Swan-Ganz Catheter (Pulmonary Artery Catheter): A Complete Guide

The Swan-Ganz catheter turned the bedside into a hemodynamics laboratory. This guide walks you through how it's threaded through the heart, the tell-tale waveform at every step, the numbers it measures, and when it's actually used today.

What is a Swan-Ganz catheter?

The Swan-Ganz catheter is a balloon-tipped, flow-directed catheter passed through the right heart into the pulmonary artery to measure pressures, cardiac output, and mixed-venous oxygen saturation. Named after Jeremy Swan and William Ganz, who introduced it in 1970, it is more formally called a pulmonary artery catheter (PAC). Its genius is the tip balloon: inflated, it lets the flow of blood carry the catheter forward and lets the operator "wedge" it to sample downstream pressure.

Parts of the catheter

A standard PAC has several lumens and ports, each with a job:

Component	Function
Distal (PA) lumen	Measures pulmonary artery and wedge pressure; samples mixed-venous blood
Proximal (RA) lumen	Measures right atrial / central venous pressure; injects saline for thermodilution
Balloon	Inflated with ~1.5 mL air to float the tip and to wedge
Thermistor	Measures blood temperature near the tip for thermodilution cardiac output

Insertion: the waveform at every chamber

The catheter is introduced through a central vein — usually the right internal jugular or subclavian — and advanced with the balloon up. As the tip crosses each chamber, the pressure tracing changes in a way you can recognise blindfolded. Reading that sequence is the single most important Swan-Ganz skill.

The give-away that you've crossed from the right ventricle into the pulmonary artery is the step-up in diastolic pressure and the appearance of a dicrotic notch. When the trace suddenly damps into a low a/v pattern, you've wedged — deflate the balloon and pull back slightly so it sits in the PA. Practise identifying these on our pressure-waveform questions.

What the Swan-Ganz catheter measures

From one catheter you get a remarkably complete hemodynamic picture:

• Right atrial / central venous pressure (CVP) — right-heart filling.
• Right ventricular and pulmonary artery pressures.
• Pulmonary capillary wedge pressure (PCWP) — an indirect read of left atrial pressure and left-ventricular filling.
• Cardiac output — by thermodilution; inject cold saline through the proximal port and the thermistor records the temperature curve.
• Mixed-venous oxygen saturation (SvO₂) — a global marker of oxygen delivery vs demand.
• Derived values — systemic and pulmonary vascular resistance, cardiac index, and stroke volume.

Normal values

Site	Normal (mmHg unless noted)
Right atrium (mean)	2–6
Right ventricle	15–30 / 2–8
Pulmonary artery	15–30 / 8–15 (mean 10–20)
PCWP (wedge)	4–12
Cardiac output	4–8 L/min
Mixed-venous O₂ sat (SvO₂)	60–80%

Full detail lives in our hemodynamics study guide.

Reading the numbers: differentiating shock

The classic reason to float a PAC is to tell one kind of shock from another when the bedside picture is unclear:

Shock type	PCWP	Cardiac output	SVR
Hypovolemic	Low	Low	High
Cardiogenic	High	Low	High
Distributive (septic)	Low/normal	High/normal	Low

See the wider comparison in shock hemodynamics.

Indications

• Diagnosing and managing complex or mixed shock
• Severe or refractory heart failure and cardiogenic shock
• Assessing pulmonary hypertension and pre-transplant evaluation
• Guiding therapy in selected high-risk cardiac surgery and mechanical support

Complications

• Arrhythmias during insertion — PVCs and non-sustained VT as the tip crosses the RV; transient right bundle branch block.
• Pulmonary artery rupture — rare but life-threatening; avoid over-wedging and prolonged balloon inflation.
• Infection, thrombosis, and catheter knotting.
• Balloon rupture and, rarely, pulmonary infarction from a persistently wedged catheter.

Is the Swan-Ganz still used?

Its use has fallen sharply since the 1990s. Trials such as ESCAPE (2005) found no routine mortality benefit in decompensated heart failure, and less-invasive monitors now cover many needs. But the PAC is far from obsolete — it remains valuable in cardiogenic shock, pulmonary hypertension, right-heart failure, and transplant/mechanical-support evaluation, where its direct pressures and cardiac output are hard to replace. The lesson: a powerful tool, used selectively rather than routinely.

Key takeaways

• The Swan-Ganz (pulmonary artery) catheter is balloon-tipped and flow-directed.
• It threads RA → RV → PA → wedge, with a recognisable waveform at each step.
• It measures RA, RV, PA, and wedge pressures, cardiac output, and SvO₂.
• Wedge pressure estimates left-atrial/left-ventricular filling pressure.
• Use is now selective — shock, pulmonary hypertension, transplant work-up.

Frequently asked questions

What is a Swan-Ganz catheter?

A balloon-tipped, flow-directed pulmonary artery catheter passed through the right heart to measure pressures, cardiac output, and mixed-venous oxygen saturation.

How is a Swan-Ganz catheter inserted?

Through a central vein (usually the right internal jugular) with the balloon inflated, it is floated through the right atrium and right ventricle into the pulmonary artery, guided by the changing pressure waveform.

What does a Swan-Ganz catheter measure?

Right atrial (central venous) pressure, right ventricular and pulmonary artery pressures, pulmonary capillary wedge pressure, cardiac output by thermodilution, and mixed-venous oxygen saturation.

What is the pulmonary capillary wedge pressure?

The pressure measured with the balloon wedged in a small pulmonary artery; it approximates left atrial pressure and left-ventricular filling pressure, normally 4–12 mmHg.

How do you know the catheter is in the pulmonary artery?

The diastolic pressure steps up compared with the right ventricle and a dicrotic notch appears on the tracing.

What are the complications of a Swan-Ganz catheter?

Arrhythmias during insertion, pulmonary artery rupture, infection, thrombosis, catheter knotting, and balloon rupture.

Is the Swan-Ganz catheter still used?

Yes, but selectively. Routine use fell after trials showed no mortality benefit in general heart failure, but it remains valuable in cardiogenic shock, pulmonary hypertension, and transplant evaluation.

What is a normal mixed-venous oxygen saturation?

About 60–80%. A low value suggests oxygen delivery is not keeping up with demand.