Sinus pauses or severe bradycardia results in central nervous system (CNS) underperfusion which manifests in paroxysmal presyncope or syncope. When symptoms do develop, they are usually attributed to hypo-perfusion to vital organs with high oxygen demand. In the early stages, most patients are asymptomatic. The natural history of sinus node dysfunction is usually a slow progression over decades. Several pharmacologic and toxic substances can produce a similar effect on the SA node these include class I to IV antiarrhythmic medications, digoxin, lithium and sympatholytic medications. Increased intracranial pressure (Cushing’s reflex) also causes bradycardia. Obstructive sleep apnea may cause bradycardia by profound hypoxia during episodes of apnea. Furthermore, metabolic derangements such as hypothyroidism, hyperkalemia, hypokalemia, hypocalcemia, hypoxia, and hypothermia can lead to depression of the pacing function of the SA node. These can occur in conditions where there is abnormally increased vagal tone such as carotid sinus hypersensitivity, vasovagal syncope, and autonomic dysfunction. Several external causes that can affect the pacing function of the SA node. Because the SA node is located within the atrial wall, ischemic injury by atherosclerosis of the arteries feeding the SA node is unusual. Infectious agents such as bacterial endocarditis and Chagas disease commonly result in atrioventricular conduction problems rather than sinus node dysfunction. Damage to SA node or the sinus nodal artery may occur after cardiothoracic surgery from valve replacement, correction of congenital heart disease or heart transplant. Infiltration of the SA node by sarcoidosis, amyloidosis, hemochromatosis, collagen vascular disease or metastatic cancer results in SA node dysfunction. Heart failure and atrial tachyarrhythmias have been shown to induce cellular remodeling of the sinus node in animal models. Recent studies have identified several mutations in the ion channels explaining familial and congenital forms of sick sinus syndrome. While the most common intrinsic factor leading to sinus node dysfunction is age-related degeneration of the SA node, sinus node dysfunction can be a result of congenital disorders, arrhythmias, infiltrative disorders and surgery. Blood-thinning medicines are used to help prevent a stroke.The etiologic factors leading to sinus node dysfunction can be classified into two categories: intrinsic pathology to the sinus node itself, typically results from fibrosis of the nodal tissue and external causes that affect the SA node function. Medicines might be used to prevent the heart from beating too fast. Treatment may include a pacemaker to prevent the heart from beating too slow. You may have symptoms such as palpitations and light-headedness. It can occur when the heart's natural pacemaker is damaged. This abnormal heart rhythm problem is often seen in people who have been diagnosed with atrial fibrillation. In tachy-brady syndrome, also called tachycardia-bradycardia syndrome, the heart sometimes beats too quickly (tachy) and sometimes beats too slowly (brady). You and your doctor can decide what treatment is right for you. If the syndrome doesn't cause symptoms, it may not be treated. Treatment of sick sinus syndrome depends on what is causing it. Periods of fast arrhythmias (supraventricular tachycardias), especially atrial fibrillation or atrial flutter, alternating with periods of very slow heart rates ("tachy-brady" syndrome).Prolonged periods of time when the heart rate is spontaneously very slow and does not increase as it should with activity (persistent sinus bradycardia).Periods of time when the sinus node does not fire at all (sinus pauses) and other areas of the heart take over and cause the heart to beat.People with this syndrome can have slow arrhythmias or a combination of fast and slow arrhythmias. Various irregular heart rates (arrhythmias) or combinations of arrhythmias can occur in this condition. As we get older, scarring of the sinus node can occur and, in some people, it can be so severe that it causes this syndrome. It most commonly results from the effect of age on the sinus node. Sick sinus syndrome can occur for various reasons. Sick sinus syndrome is also called sinus node dysfunction.įor more information on other types of sinus node problems, see Types of Bradycardia. Sick sinus syndrome is the name given to a group of arrhythmias that occur because the normal pacemaker of the heart (the sinus node) does not work properly.
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