In this condition, because of coronary heart disease, degenerative disease, or unknown cause the normal sinus node pacemaker may have been destroyed because of lack of blood supply or replaced by fibrous tissue. The heartbeat then becomes erratic and the heart may beat very slowly (28–42 beats per minute) and at other times may beat very quickly (100–150 per minute). Thus the condition is sometimes called bradytachycardia or sick sinus syndrome.
With sick sinus syndrome the patient may complain of dizziness or transient loss of consciousness (syncope) that occurs without warning. This condition is common and is most often seen in individuals over age 65. It is impor¬tant to document that these symptoms are due to a sick sinus, because they can also be caused by several other conditions including cerebral arterial disease which causes lack of blood circulation to the brain for which a pacemaker will not help. If the diagnosis is established as sick sinus syndrome, a permanent pacemaker is inserted and the patient gets complete relief of symptoms.