**18. Mechanics of IAB functioning**

IAB therapy is often referred to as counterpulsation therapy as the balloon inflates in diastole or counter to the hearts contraction (systole). The IAB is a polyethylene balloon catheter placed percutaneously in the thoracic aorta through the groin (Fig 15).

Fig. 15. Femoral Insertion of IAB Catheter

Balloon inflation actively pushes blood into the coronary arteries, increasing myocardial oxygen supply. Balloon deflation decrease AEDP thereby directly reducing myocardial work load and myocardial oxygen consumption by reducing the time period for isovolumetric contraction. This gives the heart time to rest and gives a chance for hibernating myocardium to recover.

IAB therapy is often referred to as counterpulsation therapy as the balloon inflates in diastole or counter to the hearts contraction (systole). The IAB is a polyethylene balloon

Balloon inflation actively pushes blood into the coronary arteries, increasing myocardial oxygen supply. Balloon deflation decrease AEDP thereby directly reducing myocardial work load and myocardial oxygen consumption by reducing the time period for isovolumetric contraction. This gives the heart time to rest and gives a chance for

catheter placed percutaneously in the thoracic aorta through the groin (Fig 15).

of peripheral vascular disease (*Datt B 2007*)

Fig. 14. Trans-thoracic Insertion of IAB Catheter

**18. Mechanics of IAB functioning** 

Fig. 15. Femoral Insertion of IAB Catheter

hibernating myocardium to recover.

removed and the chest closed. The patient was extubated post-op day 9 and discharged after 25 days. No post-operative morbidity noted other than associate with his history The IAB is connected by a driveline to a helium chamber or pressurized gas reservoir which is connected to the IAB catheter via a solenoid valve. The inflation or helium supply is linked to a trigger for the balloon which is usually a synchronized ECG (Electrocardiogram) or the patient's blood pressure. Earlier on in IAB development CO2 was used due to its high solubility and safety in case of balloon leak/rupture and gas embolization. Helium started being used due to its smaller Reynold's number (lower density), thereby allowing a smaller drive line/catheter. Smaller balloon catheters improved gas shuttle speeds, reduced trauma to the groin and resulted in fewer complications post-insertion.

The balloon is usually placed 2 cms below the subclavian artery in the second to third intercostals space. This optimizes coronary perfusion and decreases the chances for renal artery occlusion. Balloon placement is verified in the OR by TEE or post-operatively by CXR (Fig 16).

Fig. 16. Chest X-ray Confirmation of IAB Placement

Synchronization of the IAB is achieved usually by using the R wave of the QRS complex to deflate the IAB catheter. In the operating room some practitioners tend to use pressure trigger to circumvent electrical interference from the cautery or other devices. If the patient is pacer dependent, the pacer spike can also be use to trigger IAB deflation. Correct timing is verified by observing the dicrotic notch on the arterial pressure waveform on the balloon console and making sure that balloon inflation takes place just after the dicrotic notch (aortic valve closure) and deflates prior to LV ejection (R wave on QRS complex-Fig 17 & Fig 18)

While using the pressure trigger, it's important to use the dicrotic notch as the marker for inflation. This will prevent the balloon from impinging on LV ejection and adding to the hearts afterload.

At Southlake we use the Maquet IAB console (fig 19) CS 100 which has an auto feature for timing. Another IAB console which the reader may come across would be the ACAT II WAVE console (fig 20) marketed by Arrow international.

The console uses a unique algorithm to establish the initial timing using the ECG or arterial pressure waveforms. It will also automatically readjust the inflation and deflation timing for changes in heart rate or rhythm. This allows for ease of nursing care post-operatively and decreases the necessity of the perfusionist except for troubleshooting. The IAB has three choices for augmentation. 1:1, 1:2 and 1:3. The IAB is generally initiated at 1:2 in order to be

Intra-Aortic Balloon Counterpulsation Therapy

Fig. 19. CS100 MAQUET IABP

Fig. 20. ACAT II WAVE Arrow IABP

and Its Role in Optimizing Outcomes in Cardiac Surgery 61

able to check the timing of the IAB catheter. The timing can be verified by using the inflation interval option on the console. Generally at a higher heart rate (>100), a better augmentation pressure is achieved by lowering the ratio to 1:2 or 1:3. The (stroke) volume of the balloon used is dependent on the size of the balloon and is chosen based on the height of the target patient (fig 21).

Recently, due to the reduction in french size of the IAB catheters to 7Fr, it is possible to insert 40cc balloons in most patients, except those very small or very large.

Fig. 17. Inflation (1:1) After timing IAB (pacing trigger)

Fig. 18. Proper IAB Timing

able to check the timing of the IAB catheter. The timing can be verified by using the inflation interval option on the console. Generally at a higher heart rate (>100), a better augmentation pressure is achieved by lowering the ratio to 1:2 or 1:3. The (stroke) volume of the balloon used is dependent on the size of the balloon and is chosen based on the height of the target

Recently, due to the reduction in french size of the IAB catheters to 7Fr, it is possible to

insert 40cc balloons in most patients, except those very small or very large.

Fig. 17. Inflation (1:1) After timing IAB (pacing trigger)

Fig. 18. Proper IAB Timing

patient (fig 21).

Fig. 19. CS100 MAQUET IABP

Fig. 20. ACAT II WAVE Arrow IABP

Intra-Aortic Balloon Counterpulsation Therapy

Fig. 22. Early Inflation

Fig. 23. Late Inflation

and Its Role in Optimizing Outcomes in Cardiac Surgery 63

with myocardial oxygen consumption. Hemodynamics deteriorate rapidly.

the deflation is. Physiologically, afterload reduction is absent. IAB is actually impeding LV ejection and increasing afterload. Isovolumetric contraction phase increases along

Fig. 21. Size Selection Criteria for IAB Catheter
