Commotio cordis is a disruption of the heart's natural rhythm caused by a blow to the thorax during a specific time in the heart's cycle. It occurs most frequently in sports including baseball, boxing, lacrosse, rugby, football and others. It occurs most commonly in males with a mean age of 14.7 years.
What are the symptoms?
Commotio cordis is a relatively simple phenomenon is so far that it can occur without a pre-existing condition and, in fortunate cases, can have no lasting damage. When it occurs, commotio cordis causes a cardiac arrest in the patient which must be treated with a defibrillating shock. The symptoms and lasting effects depend how quickly this shock is applied and on the quality of cardiopulmonary resuscitation (CPR) performed on the patient. CPR must be started within 3 minutes for the best chance of survival.
Unfortunately, there is a high death rate associated with commotio cordis as Automated External Defibrillators (AEDs) are not widely available at schools in the UK.
What causes commotio cordis?
Commotio cordis is caused by a blow to the area of the chest directly above the heart during the ascending half of the T wave of the heart's rhythm cycle. This 'window' is only 10-30 milliseconds long (explaining the rarity of commotio cordis occurring) when the ventricular myocardium is repolarising, moving from systole to diastole.
It is estimated that an impact of 50 joules or greater is needed to cause commotio cordis. Impacts of 130j, 450j and over 1000j have been measured by hockey pucks, karate punches and certain professional boxers' punches respectively, highlighting the heightened risk of commotio cordis during sporting activities. The 50j threshold may be significantly lower, however, if the patient has a pre-existing heart condition which restricts blood flow to the heart and coronary artery. Young people are also more likely to have an underdeveloped thorax which could cause a greater vulnerability.
Because commotio cordis disrupts the heart's rhythm and causes ventricular fibrillation, the only effective treatment is a shock from an AED, although cardiopulmonary resuscitation can maintain around 30% of cardiac output before a shock is applied. It has been estimated that the survival rate of commotio cordis has increased from 15% to 35% because of the increasing availability of AEDs at schools and sporting venues.