Final answer:
The correct spelling of the prefix for "fast heartbeat" is 'tachy-', forming the term tachycardia. It represents a heart rate above 100 beats per minute in a resting adult and requires professional assessment for appropriate treatment.
Step-by-step explanation:
The prefix for the term "fast heartbeat" is spelled tachy-. This prefix is used to form the medical term tachycardia, which refers to a condition where the heart rate is too fast, typically above 100 beats per minute in adults. While a fast heartbeat can be normal during exercise or as a result of stress, it is not normal in a resting patient and can be indicative of various conditions, including disorders of the autonomic nervous system, fever, anemia, hypoxia, or hyperthyroidism.
It is important to differentiate between the normal variations in heart rate among individuals and potential medical issues. In children, for instance, a resting heart rate above 100 beats per minute is not necessarily considered tachycardia. Treatment for tachycardia depends on the underlying cause but may involve medications, implantable cardioverter defibrillators, ablation, or surgery.