Swan-Ganz Catheter Waveforms

As a Swan-Ganz (pulmonary artery) catheter is floated from the right atrium to the wedge position, each chamber writes its own signature pressure waveform. Learn to read all four — RA, RV, PA, and PCWP — recognise the transitions on the way in, and spot the abnormal patterns the RCIS exam loves.

The short answer

The single most useful skill is reading the transitions — the moment the diastolic pressure steps up tells you the tip has crossed the pulmonic valve into the PA, and the moment the tracing suddenly damps tells you it has wedged. Everything below builds that skill, starting with a live tracing you can play with.

See the waveforms live

Static pictures only get you so far. The interactive atlas below draws each pressure tracing in real time, synced to an ECG, with the a/c/v waves labelled. Switch chambers on and off, flip between a normal and an abnormal heart, and watch how breathing changes the pressures.

Open the interactive atlas full-screen → · Prefer paper? Grab the printable pressure-waveform poster.

The catheter's journey: RA → RV → PA → wedge

A Swan-Ganz catheter is flow-directed. You inflate a small balloon at the tip and let the bloodstream carry it forward — from a central vein into the right atrium, across the tricuspid valve into the right ventricle, out through the pulmonic valve into the pulmonary artery, and finally into a branch small enough that the balloon "wedges" and occludes it. Each stop has a distinct pressure signature, so the waveform on the monitor is your map.

Because the tip physically moves through the heart, you should always know which waveform you're looking at before you trust a number. Reading a "PA pressure" that is actually a damped RV tracing is a classic error — and one the transitions below help you avoid.

Right atrial (RA) waveform

The right atrial tracing is low and gentle, with a mean pressure of just 2–6 mmHg. It carries three positive waves and two descents:

• a wave — atrial contraction (follows the P wave on the ECG).
• c wave — the tricuspid valve bulging back as the ventricle starts to contract.
• x descent — atrial relaxation.
• v wave — the atrium filling against a closed tricuspid valve.
• y descent — the tricuspid opens and the atrium empties.

In a normal heart the a wave is slightly taller than the v wave. When those waves change shape, they tell a story: a giant a wave points to tricuspid stenosis or a stiff, hypertensive right ventricle, while a broad cv wave that makes the atrium look ventricular is the hallmark of tricuspid regurgitation.

Right ventricular (RV) waveform

Cross the tricuspid valve and the picture changes dramatically. The right ventricle produces a tall, sharp systolic spike — normally around 15–30 mmHg — that falls almost to zero in early diastole before a small end-diastolic rise (about 2–8 mmHg) from atrial filling.

Two features define the RV tracing: a rapid upstroke and a low, near-zero diastole. That near-zero diastolic pressure is the key to the next transition — because the pulmonary artery, which shares the RV's systolic height, will not let the diastole fall back to zero.

Pulmonary artery (PA) waveform

Once the tip clears the pulmonic valve, the systolic pressure stays about the same (15–30 mmHg) but two things give the pulmonary artery away:

1. The diastolic pressure steps up to roughly 8–15 mmHg — it no longer drops toward zero, because the closed pulmonic valve holds a column of blood back.
2. A dicrotic notch appears on the downstroke, marking pulmonic valve closure.

That diastolic step-up is the most reliable sign you've entered the PA. In the absence of lung disease, the PA diastolic pressure roughly tracks the wedge pressure, which is why clinicians sometimes use it as a quick estimate of left-heart filling.

Pulmonary capillary wedge pressure (PCWP)

Inflate the balloon and advance a little further and the pulsatile PA tracing suddenly damps down into a low, rounded waveform with a mean of 6–12 mmHg. This is the wedge — the catheter now "sees" through the still column of blood to the left atrium, so the wedge tracing carries a and v waves just like an atrial pressure (only slightly delayed).

Because it reflects left atrial pressure, the wedge is where left-sided disease shows up. A giant v wave is the classic sign of mitral regurgitation, and a persistently high mean suggests left-heart failure or volume overload. Deflate the balloon the moment you've recorded the wedge — leaving it inflated risks pulmonary infarction or, rarely, artery rupture.

Normal pressures at a glance

Site	Systolic / Diastolic	Mean	Waveform clue
Right atrium (RA)	—	2–6	Small a, c, v waves
Right ventricle (RV)	15–30 / 2–8	—	Sharp spike, diastole ≈ 0
Pulmonary artery (PA)	15–30 / 8–15	10–20	Diastole steps up + dicrotic notch
Wedge (PCWP)	—	6–12	Damped, a and v waves

Want these on one page? The printable normal hemodynamic values cheat sheet has every chamber pressure, oxygen saturation, and derived value, and the hemodynamic calculator works out cardiac output, resistances and more from your own numbers.

