Electrophysiology (EP) study: a Cath Lab 101 guide
Reviewed by Rodnie Oro, cath lab charge nurse · Last reviewed: October 2026 · Education only, not medical advice
EP study in one minute
What it is: a test where thin catheters inside the heart record its electrical signals and use small pulses to test how the electrical system works.
Who it is for: people with palpitations, fast heart rhythms, unexplained blackouts or a slow heart rate, to find the cause; often combined with ablation.
Main risks: bruising in the groin, rhythm problems during the test, and rarely damage to a vessel or the heart.
Usually: under local anaesthetic with sedation, 1–2 hours, often home the same day.
On this page: What is an EP study? · Who is it for? · When is it done? · Step by step · Recovery · Risks · Kit list · First time in the lab? · FAQ
What is an EP study?
The heart's electrical system sets its rhythm. An electrophysiology (EP) study maps it from the inside.
- catheters with electrodes are placed in the right atrium, near the His bundle, and in the right ventricle
- they record electrical signals at each point
- small pacing pulses are used to trigger and study abnormal rhythms safely
If a treatable rhythm is found, ablation can often be done in the same session.
New to the acronyms? See the Cath Lab Abbreviations A–Z.
Who is it for?
It may be considered for people with:
- palpitations or fast rhythms such as SVT
- unexplained blackouts
- some slow heart rhythms
- assessing risk in some heart conditions
The decision is made by your heart team, who will talk through the reasons, the alternatives and the risks with you.
When is it done?
It can be planned in advance or done urgently. Before it, you usually have:
- blood tests, including kidney function and blood count
- an ECG, and often an echo or other scan
- a review of your medicines, especially blood thinners and diabetes medicines, as per centre protocol
- a chance to ask questions and give consent
Step by step
1. Getting ready
You lie on the table. Sticky pads go on your chest and back, and ECG, blood pressure and oxygen are monitored. You usually have sedation or a general anaesthetic, as per centre protocol. The groin is cleaned and numbed.
2. Access
Using ultrasound, sheaths are placed in the femoral vein in the groin, sizes per device and operator. Catheters are passed up to the heart under X-ray and a 3D mapping system.
3. Recording and testing
- A. Catheters in. Catheters are placed in the heart.
- B. Baseline. Normal signals are recorded.
- C. Pacing. Small pulses test the electrical system.
- D. Trigger. Abnormal rhythms are triggered and studied.
You may feel your heart racing during testing. This is expected and the team can stop it quickly.
4. Finishing
The catheters and sheaths are removed. The groin is closed with pressure or a stitch, per device and operator.
Recovery and aftercare
- First hours: bed rest while the groin settles; checks of the groin, rhythm and blood pressure, as per centre protocol.
- Going home: often the same day or the next morning.
- Groin: avoid heavy lifting and strenuous exercise for about a week.
- Medicines: take blood thinners and rhythm medicines exactly as advised.
- Driving: DVLA rules depend on the rhythm problem; ask your team.
- Follow-up: clinic review, sometimes with an ECG or heart monitor.
Call 999 if you have chest pain, breathlessness, fainting, signs of a stroke, or heavy bleeding or swelling at the access site.
Risks and complications
Your team will explain the risks that apply to you. Possible problems include:
- bruising in the groin
- fast rhythms during the test (expected, controlled)
- damage to a vein (uncommon)
- heart block (rare)
- fluid around the heart (rare)
Cath lab kit list (printable)
Barts example kit list
An example from one UK centre, written generically. Every lab has its own protocol, and sizes and doses vary.
- venous sheaths in the groin, sizes per device and operator
- diagnostic EP catheters, per operator
- recording system and stimulator
- ultrasound for vein access
- heparin, as per centre protocol
- sedation or anaesthetic, as per centre protocol
Procedural steps (Barts example)
- Pads on; monitoring; sedation
- Ultrasound-guided femoral venous access
- Catheters to high right atrium, His, right ventricle
- Baseline intervals recorded
- Pacing protocol; induction
- Ablation if planned; catheters out
First time in the cath lab?
đź’ˇ First-time tip
- Pads on first. Defibrillator pads on before starting.
- Talk to the patient. Warn about racing feelings.
- Annotate events. Mark inductions on the recording.
- Groin care. Bed rest as per centre protocol.
FAQ
Will I be awake?
Usually, with sedation.
Does it treat the problem?
The study diagnoses; ablation may treat it in the same session.
Is it painful?
Usually not, apart from local anaesthetic.
Related Cath Lab 101 guides
Sources
All checked on 10 October 2026. Each page's own date is shown where it gives one.
- Zeppenfeld K, et al. 2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Eur Heart J 2022;43(40):3997–4126. PubMed 36017572
- StatPearls (NCBI Bookshelf), search: electrophysiology study. ncbi.nlm.nih.gov/books
Disclaimer
Education only. This page is for general education for healthcare students, cath lab staff and curious readers. It isn't medical advice and doesn't replace advice from your own doctor, heart team or local unit protocols. Equipment and medicines are described generically. No product or manufacturer is recommended. If you think someone is having a heart emergency, call 999.
Disclosure: I work for a company that makes a device used in this procedure. This page is independent education, isn't sponsored or reviewed by any company, and doesn't recommend any product.
All diagrams on this page are original illustrations created for rodnieoro.com.
