Which of the following is a symptom of myocardial contusion?

Myocardial contusion, which is a bruising of the heart muscle typically resulting from blunt chest trauma, primarily presents with symptoms related to the cardiovascular system. Sharp, retrosternal chest pain is a common symptom due to inflammation and irritation of the cardiac muscle and surrounding structures. This pain can be similar to that experienced in myocardial infarction, but it is specifically related to the trauma impacting the heart.

In contrast, symptoms such as high-grade fever and rash are more indicative of infections or inflammatory diseases rather than trauma to the heart. Prolonged unconsciousness can occur in severe injury scenarios but is not specifically characteristic of myocardial contusion alone; it might be indicative of other complications such as head injury or shock. Severe headaches and dizziness are also nonspecific and could point to a variety of conditions ranging from neurological issues to dehydration. Thus, sharp, retrosternal chest pain is the most relevant symptom associated with myocardial contusion among the given choices.