Reading the transitions (the exam favourite)

Registry exams and real cath labs both test whether you can name the chamber from the waveform alone. Anchor on these three moments:

Transition	What changes on the monitor
RA → RV	Systolic pressure jumps up (≈5 → ≈25 mmHg); a tall spike appears.
RV → PA	Systolic stays the same but diastole rises off zero and a dicrotic notch appears.
PA → wedge	The pulsatile trace damps to a low mean with a and v waves.

Abnormal waveforms to recognise

Once the normals are automatic, the abnormal patterns become easy to spot — and each one maps to a diagnosis:

• Giant v wave on the wedge → acute mitral regurgitation.
• Tall a wave on the RA → tricuspid stenosis, or a non-compliant right ventricle (pulmonary hypertension).
• Broad cv wave / "ventricularised" RA → tricuspid regurgitation.
• Blunted y descent with elevated, equal pressures → cardiac tamponade.
• Prominent, steep y descent with an M/W shape and a ventricular dip-and-plateau → constrictive pericarditis.

You can flip through every one of these in the interactive atlas above (choose the condition from the list), then test yourself on the pressure-waveform question bank.

Common artefacts & troubleshooting

Not every odd-looking tracing is a disease. Know the artefacts:

• Overdamping (air bubble, clot, kink, or a loose connection) — the waveform looks sluggish and loses its dicrotic notch. Flush the line and check connections before you trust the reading.
• Underdamping / catheter "whip" — an over-shooting, ringing trace that overestimates systolic pressure. Remove excess tubing or air.
• Over-wedging — the pressure keeps climbing after balloon inflation because the balloon is over-distended. Deflate immediately.
• Spontaneous or persistent wedge — a wedge tracing with the balloon down means the tip has drifted too far distally. Pull it back to avoid pulmonary infarction.

Why these waveforms matter clinically

Beyond passing the exam, the pulmonary artery catheter answers real bedside questions. The pressures and waveforms help clinicians differentiate the types of shock, measure cardiac output by thermodilution, gauge left- and right-heart filling, detect valve lesions, and track a patient's response to fluids, inotropes, or diuretics. Reading the tracing correctly is the foundation for all of it.

For the bigger picture, our hemodynamics study guide ties waveforms, pressures, and cardiac-output calculations together, and the Swan-Ganz catheter overview covers insertion, indications, and complications.

Frequently asked questions

What are the four Swan-Ganz catheter waveforms?

As the catheter advances it records four tracings in order: right atrium (small a, c, v waves, mean 2–6 mmHg), right ventricle (sharp systolic spike with near-zero diastole, ≈25/4), pulmonary artery (same systolic height but a higher diastole with a dicrotic notch, ≈25/10), and the pulmonary capillary wedge (a damped, atrial-looking trace, 6–12 mmHg).

How do you tell the RV waveform from the PA waveform?

Look at the diastolic pressure. The right ventricle's diastole falls almost to zero, while the pulmonary artery's diastole stays elevated (8–15 mmHg) and shows a dicrotic notch. The systolic pressures are similar, so the diastole is the giveaway.

What does the wedge pressure represent?

With the balloon inflated, the catheter tip reads through a static column of blood back to the left atrium, so the pulmonary capillary wedge pressure (PCWP) estimates left atrial and left-ventricular filling pressure — normally 6–12 mmHg.

What causes a giant v wave on the wedge tracing?

A tall v wave on the wedge is classic for mitral regurgitation, where blood leaks back into a non-compliant left atrium during systole. Acute, severe regurgitation produces the biggest v waves.

What are the a, c, and v waves?

The a wave is atrial contraction, the c wave is the AV valve bulging in early systole, and the v wave is atrial filling against a closed valve. The x descent follows atrial relaxation and the y descent follows valve opening.

Why must you deflate the balloon after wedging?

Leaving the balloon inflated occludes the pulmonary artery branch and can cause pulmonary infarction or, rarely, arterial rupture. Record the wedge quickly, then deflate.

What is a normal pulmonary artery pressure?

About 15–30 mmHg systolic over 8–15 mmHg diastolic, with a mean of roughly 10–20 mmHg. A markedly elevated PA pressure suggests pulmonary hypertension.

Is the Swan-Ganz catheter still used?

Yes, though more selectively than in the past. It remains valuable in complex shock, severe heart failure, pulmonary hypertension work-ups, and cardiac surgery, where direct pressure and cardiac-output data guide management.