Final answer:
Tachycardia, or a heart rate above 100 bpm, can be caused by pregnancy, stress, medical conditions like fever, anemia, or hyperthyroidism, and many other factors. It is abnormal in resting adults and treatment depends on the specific underlying cause.
Step-by-step explanation:
Tachycardia, defined as a heart rate (HR) above 100 beats per minute (bpm), can have various triggers in an individual. Situations such as pregnancy or extreme stress can stimulate the autonomic nervous system or the limbic system, leading to an increase in heart rate. Additionally, tachycardia may be caused by medical conditions like fever, anemia, hypoxia, hyperthyroidism, or even cardiomyopathies and certain valve disorders. Hypersecretion of catecholamines and acute exposure to radiation are other potential causes. While in children, resting heart rates above 100 bpm can be normal, in adults it indicates an abnormal heart rhythm, unless they are athletes with typically lower heart rates. Treatment options vary depending on the underlying cause but may include medications, implantable cardioverter defibrillators (ICD), ablation, or surgery.