Medically Reviewed By: Dr Paul Lim – MBBS, M.Med (Int Med), MRCP (UK), FAMS (Cardiology)
Bradycardia is a slower-than-normal heart rate — a resting heart rate below 60 beats per minute. For some people, particularly athletes and during sleep, a slow heart rate is perfectly normal. For others it is a sign that the heart’s electrical system is not firing or conducting as it should — as in sick sinus syndrome or heart block. When bradycardia causes symptoms such as fatigue, dizziness or fainting, treatment — most often a pacemaker — can restore a reliable heartbeat.
Senior Consultant Cardiologist & Cardiac Electrophysiologist
Dr Paul Lim subspecialises in heart rhythm disorders, including bradycardia, sick sinus syndrome and heart block. He implants pacemakers and defibrillators, manages rate-slowing medication and reversible causes, and investigates unexplained fainting and dizziness. He completed advanced fellowship training at Barts Heart Centre, London under Singapore’s HMDP award.
Bradycardia is the medical word for a slow heart rate — specifically, a resting heart rate below 60 beats per minute. A normal resting heart rate for most adults is 60 to 100 beats per minute. Like its opposite, tachycardia (a fast heart rate), bradycardia is a description of the speed rather than a single condition, and it ranges from an entirely healthy finding to a problem that needs treatment.
Each heartbeat normally begins in the heart’s natural pacemaker (the sinus node) and travels through the atrioventricular (AV) node to the lower chambers. Bradycardia happens when this system slows down: either the sinus node fires too slowly (sinus node problems), or the signal is delayed or blocked on its way to the ventricles (heart block).
No — and this is an important point. A slow heart rate can be a sign of a healthy, efficient heart. Endurance-trained athletes often have resting rates well below 60, and everyone’s heart slows during sleep. A slow rate only needs attention when it causes symptoms such as tiredness, dizziness or fainting, or when it is caused by a fault in the heart’s electrical system. If your pulse is persistently slow and you feel unwell with it, it is worth being assessed by a cardiologist in Singapore.
A slow heartbeat looks different depending on its cause. In sinus bradycardia the beats are normal in shape but simply spaced far apart; in complete heart block, signals from the top of the heart fail to reach the bottom, so beats are dropped.
Normal-looking beats spaced far apart — a heart rate under 60 beats per minute driven by a slow sinus node. Often harmless, especially in fit people and during sleep, but a cause of fatigue and dizziness when the rate is too slow.
Signals fire in the upper chambers (P waves) but are blocked before reaching the lower chambers, so the ventricles beat slowly on their own, independently. This is a serious rhythm that generally needs a pacemaker.
A slow heart rate comes from one of two places in the heart’s electrical system — the sinus node that sets the pace, or the conduction pathway that carries each signal to the ventricles.
In sinus bradycardia, the rhythm is normal but slow — the sinus node simply fires fewer than 60 times a minute. This is frequently harmless: it is common in fit, active people and in everyone during sleep. It can also be caused by heart-rate-slowing medication, an underactive thyroid, or ageing of the sinus node. Sinus bradycardia only needs treatment when it is too slow to meet the body’s needs and causes symptoms.
Sick sinus syndrome (sinus node dysfunction) is a group of problems that arise when the sinus node becomes unreliable, usually with age. It can produce a persistently slow rate, long pauses between beats, or an alternating pattern of slow and fast rhythms known as brady-tachy syndrome — where episodes of a fast rhythm such as atrial fibrillation swing into a very slow rate afterwards. When it causes symptoms, sick sinus syndrome is generally treated with a pacemaker.
Heart block — also called atrioventricular (AV) block — is a delay or failure of the electrical signal as it passes from the upper chambers to the lower chambers. An important point: heart block is not a blocked artery. It is a problem with the heart’s electrical wiring, quite separate from the narrowed or blocked arteries of coronary artery disease (a “blockage”). Heart block is graded by severity:
The degrees of heart block are compared side by side in the table below.
A slow resting heart rate in a fit, healthy person is often simply a sign of good conditioning. A well-trained heart pumps more blood with each beat, so it needs fewer beats per minute at rest. This kind of bradycardia is normal, causes no symptoms, and needs no treatment.
When a slow heart rate is a problem, it is usually because the heart is not pumping enough blood to meet the body’s needs. Many people with a mild slow rate feel nothing at all.
