Bradycardias may be caused by a disruption or blockage anywhere in the normal conduction system. Not all bradycardias are abnormal, or a sign of illness. Some very beneficial medicines produce slow heart rates and protect the heart from stress. Tachycardias are classified by the location of abnormal conduction. Tachycardias may also originate in the lower chambers, or ventricles.
Some people have both brady- and tachyarrhythmias.
There may be a normal heart rhythm at times, followed by periods of bradycardia or tachycardia. Whether your heart beat is too slow or too fast, the result may be a decreased pumping ability of the heart. When this happens, symptoms occur. Symptoms that can occur are dizziness, tiredness, blurred vision, shortness of breath, chest pain, and loss of consciousness. Since similar symptoms may result from other problems, careful evaluation is necessary to make a proper diagnosis.