**19. Timing errors**

There are four major timing errors with the IAB. The IAB is usually timed at a 1:2 ratio (one inflation every second heart beat) and the deflation is triggered off the R wave in the QRS complex. If the IAB is timed improperly, it can actually add to the afterload of the heart by inflating prior to the closure of the aortic valve. In this situation the cardio-vascular hemodynamics can deteriorate quickly and it is important for the practitioner to understand and avoid these errors.


There are four major timing errors with the IAB. The IAB is usually timed at a 1:2 ratio (one inflation every second heart beat) and the deflation is triggered off the R wave in the QRS complex. If the IAB is timed improperly, it can actually add to the afterload of the heart by inflating prior to the closure of the aortic valve. In this situation the cardio-vascular hemodynamics can deteriorate quickly and it is important for the practitioner to understand

1. *Early inflation*: The waveform shows inflation of IAB prior to dicrotic notch, diastolic augmentation encroaches into systole (fig 22) and is not hard to miss. The physiological effects would be potential premature closure of aortic valve, increase in LVEDP, LVEDV (Left Ventricular End Diastolic Volume) and PCWP (Pulmonary Capillary Wedge Pressure). The net effect would increase afterload, myocardial oxygen

2. *Late inflation*: Inflation of IAB after the dicrotic notch, indicated by the lack of a sharp "V" on the waveform (fig 23). The physiological effects include sub-optimal coronary

3. *Early deflation*: Viewed as a sharp drop in the waveform after diastolic augmentation. Assisted AEDP can be equal to the unassisted AEDP (fig 24). There may be little or no decrease in assisted systolic pressure. There is an absence of a sharp"v" or pore-systolic dip. This error will also lead to sub-optimal coronary perfusion, mvo2 and afterload reduction. There is also a potential for causing retrograde coronary and carotid blood

4. *Late deflation*: Possibly the most dangerous of all timing errors**.** Rate of rise of assisted systolic pressure may be prolonged. Assisted AEDP may be equal to unassisted AEDP. Diastolic augmentation waveform may be dampened (fig 25), depending on how late

consumption and possibility of adding to Aortic regurgitation.

perfusion and decreased diastolic augmentation.

flow with the latter causing an increase in angina.

Fig. 21. Size Selection Criteria for IAB Catheter

**19. Timing errors**

and avoid these errors.

the deflation is. Physiologically, afterload reduction is absent. IAB is actually impeding LV ejection and increasing afterload. Isovolumetric contraction phase increases along with myocardial oxygen consumption. Hemodynamics deteriorate rapidly.

Fig. 22. Early Inflation

Fig. 23. Late Inflation

Intra-Aortic Balloon Counterpulsation Therapy

5. Cessation or reduction of angina

appear to be stable

minutes.

accurate IAB timing.

and Its Role in Optimizing Outcomes in Cardiac Surgery 65

6. When transportation or operative procedure (revascularization of left main or aortic/mitral valve repair/replacement) is completed and the patient hemodynamics

The IAB is generally weaned by reducing the ratio from 1:1 to 1:3, after which the augmentation volume of the balloon catheter can be reduced. If the IAB volume is being decreased as a part of the weaning process, ensure adequate movement of the IAB catheter in order to minimize clotting or thrombus formation. The IAB is never turned off when the IAB catheter lies in the aorta due to the risk of thrombus formation. Afterload reduction by the IAB can be explained via numbers. The stroke volume of an average sized patients in normal health is usually 70 to 80 ml. In a patient in compromised cardio-vascular state, this stroke volume is reduced to 40 or 50ml. What a 40cc IAB catheter does is to complement the native stroke volume of 30-40ml until hibernating myocardium recovery and myocardial

Considerable improvements have been made in IAB catheter and console technology in the more than 40 years since counterpulsation was introduced to clinical practice. Early IABP consoles required intensive user intervention, as all aspects of console operation were manually controlled. Early IAB catheters were 12 Fr. and required surgical insertion via a cutdown to the femoral artery. Surgical insertion could take 1-2 hours and complication rates were high. In 1979, IAB catheter insertion improved significantly with the development of percutaneous IAB insertion. Insertion time was reduced, typically to 15

Additional improvements to the catheter in the early years included the addition of an inner lumen to facilitate wire-guided insertion and the lumen could then be used to monitor the arterial blood pressure. Prefolding of the membrane during manufacturing eliminated the need for the clinician to wrap the membrane prior to insertion through the introducer sheath. Catheters were also made smaller, from 12 Fr. to 10.5 Fr. and then to 9.5 Fr. Catheters are now 7 and 7.5 Fr. and this has helped reduce the incidence of limb ischemia to less than 3%. Reducing the catheter shaft diameter required a significant change to the way catheters were designed. With early dual lumen catheters, the inner lumen used for wire guiding the insertion and monitoring the arterial pressure was a separate catheter within the balloon catheter gas lumen. With the development of a co-lumen design where the two lumens of the catheter were extruded together with the inner and outer lumens sharing a common wall, the catheter diameter was reduced while maintaining the gas shuttle lumen and maximizing the inner lumen to accommodate the largest guide wire possible. The range of balloon membrane sizes was also expanded over the years from 40 cc in the early days of counterpulsation to 25 cc, 34 cc, 40 cc, and 50 cc IAB membranes. The size of balloon used is determined by patient height. The most recent improvement in IAB catheter technology has been the addition of a fiber optic pressure sensor to acquire the arterial pressure signal. This technology is immune to artifact, resulting in a high fidelity arterial pressure waveform for

While innovations in IAB catheter technology were being developed, improvements in IAB console technology were also occurring. Major improvements to the console over the years

4. Cessation and/or improvement of ventricular and/or atrial arrhythmias

**21. Advancements in IAB catheter and IAB console technology** 

7. When the shock phase has been successfully tided over

rest result in an increased stroke volume of that patient.

Fig. 24. Early Deflation

Fig. 25. Late Deflation
