Blood pump device and method of pumping blood

The present invention pertains to a blood pump device which comprises a blood pump having blood transport ports and cannulae connected to the ports. The blood pump device also comprises a coating material covering the junction between the inner surfaces of the ports and cannulae. This forms a smooth transition so blood can flow unimpeded therefrom and collection cavities for the blood are eliminated. The invention is also related to a method of producing a smooth coating. The present invention is a blood pump device comprising a second portion having a stator mechanism and a rotor mechanism disposed adjacent to and driven by the stator mechanism. The second portion has a journal disposed about the rotor mechanism to provide support therewith. The second portion has an impeller disposed in the chamber and a one-piece seal member for sealing about a shaft of the impeller. The seal member is fixedly attached to the journal so that the seal member is supported by the journal. The present invention is also related to means for providing power to the blood pump so that blood can be pumped through a cannulae. The providing means includes a controller having means for sensing pump failure and an output terminal for actuating a safety occluder in an event of pump failure. Preferably, there is a safety occluder device disposed about the cannulae and in communication with the output terminal. Preferably, the blood pump comprises a motor having stator mechanism and a rotor mechanism driven by the stator mechanism. The sensing means comprises means for determining back electromagnetic force within the stator mechanism. Preferably, the controlling means has means for providing signals indicate of stator current and rotor speed, respectively. The providing means is in communication with the means for determining back electromagnetic force in the stator mechanism.

FIELD OF THE INVENTION 
The present invention is related in general to medical devices. More 
specifically, the present invention is related to a blood pump device for 
cardiac assist. 
Background of the Invention 
Ventricular assist devices are receiving ever-increasing attention in our 
society where 400,000 Americans are diagnosed with congestive heart 
failure each year (Rutan, P. M., Galvin, E. A.: Adult and pediatric 
ventricular heart failure, in Quall, S. H. (ed), Cardiac Mechanical 
Assistance Beyond Balloon Pumping, St. Louis, Mosby, 1993, pp. 3-24). As a 
result, collaborative efforts among health care professionals have 
focussed on the development of various systems to assist the failing 
heart. These comprise both extracorporeal and implantable pulsatile 
ventricular assist devices (VAD), as well as non-pulsatile assist pumps. 
Extracorporeal systems include the Pierce-Donachy VAD and the Abiomed 
BVS-5000 VAD. The Pierce-Donachy VAD is positioned on the patient's 
abdomen and propels blood by means of a pneumatically actuated diaphragm. 
Its use as a bridge to transplant is well-documented (Pae, W. E., 
Rosenberg, G., Donachy, J. H., et al.: Mechanical circulatory assistance 
for postoperative cardiogenic shock: A three-year experience. ASAIO Trans 
26:256-260, 1980; Pennington, D. G., Kanter, K. R., McBride, L. R., et 
al.: Seven years' experience with the Pierce-Donachy ventricular assist 
device. J Thorac Cardiovasc Surg 96:901-911, 1988). The Abiomed BVS-5000, 
also an extracorporeal device, is fixed vertically at the patient's 
bedside and is attached to the heart with percutaneous cannulae that exit 
the patient's chest below the costal margin (Champsaur, G., Ninet, J., 
Vigneron, M., et al.: Use of the Abiomed BVS System 5000 as a bridge to 
cardiac transplantation. J Thorac Cardiovasc Surg 100:122-128, 1990). 
The most frequently used implantable systems for clinical application 
include the Novacor VAD (Novacor Division, Baxter Health Care Corp.) and 
the Heartmate (Thermocardiosystems) (Rowles, J. R., Mortimer, B. J., 
Olsen, D. B.: Ventricular Assist and Total Artificial Heart Devices for 
Clinical Use in 1993. ASAIO J 39:840-855, 1993). The Novacor uses a 
solenoid-driven spring to actuate a dual pusher plate. The pusher plate 
compresses a polyurethane-lined chamber which causes ejection of blood 
(Portner, P. M., Jassawalla, J. S., Chen, H., et al: A new dual 
pusher-plate left heart assist blood pump. Artif Organs (Suppl) 3:361-365, 
1979). Likewise, the Heartmate consists of a polyurethane lined chamber 
surrounded by a pusher plate assembly, but a pneumatic system is used to 
actuate the pusher plate (Dasse, K. A., Chipman, S. D., Sherman, C. N., et 
al.: Clinical experience with textured blood contacting surfaces in 
ventricular assist devices. ASAIO Trans 33:418-425, 1987). 
