sick sinus syndrome
Sick sinus syndrome, also known as sinus node dysfunction, is abnormal functioning of the sinoatrial node (the natural pacemaker of the heart) that leads to various arrhythmias, including brachycardia (slow heart-rate), alternating brachycardia and tachycardia (fast heart-rate), or very short episodes of cardiac arrest (complete stoppage of the heartbeat.
The most common cause of sick sinus syndrome is coronary artery disease, but the conduction can also be stopped by a cardiomyopathy.
Symptoms of sick sinus syndrome include light-headedness, dizziness, fainting, and, occasionally, palpitations (awareness of the heartbeat).
The diagnosis is confirmed by a 24-hour, ambulatory walking electrocardiogram (ECG) recording.
Treatment is usually by antiarrhythmic drugs and the fitting of an artificial pacemaker.