps youth teams or leagues can take to combat commotio cordis include:

  • Having an athletic trainer present at practices and games
  • Making sure an AED is available at all athletic facilities and that coaches and others involved know how to access it easily
  • Educating trainers, coaches, parents, and athletes about how to recognize commotio cordis symptoms, perform CPR, and use an AED

Efforts to reduce the likelihood of the chest injury itself include:

  • Making sure pads and other protective equipment are worn properly and consistently
  • Teaching athletes how to avoid being hit with a ball, puck, or other implement that could cause this injury
  • Avoiding strength and weight disparities between athletes whenever possible
  • Using safety baseballs and hockey pucks, which are cushioned

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