sinus dysrhythmia, an irregular heart rhythm characterized by alternate increases and decreases in the heart rate. It is often associated with the vagal effects of respiration, which causes the heart rate to increase on inspiration and decrease on expiration. Nonrespiratory sinus dysrhythmia can be caused by multiple sclerosis, digitalis, myocardial infarction, and increased intracranial pressure. Treatment is not necessary unless the patient is symptomatic with decreased cardiac output; then atropine is given.
