Bradycardia and Heart Block in Singapore: Symptoms, Causes and Treatment

Bradycardia (a slow heart rate, usually under 60 beats per minute) is sometimes completely normal – and sometimes a sign that the heart’s electrical wiring is failing. Heart block, where electrical signals are delayed or blocked on their way from the upper to the lower chambers, is one of the most important causes. With Singapore’s population ageing, age-related conduction problems are an increasingly common reason for pacemaker implantation. This page explains slow heart rates, the three degrees of heart block in plain words, sick sinus syndrome, and how these conditions are diagnosed and treated. It is general information and not a substitute for advice from your own doctor.

What Is Bradycardia?

A normal resting heart rate is roughly 60 to 100 beats per minute. Bradycardia simply means the rate is slower than 60. Whether that matters depends on context.

Normal (physiological) bradycardia. Fit, athletic people often have resting rates of 40 to 60 because a well-trained heart pumps more blood with each beat. If you are well, exercise without difficulty and have no symptoms, a slow rate is usually a sign of fitness, not disease.

Pathological bradycardia. The rate is slow because the heart’s electrical system is not working properly – either the sinus node (the heart’s natural pacemaker) fires too slowly or unreliably, or the signal is held up on its way to the pumping chambers. This form causes symptoms and tends to worsen over time.

What Is Heart Block?

Every heartbeat starts in the sinus node and travels through a junction box called the AV node to reach the ventricles. Heart block (also called atrioventricular or AV block) means this signal is delayed or fails to get through. In plain words:

• First-degree block – every signal gets through, but more slowly than normal. Usually harmless and often needs no treatment.
• Second-degree block – some signals get through and some are dropped, so beats are intermittently missed. One form (often benign) shows a gradually lengthening delay before a dropped beat; the other form drops beats without warning and is more serious.
• Third-degree (complete) block – no signals get through at all. The ventricles fall back on a slow escape rhythm of 20 to 40 beats per minute. This is dangerous and usually needs a pacemaker promptly.

What Is Sick Sinus Syndrome?

In sick sinus syndrome the sinus node itself becomes worn and unreliable, usually with age. The heart may run too slowly, pause for several seconds, or swing between slow and fast rhythms (tachy-brady syndrome), often alongside atrial fibrillation. It is a common reason for pacemakers in older adults.

Bradycardia and Heart Block Symptoms

Symptoms occur when the heart is too slow to pump enough blood, and may include:

• Tiredness and reduced stamina, or breathlessness on exertion
• Dizziness or light-headedness
• Fainting (syncope) or near-fainting – a sudden pause is a classic cause of blackouts in older adults
• Poor concentration or brain fog
• Chest discomfort
• In elderly people, symptoms can be vague – unexplained falls, confusion or simply “slowing down” may be the only clue

Mild bradycardia often causes no symptoms and is picked up incidentally on a routine pulse check or ECG.

When to Seek Emergency Help

Call 995 if a slow heart rate occurs together with:

• Fainting or collapse
• Severe dizziness with confusion or drowsiness
• Chest pain
• Severe breathlessness

Complete heart block can develop suddenly and needs urgent hospital treatment.

Causes and Risk Factors

• Ageing – gradual wear and fibrosis (scarring) of the sinus node and conduction fibres is the most common cause
• Medications – beta-blockers, some calcium channel blockers and anti-arrhythmic drugs slow the heart deliberately; the dose sometimes needs adjusting
• Heart attack or coronary artery disease – can damage the conduction system
• Hypothyroidism (an underactive thyroid)
• Electrolyte disturbances, such as high potassium
• Obstructive sleep apnoea – common in Singapore and a recognised cause of night-time slow rhythms and pauses
• Infections and inflammation of the heart, and previous heart surgery or ablation
• Congenital heart block, present from birth, in a small number of people

How Bradycardia and Heart Block Are Diagnosed

• Electrocardiogram (ECG) – a resting electrocardiogram (ECG) shows the heart rate and identifies the type and degree of block within minutes if it is present at the time.
• 24-hour Holter monitor – because slow rhythms and pauses often come and go, a 24-hour Holter monitor (or a 7-day or patch recording) is used to capture them during normal daily life and match them to symptoms such as dizziness.
• Blood tests – thyroid function and electrolytes, to find reversible causes.
• Treadmill (exercise stress) test – checks whether the heart rate rises appropriately with activity.
• Electrophysiological (EP) study – in selected cases, an electrophysiological (EP) study maps the heart’s wiring from inside to pinpoint where conduction is failing.

Treatment Options

• Treat the reversible causes first. Adjusting or stopping rate-slowing medication, correcting thyroid or electrolyte problems, and treating sleep apnoea may restore a normal rate without any procedure.
• No treatment is needed for physiological bradycardia in fit people, first-degree block, or the benign form of second-degree block without symptoms – these are usually just monitored.
• Pacemaker implantation. For symptomatic sick sinus syndrome, the more serious form of second-degree block and complete heart block, a permanent pacemaker is the standard treatment. This small device, implanted under the skin below the collarbone and connected to the heart by thin leads, monitors every beat and fills in missing ones so the rate never falls too low. Implantation is a minimally invasive procedure done under local anaesthetic, usually with a short hospital stay – see our cardiac pacemakers and devices service for what implantation involves. Bradycardia is one of several heart rhythm disorders where device therapy has transformed the outlook.

When to See a Cardiologist

See a cardiologist if your resting heart rate is persistently below 50 with tiredness, dizziness or breathlessness, if you have fainted without explanation, or if a slow rate or heart block has been noted on an ECG or wearable device. Unexplained blackouts in anyone over 60 should always prompt a heart rhythm assessment.

Frequently Asked Questions

Is a heart rate of 50 dangerous?

Not necessarily. In a fit person with no symptoms, 50 beats per minute can be entirely normal. It matters when it comes with tiredness, dizziness or fainting, or when an ECG shows the slowness is due to heart block – so symptoms and context decide.

Does heart block go away on its own?

Sometimes. Block caused by medication, electrolyte problems or a recent heart attack may recover once the cause is treated. Age-related heart block, however, tends to be permanent and progressive, which is why the more advanced degrees are treated with a pacemaker.

Do all types of heart block need a pacemaker?

No. First-degree block and the benign form of second-degree block usually need no treatment, only monitoring. The more serious form of second-degree block and complete (third-degree) block generally do need a pacemaker.

Can I exercise with bradycardia?

If your slow rate is physiological and your rate rises normally with activity, exercise is safe and encouraged. If bradycardia limits your stamina or causes dizziness during exertion, get assessed first – and after pacemaker implantation, most people return to normal exercise.

What is tachy-brady syndrome?

It is a form of sick sinus syndrome in which the heart alternates between abnormally fast rhythms (often atrial fibrillation) and slow rhythms or pauses. Treatment commonly combines a pacemaker to prevent the slow phases with medication to control the fast ones.