Private ECG
A 12-lead ECG for palpitations, irregular pulse, dizziness, chest symptoms and cardiac screening.
Private ECG London · Palpitations · Rhythm checks
Irregular Heartbeat Explained: What Can an ECG Detect?
An irregular heartbeat can feel like fluttering, racing, skipped beats or sudden pauses. A 12-lead ECG is often the first test used to assess the heart’s electrical rhythm and identify important arrhythmias, including atrial fibrillation, atrial flutter, SVT, bradycardia, heart block and other conduction abnormalities.
Quick testNon-invasive 12-lead ECG
Best forRhythm, rate and conduction
Next stepHolter or Echo if needed
Quick answer: what can an ECG detect?
An ECG records the electrical activity of the heart. It can detect rhythm problems such as atrial fibrillation, atrial flutter, supraventricular tachycardia, bradycardia, heart block, long QT patterns, ectopic beats and some signs of previous or current heart strain.
A normal ECG is reassuring, but it is only a short recording. If symptoms come and go, ambulatory ECG or Holter monitoring may be recommended to record the rhythm over a longer period.
An irregular heartbeat, medically known as an arrhythmia, occurs when the electrical system that controls the heart’s rhythm is disrupted. Some arrhythmias are harmless, while others may increase the risk of stroke, heart failure, fainting, blood clots or serious cardiac events.
What is an ECG?
An electrocardiogram, or ECG, is a simple, painless and non-invasive test that records the heart’s electrical signals. Small sticky electrodes are placed on the chest, arms and legs. The machine then records the heart rhythm as waveforms that can be interpreted by a trained clinician.
An ECG helps assess heart rate, rhythm, conduction pathways, electrical strain, some inherited electrical conditions, some electrolyte-related changes and evidence suggestive of previous heart muscle injury.
At London Private Ultrasound, patients can book a private ECG in London for palpitations, dizziness, chest symptoms, cardiovascular screening or rapid rhythm assessment.
How does the heart’s electrical system work?
The heartbeat begins in the sinoatrial node, often called the heart’s natural pacemaker. Electrical impulses then travel through the atria, the atrioventricular node, the Bundle of His, the Purkinje fibres and finally the ventricles. This sequence allows the heart to pump blood efficiently.
Disruption anywhere in this pathway can cause an irregular, fast, slow or unpredictable heartbeat.
What does an irregular heartbeat feel like?
Common sensations
Fluttering, skipped beats, thumping, racing, pauses or a “flip-flop” sensation in the chest.
When it happens
Symptoms may occur at rest, during exercise, at night, after caffeine, during illness or during stress.
How long it lasts
Episodes may last seconds, minutes or hours. Intermittent symptoms may not appear on a short ECG.
8 rhythm problems an ECG can help detect
| ECG finding | What it means | Why it matters |
|---|---|---|
| 1. Atrial fibrillation | An irregular and often fast rhythm from the upper chambers. | AF can increase stroke risk and often needs structured assessment. |
| 2. Atrial flutter | A more organised rapid atrial rhythm, sometimes with a saw-tooth ECG pattern. | May cause palpitations, breathlessness and stroke-risk concerns. |
| 3. Supraventricular tachycardia | A fast rhythm starting above the ventricles. | Often causes sudden racing heartbeat, dizziness or chest tightness. |
| 4. Premature atrial contractions | Extra beats from the atria. | Often benign, but frequent episodes may need review in context. |
| 5. Premature ventricular contractions | Extra beats from the ventricles. | Usually harmless when occasional, but frequent PVCs may need Echo or cardiology assessment. |
| 6. Bradycardia | A slower-than-expected heart rate. | May be normal in athletes or during sleep, but can cause dizziness or blackouts. |
| 7. Heart block | Electrical signals are delayed or interrupted. | Severe forms may cause fainting, collapse or require urgent specialist care. |
| 8. Long QT pattern | Delayed electrical recovery after each heartbeat. | Can be associated with dangerous arrhythmias in selected patients. |
Atrial fibrillation and stroke risk
Atrial fibrillation is one of the most common sustained arrhythmias. The atria beat chaotically and the heartbeat becomes irregular. Some patients feel palpitations, fatigue, dizziness or breathlessness, while others have no symptoms.
AF is clinically important because sluggish blood flow in the atria can allow clots to form. These clots may travel to the brain and cause a stroke or transient ischaemic attack. NICE guidance covers diagnosis and management of AF, including stroke and bleeding risk assessment.
Patients with AF or cardiovascular risk factors may also benefit from wider vascular assessment, including carotid Doppler ultrasound or heart health and stroke-risk screening.
Can an ECG detect a heart attack or heart failure?
Heart attack
An ECG is a key urgent test for suspected heart attack and may show changes suggesting reduced blood flow, current injury or previous heart muscle damage. A normal ECG does not always exclude coronary artery disease, so further assessment may be needed depending on symptoms.
