Invasive Electrophysiology

Electrophysiology Study (EPS)

An electrophysiology study records electrical signals from inside the heart. These recordings may help identify the mechanism and origin of a rhythm disorder and support treatment planning.

Book an Appointment
Catheter Ablation
INTRACARDIAC CATHETERSHPACING STIMULUSATRIAL ELECTROGRAMAHIS ELECTROGRAMHVENTRICULAR ELECTROGRAMVACTIVATION SEQUENCE A → H → VEP STUDY — CATHETER RECORDING AND PACING

On this page

Understanding EPS

What Is an Electrophysiology Study?

An electrophysiology study (EPS) is a catheter-based test that records the heart’s electrical signals from inside the heart. Thin, flexible catheters with electrodes are placed at selected locations, so that electrical activity can be recorded directly where it occurs.

It allows the physician to assess how electrical signals are conducted through the heart and to analyse the mechanism of a rhythm disorder.

  • Intracardiac recordings
  • Assessment of electrical conduction
  • Analysis of the rhythm mechanism

Intracardiac recording from catheter electrodes

Purpose

Why Is EPS Performed?

An EPS may be considered when other tests do not give enough information, or when treatment is being planned. Its purposes may include:

Rhythm mechanism assessment

Understanding how a rhythm disorder starts and is sustained.

Arrhythmia diagnosis

Clarifying the type of arrhythmia when it is not clear from other tests.

Localisation

Identifying where in the heart an arrhythmia arises.

Treatment planning

Informing decisions about how the rhythm disorder may be treated.

Evaluation before or during ablation

Assessing the rhythm where ablation is considered or performed.

Vascular access routes to the heart

Getting to the heart

Catheter Access

Catheters reach the heart through blood vessels. In general terms, thin catheters are introduced through a vein, commonly in the groin, and guided towards the heart using imaging guidance.

The access route depends on the study being performed and on the individual patient. It is explained to each patient before the procedure.

Recording sites

Catheter Positions

Catheters may be positioned at different locations inside the heart so that electrical activity can be recorded from several regions at the same time. The locations used depend on the rhythm problem being studied.

Catheter positions within the heart

Locations commonly used, depending on the study:

  • High right atrium
  • His-bundle region
  • Right ventricle
  • Coronary sinus

Intracardiac signals

Reading Signals From Inside the Heart

Electrodes on the catheters record electrograms: electrical signals from the tissue they touch. Comparing the timing and sequence of these signals helps the electrophysiologist understand how activation spreads through the heart.

Atrium

Atrial electrograms

Record the electrical activation of the atria.

His region

His-region signals

Recorded near the His bundle, part of the normal conduction pathway between the atria and the ventricles.

Ventricle

Ventricular electrograms

Record the electrical activation of the ventricles.

Testing conduction

Programmed Stimulation

During an EPS, the heart can be paced through the catheters using carefully timed electrical impulses. This is called programmed stimulation. It may be used to:

  • Assess conduction through the heart's electrical pathways
  • Deliver programmed pacing at selected rates and timings
  • Induce an arrhythmia where clinically indicated, so its mechanism can be studied
  • Assess the rhythm mechanism

Arrhythmia induction is performed only where clinically indicated and under careful monitoring.

Programmed pacing and arrhythmia assessment

Interpreting the recordings

Arrhythmia Localisation

By comparing the timing and sequence of recorded signals, the electrophysiologist may be able to work out where an arrhythmia arises and how it is sustained. What can be identified depends on the type of arrhythmia.

Focal origin

A small area from which abnormal electrical activity spreads outward.

Abnormal pathway

An extra electrical connection that bypasses the normal conduction route.

Re-entry circuit

A loop in which an electrical impulse travels repeatedly.

Substrate

Tissue whose electrical properties allow an arrhythmia to start or continue.

Before the study

Preparation

You will be given individual instructions. These may cover eating and drinking beforehand and whether to continue or pause some medicines, especially rhythm medicines or blood thinners. Do not change any medicine unless the team has told you to.

