Right and left heart catheterisation: a Cath Lab 101 guide
Reviewed by Rodnie Oro, cath lab charge nurse · Last reviewed: October 2026 · Education only, not medical advice
Right and left heart catheterisation in one minute
What it is: a test where thin tubes (catheters) measure pressures and oxygen levels inside the heart: one through a vein to the right side, and one through an artery to the left side.
Who it is for: people with valve disease, heart failure, pulmonary hypertension, congenital heart disease, or before a heart transplant or valve procedure.
Main risks: bruising at the wrist, arm, neck or groin, brief rhythm disturbances, and rarely damage to a vessel, heart attack or stroke.
Usually: under local anaesthetic, about 30–60 minutes, often home the same day.
On this page: What is right and left heart catheterisation? · Who is it for? · When is it done? · Step by step · Recovery · Risks · Kit list · First time in the lab? · FAQ
Right heart catheter (vein) and left heart catheter (artery).
What is right and left heart catheterisation?
The heart has two sides. The right side collects blood from the body and pumps it to the lungs; the left side pumps oxygen-rich blood to the body.
In this test:
a catheter goes through a vein (in the arm, neck or groin) into the right atrium, right ventricle and pulmonary artery
a second catheter goes through an artery (wrist or groin) into the aorta and often the left ventricle
the team records pressures, takes small blood samples to measure oxygen, and works out how much blood the heart pumps (cardiac output)
The numbers help the heart team understand how well the heart and valves are working and how much strain there is on the lungs. A coronary angiogram is often done at the same time.
How the pressures are measured
Each catheter is filled with fluid and connected to a pressure transducer, zeroed to air and levelled at the mid-chest. Every chamber has its own typical waveform. The team can also measure the gradient, the pressure drop across a narrowed valve, by recording either side of it, sometimes at the same time.
How cardiac output is measured
Cardiac output is how much blood the heart pumps each minute. Two main methods are used:
Thermodilution: cool saline is injected into the right atrium and a sensor near the catheter tip in the pulmonary artery measures the temperature change; usually three readings are averaged
Fick method: uses the oxygen levels in pulmonary artery and arterial blood, with the body's oxygen use, to calculate flow
The result is often divided by body size to give the cardiac index.
New to the acronyms? See the Cath Lab Abbreviations A–Z.
Who is it for?
It may be considered for people with:
narrowed or leaking heart valves, to measure how severe the problem is
heart failure, to guide treatment or before an advanced therapy such as a transplant
suspected or known pulmonary hypertension (high pressure in the lung arteries)
congenital heart disease or a suspected shunt (abnormal flow between the two sides)
unexplained breathlessness where scans have not given a clear answer
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
Before the procedure: tests and consent, medicine advice, checks on the day, then the cath lab.
Step by step
1. Getting ready
You lie on the X-ray table. ECG, blood pressure and oxygen levels are monitored. The skin over the access site is cleaned and numbed with local anaesthetic; some people also have light sedation, as per centre protocol.
2. Access
A sheath is placed in a vein, often at the elbow, neck or groin, and another in an artery, often the radial artery at the wrist or the femoral artery in the groin. Sizes per device and operator. Heparin may be given, dose as per centre protocol.
Access: Catheter in the right heart; Inferior vena cava; Sheath in right femoral vein.
3. Measurements
A. Right heart. A balloon-tipped catheter is floated through the right atrium and right ventricle into the pulmonary artery, recording pressures at each point.
B. Wedge pressure. The balloon is briefly wedged in a small lung artery to give an indirect reading of the left atrial pressure.
C. Samples and output. Small blood samples are taken for oxygen levels, and cardiac output is measured.
D. Left heart. The arterial catheter records the aortic and left ventricular pressures, sometimes at the same time as the right heart readings.
You may feel the occasional skipped beat as the catheter passes through the heart. This is expected and usually settles straight away.
A: right heart. B: wedge pressure. C: samples and output. D: left heart.
4. Finishing
The catheters are removed. The sheath is taken out and the site closed with pressure, a band or a closure device, per device and operator.
Recovery and aftercare
First hours: you rest while the nurses check the access site, pulse and blood pressure, as per centre protocol.
Going home: usually the same day, with someone to take you home.
Access site: avoid heavy lifting and strenuous activity for a few days; a small bruise is common.
Results: the team will usually explain the findings before you go home, and send a report to your own doctor.
Driving: ask your team; for a planned test it is often a couple of days, but it depends on your heart condition.
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 or bleeding at the access site (common, usually minor)
damage to the artery or vein at the access site (uncommon)
reaction to the contrast dye, or effects on kidney function
heart rhythm disturbances, usually brief
heart attack, stroke or serious complications (rare)
X-ray exposure, kept as low as possible
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 sheath, size per device and operator
arterial sheath (radial or femoral), size per device and operator
balloon-tipped flotation catheter for the right heart
pigtail or similar catheter for the left ventricle, per operator
pressure transducers zeroed and levelled at the mid-chest
blood gas syringes for oxygen samples
heparin, as per centre protocol
Main kit (generic): Sheath; Guidewire; Catheter; Pressure transducer.
Procedural steps (Barts example)
Transducers zeroed and levelled; baseline observations
Venous and arterial access
Right heart pressures: RA, RV, PA, wedge
Oxygen saturation samples; cardiac output
Left heart pressures: aorta and LV; simultaneous readings if needed
Catheters and sheaths out; haemostasis
After the procedure: (1) Site and rhythm checks; (2) Home for most; (3) Avoid heavy lifting; (4) Results and plan.
First time in the cath lab?
đź’ˇ First-time tip
Zero and level first. Every reading depends on the transducer being at the right height.Watch the ECG. Extra beats are common as the catheter crosses the valves.Label every sample. Mixing up blood gas syringes ruins the shunt and output calculations.Call out the numbers. Read pressures aloud for the recorder, in a set order.Balloon down before pulling back. Always deflate the flotation balloon before withdrawing it.
FAQ
Is it painful?
Most people feel only the local anaesthetic and some pressure. You may notice a few skipped beats.
Will I be awake?
Yes, usually, although light sedation is sometimes given.
Can it be done with an angiogram?
Yes. The coronary arteries are often checked in the same session.
When will I get the results?
Often before you go home, with a report sent to your own doctor.
Related Cath Lab 101 guides
Sources
All checked on 10 October 2026. Each page's own date is shown where it gives one.
McDonagh TA, et al. 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure. Eur Heart J 2021;42(36):3599–3726. PubMed 34447992
Vahanian A, et al. 2021 ESC/EACTS Guidelines for the management of valvular heart disease. Eur Heart J 2022;43(7):561–632. PubMed 34453165
British Heart Foundation. Tests and procedures. bhf.org.uk/informationsupport/tests
StatPearls (NCBI Bookshelf), search: right heart catheterization. ncbi.nlm.nih.gov/books
StatPearls (NCBI Bookshelf), search: cardiac output thermodilution Fick. 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 in the medical device industry. This page is independent education and isn't sponsored or reviewed by any company.
All diagrams on this page are original illustrations created for rodnieoro.com.
