Syndrome, sick sinus: Symptoms of dizziness, confusion, fainting, and heart failure due to a problem with the sinus node of the heart, which acts as the body's natural pacemaker. If the sinus node is not functioning normally, it is reflected in an abnormally slow heart rate (bradycardia). This can cause poor pumping by the heart, which can impair the circulation.
Diagnosis is usually by electrocardiogram (EKG). Treatment includes medications, such as the class of drugs called calcium antagonists.