What Causes a Rapid Heartbeat?

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A rapid heartbeat, also known as tachycardia, is caused by a number of factors, including exercise, anxiety or fear, a current or previous heart attack, blocked arteries, high blood pressure, thyroid disorders, substance abuse, stress and some medications and supplements, according to Mayo Clinic. Tachycardia can be normal or a symptom of a bigger problem.

Tachycardia is defined as a resting heart rate that is above 100 beats per minute. Normal heart rates are between 60 to 100 beats per minute, according to Mayo Clinic.

There are three types of tachycardias, which are sinus tachycardia, atrial or supraventricular tachycardia and ventricular tachycardia, according to the American Heart Association. Sinus tachycardias are an increase in a normal heart rate, which happens when someone is scared or anxious, has a fever, is under severe stress or has exercised heavily. Atrial or supraventricular tachycardias originate in the upper chambers of the heart. This type is most common in children and women, those with anxiety, those who are tired or those who drink a lot of caffeine or alcohol or smoke a lot. The most common symptoms are dizziness, palpitations, chest pain and shortness of breath.

Ventricular tachycardias originate in the lower chambers of the heart and are the most dangerous type of tachycardia, notes the AHA. The most common causes are a restriction of the blood flow to the heart, cardiomyopathy and sarcoidosis. Symptoms include dizziness, unconsciousness and cardiac arrest.