Sick sinus syndrome is characterised by persistently slow heart rate, decreased heart rate response to exercise (chronotropic incompetence), sudden pauses in the heart beat (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 diseases in elderly patients.
The symptoms result either from the slowness of heart rate (breathlessness and other symptoms suggestive of heart failure, reduced exercise tolerance) or from 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.
Diagnosis and treatment
The diagnosis of sick sinus syndrome is based on an ECG recording taken during symptoms (for example, ambulatory ECG recording Ambulatory ECG Monitoring).
Before the diagnosis is made it must be ascertained that the signs and symptoms are not caused by an acute illness, such as myocardial infarction or carditis.
If the patient's symptoms are evoked by bradycardia, any drugs that depress the functioning of the sinus node or block impulse conduction must be withdrawn (beta-blockers, digoxin, rate-slowing calcium-channel blockers, anti-arrhythmic drugs).
Remember also eye drops that contain beta-blockers.
If, after this, bradycardia continues to cause difficult symptoms, the patient needs a permanent pacemaker Cardiac Pacemakers and Monitoring Their Function. A pacemaker is also warranted in patients whose tachycardic episodes cannot be effectively treated with drug therapy due to intermittent bradycardia.