Prolonged partial left heart bypass in sheep: successful use of a new type of pump.

A method of partial left heart bypass is described. A non-pulsatile atraumatic pump capable of handling 2 to 4 litres of blood a minute has been developed and tested. It lends itself to easy adjustment to meet changes in left atrial and systemic pressures and can function for many hours without adjustment. Partial left heart bypass for 24 hours was carried out on sheep. No damage to the blood resulted from its use and air embolism was completely excluded. Initial difficulties associated with 24 hours' anaesthesia were solved by maintaining the animal erect in a cage. In the last series of experiments only one out of 11 sheep had an unexplained death that could have been associated with bypass. The equipment appears to be suitable for clinical trial.