What causes a high heart rate, or tachycardia can be many things. Tachycardia is identified by how fast the heart is beating and by how the heart rhythm looks on an electrocardiogram. A regular heart rhythm over 100 beats per minute is called sinus tachycardia. An irregular heart rhythm over 180 bpm is probably atrial fibrillation. Identifying the heart rhythm can help you identify the cause of the tachycardia. A thorough patient history is needed too.
Stress
Donna D. Ignatavicius, M.S., R.N., and M. Linda Workman, Ph.D, authors of "Medical-Surgical Nursing--Critical Thinking for Collaborative Care," explain that part of the human response to stress, both psychological and physical, is an increase in heart rate. The heart pumps faster and harder to provide muscles with necessary energy for self defense, escape or exertion.
Stimulants
Stimulants like caffeine can cause a high heart rate. Certain medications that contain stimulants like ephedrine or epinephrine can cause tachycardia, as do many street drugs.
Low Fluid Volume
Barbara McLean, Critical Care Nurse Practitioner, and Dr. Janice Zimmerman, authors of "Fundamental Critical Care Support" discuss how a low fluid volume in the body causes tachycardia. In response to severe dehydration or blood loss, the body increases the heart rate to help maintain blood pressure
Anemia
A low hemoglobin, or red blood cell count, is called anemia. Anemia means there is not enough oxygen for tissues and organs; the body increases the heart rate to increase tissue oxygenation.
Infection
Fever that accompanies an infection can cause tachycardia. When the body has a fever it demands more energy. A rapid heart rate delivers more nutrient-rich blood to the body to fight the infection.
An infection that is affecting the entire body is called a systemic infection, or sepsis. Sepsis, if left untreated, can lead to shock and death. Early in the course of sepsis, a person's heart rate will increase in order to provide adequate blood flow to vital organs in an attempt to prevent low blood pressure and shock.
Conduction Abnormalities
As discussed earlier, there are different types of tachycardia. Conduction abnormalities are problems in the heart that interfere with normal heart rate and rhythm. The American Heart Association explains that a problem with how the heart sends and receives signals to beat can come from either the upper chambers of the heart, the atria, or from the lower chambers of the heart called the ventricles.
Sometimes the natural pacemaker of the heart is sick and causes irregular and fast heart rates. Sometimes another part of the heart muscle in the atria competes with the natural pacemaker and causes a very high heart rate of 300 to 600 bpm.
A heart attack or thyroid disease can cause conduction abnormalities in the heart and lead to a condition called ventricular tachycardia. This rapid heart rate in the ventricles prevents the heart chambers from filling with blood properly, resulting in low blood pressure. The cause of this very high heart rate must be corrected quickly.
References
- "Medical-Surgical Nursing--Critical Thinking for Collaborative Care"; Donna D. Ignatavicius M.S., R.N., & M. Linda Workman Ph.D; 2006
- "Fundamental Critical Care Support (4th ed.)"; McLean, B. & Zimmerman, J. L.; 2007
- American Heart Association: Tachycardia
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