Page 553 - Handbook of Biomechatronics

546 Graham Brooker

left ventricular diastolic filling when the inlet pressure is lower and the pres-
sure differential is a maximum. Minimal pulsatility occurs in patients with
very poor left ventricles or if the pump speed is too high and the ventricle
is driven to collapse.
For various reasons mostly related to problems with hemolysis and bear-
ing support the next-generation pumps were mostly centrifugal or mixed
flow types as these pumps could run at much lower speeds. An example
of a typical centrifugal pump is the Mohawk Technology MiTiHeart shown
in Fig. 20.
The cylindrical pump consists of four components: the pump housing,
the stator, rotor with integrated vanes, and an end cap. It is 80mm long with
a diameter of 50mm and a total mass of 640g. The pump is designed with a
nominal operating point of 5L/min and 100mmHg occurring at 4000rpm
as shown in Fig. 21.
The VentraCor VentrAssist centrifugal pump shown in Fig. 22, com-
bines the motor and impellor into an integrated unit to reduce size and

Fig. 20 The MiTiHeart design. (A) Cutaway view of the pump, (B) exploded 3D rendering
of the pump components, and (C) a photograph of the pump. (Reproduced with permis-
sion, copyright MiTiHeart corporation.)