Cardiac electrophysiology · Patient guide
EP study, the cardiac electrophysiology test explained — what to expect from a diagnostic and ablation procedure.
An EP (electrophysiology) study is a catheter test that maps the heart’s electrical wiring. It pinpoints where a complex arrhythmia is coming from. Most cases are treated with an ablation in the same session.
Key facts
What an EP study is — at a glance.
Six facts that frame every conversation about an EP study — the access, the mapping, the team, the numbers.
- 01
Definition
A catheter mapping study of the heart’s wiring, usually with an ablation in the same session.
- 02
Day-case or short-stay
Performed as a day-case, or with a short overnight stay in complex cases.
- 03
Femoral venous access
Multipolar catheters are introduced via the femoral vein under conscious sedation.
- 04
3D electroanatomic mapping
CARTO and EnSite systems improve accuracy, safety and long-term outcomes.
- 05
> 95% success for typical cases
Success rates exceed 95% for typical atrial flutter and AVNRT.
- 06
Multi-disciplinary EP team
Consultant electrophysiologist, cardiac physiologists, anaesthetist and imaging support.
This page is a focused guide to the EP study itself. For the wider discipline — cardiac electrophysiology and its full range of diagnostic and therapeutic procedures — see our full cardiac electrophysiology page.
Diagnosis and preparation
From consultation to catheter — what happens, in order.
Seven steps take you from first EP consultation through the mapping study and onward follow-up.
Phase 1 · Before the procedure
Consultation, medication review, fasting
Phase 2 · On the day
Access, mapping, ablation
Phase 3 · After
Same-day follow-up
- 01
Before
EP consultation
A consultant electrophysiologist reviews your rhythm history, ECGs and monitoring, and consents you for the study.
- 02
Before
Withhold antiarrhythmics if requested
Some antiarrhythmic drugs are stopped a few days beforehand so the arrhythmia can be provoked and mapped.
- 03
Before
Fasting 6 hours
Nil by mouth for 6 hours before the procedure; take usual medications with a sip of water unless otherwise advised.
- 04
On the day
Femoral venous access
Multipolar catheters are placed via the femoral vein under conscious sedation or light general anaesthetic.
- 05
On the day
Diagnostic mapping and provocation
Programmed stimulation and 3D mapping identify the arrhythmia mechanism and its exact origin.
- 06
On the day
Ablation as indicated
Where a target is identified and consented, radiofrequency or cryoablation is delivered in the same session.
- 07
After
Same-day cardiology follow-up
Access-site check, rhythm confirmation and a plan for anticoagulation and structured EP review.
What it shows
The arrhythmias an EP study identifies.
The study identifies the mechanism — reentrant, focal or accessory — and, where safe, treats it in the same session.
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AVNRT (AV nodal re-entry)
The commonest supraventricular tachycardia in young adults — highly amenable to slow-pathway ablation.
-
Accessory pathway (WPW)
Wolff–Parkinson–White syndrome — pre-excitation and orthodromic AVRT, ablated at the pathway.
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Focal atrial tachycardia
A focal driver rather than a reentrant circuit — mapped and ablated at the origin.
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Atrial flutter
Typical isthmus-dependent flutter is defined electrophysiologically and ablated in the same session.
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AF triggers
Pulmonary vein and non-pulmonary vein triggers of atrial fibrillation are identified and isolated.
-
Ventricular tachycardia foci
Idiopathic and scar-related VT foci are mapped and, where safe, ablated.
-
Congenital arrhythmia substrates
Complex substrates in adult congenital heart disease benefit from 3D mapping and multi-disciplinary planning.
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Red flag: tamponade or complete heart block — urgent management
Rare but time-critical — recognised on-table and escalated immediately.
Next steps
After the study — what happens next.
An EP study is a moment in a longer rhythm-control pathway. These eight steps are how good electrophysiology teams follow through.
-
Radiofrequency ablation
Heat energy delivered through the catheter tip creates focal lesions that interrupt the arrhythmia.
-
Cryoablation
Freezing energy creates reversible and then permanent lesions — favoured for pathways near the AV node.
-
Pulmonary vein isolation
Electrical isolation of the pulmonary veins is the cornerstone of paroxysmal AF ablation.
-
WPW accessory-pathway ablation
Definitive treatment for symptomatic Wolff–Parkinson–White syndrome.
-
Substrate-based VT ablation
Scar mapping and substrate modification for scar-related ventricular tachycardia.
-
Anticoagulation post-procedure
Peri-procedural anticoagulation continues for a defined period depending on the substrate.
-
Structured EP follow-up
Scheduled review with the electrophysiology team, rhythm monitoring and echocardiography as indicated.
-
Repeat ablation if recurrence
A second, mapped procedure is offered where arrhythmia recurs — success rates remain high.
Red flags and complications
The complications every patient should know about.
