Sick sinus syndrome
Sick sinus syndrome is characterised by persistently slow heart rate, decreased heart rate response to exercise, sudden pauses in the normal activity of the sinusnode (sinus arrest or sinoatrial block) and occasional episodes of nodal or atrial escape rhythm. The syndrome refers to a disease affecting the sinus node itself and not to a disturbed regulation of the functioning of the node as is seen in reflex bradycardia. It is usually seen in association with other cardiac problems in elderly patients. The symptoms are brought on by the slowness of the heart rate (breathlessness and other symptoms suggestive of heart failure) or the sinus pauses (presyncope or syncope). Atrial fibrillation is also common as are other atrial tachyarrhythmias (bradycardia-tachycardia syndrome). In these patients, long sinus pauses are often noted following the discontinuation of the atrial arrhythmia.