Heart failure
An ECG can show clues associated with heart failure, but it cannot accurately measure pumping function. An echocardiogram is the main ultrasound test used to assess heart muscle strength, valve function, chamber size and cardiac structure.
ECG vs echocardiogram: what is the difference?
Many patients confuse ECG with echocardiogram. The tests are different and often complementary.
| Test | Main purpose | Useful for |
|---|---|---|
| ECG | Records electrical activity. | Arrhythmias, heart rate, rhythm disorders, conduction abnormalities and some heart attack patterns. |
| Echocardiogram | Uses ultrasound to show structure and function. | Heart failure, valve disease, cardiomyopathy, pulmonary hypertension and chamber enlargement. |
If palpitations are linked with breathlessness, abnormal ECG findings, high blood pressure, valve concerns or family history, a cardiologist consultation with ECG and echocardiogram may provide a more complete assessment.
What causes irregular heartbeats?
Lifestyle triggers
Stress, anxiety, poor sleep, caffeine, alcohol, dehydration and smoking can all contribute to palpitations.
Medical causes
High blood pressure, thyroid disease, coronary artery disease, valve disease, heart failure and cardiomyopathy may contribute.
Blood and medication factors
Low potassium, low magnesium, anaemia, dehydration and certain medicines can affect rhythm.
When is Holter monitoring needed?
A standard ECG records a short rhythm snapshot. If symptoms are intermittent, the ECG may look normal if the episode is not happening during the test. In this situation, ambulatory ECG monitoring or Holter monitoring can record the rhythm during normal daily activities over a longer period.
Holter monitoring may be useful for intermittent palpitations, dizziness, unexplained near-fainting, suspected arrhythmia, treatment monitoring or symptoms not captured during a standard ECG.
Who should consider an ECG?
You may consider an ECG if you experience palpitations, irregular heartbeat, dizziness, blackouts, chest discomfort, breathlessness, high blood pressure, known cardiovascular disease or a family history of sudden cardiac death. Preventive ECG screening may also be useful in selected patients as part of a wider cardiovascular review.
Seek urgent medical help immediately if palpitations are associated with severe chest pain, collapse, loss of consciousness, severe breathlessness, sudden weakness, rapid sustained symptoms or signs suggestive of heart attack, stroke or serious arrhythmia.
London Private Ultrasound heart rhythm and cardiac services
Holter Monitoring
Extended ECG monitoring to capture rhythm problems that may not appear during a short ECG.
Echocardiogram
Assesses heart structure, valves, chambers, pumping strength and possible structural causes of symptoms.
Cardiologist + ECG + Echo
A joined-up specialist appointment for symptoms or more complete cardiac assessment.
Heart Health Checks
Structured packages combining ECG, echocardiogram, cardiology assessment and selected blood tests.
Heart & Stroke Screening
Cardiac and vascular screening for selected patients with cardiovascular risk factors.
Concerned about an irregular heartbeat?
Book a private ECG, Holter monitor, echocardiogram or cardiology pathway with London Private Ultrasound.
Irregular heartbeat ECG FAQs
Can an ECG detect an irregular heartbeat?
Yes. An ECG records the electrical rhythm of the heart and can detect many arrhythmias, including atrial fibrillation, atrial flutter, SVT, bradycardia and heart block, if they are present during recording.
What if my ECG is normal but I still get palpitations?
A normal ECG may mean the rhythm was normal during the short recording. If symptoms are intermittent, ambulatory ECG or Holter monitoring may be needed.
Can an ECG detect atrial fibrillation?
Yes. A 12-lead ECG is a key test for diagnosing atrial fibrillation when an irregular rhythm is present.
Do I need an echocardiogram as well as ECG?
You may need an echocardiogram if there are symptoms or risk factors suggesting structural heart disease, such as breathlessness, murmur, abnormal ECG, high blood pressure, heart failure concern or frequent ectopic beats.
Is an ECG painful?
No. A standard ECG is painless, non-invasive and does not use radiation.
Can I book a private ECG without a GP referral?
At London Private Ultrasound, many ECG, echocardiogram, Holter and heart health pathways can be booked directly without a GP referral.
Trusted medical references
These followed outbound links are included for patient education and Rank Math-recognised external authority signals.
NHS: Heart rhythm problems (arrhythmia) NHS: Heart palpitations NICE NG196: Atrial fibrillation diagnosis and management British Heart Foundation: Atrial fibrillation American Heart Association: Arrhythmia British Society of EchocardiographyArticle preparation and clinical review
This patient information page was prepared with AI-assisted editorial support and reviewed for clinical accuracy by:
Dr Pedram Aghaei — Vascular Scientist, SVT reg. SVT 679 · Registered Clinical Technologist, RCT reg. 93290 · BMUS: 20702
Dr Hosna Rashidi — BMUS 29386 · SVT reg: 1756
This article is intended for general patient information only and does not replace a medical consultation.