Bradycardia


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Patient Information


	What is Bradycardia?
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	Bradycardia is a term that describes a number of different conditions in which the heart beats at an unusually slow rate. Sinus bradycardia is an unusually slow heartbeat due to normal causes and commonly occurs in athletes or during a state of deep relaxation. This is perfectly normal and should not usually cause any difficulties. Sinus bradycardia can also occur in patients with heart disease or in response to different medications. The severity of and treatment required for the bradycardia depends on the area of the heart affected. If impulses are sent from the sinoatrial node at a slow rate, or if the impulses are delayed as they travel through the conduction system, the heartbeat will be slow. Bradycardia may also be caused by age–related degeneration of the heart’s electrical conduction system, coronary heart disease or by medications prescribed to treat arrhythmia or high blood pressure. Once these medications have been reduced or discontinued, the bradycardia will usually resolve on its own.

	Signs and Symptoms of Bradycardia

	Some types of bradycardia produce no symptoms, and others may cause dizziness, breathlessness on exertion or fainting (syncope).

	Sick Sinus Syndrome

	This occurs when the hearts natural pacemaker, the SA node fails, causing an irregular heartbeat. Patients with sick sinus syndrome may experience a slow heartbeat (bradycardia), a fast heartbeat (tachycardia) or heartbeats that swap between fast and slow (brady–tachy syndrome or tachy–brady syndrome). Patients may experience dizziness, tiredness, weakness or fainting (syncope). Although, it is more common in elderly people it can occur in children, often after cardiac surgery.

	Syncope


	There are many causes of syncope, some common and some rare. Most cases of syncope are due to the ‘common’ faint however other important causes includes defects of the ‘wiring’ of the heart. Syncope can occur when the heart slows or momentarily stops (asystole) therefore oxygenated blood is not pumped to the brain causing light-headedness, dizziness, fading of vision, buzzing in the ears before loss of consciousness. Often patients will recognise these symptoms and be able to sit or lie down before losing consciousness. However for many there are no symptoms, just an abrupt loss of consciousness. People of all ages experience syncope, including children (reflex anoxic seizures/reflex asystolic syncope due to unexpected stimuli such as a bump or fright). Syncope involving bradycardia can easily be diagnosed by taking a detailed history and using an event monitor if occurrence is regular and frequent or an Implantible loop recorder if irregular and less frequent. There is a separate booklet available explaining the various types of syncope. If you require an implantible loop recorder your doctor, nurse or physiologist will discuss this with you and provide you with a separate booklet explaining in more detail.

	Heart Block
	Heart Block (atrioventricular block or AV block) occurs when electrical impulses are slowed or blocked as they travel from the top chamber of the heart (atria) through the atrioventricular node (AV node) into the bottom chambers (ventricles). The symptoms and treatments for heart block depend on its severity, the different types of heart block and the treatment options available are explained below.

	First degree heart block
	This occurs when the electrical impulses slow as they pass through the AV node, however all impulses reach the ventricles. First-degree heart block rarely causes any symptoms and is often found in athletes. No other treatments are generally necessary Patients with known first degree heart block should not be prescribed beta-blockers unless very carefully supervised

	Type I second-degree heart block

	This occurs when the electrical impulses are delayed to a greater extent with each heartbeat until a beat is skipped entirely and the cycle then repeats. This may rarely cause dizziness and other symptoms. In such cases, a pacemaker may be required.

	Type II second-degree heart block

	This occurs when some of the electrical impulses from the SA node are unable to reach the ventricles, for example every third or fourth impulse. This is usually because of an underlying disease. Usually a pacemaker may be required to control and regulate the heart rhythm.

	Third degree heart block
	Third degree heart block (complete heart block) occurs when no electrical impulses reach the ventricles, this is usually as a result of underlying disease or medications. In the absence of any electrical impulses from the atria, the ventricles produce impulses on their own; these are called ventricular escape beats. However, these heartbeats are usually slow and the patient may feel very unwell. This type of heart block can sometimes occur for a short time in certain types of heart attack and may require a temporary pacemaker. Sometimes the patient remains relatively well anda pacemaker can be implanted after a few days. On other occasions this condition needs to be treated more quickly and if a pacemaker cannot be implanted immediately, the doctors will put a temporary pacemaker wireinto the heart to keep the heart pumping regularly until the permanent system is implanted.

	Treatment options for Bradycardia
	Commonly symptomatic bradycardia is treated by discontinuing any medications that slow the heartbeat and treating any underlying conditions and/or by implanting a permanent pacemaker. Pacemakers are implanted under the skin and the wires are permanently attached to the heart. When a slowed or abnormal heart rhythm is detected, the pacemaker fires a very small electrical impulse to regulate the heartbeat. If you require a permanent pacemaker your doctor, and nurse and/or physiologist will discuss this with you and provide you with a booklet explaining this in more detail. For further information, see Pacemaker Patient Information.