What is the cause of sick sinus syndrome?

As a medical professional with expertise in cardiology, I can provide you with an informed explanation of the causes of sick sinus syndrome (SSS). Sick sinus syndrome is a group of abnormal heart rhythms that originate in the sinus node, which is the heart's natural pacemaker. The causes of SSS can be categorized into intrinsic (related to the heart itself) and extrinsic (related to factors outside the heart) factors. Intrinsic causes often involve structural changes or damage to the sinus node or the surrounding tissue. These can include: 1. Age-related degeneration: The most common cause of SSS is the natural aging process, which can lead to fibrosis and scarring within the sinus node. 2. Endocardial fibroelastosis: This is a condition where the endocardium (inner lining of the heart) becomes thickened and can affect the sinus node. 3. Cardiomyopathy: This is a disease of the heart muscle that can impair the function of the sinus node. 4. Congenital heart disease: Some people are born with a malformed sinus node or other heart abnormalities that can lead to SSS. Extrinsic causes can include: 1. Viral infections: Certain viral infections can cause inflammation of the heart, known as myocarditis, which can affect the sinus node. 2. Autoimmune diseases: Conditions like lupus can lead to inflammation that affects the heart and its rhythm. 3. Toxins and medications: Some substances, including alcohol, tobacco, and certain medications (especially those that affect the heart rhythm), can cause SSS. 4. Elective cardiac procedures: Procedures like catheter ablation or implantation of a pacemaker can sometimes damage the sinus node. It's important to note that in some cases, the cause of SSS may remain unknown, which is referred to as idiopathic SSS.

Sick sinus syndrome (SSS) is a general term for a group of disorders caused by a malfunctioning sinus node. The sinus node acts as a pacemaker inside of the heart. Sinus rhythm (the normal beating of the heart) is controlled by electrical impulses from the sinus node.