Tell the team about allergies, previous procedures and any recent illness. Recent tests such as an ECG or blood tests may be requested.

Step by step

Procedure Steps

The sequence below is general. The steps performed depend on the patient and the findings.

Vascular access

Catheters are introduced through blood vessels.

Catheter placement

Catheters are guided to selected positions in the heart.

Signal recording

Intracardiac signals are recorded.

Programmed stimulation

The heart is paced with timed impulses where needed.

Arrhythmia assessment

The rhythm mechanism is analysed.

3D mapping

A 3D map is created where appropriate.

Ablation if indicated

Treatment is delivered only if it is appropriate.

Reassessment

Electrical behaviour is checked again.

Before Your Procedure

Patient experience

What You May Experience

An EPS is carried out in a specialised procedure room by an electrophysiology team. Catheters are introduced through a vein, usually in the groin, and the entry site is prepared so that you are comfortable. You will be told beforehand whether you will be awake, sedated or under anaesthesia.

You may feel some pressure at the entry site. When pacing is used to bring on a rhythm, you may notice your heartbeat change, for example palpitations or a racing heart. The team monitors you closely throughout. Tell the team about anything you feel.

Related technology

3D Mapping, When It Is Used

In some studies a 3D electroanatomical mapping system is used alongside the catheter recordings. It combines the tracked position of the catheter with recorded electrical signals to build a three-dimensional model of a heart chamber and to show how activation spreads across it.

It is not part of every EPS. Whether it is useful depends on the arrhythmia being studied and on whether treatment is being planned. Activation maps, voltage maps and how targets are identified are explained on the dedicated page.

3D Electroanatomical Mapping Page

If treatment is appropriate

If Ablation Is Performed

When ablation is appropriate, the study continues into treatment. These are the general stages.

EPS

Recordings and stimulation assess the rhythm.

Mapping

A 3D map shows the electrical activity.

Target Identification

The relevant region is identified.

Ablation

Energy is delivered to the selected area.

Reassessment

Electrical behaviour is checked again.

Catheter Ablation

After the study

Results and Next Steps

The recordings show how electrical signals travel through your heart and whether an arrhythmia can be started and explained. Findings may confirm the type of arrhythmia, show where it arises or how it is sustained, or show no abnormality at the time of the study. They are interpreted together with your symptoms and other tests.

Not every arrhythmia has a target suitable for ablation. Depending on the findings, the team may recommend ablation, medicine, further monitoring or no treatment, and the plan is discussed with you.

Recovery and follow-up

After the Procedure

Monitoring

Heart rhythm and general condition are observed after the procedure.

Access-site care

The area where catheters were introduced is checked, and instructions for care are given.

Rhythm assessment

The findings are reviewed and the heart rhythm is assessed.

Follow-up

A follow-up plan is explained, based on the findings and any treatment given.

After Your Procedure

Questions

Frequently Asked Questions

A catheter-based test in which electrical signals are recorded from inside the heart to assess conduction and the mechanism of a rhythm disorder.

It may be considered when other tests do not give enough information, or when treatment such as ablation is being planned.

No. Whether ablation is carried out depends on the findings and on clinical assessment.

Electrical signals recorded by catheter electrodes from inside the heart, such as atrial, His-region and ventricular electrograms.

Pacing of the heart with carefully timed impulses to assess conduction and, where clinically indicated, to study an arrhythmia.

No. 3D mapping is used in some studies, particularly when treatment is being planned. It builds a model of a heart chamber and shows how activation spreads across it. It is explained on the 3D Electroanatomical Mapping page.

You will be given instructions beforehand and told whether you will be awake, sedated or under anaesthesia. You may feel pressure at the entry site and may notice your heartbeat change when a rhythm is brought on. The team monitors you throughout.

A follow-up plan is explained after the procedure, based on the findings and any treatment given.

Continue reading

Related Topics

Scroll to Top