Heart Arrhythmia

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What is heart arrhythmia?

Heart arrhythmia is an abnormality in the heartbeat caused by disruptions to the electrical impulses that control heartbeats. This could mean that the heart beats too fast, too slow, or at an irregular pace.

Heart arrhythmias can sometimes be harmless and their severity depends on the type of arrhythmia involved. However, if you experience irregularities in your heartbeat often, or for an extended period of time, it might be a sign of a more serious condition, or may even lead to complications if left untreated.

What is considered a normal heartbeat?

The heart is made up of four chambers — two upper chambers (atria) and two lower chambers (ventricles). The heart rhythm is normally controlled by a natural pacemaker (sinus node) located in the right atrium. The sinus node produces electrical impulses that normally start each heartbeat. These impulses cause the atria muscles to contract and pump blood into the ventricles.

The electrical impulses then arrive to the atrioventricular (AV) node. The AV node sends the electrical signal to the ventricles. When electrical impulses reach the muscles of the ventricles, they contract, causing them to pump blood to the lungs and the rest of the body.

In a healthy heart, a normal resting heart rate lies between 60 and 100 beats per minute (bpm). The resting heart rate is the rate where your heart is pumping the least amount of blood needed by your body to perform its daily activities and not under any physical stress. It is normal for your heart rate to go through healthy variations in response to changes in body conditions or exercise.

What are the types of heart arrhythmia?

There are many types of heart arrhythmia, and they are classified according to the part of the heart it originates from and the speed of the heart rate that it causes. For example, the terms referring to the speed of heart rate are:

Tachycardia, where resting heart rate is too fast (above 100 bpm) for reasons other than exercise, high fever or stress.

Bradycardia, where resting heart rate is too slow (below 60 bpm). It could either be a sign that you are very fit. However, if it is too slow, it could indicate that your heart is not pumping enough blood for your body.

It is important to note that not all tachycardias or bradycardias indicate heart disease. At rest or while we sleep, our heartbeat is naturally slower. Conversely, during physical exercise or while we are excited, it is completely normal for our heart rate to increase.

Tachycardias in the atria

  • Atrial fibrillation
    This refers to the rapid and irregular contraction of the atria. It is the most common type of serious heart arrhythmia and can sometimes result in stroke or heart failure.
  • Atrial flutter
    This is similar to atrial fibrillation, but with a more regular contraction pattern. It is less common than atrial fibrillation but often results in the same complications.
  • Supraventricular tachycardia
    This is a broad term that includes different forms of arrhythmia above the ventricles, originating in the atria or AV node. These types of arrhythmias often cause episodes of heart palpitations that begin and end unexpectedly.
  • Wolff-Parkinson-White-Syndrome
    This congenital condition is a type of supraventricular tachycardia where there is an extra electrical pathway between the atria and the ventricles, causing a short circuit. This causes the heart to beat abnormally fast for periods of time. Often, symptoms do not occur until adulthood.

Tachycardias in the ventricles

  • Ventricular tachycardia
    This refers to the rapid and regular contraction of the ventricles and can last for only a few seconds, or for an extended period of time. If it does last for longer than a few seconds, there is a risk of developing more dangerous arrhythmias like ventricular fibrillation.
  • Ventricular fibrillation
    Ventricular fibrillation is a life-threatening arrhythmia that will require immediate medical attention. It is characterised by ventricles that quiver rather than contracting normally, leading to their inability to effectively pump blood to the rest of the body. It typically occurs in people with existing heart problems.
  • Long QT syndrome (LQTS)
    This is a rare heart rhythm condition that can potentially cause rapid, chaotic heartbeats. This is dangerous as it may trigger sudden fainting episodes, seizures, and, in severe cases, may be life-threatening.


This refers to a heart rate below 60 bpm. Generally, bradycardia does not show symptoms until the rate drops below 50 bpm.

  • Sick sinus syndrome
    Sick sinus syndrome refers to any arrhythmia caused by a dysfunction of the sinus node itself. The heart rate may alternate between too slow (bradycardia) and too fast (tachycardia). The likelihood of developing sick sinus syndrome increases with older age.
  • Heart block
    This refers to a delay or block in the electrical impulses at the AV node going to the ventricles, resulting in a much slower heart rate.

