Medically Reviewed By: Dr Paul Lim – MBBS, M.Med (Int Med), MRCP (UK), FAMS (Cardiology)
Tachycardia is a resting heart rate faster than 100 beats per minute. It is an umbrella term, not a single condition. Sometimes a fast heart rate is completely normal — the heart’s appropriate response to exercise, fever or stress (sinus tachycardia). At other times it is caused by a fault in the heart’s electrical wiring, such as supraventricular tachycardia (SVT) — which is usually not dangerous and often treatable — or ventricular tachycardia (VT), which can be serious. Identifying the type is the key to knowing whether treatment is needed, and which.
Senior Consultant Cardiologist & Cardiac Electrophysiologist
Dr Paul Lim subspecialises in heart rhythm disorders, including the different types of tachycardia. He performs catheter ablation for SVT and other fast rhythms, cardioversion, and pacemaker and defibrillator implantation, and manages rate-control, rhythm-control and medication strategies. He completed advanced fellowship training at Barts Heart Centre, London under Singapore’s HMDP award.
Tachycardia is the medical word for a fast heart rate — specifically, a resting heart rate above 100 beats per minute. A normal resting heart rate for most adults is 60 to 100 beats per minute. Because “tachycardia” simply describes the speed, it covers several very different situations, from an entirely normal response to a genuine heart rhythm disorder.
In a normal heartbeat, each beat begins in the heart’s natural pacemaker (the sinus node) and spreads in an orderly wave through the upper chambers (atria) and then the lower chambers (ventricles). When the heart beats too fast, it is usually for one of two reasons: the sinus node is appropriately speeding the heart up in response to a demand, or an abnormal electrical circuit is driving the heart faster than it should.
Getting to the bottom of which type of tachycardia is present matters, because the outlook and treatment differ enormously — from simply reassurance and treating a trigger, to a targeted procedure that can eliminate the fast rhythm in many patients.
No. A faster heart rate during exercise, a fever, pain, dehydration, anxiety or after caffeine is normal and expected — this is sinus tachycardia, and it settles as the trigger passes. A fast heart rate is more likely to need attention when it starts and stops suddenly, races very fast at rest for no clear reason, or comes with chest pain, severe breathlessness, dizziness or fainting. A 12-lead ECG is the simplest way to tell a normal fast rhythm from an arrhythmia. If your heart often races without a clear explanation, it is worth being assessed by a cardiologist in Singapore.
The two most important rhythm-disorder types of tachycardia look strikingly different on a 12-lead ECG. The width of each heartbeat (the QRS complex) is the key clue — narrow for SVT, wide for VT.
Fast, narrow QRS complexes arriving at a regular rapid rate — usually 150 to 220 beats per minute — with P waves often lost inside the preceding T wave. Covers AVNRT, AVRT and WPW syndrome, typically in otherwise healthy hearts.
Wide, bizarre-looking QRS complexes firing rapidly from the lower chambers — P waves and T waves are lost inside the wide beats. Sustained VT can progress to cardiac arrest and needs urgent care.
Tachycardia is grouped by where in the heart the fast rhythm arises. This is the single most important distinction, because it determines whether the rhythm is harmless, and how it is treated.
Supraventricular tachycardia is a fast rhythm that begins above the ventricles — in the atria or the AV node. On an ECG it produces narrow QRS complexes at a fast, usually regular rate of about 150 to 220 beats per minute. Episodes often start and stop abruptly (“paroxysmal”), and it frequently affects younger, otherwise healthy people. SVT is an umbrella term that includes:
SVT is rarely life-threatening, but it can be distressing and disruptive. The encouraging news is that it usually responds well to treatment: catheter ablation targets and interrupts the extra circuit, and has a high success rate.
Ventricular tachycardia is a fast rhythm that begins in the ventricles — the heart’s main pumping chambers. On an ECG it produces wide QRS complexes at a rapid rate. VT is more often seen in hearts that have been weakened or scarred, for example after a previous heart attack, and it can be dangerous: sustained VT reduces the heart’s ability to pump and can deteriorate into a cardiac arrest. Any sustained VT is treated as a medical emergency.
Treatment depends on the situation and the underlying heart condition, and may involve urgent stabilisation, antiarrhythmic medication, catheter ablation, and — in selected patients — an implantable cardioverter-defibrillator (ICD) to protect against dangerous episodes.
Sinus tachycardia is a fast but normal rhythm. The heart’s natural pacemaker appropriately speeds the heart up in response to a demand — exercise, fever, pain, stress, dehydration, anaemia or an overactive thyroid. It is not a fault in the heart’s wiring, and treatment is aimed at the underlying cause rather than the heart itself. It settles once the trigger is addressed.
