Final answer:
Unstable tachycardia, defined as a heart rate above 100 bpm that causes symptoms, is indeed true. Treatment varies based on the underlying cause of the tachycardia.
Step-by-step explanation:
True, unstable tachycardia exists when the heart rate is too fast for the patient's clinical condition and the excessive heart rate causes symptoms such as dizziness, shortness of breath, lightheadedness, rapid pulse, heart palpitations, chest pain, or fainting (syncope). Tachycardia is typically defined as a heart rate above 100 beats per minute (bpm) and can be due to various factors including stress, fever, anemia, hypoxia, hyperthyroidism, and more. However, it's important to note that a normal resting heart rate for children can be above 100 bpm and is not considered tachycardia. Treatment depends on the underlying cause but may include medications, cardiac procedures like ablation, or even implantable devices such as cardioverter defibrillators.