The condition may be due to atrial fibrillation or atrial flutter at the time of sleep, or it may be due to sinus tachycardia, which may also cause the patient to feel a fibrillation of the heart. There are also some people who may not have any arrhythmia or myocardial ischemia, but just feel uncomfortable on their own, which is highly considered to be caused by disturbance in the regulation of vegetative nerves or some kind of anxiety or depression. If you want to further clarify the diagnosis, it is recommended that the patient can have an electrocardiogram done when the uncomfortable condition occurs. In addition to this, heart rate and blood pressure can be measured. If arrhythmias do exist, thyroid function, serum ions, and blood tests can be further examined to help further clarify the cause of the fibrillation. Relatively more common are anemia, abnormalities in thyroid function, and ion disorders, all of which may cause the patient to experience a feeling of conscious heart flutter.