At rest, the normal heart rate in an adult ranges from 60–100 beats per min. Heart rate that exceeds this normal range, i.e. a resting heart rate over 100 beats per minute, is called tachycardia.
Excessive and rapid heartbeats cause the heart to pump less efficiently decreasing blood flow to the heart and rest of the body. Tachycardia as a response to normal physiological situations may cause no symptoms or complications. Tachycardia due to heart problems can seriously compromise normal heart function, increase stroke risk, or cause sudden cardiac arrest or heart attack.
Sinus tachycardia is a fast but steady increase in the heart rate usually in response to normal physiological situations like exercise, stress, anger, dehydration, fright, fever, pain, intake of stimulants such as caffeine, etc. It can also be a response to certain drugs, anemia, heart failure, myocardial infarction, increased thyroid secretion, pulmonary embolism, etc. The highest heart rate a person can achieve without severe problems is termed maximum heart rate. For young adults it is most commonly calculated by subtracting the age from 220. Physiologic sinus tachycardia does not require treatment. Underlying causes, if present, are treated.
Supraventricular tachycardia (SVT) is due to abnormal firing of electrical signals in the upper chambers (atria) of the heart giving rise to a series of early beats in the atria. Ventricular tachycardia is due to abnormal firing of electrical signals in the heart’s lower chambers (ventricles). They cause incomplete filling of the heart, thereby compromising the blood flow to the body. Ventricular tachycardia is usually associated with heart disorders and can be a life-threatening. Treatments are aimed at controlling the heart rate and manage the conditions causing it.