Heart & Stroke Conditions Explained



The medical term for an abnormal rhythm of the heart is arrhythmia.

If the heartbeat is too slow, it is called a bradyarrhythmia or bradycardia. If it is too fast, it is called a tachyarrhythmia or tachycardia. We consider that the normal heart rate is between 60 and 100 beats per minute but there are many exceptions.

Athletic people may have heart rates less than 60 and all of us can have rates over 100 when we are exercising or under pressure etc.


Some forms of rapid heart beating can be life-threatening

When rapid heart beating arises in the ventricles – called ventricular tachycardia – a life-threatening situation can arise.

The most serious cardiac rhythm disturbance is called ventricular fibrillation when the electrical activity is so fast and chaotic that the heart cannot pump any blood.

Collapse and sudden death follows unless cardiac pulmonary resuscitation (CPR) and further medical help is provided immediately.


Other non life-threatening forms and symptoms which may require drug treatment

Other forms of rapid heart beating are not life-threatening in the same way as ventricular tachycardia. These are called supraventricular tachycardia (SVT) during which the heart rate can increase quite suddenly to over 200 beats per minute.

This usually causes distressing palpitations often with light-headedness, chest tightness, breathlessness and other symptoms. Sometimes these episodes are short-lived and terminate spontaneously.

Other times they persist and may require drug treatment or electrical conversion in hospital. Previously, these supraventricular tachycardia required long term drug therapy but more recently curative treatment with ablation has been developed.


Atrial Fibrillation or A Fib

Is another form of supraventricular arrhythmia (SVT) during which the normal regular rhythmic activity of the upper chambers or atria is replaced by chaotic irregular activity.


Ectopic beats

Are early (premature) or extra heartbeats and can feel like your heart skips or misses beats. Ectopic beats happen when electrical activity arises from other cells in your heart other than the normal electrical cells (sinus node).

Most people have ectopic beats at some time in their lives, and most are unaware of having them.

To learn more about heartbeats and how your heart works, see our section How Your Heart Works.


Related topics: ICDs, Long QT Syndrome, Atrial Fibrillation, Pacemakers, CPR, Defibrillator, Heart Attack, Atherosclerosis, Blood Pressure, Cardiomyopathy, SmokingStress, Tests & Procedures, ECG, Ways To Live Life Better



Arrhythmia can vary from a slowing of the heart beat to rapid symptoms

Slow heart beating symptoms

Excessive slowing of the heartbeat or bradycardia can cause fatigue, dizziness, lightheadedness, fainting or near-fainting spells. These symptoms are due to slow heart beating.


Rapid heart beating symptoms

Rapid heart beating or tachycardia can produce symptoms of palpitations, dizziness, light-headedness, fainting or near fainting if the heart beats too fast to circulate blood effectively. It may be either regular or irregular in rhythm.


Collapsing and need for immediate CPR

Should ventricular fibrillation occur, collapse and sudden death follows unless cardiac pulmonary resuscitation (CPR) and further medical help is provided immediately.



There are many reasons why you may develop an arrhythmia.

It can usually be divided into 2 main reasons:


  • The beat of your heart arises from another part of your heart other than the sinus node
  • The beat of your heart arises in the normal way from the sinus node but is abnormally slow, abnormally fast or takes an abnormal pathway.


Common causes can include:


  • As a heart attack is happening
  • When there is scarring of the heart muscle from a previous heart attack
  • Blocked coronary arteries
  • High blood pressure
  • Cardiomyopathy which affects the structure of the heart
  • Certain medications including over-the-counter cold remedies (see palpitations)
  • Overactive thyroid gland (hyperthyroidism)
  • Underactive thyroid gland (hypothyroidism)
  • Smoking
  • Drinking too much alcohol or caffeine
  • Drug abuse
  • Stress



Not all arrhythmias mean you have heart disease.

During exercise it is normal for your heart to beat faster and when you are resting or asleep your heart beats more slowly. In many cases, you can’t prevent arrhythmias but being aware of the factors which may increase your risk can help to prevent these occurring.

Keeping a heart healthy lifestyle is really important to prevent heart disease and stroke.



Depending on your symptoms, your doctor may recommend certain heart tests to help diagnose the abnormal heart rhythm.

These tests may include :


ECG (electrocardiogram)

This test measures the rhythm & electrical activity of your heart. Small sticky pads are placed on your body connected to wires that link up to the ECG machine. The machine reads & records, on paper, the electrical signals from your heart.



This is a test that your doctor may request to “see” that your heart muscle is working and how your heart valves are opening. Although this might sound like a major procedure, it is in fact a simple test which uses sound waves to take a moving picture of your heart.


Holter Monitor

Holter monitoring or ambulatory E.C.G., is a recording of the electric activity of your heart. It is done while the patient is walking or moving around, wearing a small tape recorder called a Holter monitor.

Holter monitoring helps identify occurrences of abnormal electrical activity in the heart. Your doctor uses this form of test to help explain what is causing your palpitations, dizzy episodes or fainting attacks.

The heart’s electrical abnormalities may occur spontaneously or after emotional stress or exercise. Some of the electrical disturbances may be life-threatening.


Electrophysiological (EP) Study

Electrophysiological (EP) Study is a test similar in how it is performed to an angiogram and is used to help identify where abnormal electrical signals in the heart are coming from.



Depending on the type of arrhythmia, your doctor may recommend medications to stop, prevent or control the abnormal heart rhythm.

Alternatively, you may need a heart procedure such as cardioversion or ablation to treat the abnormal rhythm. In some instances a pacemaker or implantable cardioverter defibrillator (ICD) may be required.


Cases requiring CPR and or a defibrillator

The most serious cardiac rhythm disturbance is called ventricular fibrillation when the electrical activity is so fast and chaotic that the heart cannot pump any blood.

Collapse and sudden death follows unless cardiac massage and further medical help is provided immediately. The rhythm can be converted back to normal by an electrical shock from an external defibrillator.


Medication and implantable devices

Further rapid heart beating can then be prevented by medications or in certain high risk cases by implanting an electronic device called an implantable cardioverter defibrillator (ICD). This looks like a large pacemaker but of course it treats rapid heart beating rather than slow heart beating.


Pacemakers and slow heart beats

If slow heartbeats (bradycardia) don’t have a cause that can be corrected, doctors often treat them with a pacemaker because there aren’t any medications that can reliably speed up your heart.

Supports for You


The Irish Heart Foundation offers a range of free support services to those affected by heart disease or stroke that can greatly improve their quality of life. These include support groups, physical exercise classes, therapy sessions and more.

For more information on these supports, see our Patient Supports page.

If you have any questions about heart disease or stroke, you can also call the Irish Heart Foundation’s Nurse Support on (01) 668 5001 to speak to a nurse specialist who will answer your questions, and give you guidance and reassurance.



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