INTRA-AORTIC BALLOON

This is the active element in a complex device for assisting the performance of the heart in chronic failure or during a weaning phase after cardiopulmonary bypass.

A smooth polyurethane balloon, several centimetres in length, is passed into the descending aorta through the femoral artery. The balloon is rapidly inflated during early diastole, and deflated in early systole, synchronized by the ECG signal. Inflation during diastole augments arterial and coronary perfusion pressure, and deflation during systole reduces aortic impedance to ventricular ejection, thus relieving the heart of some of its load.

Although simple in concept, the exact control required over the timing and extent of inflation presents problems and requires specially trained operators. A more complex balloon design may be used to reduce the abnormally high pressures which are caused in the proximal segment of the aorta. In this case the balloon has several compartments fed by orifices of different diameter to cause the sequential inflation of the different segments of the balloon. The inflating gas may be helium or carbon dioxide, but helium is safer since it will diffuse quickly through the arterial wall in the case of leakage, and is inert. Carbon dioxide released into the blood increases the acidity.

The intra-aortic balloon may be used continuously for several months or operate intermittently. Clotting may occur if the deflated balloon remains in the aorta for any length of time and manual operation may be necessary if arrhythmias prevent automatic triggering.

Content and Design Copyright 2000 Dr. Malcolm C Brown.  See Title Page for more details