There are several causes of an irregular heart rate, or arrhythmia, but primary ones include coronary heart disease and medications, according to Healthline. Coronary heart disease is often the most serious cause of arrh... More »

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An irregular heart rate can be caused by a panic attack or by strong emotions, such as fear, stress or anxiety, according to WebMD. An irregular heartbeat can also be caused by intense exercise. More »

Causes of irregular heartbeat, called arrhythmia, include high blood pressure, overactive or underactive thyroid gland, excessive alcohol consumption and changes in the structure of the heart, according to Mayo Clinic. O... More »

Causes of irregular heartbeat, called arrhythmia, include high blood pressure, overactive or underactive thyroid gland, excessive alcohol consumption and changes in the structure of the heart, according to Mayo Clinic. O... More »

Pacemakers not only regulate heart rate, but also record the heart's electrical activity and rate, according to the National Heart, Lung and Blood Institute. After a pacemaker is surgically inserted, it must be programme... More »

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The vagus nerve affects heart rate by increasing blood vessel dilation and lowering blood pressure, according to Healthline. Vagus nerve stimulation can cause a drop in blood flow to the brain and a loss of consciousness... More »

The causes of a high heart rate include exercise, caffeine consumption, sudden stress, smoking and taking certain medications. In some cases, an elevated heart rate is a sign of heart disease, congenital heart abnormalit... More »

www.reference.com Health Conditions & Diseases Cardiac Health