When symptoms do occur, they include:
Because these symptoms are easy to put down to ageing or tiredness, bradycardia is often under-recognised. Fainting or repeated near-fainting is the symptom that most needs prompt assessment, as it can signal a high-grade heart block.
Call 995 or go to the nearest A&E immediately if a slow heartbeat comes with fainting or a collapse, chest pain, sudden severe shortness of breath, or new confusion. A very slow pulse together with these signs can indicate complete heart block, which is a medical emergency.
Note: a slow pulse can only be linked to symptoms with an ECG recording taken at the time — if you feel unwell with a slow heartbeat, please book a specialist consultation.
A normal resting heart rate is 60–100 beats per minute (BPM). Bradycardia is a rate below 60 — but a slow rate is not automatically a problem. Drag the slider into the bradycardia zone to see how a slow heartbeat compares with a normal resting pulse.
Normal resting heart rate. Most healthy adults sit in this range at rest — this is what a healthy conduction system produces when everything is working correctly.
Feeling tired, dizzy or faint with a slow pulse? Get an ECG and proper specialist evaluation.
Some causes lie within the heart’s own wiring, while others come from outside the heart and are often reversible. Identifying which applies is the key to treatment.
Because a reversible cause such as a medication can often be corrected, a careful review is always worthwhile before deciding whether a pacemaker is needed.
Heart block is graded by how much of the electrical signal reaches the lower chambers. The grade largely determines whether a pacemaker is needed.
| Type | What happens | Typical symptoms | Pacemaker usually needed? |
|---|---|---|---|
| First-degree | Every signal gets through, just more slowly | Usually none | No |
| Second-degree, Type I (Wenckebach) | Signal delay builds until one beat is dropped | Often mild or none | Not usually |
| Second-degree, Type II (Mobitz II) | Beats are dropped suddenly, without warning | Dizziness, fainting | Often yes |
| Third-degree (complete) | No signals get through; chambers beat independently | Severe — fainting, can be life-threatening | Yes |
This is why telling the degrees apart on an ECG matters so much: first-degree and Type I second-degree block are often watched rather than treated, whereas Type II second-degree and complete heart block usually call for a pacemaker to restore a reliable heartbeat.
The aim is to record the slow rhythm and link it to your symptoms. Because a slow rate often comes and goes, monitoring over time is frequently needed.
Your cardiologist will ask about your symptoms, review every medication you take (as some slow the heart), and check your pulse and blood pressure. A slow, regular pulse or dropped beats can be an early clue.
A simple, painless recording of the heart’s electrical activity. It shows the rate and, crucially, whether the slow rhythm is sinus bradycardia or heart block — and which degree of block.
Because a slow rate or pauses may be intermittent, a wearable monitor is often the key to the diagnosis:
A scan of the heart to check the chamber size, valves and pumping strength, and to look for any underlying heart disease affecting the conduction system.
Thyroid function and electrolytes are checked, because an underactive thyroid or a chemical imbalance can slow the heart and may be reversible.
If the heart rate fails to rise appropriately with activity (known as chronotropic incompetence), a treadmill test can help confirm it and guide treatment.
As with a fast heart rate, the answer depends on the cause and whether it produces symptoms.
The reassuring message is that once bradycardia is correctly identified, it responds well to treatment — a reversible cause can be corrected, and a pacemaker can restore a normal heartbeat when one is needed.
Treatment depends on the cause and on whether the slow rate is causing symptoms. Your cardiac electrophysiologist will look first for anything reversible before considering a device.
If your slow heart rate causes no symptoms and is not due to a problem with the heart’s wiring — for example a fit person with a resting rate in the 50s — no treatment is required. Reassurance and, sometimes, periodic monitoring are all that is needed.
Where an outside factor is responsible, correcting it may resolve the bradycardia. This can mean reviewing or adjusting a medication that is slowing the heart, treating an underactive thyroid, correcting an electrolyte imbalance, or managing sleep apnoea. This step is always considered first.
When bradycardia causes symptoms and no reversible cause can be corrected — or in higher-grade heart block — a pacemaker is the established treatment. This small device, implanted under the skin below the collarbone, monitors the heartbeat and gently paces the heart whenever it runs too slowly, relieving symptoms and restoring a normal rate. Implantation is a routine, minimally invasive procedure.