Premature heartbeats

A premature heartbeat may feel as if your heart missed a beat, when in fact, it may be an extra beat. Generally, this does not pose a serious issue, and may occur naturally when you are resting, under stress or exercise, or if there are stimulant triggers like caffeine. However, a premature heartbeat can still trigger a lasting arrhythmia in people with heart disease. Frequent episodes of premature heartbeats may weaken the heart.

What are the symptoms of heart arrhythmia?

Symptoms will largely depend on the type of heart arrhythmia involved, but some common symptoms to look out for include:

  • Heart palpitations
  • Dizziness
  • Feeling faint or tired
  • Chest pain or discomfort
  • Difficulty breathing or breathlessness

You should consult your cardiologist if your symptoms last for an extended period of time without getting better, or if they get worse. If you have a history of heart problems, regular checkups with your cardiologist can help with the early detection of asymptomatic heart arrhythmia.

What causes heart arrhythmia?

Heart arrhythmias can be caused by a number of different reasons. For example, they might be brought on by changes in the heart muscles and structure due to heart problems like:

  • Heart failure
  • Coronary heart disease
  • Heart attack
  • Cardiomyopathy
  • Inflammation of the heart muscle (myocarditis)
  • High blood pressure
  • Congenital heart disease

Heart arrhythmias can also be linked to other types of medical conditions such as:

  • Thyroid disorders
  • Electrolyte imbalances
  • Obstructive sleep apnoea
  • Electrolyte disorders

Sudden episodes of heart arrhythmia may be brought about by certain triggers. These include:

  • Smoking
  • Excessive alcohol consumption
  • Excessive caffeine consumption
  • Drug abuse
  • Stress or anxiety
  • Certain medications or supplements
What happens if heart arrhythmia is left untreated?

While heart arrhythmias can sometimes be harmless, it is important to visit a cardiologist for a full diagnosis and possible treatment, especially if you are at risk of any heart problems. Left untreated, a heart arrhythmia can sometimes result in:

  • Stroke
  • Heart failure
  • Sudden cardiac arrest
What can I expect during my first consultation for heart arrhythmia?

During your first consultation, your cardiologist will ask about your personal medical history, as well as your family history. Your cardiologist will also want to find potential sources of, or triggers of your heart arrhythmia.

One or more of the following tests may be performed:

  • Blood tests
  • Electrocardiography (ECG)
  • Echocardiography
  • Ambulatory ECG (Holter)
  • Exercise Treadmill ECG
  • Electrophysiological (EP) study

If treatment for heart arrhythmia is necessary, this could take the form of:

  • Medications such as antiarrhythmic drugs or anticoagulants
  • Cardioversion
  • Catheter ablation
  • Implantable cardioverter defibrillator (ICD) insertion
  • Pacemaker insertion
  • Heart surgery, such as coronary bypass surgery, maze procedure, or ventricular aneurysm surgery

Your cardiologist will assess your condition fully and decide if any of these treatments are necessary for your heart arrhythmia.

How can I prevent heart arrhythmia?

As with other disorders of the heart, prevention is key when it comes to heart arrhythmia. Unless your heart arrhythmia is caused by a genetic condition, you can generally prevent heart arrhythmias by leading a heart-healthy lifestyle.

This means maintaining a healthy weight through a proper diet and regular physical activity and avoiding bad habits like smoking and excessive alcohol or caffeine consumption.

If your heart arrhythmia is triggered by stress, it can also be important to reduce the amount of stress and anxiety you feel in your day-to-day life.

When do I need to see a doctor?

Arrhythmias may cause you to feel premature heartbeats, or you may feel that your heart is beating too fast or too slowly. Other signs and symptoms may be related to your heart not pumping effectively due to the fast or slow heartbeat. These include shortness of breath, weakness, dizziness, lightheadedness, fainting or near fainting, and chest pain or discomfort.

Seek urgent medical care if you suddenly or frequently experience any of these signs and symptoms at a time when you wouldn’t expect to feel them.


Sometimes, heart arrhythmias may not appear with any visible signs or obvious symptoms and are only detected through diagnostic testing. If you feel anything unusual or are concerned about your heart activity, you should consult your cardiologist for proper evaluation to achieve a diagnosis.

How can we help you?

We offer consultation for a comprehensive range of cardiac diagnostic tests and treatment plans.

Dr Joshua Loh

Senior Consultant Interventional Cardiologist

Medical Director at Capital Heart Centre, Dr Joshua Loh has more than 15 years of experience in the field of cardiology.

He has extensive experience in the treatment of complex coronary and interventional procedures.