Two other common fast rhythms technically fall under the “supraventricular” heading but are distinct enough to have their own guides: atrial fibrillation, an irregular fast rhythm from chaotic atrial activity, and atrial flutter, a fast, organised rhythm with a characteristic sawtooth ECG. Both raise the risk of stroke and are managed differently from the SVT types above.
Tachycardia may also be described as paroxysmal (coming and going on its own) or sustained (continuing until treated).
Symptoms depend on how fast the heart is beating, how long the episode lasts, and the state of the heart. Some people feel a dramatic racing heartbeat; others notice very little.
Common symptoms include:
A hallmark of SVT is a heartbeat that starts and stops abruptly — patients often describe it flicking on and off “like a switch”. Some tachycardia causes no symptoms at all and is discovered on an ECG or a smartwatch.
Call 995 or go to the nearest A&E immediately if a fast heartbeat comes with chest pain, sudden severe shortness of breath, fainting, or signs of a stroke (sudden weakness on one side of the body, trouble speaking, or facial drooping). A sustained very fast heart rate that does not settle also needs urgent assessment.
Note: tachycardia symptoms overlap with many other conditions, and the type can only be confirmed with an ECG — if you are unsure, please book a specialist consultation.
A normal resting heart rate is 60–100 beats per minute (BPM). Tachycardia begins above 100 BPM, and an SVT episode often sits between 150 and 220 BPM. Drag the slider to feel the difference between a normal resting pulse and a fast, tachycardia-like rate.
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.
Noticing a racing or pounding heartbeat? Get a 12-lead ECG and proper specialist evaluation.
The causes divide neatly along the same lines as the types. Some fast heart rates come from outside the heart’s wiring — a demand the heart is responding to — while others come from a genuine electrical fault.
More than one factor is often at play, and in some people a clear trigger cannot be found. A specialist assessment works out which cause is responsible and whether it needs treating.
The two rhythm-disorder types of tachycardia differ in where they start, how they look on an ECG, and — most importantly — how serious they tend to be.
| Feature | Supraventricular (SVT) | Ventricular (VT) |
|---|---|---|
| Where it starts | Above the ventricles (atria or AV node) | In the ventricles (lower chambers) |
| ECG appearance | Narrow QRS complexes | Wide QRS complexes |
| Typical rate | About 150–220 per minute | About 120–250 per minute |
| Usual danger level | Rarely life-threatening | Can be life-threatening — an emergency if sustained |
| Who it tends to affect | Often younger people with otherwise healthy hearts | More often hearts with prior damage or scarring |
| Common treatment | Vagal manoeuvres, medication, catheter ablation | Urgent stabilisation; medication, ablation, ICD |
Telling the two apart on an ECG is essential, because a wide-complex tachycardia is treated as VT — and therefore as an emergency — until proven otherwise. This is one of the reasons a proper 12-lead ECG, read by a specialist, matters so much when the heart is racing.
The aim is to capture the fast rhythm on a recording so its type can be identified. Because episodes can come and go, more than one test is sometimes needed.
Your cardiologist will ask how the episodes start and stop, how fast and regular they feel, what triggers them, and about any family history, and will check your pulse and blood pressure. A rhythm that begins and ends abruptly points towards SVT.
The key test. Captured during an episode, the ECG shows the rate, whether the QRS complexes are narrow or wide, and usually the exact type of tachycardia. A simple, painless recording that takes only minutes.
If the resting ECG is normal but episodes are suspected, a wearable monitor can capture them:
A scan of the heart to check the chamber size, valves and pumping strength, and to look for any underlying heart disease that could drive the fast rhythm.
Thyroid function, a full blood count (for anaemia) and other tests are checked, because conditions outside the heart can cause or worsen tachycardia.
For some patients, an electrophysiology (EP) study maps exactly where the fast rhythm arises. It is often carried out in the same sitting as catheter ablation, allowing the rhythm to be diagnosed and treated together.
The answer depends entirely on the type — which is exactly why it should be identified rather than ignored.
The reassuring message is that most types of tachycardia are very manageable once correctly identified — and several, particularly SVT, can often be effectively eliminated with catheter ablation.
Treatment is matched to the type of tachycardia, your symptoms and your overall heart health. Your cardiac electrophysiologist will explain the options that apply to you.
When a fast heart rate is an appropriate response to something else, the treatment is to address that cause — rehydrating, treating a fever or infection, correcting anaemia, managing an overactive thyroid, or reducing caffeine and stress. The heart rate settles as the trigger resolves.
For SVT, simple vagal manoeuvres can sometimes stop an episode by briefly slowing conduction through the AV node — for example bearing down as if straining, or applying a cold stimulus to the face. Your cardiologist can show you how to perform these safely. If they do not work, medication given in a clinic or hospital can restore a normal rhythm.
Medicines such as beta-blockers or rate-slowing calcium-channel blockers can reduce how often episodes occur and slow the heart during them. Antiarrhythmic medication is used for some patients to help maintain a normal rhythm. The choice depends on the type of tachycardia and your other health conditions.
