Sinus node disease - Sinus nodal arrhythmias

Sinus node disease

Definition

Sinus node disease or sick sinus syndrome is a tachycardia/bradycardia resulting from damage to the sinus node.

Aetiology/pathophysiology

Sinus node disease is relatively common in the elderly dueto ischaemia, infarction or degeneration of the sinus node. The condition is characterised by prolonged intervals between consecutive P waves (sinus arrest) and periods of sinus bradycardia. Pauses in the sinus rhythm may allow tachycardias (typically atrial fibrillation) from other foci to emerge. This combination of fast and slow supraventricular rhythms is known as tachybrady syndrome.

Clinical features

Tachycardia may cause palpitations, and long pauses may cause dizziness and syncope. On examination the pulse rate may be regular, bradycardic, tachycardic or variable with pauses. Carotid sinus massage typically leads to a sudden and sometimes prolonged sinus pause. It should therefore only be attempted where there is monitoring and resuscitation equipment.

Complications

The most important complication is cardiac syncope, as in other forms of bradycardia. It may develop associated AV nodal block and Increased risk of thromboembolism.

Investigations

The diagnosis is usually made with a 24-hour ECG. Twelve-lead ECG may show evidence of underlying is-chaemia or previous myocardial infarction.

Management

Permanent pacing is required for symptomatic patients. In addition antiarrhythmic drugs may be required to control any tachycardia. Patients require anticoagulation to reduce the risk of thromboembolism.