Tachycardia is defined as a faster than normal heart rate; normal being between 60 to 100 beats per minute in a healthy adult at rest. The heart is made up of four chambers, two atria at the top and two ventricles at the bottom. The rhythm of the heart is controlled by electrical impulses that allow blood to pump through the chambers. Tachycardia occurs when there is a disruption or change in the cardiovascular system which increases the rate of electrical impulses. One major physiological condition that can produce a fast heart rate is pregnancy.
Cause
A fast heart rate is a common and normal symptom in pregnant women and may begin immediately upon becoming pregnant and may last through labor and delivery. The cause of tachycardia during pregnancy is due to the presence of a growing fetus in the uterus. The heart must work harder to supply more blood to the uterus to nourish the fetus. By the end of the pregnancy, as much as one-fifth of the woman's pre-pregnancy blood supply is routed to the uterus. This significant increase in blood volume of approximately 30 to 50 percent causes an increase in the amount of blood pumped by the heart, called cardiac output, which then requires the heart to pump faster. The heart rate may increase by 10 to 20 beats per minute.
Symptoms
A pregnant woman with a fast heart rate may notice a rapid pulse rate but also a slight increase in shortness of breath, dizziness or lightheadedness. If you are pregnant and notice an increased heart rate you should discuss it with your doctor to ensure it is due to the pregnancy and not some other condition.
Diagnosis
A doctor may perform a number of tests to make sure that there are no abnormalities in the heart rhythm that could indicate an underlying condition. After asking questions about medical and personal history, he may perform an EKG to record the electrical signals through different areas of the heart. He may also ask you to wear a Holter monitor, a portable EKG device, for a 24-hour period to monitor heart activity throughout the day. Finally, he may also request an echocardiogram, or ultrasound, to look at the heart anatomy and make sure there isn't anything abnormal. If these tests all appear normal, it is most likely the rapid heart rate is pregnancy related.
Management
A pregnant woman with a fast heart rate should maintain a good diet, moderate exercise and monitor appropriate weight gain for pregnancy. Avoid taking anything into the body that could exacerbate the heart such as caffeine, alcohol and tobacco. During periods of tachycardia due to pregnancy, you should rest as much as possible and avoid stress.
Related Considerations
Pregnancy may not only cause a rapid heart rate but other cardiac conditions such as arrhythmias, palpitations and murmurs. Increased blood volume can cause irregular beats, variations in heart sounds and the feeling of the heart pounding harder than normal. Blood pressure may decrease slightly during the second trimester but will return to normal during the third trimester.
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