Final answer:
Tachycardia is a condition where the heart rhythm is rapid, usually at a rate of 150-200 BPM, and is different from bradycardia, arrhythmia, and fibrillation. The term refers specifically to a fast heart rate above 100 beats per minute in resting adults.
Step-by-step explanation:
A rapid heart rhythm, usually at a rate of 150-200 beats per minute (BPM), is called tachycardia. Bradycardia is characterized by a slow heart rate, below 60 BPM, while arrhythmia refers to any irregularity in the heart's rhythm, which can include tachycardia or bradycardia. On the other hand, fibrillation refers to a very fast and irregular heart rhythm that can be life-threatening. For a resting adult, normal heart rate ranges from 60-100 BPM, and having a heart rate above 100 BPM when at rest is generally considered to be tachycardia. Tachycardia can be caused by various conditions, including stress, fever, anemia, hypoxia, hyperthyroidism, or cardiomyopathies, and treatment depends on the underlying cause.