An elevated or fast heart rate, called tachycardia, can be a long-term, chronic condition or occur suddenly. In some cases, very rapid heart rate can lead to palpitations and fluctuations in heart rhythms. It can also cause symptoms such as weakness, dizziness, shortness of breath and sweating. Normal heart rates vary but are considered to be between 60 to 100 beats a minute. A heart rate of more than 100 beats per minute is considered elevated. There are many causes of elevated heart rate.
Stress and Emotions
Stress and strong emotions such as anger, grief and joy can lead to an elevated heart rate. This is caused by the release of the hormone adrenaline or norepinephrine by the sympathetic nervous system in response to stress stimuli. If stress is chronic, the heart rate can remain elevated; Cleveland Clinic warns that this may be a factor in eventually causing high blood pressure or hypertension and damage to the arteries.
Fever and Infections
Infections and fevers can temporarily raise the heart rate, which usually subsides with the treatment of the underlying illness. The University of Illinois Medical Center explains that the elevated heart rate occurs because the infection puts the body under stress, causing the brain to signal the immune system to fight the invading pathogen. The heart rate increases in order to circulate more blood to the body tissues as the blood also carries the white blood cells and other immune cells.
Sinoatrial Node
The sinoatrial or sinus node is the heart's pacemaker because it controls the beating of the heart. If the sinus node begins firing electrical stimuli at a fast rate, sinus tachycardia or a rapid heart rate occurs. The American Heart Association notes that the sinus node can be triggered to increase the heart rate due to factors including stress, anxiety, anemia, an overactive thyroid gland, severe blood loss, dehydration and some medications.
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