If a very slow heart rate causes collapse or dangerous pauses — for example in complete heart block — a temporary pacing wire can support the heart in hospital until a permanent pacemaker is fitted or the cause is reversed.
Most people with bradycardia — including those with a pacemaker — lead full, active lives.
Contact us to schedule a consultation or to find out more about our cardiac services.
Answers to the most common questions about a slow heart rate, its causes, and how it is treated.
Bradycardia means a slow heart rate — a resting heart rate below 60 beats per minute. It can be completely normal, for example in athletes and during sleep, or it can be a sign that the heart’s electrical system is not firing or conducting properly, as in sick sinus syndrome or heart block.
A normal resting heart rate for most adults is 60 to 100 beats per minute. A resting rate below 60 is bradycardia. A slow rate is not automatically a problem — many fit people and most people during sleep have rates below 60 with no ill effects. It matters when it comes with symptoms such as tiredness, dizziness or fainting.
A slow heart rate is a concern when it is too slow to meet the body’s needs and causes symptoms such as fainting, extreme fatigue or breathlessness. There is no single dangerous number, but rates that cause loss of consciousness, or that come with long pauses between beats, need urgent assessment. A very slow rate from complete heart block can be life-threatening and requires emergency care.
Common causes include ageing of the heart’s electrical system, sinus node dysfunction (sick sinus syndrome), heart block, and heart-rate-slowing medicines such as beta-blockers. Other causes include an underactive thyroid, electrolyte imbalance, a previous heart attack, and sleep apnoea. In very fit people a slow rate is often simply a sign of good conditioning.
When a slow heart rate causes symptoms, they include tiredness, dizziness or light-headedness, breathlessness, reduced ability to exercise, and fainting or near-fainting. Some people also notice difficulty concentrating. Many people with a mild slow rate have no symptoms at all.
No. A slow heart rate can be a normal, healthy finding — endurance-trained athletes often have resting rates well below 60 because their hearts pump efficiently, and everyone’s heart slows during sleep. A slow rate only needs treatment when it causes symptoms or is due to a problem with the heart’s electrical system.
Sick sinus syndrome is a group of problems caused by the heart’s natural pacemaker, the sinus node, working unreliably. It can cause a persistently slow rate, long pauses, or an alternating pattern of slow and fast rhythms known as brady-tachy syndrome. It becomes more common with age and, when it causes symptoms, is usually treated with a pacemaker.
Heart block is not a blocked artery. It is a problem with the heart’s electrical wiring, where signals from the upper chambers are delayed or fail to reach the lower chambers. A blocked artery (coronary artery disease) is a separate, plumbing problem. Heart block is graded as first, second or third degree, and higher grades often need a pacemaker.
In first-degree heart block every signal still reaches the ventricles, just more slowly, and it usually causes no symptoms. In second-degree block some signals are dropped. In third-degree (complete) heart block no signals get through and the upper and lower chambers beat independently, which is serious and generally needs a pacemaker.
The key test is an ECG, which records the heart’s electrical activity. Because a slow rate can come and go, a Holter monitor, event recorder or implantable loop recorder is often used to capture it. An echocardiogram, blood tests (including thyroid function) and sometimes an exercise test complete the assessment.
Not everyone with a slow heart rate needs a pacemaker. If the cause is reversible — such as a medication or an underactive thyroid — treating that may be enough. A pacemaker is usually recommended when bradycardia causes symptoms, or in higher-grade heart block, because it restores a normal heartbeat and relieves symptoms.
Sometimes. If a slow heart rate is caused by a medication, adjusting or changing it may resolve the problem, and treating conditions such as an underactive thyroid or an electrolyte imbalance can help. When the cause is age-related wear of the conduction system or high-grade heart block, a pacemaker is usually the recommended treatment.
Call 995 or go to the nearest A&E if a slow heartbeat comes with fainting or a collapse, chest pain, severe breathlessness, or sudden confusion. A very slow pulse with these symptoms can indicate high-grade heart block and needs emergency care. A slow rate without symptoms can be assessed at a non-urgent specialist consultation.
Costs depend on the type of pacemaker and your case. Singapore’s Ministry of Health publishes fee benchmarks for pacemaker procedures, and hospital facility, anaesthesia and device charges are billed separately. See our pacemaker implantation page for more detail; exact costs are confirmed at consultation.
