86y old gentleman came with a history of frequent spells of extreme fatigue when he would feel blank and spaced out. His ECG and Echo were within normal limits. We connected a 24-hour Holter device with online monitoring. Within 20 minutes, we noted long pauses in heart beat 4 and 6 seconds long. We called him back to the hospital, admitted him, and put in a permanent pacemaker device. #MedTwitter #CardioTwitter

Sick sinus syndrome is a type of heart rhythm disorder. It affects the heart's natural pacemaker (sinus node), which controls the heartbeat. Sick sinus syndrome causes slow heartbeats, pauses (long periods between heartbeats) or irregular heartbeats (arrhythmias).
Sick sinus syndrome is relatively uncommon. The risk of developing it increases with age. Many people with sick sinus syndrome eventually need an implanted device called a pacemaker to keep the heart in a regular rhythm.

Signs and symptoms of sick sinus syndrome may include:
A sensation of rapid, fluttering heartbeats (palpitations)
Chest pain or discomfort
Confusion
Dizziness or lightheadedness
Fainting or near fainting
Fatigue
Shortness of breath
Slower pulse (bradycardia)

Causes of sick sinus node syndrome can include:
Age-related wear and tear of heart tissues
Damage to the sinus node or scarring from heart surgery
Heart disease
Inflammatory diseases affecting the heart
Medications to treat high blood pressure, including calcium channel blockers and beta blockers
Medications to treat irregular heartbeats (arrhythmias)
Some Alzheimer's disease medications
Neuromuscular diseases, such as muscular dystrophy
Obstructive sleep apnea
Rare genetic changes

Features of sick sinus syndrome include:
Sinus bradycardia. The sinus node produces a slow heartbeat.
Sinus arrest. Signals from the sinus node pause, causing skipped beats.
Sinoatrial exit block. Signals to the upper heart chambers are slowed or blocked, causing pauses or skipped beats.
Chronotropic incompetence. The heart rate is within regular range at rest but doesn't increase as much as it should with physical activity.
Tachycardia-bradycardia syndrome. The heart rate alternates between unusually slow and fast rhythms, often with a long pause between heartbeats

Complications
Complications of sick sinus syndrome include:
Atrial fibrillation, a type of irregular heartbeat (arrhythmia)
Heart failure
Stroke
Cardiac arrest

The treatment in many cases is to implant a permanent pacemaker device.