Efficacy of both the extracorporeal and implantable pulsatile systems has 
been shown (Rowles, J. R., Mortimer, B. J., Olsen, D. B.: Ventricular 
Assist and Total Artificial Heart Devices for Clinical Use in 1993. ASAIO 
J 39:840-855, 1993). However, certain complications are associated with 
the use of extracorporeal systems, including relatively lengthy surgical 
implantation procedures and limited patient mobility. The use of totally 
implantable systems raises concerns such as high cost of the device, 
complex device design, and again, relatively difficult insertion 
techniques. 
Centrifugal pump VADs offer several advantages over their pulsatile 
counterparts. They are much less costly; they rely on less complicated 
operating principles; and, in general, they require less involved surgical 
implantation procedures since, in some applications, cardiopulmonary 
bypass (CPB) is not required. Thus, an implantable centrifugal pump may be 
a better alternative to currently available extracorporeal VADs for short- 
or medium-term assist (1-6 months). In addition, the use of centrifugal 
pumps in medium-term applications (1-6 months) may allow the more complex, 
expensive VADs, namely the Novacor and the Heartmate, to be used in longer 
term applications where higher cost, increased device complexity, and 
involved surgical procedures may be justified. 
Prior art relating to centrifugal blood pumps is Canadian Patent No. 
1078255 to Reich; U.S. Pat. No. 4,927,407 to Dorman; U.S. Pat. No. 
3,608,088 to Dorman; U.S. Pat. No. 4,135,253 to Reich; Development of the 
Baylor-Nikkiso centrifugal pump with a purging system for circulatory 
support, Naifo, K., Miyazoe, Y., Aizawa, T., Mizuguchi, K., Tasai, K., 
Ohara, Y., Orime, Y., Glueck, J., Takatani, S., Noon, G.P., and Nose', Y., 
Artif. Organs, 1993; 17:614-618; A compact centrifugal pump for 
cardiopulmonary bypass, Sasaki, T., Jikuya, T., Aizawa, T., Shiono, M., 
Sakuma, I., Takatani, S., Glueck, J., Noon, G.P., Nose', Y., and Debakey, 
M. E., Artif. Organs 1992;16:592-598; Development of a Compact Centrifugal 
Pump with Purging System for Circulatory Support; Four Month Survival with 
an Implanted Centrifugal Ventricular Assist Device, A. H. Goldstein, MD; 
U.S. patent application titled "Radial Drive for Implantable Centrifugal 
Cardiac Assist Pump", University of Minnesota; Baylor Multipurpose 
Circulatory Support System for Short-to-Long Term Use, Shiono et al., 
ASAIO Journal 1992, M301. 
Currently, centrifugal pumps are not implantable and are used clinically 
only for CPB. Examples include the Biomedicus and the Sarns centrifugal 
pumps. The Biomedicus pump consists of an impeller comprised of stacked 
parallel cones. A constrained vortex is created upon rotation of the 
impeller with an output blood flow proportional to pump rotational speed 
(Lynch, M. F., Paterson, D., Baxter, V.: Centrifugal blood pumping for 
open-heart surgery. Minn Med 61:536, 1978). The Sarns pump consists of a 
vaned impeller. Rotation of the impeller causes flow to be drawn through 
the inlet port of the pump and discharged via the pump outlet port (Joyce, 
L. D., Kiser, J. C., Eales, F., et al.: Experience with the Sarns 
centrifugal pump as a ventricular assist device. ASAIO Trans 36:M619-M623, 
1990). Because of the interface between the spinning impeller shaft and 
the blood seal, several problems exist with both these pumps, including 
excessive wear at this interface, thrombus formation, and blood seepage 
into the motor causing eventual pump failure (Sharp, M. K.: An orbiting 
scroll blood pump without valves or rotating seals. ASAIO J 40:41-48, 
1994; Ohara, Y., Makihiko, K., Orime, Y., et al.: An ultimate, compact, 
seal-less centrifugal ventricular assist device: baylor C-Gyro pump. Artif 
Organs 18:17-24, 1994). 