Most are uncommon, several are rare — all are discussed as part of informed consent.
-
Cardiac tamponade
A rare but life-threatening peri-procedural complication requiring immediate pericardiocentesis.
-
Femoral vascular injury
Haematoma, pseudoaneurysm or arteriovenous fistula at the venous access site.
-
Cerebrovascular event
Peri-procedural stroke or transient ischaemic attack despite anticoagulation.
-
Phrenic nerve injury
A recognised risk of right-sided and pulmonary vein ablation — usually transient.
-
Complete heart block
AV nodal injury with a small risk of permanent pacemaker requirement.
-
Recurrent arrhythmia post-ablation
Recurrence warrants prompt electrophysiology review and consideration of redo ablation.
-
Post-op infection
Access-site or systemic infection is uncommon and managed on standard pathways.
-
Contrast-induced kidney injury
A recognised risk where iodinated contrast is used — mitigated by hydration and dose limitation.
-
Late-onset atypical flutter
An atypical, often left atrial circuit may emerge later and require 3D mapping and reintervention.
Sources
The guidelines this guide follows.
Clinically reviewed by Pulse Atlas Editorial Board (). Next review 2027-07-30. Reading time 6 minutes.
- 01 Guideline
European Society of Cardiology — Guidelines on the management of supraventricular tachycardia and atrial fibrillation.
European Society of Cardiology — Guidelines on the management of supraventricular tachycardia and atrial fibrillation. - 02 Guideline
Heart Rhythm Society — Expert consensus statements on catheter and surgical ablation.
Heart Rhythm Society — Expert consensus statements on catheter and surgical ablation. - 03 Guideline
British Heart Rhythm Society — Standards and clinical guidance for electrophysiology.
British Heart Rhythm Society — Standards and clinical guidance for electrophysiology. - 04 Guideline
NICE. Atrial fibrillation: diagnosis and management (NG196).
NICE. Atrial fibrillation: diagnosis and management (NG196).
Frequently asked
Everything patients ask about the EP study.
What it is, whether it always includes ablation, which arrhythmias it treats, and how it fits with the full cardiac electrophysiology page.
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What is an EP study?
An electrophysiology (EP) study is an invasive cardiac catheter procedure that maps your heart’s electrical system. Multipolar catheters are placed via the femoral vein, programmed stimulation is used to provoke arrhythmias, and 3D electroanatomic mapping localises the mechanism. Where a target is identified and consented, catheter ablation is delivered in the same session.
-
Is an EP study always combined with ablation?
Not always, but frequently. Where the arrhythmia mechanism is confirmed and a safe ablation target is identified, most modern EP labs proceed to catheter ablation in the same session — sparing the patient a second procedure.
-
What arrhythmias can be mapped and treated?
AVNRT, accessory pathways (Wolff–Parkinson–White syndrome), focal atrial tachycardia, atrial flutter, atrial fibrillation triggers, and selected ventricular tachycardia foci — including complex substrates in adult congenital heart disease.
-
How long does an EP study take?
A diagnostic study takes 60–90 minutes. Combined with ablation, procedures typically take 2–4 hours depending on the substrate. Most patients are day-cases; complex cases may need an overnight stay.
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What are the risks of an EP study?
Serious complications are uncommon and include cardiac tamponade, femoral vascular injury, cerebrovascular events, phrenic nerve injury and — very rarely — complete heart block requiring a pacemaker. All are discussed as part of informed consent.
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How is an EP study different from the full electrophysiology page?
This is a focused patient guide to the EP study itself. For the wider context — the discipline of cardiac electrophysiology, its full range of diagnostic and therapeutic procedures — see our full cardiac electrophysiology page.
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In practice, in London
Booking ep study privately in London — what actually happens
With ep study, the London question is usually about report turnaround and the radiologist reading it — not whether the scan is available. The NHS route for ep study is thorough, but the queue is real. Most patients we speak with have been told to expect anywhere from a handful of weeks to several months, depending on their local trust and how the referral is graded. Going private in London usually collapses that window to a matter of days — often the same week if the diary allows. It isn’t about jumping a queue so much as buying time back while you still have the flexibility to plan around it.
A typical private booking for ep study in London starts with a consultant conversation — sometimes in person on Harley Street or Marylebone, sometimes on video if that suits better. Any imaging or diagnostics happen at a nearby CQC-registered facility, and reports usually land within 24 to 72 hours. The whole loop, from first call to written report, is often done inside a fortnight. For ep study specifically, the difference between a routine report and a sub-speciality read is where private care earns its keep.
There are a lot of consultants in London who can technically handle ep study. Fewer who do it week in, week out for the exact question you’re bringing. We spend most of our time working out which is which — and being straight when a different test or a different specialist would serve you better. Everything runs to CQC, GMC and Royal College standards; the choice is about fit, not floor.
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