Describe the mechanism by which IABP augments coronary perfusion. What are the indications and contra indications for the use of IABP?

Intra-aortic balloon pumps are an important adjunct to temporary support of the failing myocardium,it's counter pulsation mechanism of action augments the cardiac output by reducing the after load stress of the left ventricle and increasing the coronary artery perfusion during diastole.

Mechanism of action

IABP are placed per cutaneous into the descending aorta and has a balloon tip which is placed 3-5 cm distal to the left subclavian artery and is inflated with 30-50ml of helium.

The device is triggered to inflate shortly after the aortic valve closure and deflate just prior to ventricular contraction,the timing of the inflation and deflation are so adjusted to allow maximal diastolic coronary perfusion and maximal ventricular systolic unloading.As the IABP is timed with the cardiac cycle hence a regular rhythm is desirable for its proper functioning and any tachyarrhythmias should be controlled.

The timing is best monitored with the arterial pressure trace and daily chest radiograph are taken to see the position of the balloon tip as proximal migration of the tip into the left common carotid or the subclavian artery can cause damage or dissection while distal migration can lead to obstruction and possible embolisation  of the mesenteric or the  renal arteries.

Indications of IABP 

1) Severe cardiac pump failure following cardiopulmonary bypass and inability to wean.

2)Refractory angina after maximal medical treatment

3)Treatment of complications of myocardial infarction in patients being prepared for revascularization either with surgery or angioplasty

4)To support patients after cardiac transplantation

Contraindications of IABP

1) Severe aortic regurgitation

2)Mobile atheroma of the descending aorta

3)Aortic dissection

4)Dynamic left ventricle outflow tract obstruction