The AB-180 is another type of centrifugal blood pump that is designed to 
assist blood circulation in patients who suffer heart failure. As 
illustrated in FIG. 1, the pump consists of seven primary components: a 
lower housing 1, a stator 2, a rotor 3, a journal 4, a seal 5, an impeller 
6, and an upper housing 7. The components are manufactured by various 
vendors. The fabrication is performed at Allegheny-Singer Research 
Institute in Pittsburgh, Pa. 
The rotor 3 is in the lower housing 1 and its post protrudes through a hole 
in the journal 4. The impeller 6 pumps blood in the upper housing 7 and is 
threaded into and rotates with the rotor 3. The impeller shaft passes 
through a rubber seal 5 disposed between the upper housing 7 and the 
journal 4, rotor and stator assembly. The upper housing 7 is threaded into 
the lower housing 1 and it compresses the outer edge of a rubber seal 5 to 
create a blood contacting chamber. In this manner, blood does not contact 
the rotor 3, journal 4, or lower housing 1. The upper housing 7 is 
connected to an inlet and outlet flow tubes 8, 9, called cannulae, that 
are connected to the patient's circulatory system, such as between the 
left atrium, LA, and the descending thoracic aorta, DTA, respectively. 
Through this connection, blood can be drawn from the left atrium, LA, 
through the pump, and out to the aorta, DTA. 
The impeller 6 spins by means of the rotor 3 and stator 2 which make up a 
DC brushless motor. The base of the rotor 3 has four magnets that make up 
two north-south pole pairs which are positioned 90 degrees apart. The 
stator 2 is positioned around the rotor 3 on the lower housing 1. The 
stator 2 comprises three phases. When it is energized, it creates a 
magnetic force that counteracts the magnets in the rotor 3 causing the 
rotor 3 and impeller 6 to spin, as is well known with brushless DC motors. 
A peristaltic pump infuses lubricating fluid into a port of the lower 
housing to lubricate the spinning rotor. The fluid prevents contact 
between any solid internal pump components during pump activation. It 
forms a layer of approximately 0.001 inches around the rotor and the 
impeller shaft. This fluid bearing essentially allows wear-free operation 
of the pump. The fluid passes around the rotor and flows up along the 
rotor post. Eventually, it passes out through the rubber seal 5 and into 
the upper housing 7 at the impeller shaft/seal interface. Fluid does not 
escape through the outer periphery of the housing seal because the upper 
housing is tightened down and sealed with a rubber O-ring to prevent 
leakage. 
The spinning impeller 6 within the top housing 7 causes fluid to be drawn 
from the inlet flow tube 8 toward the eye of the impeller. The impeller 6 
then thrusts the fluid out to the periphery of the upper housing 7. At 
this point, the fluid is pushed through the outlet tube 9 by centrifugal 
force. The pump typically consumes 3-5 Watts of input power to perform the 
hydraulic work necessary to attain significant physiologic benefits. 
The prior art AB-180 pump has certain drawbacks which limit its efficacy as 
a cardiac assist device. The present invention describes several 
discoveries and novel constructions and methods which vastly improve such 
a pump's operation. 
SUMMARY OF THE INVENTION 
The present invention pertains to a blood pump device. The blood pump 
device comprises a blood pump having blood transport ports and cannulae 
connected to the ports. The blood pump device also comprises a coating 
material covering the junction between the inner surfaces of the ports and 
cannulae. This forms a smooth transition so blood can flow unimpeded 
therefrom and collection cavities for the blood are eliminated. The 
invention is also related to a method of producing a smooth coating. 
The present invention is a blood pump device comprising a second portion 
having a stator mechanism and a rotor mechanism disposed adjacent to and 
driven by the stator mechanism. The second portion has a journal disposed 
about the rotor mechanism to provide support therewith. The second portion 
has an impeller disposed in the chamber and a one-piece seal member for 
sealing about a shaft of the impeller. The seal member is fixedly attached 
to the journal so that the seal member is supported by the journal. 
Preferably, the rotor has a rotor post connected to the impeller shaft and 
an end adjacent to the seal member. The end has rounded edges to prevent 
abutment against any adhesive material disposed between the seal member 
and the journal. 
The present invention is also a blood pump device which has an infusion 
port for providing lubricant material about the rotor, the infusion port 
has an inner diameter greater than 0.05 inches for minimizing pressure 
needed to introduce lubricant material into the blood pump. 
