Irregular heartbeats are called arrhythmia. One of the causes of arrhythmia is a blunt trauma or injury to the heart called Traumatic myocarditis. Direct heart injury may not be necessary for development of post traumatic arrhythmia. Ventricular tachyarrhythmias are more common than others. These are relatively slow and therefore detected only during pauses in the normal rhythm. They are also called accelerated idioventricular rhythms (AIVRs). Usually they are harmless; however, they can turn dangerous and can even cause sudden death.
Usually signs would appear within 48 hours or less of trauma which may include arrhythmias, poor blood flow to the body, weakness and pale gums.