Sinus Node Dysfunction

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Sinus Node Dysfunction refers to the condition in which a patient experiences an abnormality in the heartbeat or experiences arrhythmias (irregular heart beats) due to a malfunction of the Sino Atrial Node or the Sinus Node. The Sinus node is where the electrical pulse, which initiates the pumping action of the heart, originates. The earliest known version of the condition was known as “Sick Sinus Syndrome” and today it refers to the abnormalities arising in the formation of the pulse in the sinus node and it’s propagation. Namely conditions like sinus bradycardia, sinus pause, chronotropic incompetence and sinoatrial exit block.

Sinus Node Dysfunction is a disease primarily associated with the elderly. It is mainly caused by the organic process of aging of the sinus node. Just as objects in day to day life are susceptible to wear and tear and become increasingly less efficient, so does the Sinus node become increasingly incompetent with age. This is often accompanied by similar inefficiency of the atrium and the conduction system of the heart. Thus resulting in abnormal heart rhythms.

It is relatively uncommon in young adults and if it does occur early in life it will be secondary to some other existing heart condition. Sinus Node Dysfunction has a variable natural history even though the disease is seen to be progressive in nature.

Certain medications are also known to cause or worsen abnormal heartbeat in patients. For instance medicines such as digitalis, calcium channel blockers, beta blockers, anti-arrhythmic etc. Some heart disorders also cause scarring, degeneration or damage to the conduction system and these eventually cause Sinus Node Dysfunction.

The following symptoms are associated with Sinus Node Dysfunction: 

  • Stokes-Adams attacks, which is a case of fainting due to insufficient blood to the brain. It is caused by improper contraction of the ventricles. 
  • Dizziness or feeling light headed. 
  • Angina or chest pain 
  • Fatigue 
  • Headache 
  • Nausea 
  • Palpitations 
  • Shortness of Breath.

Sinus Node Dysfunction occurs in approximately one out of 600 patients older than the age of 65. Since the disease shares a linear relationship with age it is seen to be more prevalent in countries where the average life expectancy is more. SND affects men and women with equal frequency displaying no gender preferences. Incidence of sudden death owing directly to Sinus Node Dysfunction is extremely low.

Diagnosis procedure involves ambulatory monitoring of the ECG, i.e. the patient is made to walk on a treadmill and the ECG is observed.

Treatment is done by Pacemaker therapy wherein a device called a pacemaker which artificially stimulates the heartbeat is surgically implanted on the patient’s chest.

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