Question: Can thyroid conditions affect my risk of developing an abnormal heart rhythm?
Answer :Thyroid conditions can increase the risk arrhythmia. Most of the information applies to an overactive thyroid or hyperthyroidism. The classic arrhythmia with hyperthyroidism is atrial fibrillation. This occurred in the previous president by the name of George Bush rather than our current president George Bush.
So Graves Disease, a cause of hyperthyroidism, is often associated with atrial fibrillation. An over active thyroid state can also cause a rapid normal rhythm or sinus tachycardia. On the other side of the spectrum hypothyroidism, an under active thyroid, can lead to ventricular enlargement -- enlargement of the lower chambers of the heart.
You may be subject to a prolongation of the QT interval, an interval on the electrocardiogram, beginning at the QRS complex ending at the end of the T-Wave. Prolongation of this QT interval can increase the risk of polymorphic ventricular arrhythmias which can cause sudden death.
So arrhythmias are more common and very common with hyperthyroidism, especially with atrial fibrillation, but they can also occur with hypothyroidism.