The present invention is also related to means for providing power to the 
blood pump so that blood can be pumped through a cannulae. The providing 
means includes a controller having means for sensing pump failure and an 
output terminal for actuating a safety occluder in an event of pump 
failure. Preferably, there is a safety occluder device disposed about the 
cannulae and in communication with the output terminal. Preferably, the 
blood pump comprises a motor having stator mechanism and a rotor mechanism 
driven by the stator mechanism. The sensing means comprises means for 
determining back electromagnetic force within the stator mechanism. 
Preferably, the controller means has means for providing signals indicate 
of stator current and rotor speed, respectively. The providing means is in 
communication with the means for determining back electromagnetic force in 
the stator mechanism. 
The present invention pertains to a blood pump device. The device comprises 
a blood pump for implantation in a patient. The device comprises an inlet 
cannula connected to the blood pump and for connection to a patient's 
circulatory system through which blood of the patient passes to the blood 
pump and is pumped when the blood pump is implanted in the patient. The 
device comprises an outlet cannula connected to the blood pump and for 
connection to the patient's circulatory system through which blood of the 
patient passes from the blood pump when the blood pump is implanted in the 
patient. The device comprises a safety occluder device disposed about the 
outlet cannula. The blood pump, cannulae and safety occluder device 
together for implantation into the chest of the patient. Also, the device 
comprises means for providing power to the blood pump so that blood can be 
pumped through the outlet cannula that is received from the inlet cannula. 
The providing means comprises a controller having means for sensing pump 
failure and an output terminal for actuating the safety occluder device in 
an event of pump failure so the safety occluder device prevents retrograde 
pump flow through the outlet cannula. The safety occluder device is in 
communication with the output terminal. 
Preferably, the blood pump comprises a motor having a stator mechanism and 
a rotor mechanism driven by the stator mechanism, The sensing means 
preferably comprises means for determining back electromagnetic force 
within the stator mechanism that occurs when the rotor mechanism stops. 
Preferably, the power providing means provides stator current to the 
stator mechanism to operate the stator mechanism and the controller has 
means for providing signals indicative of stator current and rotor speed, 
respectively. The providing means is in communication with the means for 
determining back electromagnetic force with the stator mechanism. 
The device preferably includes means for supplying lubricant to the motor 
so the rotor mechanism rotates smoothly in regard to the stator mechanism. 
The supplying means is in fluidic communication with the blood pump. The 
controller has means for measuring lubricant pressure to determine if a 
desired lubricant pressure exists in the pump. 
The power providing means preferably comprises a modular driver unit remote 
from the pump and in communication therewith to provide current to the 
stator mechanism. Preferably, the controller comprises means for adjusting 
speed of the motor mechanism so the speed of the motor is within a greater 
than 5% accuracy of a desired speed. Preferably, the controller comprises 
a display mechanism for providing values of stator current, rotor speed 
and lubricant pressure. 
Preferably, the occluder device is disposed about the outlet cannula such 
that the occluder device does not obstruct blood flow in the patient when 
the occluder device is in a non-activated state, and the occluder device 
prevents retrograde blood flow through the cannulae in the activated 
state. 
The present invention pertains to a method for pumping blood of a patient. 
The method comprises the steps of implanting a blood pump having an inlet 
cannula and an outlet cannula connected to it and a safety occluder device 
connected to the outlet cannula all together into the patient. Then there 
is the step of pumping blood in the patient which is received through the 
inlet cannula connected to the blood pump and out through the outlet 
cannula connected to the blood pump. Next there is the step of sensing 
with a controller having a mechanism for sensing pump failure and 
activating the safety occluder device whether the blood pump is working 
properly. Then there is the step of activating the safety occluder device 
connected to the outlet cannula with the controller if the blood pump 
stops working properly so blood will not flow back into the outlet 
cannula.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings wherein like reference numerals refer to 
similar or identical parts throughout the several views, and more 
specifically to FIG. 2 thereof, there is shown a blood pump device 10. The 
blood pump 10 comprises a blood pump 12 having a blood transport port 14 
and a cannula 16 connected to the port 14. As best shown in FIG. 3b, the 
blood pump device 10 also comprises a coating material 18 covering the 
junction between the inner surfaces of the port 14 and cannula 16 so that 
a smooth transition surface 20 is formed and blood can flow smoothly 
therefrom and collection cavities for the blood are eliminated. 
