sick sinus syndrome
Also known as sinus node dysfunction, 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.
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.