Intra-Aortic Balloon Pump

Take home messages

• Don't switch it off
• The goal is to improve blood supply to the myocardium, while also reducing its oxygen demand
• Patients need to be anticoagulated
• Check renal function to ensure the renal arteries are not occluded
• Balloon pumps cause haemolysis
• If the timing isn't right, then the patient can become very unstable

What is it?

What, the intra-aortic balloon pump? Well it's a balloon, and it sits...

Because clearly the logical next step when you've got a clapped out cardiovascular patient is to plumb a balloon into the biggest artery in their body and do the Hokey Cokey with a bunch of helium right?

Well read on, because there is some method in the madness.

What is counterpulsation?

The idea is volume displacement of arterial blood, to help the heart send it to the two places where it needs to be:

• The coronary arteries
• The rest of the systolic circulation

So the balloon sits in the descending aorta, inflates during diastole, and then deflates again during systole.

All very quickly, in time with the ECG (or arterial pressure trace).

Theoretically this means that systolic blood flow to the body is unimpeded, but as soon as the heart relaxes, the balloon inflates and displaces the blood in the aorta both forwards and backwards, encouraging the blood to flow down the coronary arteries, as well as giving it an extra little shove to the rest of the body.

Then when the balloon deflates again immediately prior to systole, it causes a slight negative pressure in the aorta, reducing afterload on the left ventricle by reducing the pressure gradient across the aortic valve.

Effects on the heart

• Reduces systolic pressure and increases diastolic pressure in the aorta
• Reduces end-diastolic pressure and afterload on the left ventricle
• Increases cardiac output and hopefully coronary blood flow

The Timing Sequence and Arterial Waveform

You need to be able to draw and explain this bit.

We've borrowed the following image from the amazing Deranged Physiology website, because it explains it perfectly.

The dicrotic notch on the arterial waveform occurs when the aortic valve closes. The balloon inflates immediately after this, and then deflates again just before the valve opens in systole. This point is the lowest point of the arterial pressure waveform.

When the balloon inflates, it obstructs arterial blood flow, causing a rapid drop in blood pressure at the point of the dicrotic notch. However by increasing or augmenting diastolic pressure, it produces a large second peak, which is unsurprisingly labelled 'diastolic augmentation'.

Hopefully the diastolic augmentation will be higher than the systolic pressure.

You can then set the pump to assist every beat, every alternate beat, or any ratio that is required. As the patient's cardiovascular status improves, the support can be weaned off with less and less augmentation. It should never, however, be left deflated, as it is a huge thrombosis risk.

Indications and Contraindications for IABP

Indications:

• Acute Myocardial Infarction
• Refractory left ventricular failure
• Cardiogenic shock not responding to pharmacological therapy
• Sepsis
• Cardiac surgery and weaning from cardiac bypass
• Acute MR and VSD
• Infant with cardiac abnormalities
• Refractory unstable angina

Absolute contraindications:

• Aortic dissection
• Aortic regurgitation
• Previous Aortic stenting
• Chronic end stage heart failure deemed inoperable

Relative contraindications:

• Severe uncontrolled sepsis
• Severe peripheral vascular disease
• Abdominal aortic aneurysm
• Anatomical abnormalities or previous arterial reconstructive surgery
• Tachyarrhythmias

The Balloon

The intra aortic balloon pump is divided in to two parts - the balloon itself and the control pump.

The polyethylene balloon is usually between 25 and 50ml and is loaded onto a double-lumen 8 - 9.5 Fr catheter.

The control pump coordinates the timing of inflation and deflation, and often uses helium for two reasons:

• Its very low density makes it ideal for rapid inflation and deflation
• It's very rapidly absorbed by the blood, which is helpful if the balloon ruptures

Complications

As you might imagine, inserting a large catheter into the aorta of a patient with heart problems, and then attempting to inflate and deflate a balloon to occlude the aorta in time with the heartbeat, can sometimes go wrong.

• Balloon rupture and gas embolus
• Haemolysis and thrombocytopenia
• Occlusion of cerebral or renal arterial supply
• Limb ischaemia
• Aortic trauma or dissection
• Bleeding and infection
• Tamponade
• Thromboembolism
• Compartment syndrome
• Balloon entrapment

Our favourite YouTube video

Check out this amazing infographic from Dr Mark

I asked ChatGPT to write a poem about the complications of IABP.

“Beneath the Balloon’s Duet: Complications Unveiled”

“What are the complications of intra-aortic balloon pumps?”

AnaestheasierAnaestheasier ltd.

Useful Tweets and Resources:

References and Further Reading:

Principles of intra-aortic balloon pump counterpulsation

Intra-aortic balloon pump (IABP) remains the most widely used circulatory assist device in critically ill patients with cardiac disease. The National Centre of

OUP AcademicMurli Krishna, MBBS FRCA FFPMRCA

Anatomy of the intra aortic balloon pump

Yes, its a very strange thing to have in your aorta. An no, its not at all uncomfortable. Apart from the unpleasantness of having one’s femoral artery punctured, most people don’t find the experience particularly alarming. I have asked them; they cant feel the movements of the balloon. In any case, I am sure that any adverse components of their experience are drowned out by the appreciation of the fact that one is alive in spite of a massive coronary event.

Deranged PhysiologyAlex Yartsev