What is sick sinus syndrome?
In sick sinus syndrome, also called sinus node syndrome, the sinus node in the heart is damaged. As the body’s own pacemaker, it triggers the electrical impulses that cause the heart muscle to contract with each heartbeat. The faulty function of the sinus node leads to different types of cardiac arrhythmias.
The most common are sinus bradycardia, in which the heart beats too slowly, and sinus arrhythmia, in which the heart beats irregularly. In some cases, phases of slow and fast heartbeats alternate in sick sinus syndrome.
In some cases, the transmission of electrical signals from the sinus node to the heart muscle cells is temporarily or permanently disturbed. Doctors then speak of a sinuatrial block (SA block). In the worst case, no signals reach the heart muscle at all. In this case, it is a so-called sinus node arrest (sinus node standstill). Sinus node arrest and total SA block are life-threatening.
Sick sinus syndrome often occurs in older people whose hearts are weakened. They often already suffer from another arrhythmia.
Symptoms
When the heartbeat is too fast, so-called palpitations occur. This means that those affected experience their own heartbeat as unusually strong, fast or irregular, for example. Other symptoms of a cardiac arrhythmia are also possible, for example shortness of breath, chest pain and fatigue.
Causes and risk factors
The sinus node in the heart is responsible for generating a heartbeat and its speed. It generates approximately 60 to 80 electrical signals per minute that are sent to the heart muscle cells. When the muscle cells receive the electrical signal, they contract to form a heartbeat.
In sick sinus syndrome, the sinus node is scarred and thus loses its function. This is often caused by a heart disease such as coronary artery disease, muscular dysfunction of the heart (cardiomyopathy) or inflammation of the heart muscle (myocarditis).
Some affected individuals also suffer from a congenital malfunction of certain ion channels. Ion channels are proteins involved in the transport of electrolytes. Electrolytes are minerals such as sodium, potassium and magnesium. Electrolyte shifts via ion channels are essential for the transmission of electrical impulses generated by the sinus node.
Examination and diagnosis
Sometimes the doctor performs the ECG under physical stress on the ergometer. If the heart rate rises insufficiently under stress, this may be an indication of sick sinus syndrome.
In a so-called atropine test, the affected person receives atropine via the vein. Atropine actually causes an increase in heart rate. If sick sinus syndrome exists, the increase in heart rate does not occur.
Treatment
Sick sinus syndrome requires the use of a pacemaker to take over the job of the sinus node. The pacemaker is usually implanted under the skin above the right breast. The device is connected to the heart via two probes. If the function of the sinus node fails, the pacemaker takes over its task. If the heart races, medication is required. If phases of a too slow heartbeat alternate with palpitations, those affected receive a pacemaker and medication.
Since sick sinus syndrome is often based on another heart disease, it is necessary to treat this as well.
