An increased heart rate over 100 is considered a tachycardia. In most patients, high rates cause patients to become symptomatic. This occurs because an increased heart rate does not allow the heart enough time to fill with blood and in turn reduces the amount of blood pumped into the body. When the top portion of the heart, known as the atrium has a very high rate this can result from conditions such as supraventricular tachycardia, atrial flutter, and/or atrial fibrillation. This can result in symptoms such as shortness of breath, palpitations, weakness, chest discomfort, and an increased risk of blood clots. These arrhythmia’s usually can be treated with medication and/or cardiac procedures.

A sustained fast heart rate in the lower portion of the heart, the ventricles, can be life threatening due to the fact that the bottom portion of the heart is critical in pumping oxygenated blood to the body. Ventricular arrhythmias may also cause dizziness, palpitations, chest pain, nausea, and shortness of breath.