Final answer:
Tachycardia is a faster than normal heart rate, diagnosed using an electrocardiogram (ECG).
Step-by-step explanation:
Tachycardia is a faster than normal heart rate. It can be caused by various factors, such as stress, exercise, or underlying medical conditions. Tachycardia is commonly diagnosed using an electrocardiogram (ECG), which measures the electrical activity of the heart. It is important to identify and treat tachycardia as it can lead to complications if left untreated.