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Implantable Cardiac Defibrillator (cont.)

How do abnormal heart rhythms decrease blood delivery by the heart?

Abnormal heart rhythms, either too slow or too fast, decrease the delivery of blood by the heart. Bradycardia is a condition in which the heart rate is too slow. Bradycardias can be due to diseases of the SA node or the conduction tissues of the heart. The slow-beating heart delivers an insufficient amount of blood to the body.

Tachycardia is a condition in which the heart rate is too rapid. When the heart pumps too fast, the ventricles do not have enough time to fill their chambers with blood before the next contraction. Therefore, tachycardias can decrease the amount of blood delivered to he body. One of the effects of decreased blood delivery to the body is low blood pressure.

What is the cause of tachycardias?

Abnormally fast heart rates are called tachycardias. Tachycardias are caused by rapidly firing electrical signals arising from the walls of the atria or the ventricles. These rapidly firing signals override the signals generated by the SA node and cause the heart to beat too fast.

Tachycardias caused by electrical signals from the atria are called atrial tachycardias. Tachycardias caused by electrical signals from the ventricles are called ventricular tachycardias.

What are the symptoms of tachycardias?

Symptoms of tachycardias include:

  1. Palpitations or fluttering sensations in the heart;
  2. Lightheadedness (due to low blood pressure);
  3. Fainting spells or loss of consciousness (due to low blood pressure);
  4. Fatigue and weakness (due to lack of blood supply); and
  5. A flushing sensation.
Medically Reviewed by a Doctor on 9/13/2016


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