The present invention pertains to a blood pump device 10. The device 10 
comprises a blood pump 12 for implantation in a patient. The device 10 
comprises an inlet cannula 15 connected to the blood pump 12 and for 
connection to a patient's circulatory system through which blood of the 
patient passes to the blood pump 12 and is pumped when the blood pump 12 
is implanted in the patient. The device 10 comprises an outlet cannula 16 
connected to the blood pump 12 and for connection to the patient's 
circulatory system through which blood of the patient passes from the 
blood pump 12 when the blood pump 12 is implanted in the patient. The 
device 10 comprises a safety occluder device 83 disposed about the outlet 
cannula 16. The blood pump 12, cannulae 15, 16 and safety occluder device 
83 together for implantation into the chest of the patient. Also, the 
device 10 comprises means for providing power to the blood pump 12 so that 
blood can be pumped through the outlet cannula 16 that is received from 
the inlet cannula 15. The providing means comprises a controller 80 having 
means for sensing pump failure and an output terminal for actuating the 
safety occluder device 83 in an event of pump 12 failure so the safety 
occluder device 83 prevents retrograde pump flow through the outlet 
cannula 16. The safety occluder device 83 is in communication with the 
output terminal. 
Preferably, the blood pump 12 comprises a motor 888 having a stator 
mechanism 34 and a rotor mechanism 36 driven by the stator mechanism 34. 
The sensing means preferably comprises means 92 for determining back 
electromagnetic force within the stator mechanism 34 that occurs when the 
rotor mechanism 36 stops. Preferably, the power providing means provides 
stator current 84 to the stator mechanism 34 to operate the stator 
mechanism 34 and the controller 80 has means for providing signals 
indicative of stator current 84 and rotor speed 86, respectively. The 
providing means is in communication with the means 92 for determining back 
electromagnetic force with the stator mechanism 34. 
The device 10 preferably includes means for supplying lubricant to the 
motor so the rotor mechanism 36 rotates smoothly in regard to the stator 
mechanism 34. The supplying means is in fluidic communication with the 
blood pump 12. The controller 80 has means for measuring lubricant 
pressure to determine if a desired lubricant pressure exists in the pump 
12. 
The power providing means preferably comprises a modular driver unit remote 
from the pump 12 and in communication therewith to provide current to the 
stator mechanism 34. Preferably, the controller 80 comprises means for 
adjusting speed of the motor mechanism so the speed of the motor is within 
a greater than 5% accuracy of a desired speed. Preferably, the controller 
80 comprises a display mechanism 89 for providing values of stator current 
84, rotor speed 86 and lubricant pressure 88. 
Preferably, the occluder device 83 is disposed about the outlet cannula 16 
such that the occluder device 83 does not obstruct blood flow in the 
patient when the occluder device 83 is in a non-activated state, and the 
occluder device 83 prevents retrograde blood flow through the cannulae 15, 
16 in the activated state. 
The present invention pertains to a method for pumping blood of a patient. 
The method comprises the steps of implanting a blood pump 12 having an 
inlet cannula 15 and an outlet cannula 16 connected to it and a safety 
occluder device 83 connected to the outlet cannula 16 all together into 
the patient. Then there is the step of pumping blood in the patient which 
is received through the inlet cannula 15 connected to the blood pump 12 
and out through the outlet cannula 16 connected to the blood pump 12. Next 
there is the step of sensing with a controller 80 having a mechanism for 
sensing pump failure and activating the safety occluder device 83 whether 
the blood pump 12 is working properly. Then there is the step of 
activating the safety occluder device 83 connected to the outlet cannula 
16 with the controller 80 if the blood pump 12 stops working properly so 
blood will not flow back into the outlet cannula 16. 
The inlet cannula 15 can be inserted into the left atrium of the patient 22 
and fixed with a double purse string suture. The outlet cannula 16 can be 
sewn to the aorta of the patient 22. The inner junctions of the cannulae 
15, 16 are coated with a polyurethane coating material 18 such as Biomer, 
manufactured by Ethicon, Inc. The coating material 18 provides a smooth 
transition surface 20 for the blood to flow on. This uniform transition is 
essential for reduction of clot formation. 
