Description: an abnormally accelerated heart rate, usually caused by a cardiac arrhythmia.
Some causes related to cardiovascular disease: There are several types of abnormal tachycardias (called "tachyarrhythmias"). Most of these are relatively benign in nature (though they can produce significant symptoms), but in patients whose tachycardia occurs in the setting of underlying heart disease, the malignant forms of tachycardia - ventricular tachycardia and ventricular fibrillation - can be the cause.
Some causes related to other disorders: A reactive tachycardia can occur in the setting of severe anemia, fever, thyroid disease, or other medical conditions.
Significance: The benign forms of tachycardia can produce significant symptoms and functional disability if it occurs often enough. The malignant forms of tachycardia - again, seen almost exclusively in patients with underlying heart disease - are an extremely common cause of sudden death. Symptoms of significant palpitations, and especially symptoms of sudden lightheadedness or syncope, need to be carefully evaluated by a physician.