**12. Indications for IAB insertion**

In cardiac surgery the IAB is indicated for the following situations:

A. Pre-op predictors:

50 Special Topics in Cardiac Surgery

output, decrease in oxygen supply, increase in heart rate and increase in oxygen demand.

The final stage of LV failure (Fig 9) is the manifestation of tissue hypoxia. Decreased cardiac output, decreased MAP, decreased oxygenation coupled with pulmonary edema causes acceleration of anaerobic metabolism, lactic acid production, Tissue anoxia and finally tissue death. Its ideal to insert the IAB in stage one or by stage two, so that we prevent the final

Before we cite specific indications for IAB insertion, we should discuss indications for mechanical circulatory support. In other words, we should be able to delineate or define ventricular failure. LV failure would be defined as cardiac index (CI) of less than 1.8 L/min/m² with a systolic blood pressure of less than 90 mmhg (ref: Hensley Martin) despite maximized preload (mean atrial pressure > 20 mmhg), optimized heart rate (> 80) and normalized ionized calcium. This could be extrapolated to RV failure except for the systolic blood pressure. RV work is the function of the difference between the RA and PA mean pressure. As the difference between the two approaches zero, pulmonary blood flow is passive and RV failure is present. RV failure can occur with or without pulmonary hypertension. Mechanical support is suggested when the above criteria are present despite maximum inotropic support. Maximum inotropic support can be defined as any two or more (*High et* 

For patients with severe forms of LV failure, ventricular assist devices (VAD) are indicated. The initial indicated mechanical support in these scenarios is the IABP. Large and prolonged

There is an increase in pulmonary artery wedge pressures.

Fig. 9. Stage 3 - Tissue Hypoxia and Apoptosis

*al., 1995*) of the following combinations: 1. > 10 µg/kg/min of Dopamine 2. > 10 µg/kg/min of Dobutamine 3. > 0.2 µg/kg/min of Epinephrine

5. > 10 µg/kg/min of Nor–epinephrine

4. > 0.75 µg/kg/min of Milrinone after loading dose

**11. Indications for mechanical circulatory support**

stage of heart failure.

	- 1. Pre/post CPB ischemia
	- 2. Incomplete repair or bypass
	- 3. Prolonged CPB time
	- 4. Large ventriculotomy or LV resection for LV aneurysm repair.
	- 5. Particulate or air embolus in coronary arteries.
	- 6. Persistent ST changes post CPB.

Clinical indications for the IAB are listed below (fig 10 showcases benchmarks in 2005 for IAB use)


Intra-Aortic Balloon Counterpulsation Therapy

**14. Relative contraindications for IAB insertion** 

diseased aortic wall may result in aortic dissection

5. Coagulopathy or coagulopathic disorder

reporting inconsistent results.

inconclusive (*Quaal 1993*)

**16. Complications of IAB insertion** 

spontaneously or after IAB removal.

the false lumen.

3. Sepsis or infection 4. Severe thrombocytopenia

conducted a little later.

6. End stage terminal disease

8. Severe atherosclerosis

*al,.1988*).

and Its Role in Optimizing Outcomes in Cardiac Surgery 53

2. Aortic dissection. Precludes IAB insertion. Attempting to Place an IAB in this situation may lead to placement in the false lumen or at the very least increase circulation into

1. Severe peripheral vascular disease (PVD). Although this sometimes precludes insertion, we have had some experience with this. A discussion on PVD patients will be

2. Unresected thoracic, abdominal or thoraco-abdominal aneurysm. An insertion of a mechanical device like the IAB and the counterpulsation of such a device against a

1. Age- Increased age appears to be an increased risk. It is probably because of increased atherosclerosis associated with increased age (*Goldberger 1986*). There are other studies

2. Gender- women tend to have a greater risk of complication due to their smaller stature. This is probably due to the smaller lumen size of the femoral artery in women. The IAB catheter was expected to occupy greater lumen space in women thereby increasing the likelihood of ischemia and/or thrombus formation. Women are 1.6 to 1.8 more likely to experience limb ischemia/vascular complications than men (*Skillman JJ et al, 1988*). 3. Peripheral vascular disease (PVD) - These patients have higher likelihood for IAB complications due to insertion difficulties. Gottlieb suggested a three times likelihood for complications (*Gottlieb SO et al.,1984),* others have suggested less (*Skillman JJ et* 

4. Type-II diabetes- Due to severe and diffuse atherosclerotic disease, higher incidence of hypertension and dampened resistance to bacterial contamination, diabetics tend to have a higher risk of complication post IAB. Some investigators found that diabetics (*Wasfie T et al.,1988*) had a 22% incidence of complications post IAB insertion as compared to 14% for non-diabetics. For insulin dependent diabetes a higher

5. Duration of IAB therapy- Findings for the duration of safe use of IAB therapy remain

1. Loss of pedal pulses- Occurs in 15 – 25% of patients (*funk M et al.,1989*). Asymptomatic loss occurs transiently without resulting in limb ischemia and usually returns

complication rate of 34% (*Alderman JD et al., 1987*) was suggested.

7. End stage cardiomyopathy unless bridge to transplant/destination therapy

**15. Pre-insertion predictors of risks associated with IAB insertion** 

Fig. 10. BENCHMARK for IAB use (2005)


Freedman coined the term "Myoconservation" (*Quaal 1993*). It is defined as the hemodynamic support provided within the crucial window of opportunity, ensuring that enough myocardium remains viable to permit normal function of the heart following definitive coronary therapy-whether it be CABG or coronary stenting/PTCA. The IAB is one of the very important modalities available to the cardiac surgeon/cardiologist which supports myoconservation by supporting the coronary circulation, supporting the systemic circulation, reduction in LV stress and reduction in LV workload.

Miller et al in 1986 summarize "The result of our clinical experience suggest that more aggressive use of IAB is likely to save lives of coronary disease patients who develop severe complications of their disease. There have been no deaths reported among our patients with refractory unstable angina who had an IAB inserted and all evidence suggests that short of actually opening the vessel to obtain relief from angina, IAB insertion is the most effective method to treat these patients"

More recent studies (*Christenson JT 1999*) have confirmed the efficacy of pre-operative IAB use in high-risk coronary patients.

### **13. Absolute contraindications for IAB insertion**

1. Aortic regurgitation or insufficiency. In this physiology, raising AEDP would result in increase of regurgitant factor thereby increasing workload of the heart. In instances of mild AI a decision can be made if the benefits outweigh the risks.

2. Aortic dissection. Precludes IAB insertion. Attempting to Place an IAB in this situation may lead to placement in the false lumen or at the very least increase circulation into the false lumen.