Catheter ablation is a minimally invasive procedure that uses energy delivered through a thin tube (catheter) to interrupt the abnormal circuit driving the fast rhythm. For most types of SVT it has a high success rate and can effectively eliminate the abnormal circuit in many patients, which is why it is often recommended early. Ablation is also used for selected cases of VT. Dr Paul Lim’s standard is an overnight stay, with most patients going home the next day.
Electrical cardioversion — a brief, controlled shock under sedation — can reset the heart to a normal rhythm when needed. For patients at risk of dangerous ventricular rhythms, an implantable cardioverter-defibrillator (ICD) continuously monitors the heartbeat and can deliver a life-saving shock if VT or cardiac arrest occurs.
Many people with tachycardia lead full, active lives once the type is identified and managed.
Contact us to schedule a consultation or to find out more about our cardiac services.
Answers to the most common questions about a fast heart rate, its types, and how it is treated.
Tachycardia means a fast heart rate — a resting heart rate above 100 beats per minute. It is an umbrella term. Some tachycardia is a normal response to exercise, fever or stress (sinus tachycardia), while other types are electrical rhythm disorders, such as supraventricular tachycardia (SVT) and ventricular tachycardia (VT).
A normal resting heart rate for most adults is 60 to 100 beats per minute. A resting rate above 100 is called tachycardia. A fast rate during exercise or stress is normal; the concern is a fast rate at rest, or one that starts and stops suddenly, races very fast, or comes with symptoms such as chest pain, breathlessness or fainting.
Common causes include fever, dehydration, anaemia, an overactive thyroid, anxiety, caffeine, alcohol and some medications. Heart-related causes include an extra electrical circuit in the heart, coronary artery disease, previous heart attack, heart failure and high blood pressure. Establishing the cause usually needs an ECG and a few simple tests.
Supraventricular tachycardia (SVT) starts above the ventricles and produces narrow QRS complexes on the ECG; it is usually not life-threatening and is often treatable with catheter ablation. Ventricular tachycardia (VT) starts in the lower chambers, produces wide QRS complexes, and can be dangerous — sustained VT is a medical emergency.
It depends on the type. Sinus tachycardia and many episodes of SVT are not immediately dangerous, though they can be distressing. Ventricular tachycardia can be life-threatening. A persistently fast heart rate of any type can, over time, weaken the heart muscle. This is why a fast heart rate should be assessed to identify which type is present.
A faster heart rate during exercise, fever, anxiety or after caffeine is usually sinus tachycardia — the heart’s normal, appropriate response to a demand, and not a rhythm disorder. It settles as the trigger passes. A rate that starts and stops abruptly, or races very fast at rest for no clear reason, is more likely to be SVT or another arrhythmia.
Common symptoms are palpitations (a racing, pounding or fluttering chest sensation), breathlessness, dizziness or light-headedness, chest discomfort and fatigue. A very fast rate can cause fainting. Some people have no symptoms and the fast rate is found incidentally on an ECG or a wearable device.
Vagal manoeuvres can sometimes stop an SVT episode — for example bearing down as if straining, or applying a cold stimulus to the face. Your cardiologist can show you how to do these safely. If an episode does not stop, lasts a long time, or is accompanied by chest pain, severe breathlessness or fainting, seek urgent medical care.
The key test is a 12-lead ECG, which records the heart’s electrical activity and shows the type of tachycardia. If episodes come and go, a Holter monitor, event recorder or implantable loop recorder can capture them. An echocardiogram, blood tests and sometimes an electrophysiology study complete the assessment.
Many types of SVT can be effectively eliminated with catheter ablation, which interrupts the extra circuit responsible for the fast rhythm and has a high success rate. Sinus tachycardia is treated by addressing its cause. Ventricular tachycardia is managed with medication, ablation and, in selected patients, an implantable defibrillator; the approach depends on the underlying heart condition.
Call 995 or go to the nearest A&E if a fast heartbeat comes with chest pain or pressure, severe shortness of breath, fainting or near-fainting, or signs of a stroke. A sustained very fast heart rate that does not settle also needs urgent assessment. Otherwise, book a non-urgent specialist consultation for a proper evaluation.
A rate of 150 to 170 at rest is faster than expected and should be checked, especially if it starts suddenly or comes with symptoms. During vigorous exercise, however, a rate in this range can be normal for many people. What matters is the context and whether the rhythm is normal (sinus) or an arrhythmia such as SVT — an ECG tells them apart.
Costs depend on the type of tachycardia and the treatment. Many patients need only a consultation, ECG and simple tests. For procedures such as catheter ablation, Singapore’s Ministry of Health publishes fee benchmarks, and hospital facility, anaesthesia and device charges are billed separately. See our catheter ablation page for an indication of procedure fees; exact costs are confirmed at consultation.
