Iabp

What is an intra-aortic balloon pump (IABP) and how does it work as a circulatory assist device?

IABP has two parts:

(1) a large bore catheter with a long sausage-shaped balloon at the distal tip, and

(2) a console containing a pump that inflates the balloon.

The balloon is designed to sit in the proximal descending aorta. It comes in various lengths according to body height, with balloon volumes of about 30-50 mL. The balloon is usually filled with helium gas, and when inflated should fill up 80-90% of the aortic diameter.

The IABP works by inflating and deflating at different phases of the cardiac cycle. Balloon inflation augments diastolic blood pressure and balloon deflation decreases afterload during systole .

IABP effects on the aortic pressure cycle. The dicrotic notch immediately precedes point C. Key: A. Unassisted End Diastolic Pressure, B.Unassisted Systolic Pressure, C.Unassisted Diastole, D. Reduced Systolic Pressure, E. Diastolic Augmentation, F. Assisted End Diastole Pressure (the unlabeled arrow!) (from www.ecp-india.net)

Balloon inflation in early diastole (usually triggered by the R wave on the ECG) increases diastolic blood pressure (E). This in turn increases systemic perfusion and coronary perfusion (at least in the hypotensive patient). Balloon inflation thus displaces blood both proximally and distally. The increase in coronary perfusion increases myocardial oxygen supply.

Balloon deflation occurs at the end of diastole resulting in a decreased end diastolic blood pressure (F). This reduces the aortic pressure at the start of systolic ejection, thus decreasing the afterload that the heart has to pump against. This decreases myocardial oxygen demand and improves systemic perfusion during systole.

What are the indications for IABP use?

* Cardiogenic shock after coronary artery bypass grafting (CABG) or acute myocardial infarction

* unstable angina

* Acute mitral incompetence

* Planned cardiac transplant

*...