Sinus node dysfunction: Clinical manifestations, diagnosis, and evaluation. Sinus node dysfunction: Epidemiology, etiology, and natural history. In: Clinical Arrhythmology and Electrophysiology: A Companion to Braunwald's Heart Disease.
Atrial fibrillation, a type of irregular heartbeat (arrhythmia). Risk factors for heart disease include:Ĭomplications of sick sinus syndrome include: Common heart disease risk factors might increase the risk of sick sinus syndrome. It's most common in people in their 70s or older. Sick sinus syndrome can occur at any age. The heart rate alternates between unusually slow and fast rhythms, often with a long pause between heartbeats. The heart rate is within regular range at rest but doesn't increase as much as it should with physical activity. Signals to the upper heart chambers are slowed or blocked, causing pauses or skipped beats. Signals from the sinus node pause, causing skipped beats. The sinus node produces a slow heartbeat. Neuromuscular diseases, such as muscular dystrophy. Medications to treat irregular heartbeats (arrhythmias). Medications to treat high blood pressure, including calcium channel blockers and beta blockers. Inflammatory diseases affecting the heart. Damage to the sinus node or scarring from heart surgery. Age-related wear and tear of heart tissues. Sick sinus syndrome is relatively uncommon, but the risk of developing it increases with age.Ĭauses of sick sinus node syndrome can include: The heartbeat can be too fast, too slow, interrupted by long pauses - or an alternating combination of these rhythm issues. In sick sinus syndrome, the electrical signals are irregularly paced. 
The pace changes depending on activity, emotions and other factors. Typically, the sinus node creates a steady pace of electrical impulses. From the sinus node, electrical signals travel across the atria to the ventricles, causing them to contract and pump blood to the lungs and body. This natural pacemaker produces electrical signals that trigger each heartbeat. The rhythm of the heart is typically controlled by the sinus node, an area of specialized cells in the right upper heart chamber (right atrium). The heart is made up of four chambers - two upper (atria) and two lower (ventricles).
To understand the cause of sick sinus syndrome, it may be helpful to know how the heart typically beats. The signal then travels through the atria to the atrioventricular (AV) node and into the ventricles, causing them to contract and pump blood. In a typical heart rhythm, a tiny cluster of cells at the sinus node sends out an electrical signal.
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