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Sinus Bradycardia - Symptoms, Causes, Treatment

Updated on January 7, 2014

What is Sinus Bradycardia?

Sinus bradycardia is the condition characterized by a slow heartbeat of approximately 60 beats per minute or less. The rate of the heartbeat in sinus bradycardia is generally normal except when the rate has reached 50 beats per minute or lower.

The frequency of sinus bradycardia in the general population remains vague as most cases signify a normal variant. The danger of bradycardia on the hand is when there is an insufficiency in the supply of oxygen-rich blood in the body as a result of diminished heart beat or the inability of the heart to pump enough blood. The mortality and morbidity of sinus bradycardia depend on the underlying condition that influences the slow rate of heartbeat. The prognosis is relatively poor in patients with sick sinus syndrome associated with sinus bradycardia although there has been no clear relation of sinus bradycardia with regards to mortality.

Healthy individuals, young adults and athletes would normally have no problem with a resting heart rate of 60 beats per minute or lower and therefore does not consider bradycardia as a health issue or threat. The electrical impulses generally produced by the sinus node usually have a normal of 60 to 100 beats per minute during rest. A sinus rate that is that is faster than 100 beats per minute is referred to as sinus tachycardia while the rate of slower than 60 beats per minute is referred to as sinus bradycardia.

The sinus node or the sinoatrial is an impulse generating tissue and a group of cells that is situated on the wall of the right atrium of the heart and functions by generating a normal sinus rhythm. The sinus node is responsible for producing electrical impulses that will generate each heartbeat. It is a natural pacemaker that controls the rhythm of the heart.


The onset of sinus bradycardia may be asymptomatic and may have no significance in healthy individuals, young adults and the athletes. A normal heart rate at rest is 60 to 100 beats per minute and is considered bradycardia when it goes slower than 60 beats a minute. The symptoms of sinus bradycardia manifest when the rate has reached a beat of lower than 50 beats per minute. The manifestation of symptoms is relative to the insufficiency in the supply of oxygen-rich blood in the brain and other organs of the body.

The symptoms of sinus bradycardia include the following:

  • Episode of syncope or sudden loss of consciousness or fainting
  • Dizziness and lightheadedness
  • Shortness of breath or difficulty in breathing
  • Vertigo
  • Hypotension
  • Weakness and fatigue
  • Intolerance to strenuous physical activities
  • Memory problems and confusions

It is important to have a doctor consulted when these signs and symptoms are being experienced. Sinus bradycardia may not be medically significant but it is still wise to have an early diagnosis and prompt treatment to prevent further complications and determine the existing underlying condition that is influencing bradycardia.

An episode of chest pains, shortness of breath or difficulty in breathing and syncope that are lingering for more than a few minutes during the episode of bradycardia requires an immediate medical attention as it could be potentially life-threatening.

A slow and regular heart rate may be revealed during the process of auscultation and palpation during the physical examination. The result however, may be medically non-specific except when bradycardia is associated with an existing underlying condition.


Sinus bradycardia occurs when there is a disruption in the normal electrical impulses. The electrical impulses are responsible for controlling the rate of the pumping action of the heart. Many factors and diseases can disrupt the normal electrical impulses which can lead to sinus bradycardia.

The causes of sinus bradycardia include the following:

Sick sinus syndrome is the most common cause of sinus bradycardia. It is also referred to as sinus node dysfunction and is a term for a group of arrhythmias that resulted from the dysfunction of the sinus node. It is a rare condition with a high risk of developing as the age increases. The syndrome is characterized by either a rapid heart rate or a sluggish heart rate and is accompanied by long pauses of heart rhythm. The individual with sick sinus syndrome may experience arrhythmias alternating or they may experience it in combination. Patient with this syndrome may later on require a pacemaker to keep a regular heartbeat. Sick sinus syndrome has a poor prognosis and occurs in elderly people while the syndrome may also be a symptom of an infection such as rheumatic fever, viral myocarditis and diphtheria.

Coronary artery disease is a cardiac condition that can influence the pumping action of the heart which can cause it to slow down. The disease is characterized by an obstruction in the coronary arteries as a result of plaque buildup.

Hypothyroidism is a condition characterized by an insufficiency in the production of thyroid hormone which may or may not directly involve the thyroid gland. The thyroid gland produces a hormone that is essential for the metabolism of the cells.

Hypothermia is characterized by rapid loss of heat of the body than it can produce heat leading to a low body temperature. It is an emergency medical situation that rapid drop in the body temperature can lead to heart and respiratory failure potentially to death.

Sleep apnea is a potentially dangerous sleep disorder marked by the repeated cessation of breathing during sleep. The cessation in breathing can linger for a few seconds to a minute with a frequency of 5 to 30 times in a matter of one hour.


Sinus bradycardia is recommended for treatment when the rate of the heart beat is slow enough to cause or manifest the symptoms of lightheadedness, fatigue and syncope.

The treatment of sinus bradycardia depends on the existing underlying condition and whether the underlying condition is reversible or not. Reversible condition influencing the bradycardia can be treated appropriately by addressing the underlying condition. Increased vagal tone, hypothyroidism, drug therapy and infectious diseases are among the reversible condition causing bradycardia.

The pacemaker is indicated for patients with sinus bradycardia that resulted from an irreversible medical condition such as sick sinus syndrome. The pacemaker is a device operated by a battery and is about the size of a cell phone. This device is implanted under the collarbone with threads that are attached to the veins and into the heart. It generates electrical impulses whenever needed to meet and maintain the appropriate rate of heartbeat as it also works in monitoring the heart rate. Regular visits to the doctor or cardiologist is required to monitor and ensure the proper function of the pacemaker.


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