Syndrome of weakness of the sinus node

Dysfunction of the sinus node (syndrome of weakness of the sinus node) leads to the development of conditions in which the frequency of the atrial impulses does not correspond to physiological needs. Symptoms may be minimal or include weakness, palpitation, and syncope. The diagnosis is based on ECG data. Patients with clinical symptoms require the implantation of an artificial pacemaker.

Dysfunction of the sinus node (syndrome of weakness of the sinus node) includes a pronounced sinus bradycardia, recurring sinus bradycardia and atrial tachyarrhythmias (bradycardia-tachycardia syndrome), a stop or pause in the work of the sinus node and a sinus-atrial transient blockade. Sinus dysfunction occurs mainly in the elderly, especially those with other heart diseases or diabetes mellitus.

The pause of the sinus node is a temporary weakening of its activity, which is manifested on the electrocardiogram by the disappearance of the teeth within a few seconds or minutes. The pause usually provokes the slipping activity of the rhythm drivers located below (for example, atrial or nodal rhythm), which helps maintain heart rate and heart function, but long pauses lead to dizziness and syncope.

With the development of a transient sinus-atrial blockade, the SP node is depolarized, but the impulse to the atrial tissue is disturbed. With a sinus-atrial block of the 1st degree, the impulses of the sinus node slow down, and the ECG data remain normal.

• At type 1 degree (the wenke-bach periodical) of the sinus-atrial blockade, the pulse is delayed until the blockade occurs. This is recorded on the electrocardiogram in the form of progressive lengthening of the P-P interval , until the R- wave fails, causing a pause and the appearance of group contractions. The pause duration is less than two P-P intervals .
• In type 2 of the degree of sinus-atrial blockade, the pulse is blocked without a preliminary lengthening of the interval, which leads to the appearance of a pause, the duration of which is several times (more than twice) greater than the duration of the P-P interval , and group contractions.
• At 3 degrees of the sinus-atrial blockade, the procedure is completely blocked. There are no prongs, which reflects the stopping of the sinus node.

The most common cause of sinus node dysfunction is idiopathic fibrosis of the sinus node, which can be combined with degeneration of the underlying elements of the conducting system. Other causes include medicinal effects, excessive hypertension of the vagus nerve, as well as a large number of ischemic, inflammatory and infiltrative changes.

Symptoms of sinus node weakness syndrome

Many patients have no clinical manifestations, however, depending on the heart rate, all signs of brady- and tachycardia may appear. A slow irregular pulse indicates this diagnosis, which is confirmed by ECG data, pulsometry or 24-hour ECG monitoring. Some patients develop AF, and the underlying sinus node dysfunction is revealed only after the restoration of the sinus rhythm.

Prognosis and treatment of sinus node weakness syndrome

The forecast is ambiguous. In the absence of treatment, mortality is 2% per year, mainly due to primary organic heart disease. Annually, 5% of patients develop AF - a risk factor for heart failure and stroke.

Treatment involves the implantation of an artificial pacemaker. The risk of AF is significantly reduced when using physiological ECS (atrial or atrial-ventricular) compared with the use of ventricular stimulants. Antiarrhythmic drugs can prevent the development of paroxysmal tachycardia after implantation of ECS. Theophylline and hydralazine are a means of increasing heart rate in young patients with a bradycardia without syncope.