The technique used to apply this coating material 18 is novel. It involves 
applying the polyurethane material 18 to the collection cavity 93 at the 
cannulae/port internal interface with a needle and syringe. After the 
polyurethane 18 is deposited, it is distributed evenly by hand rotation of 
the housing. 
Next, as shown in FIGS. 9 and 10a and 10b, the upper housing 26 is spun 
axially for each cannula 15, 16 in a motor driven coating chamber 92 for 
24 hours. This promotes more uniform distribution of the polyurethane 18 
and allows full curing. It also assures that the polyurethane coating 18 
fills the step-off between the housing ports and the cannulae. The coating 
chamber 92 consists of a motor shaft 94 enclosed by a plexiglass box 96. 
The shaft 94 is connected to a variable speed motor 95 protruding through 
the rear of the box. Nitrogen is passed through a jig 97 which fastens to 
the motor 95 and holds the pump housing 26 and cannulae 15, 16. The jig 97 
directs nitrogen from container 98 to pass over the junction being coated. 
The nitrogen carries away the solvent gases from the polyurethane 18 that 
would otherwise attack and degrade other areas of the pump housing 26. The 
custom jig 97 functions to hold the top housing 26 in both configurations, 
one for coating the inlet flow cannula 15 and the other for coating the 
outlet flow cannula 16. Once the polyurethane 18 is cured and evenly 
distributed, the housing 26 is removed and the process is repeated for the 
other cannula. 
As shown in FIG. 3a, a prior art pump without the coating technique forms a 
collection cavity 93. The prior art blood pump was implanted in 14 sheep 
in an experiment from December 1988 to October 1990. (Modified Fabrication 
Techniques Lead to Improved Centrifugal Blood Pump Performance, John J. 
Pacella et al., presented at the 40th Anniversary Meeting of the American 
Society for Artificial Internal Organs, San Francisco, Calif., April 1994, 
incorporated by reference herein). The pump was arranged extracorporeally 
in a left atrial to descending aortic cannulation scheme and the animals 
survived up to 13 days with the implanted prior art device. These 
experiments revealed that a major problem of the prior art pump was 
thrombus formation within the collection cavity 93 at the cannulae/housing 
interfaces. 
In contrast, using the described antithrombogenic coating technique with 
coating material 18, 44 sheep were implanted with the blood pump device 
from 1992-1993 for periods of 1 day to 154 days and no thrombus was found 
at the interface. This represents a 100% success rate to date. 
As shown in FIG. 2, the blood pump device 10 comprises a first portion 28 
having a chamber 30 and an inlet and outlet port 13, 14 in fluidic 
communication with the chamber 30, respectively. The blood pump device 10 
also comprises a second portion 32 having a stator mechanism 34 and a 
rotor mechanism 36 disposed adjacent to and driven by the stator mechanism 
34. Together, the stator mechanism 34 and the rotor mechanism 36 form the 
motor 888. Preferably, the motor 888, shown in FIG. 13 is a brushless DC 
motor (BLDC) 888. The second portion 32 has a journal 38 disposed about 
the rotor mechanism 36 to provide support therewith. The second portion 32 
also has an impeller 40 disposed in the chamber 30 and a one-piece seal 
member 42 for sealing about a shaft of the impeller 40. The seal member 42 
is fixedly attached to the journal 38, such as with adhesive, so that the 
seal member 42 is supported by the journal 38. Preferably, the seal member 
42 comprises a coating surrounding and sealing its outer surface. Further, 
the rotor 36 preferably has a surface 44 which has been polished to a 
surface finish of less than 2.54 .mu.m for enhanced low friction 
operation. The amount of material removed from the rotor 36 during the 
polishing process is less than 0.0001 inches (2.54 um). 
As shown in FIGS. 4a and 4b, the hard plastic journal 38 and seal member 42 
is fastened together, such as with Loctite 401 adhesive, to achieve seal 
stiffness, which was previously provided by the metal insert 45 molded 
into the prior seal 43. Also, the seal member 42 can be coated with Biomer 
(Ethicon, Inc.) polyurethane for enhanced antithrombogenicity. 
Two improvements in pump characteristics have been made through this new 
seal 42. First, the cost of production of the seal member 42 has been 
decreased significantly. The prior seal 43 had a metal insert 45 that was 
required to maintain seal stiffness, since the seal 43 is made of soft, 
flexible rubber. The disclosed construction of the present invention 
eliminates the need for an insert and simplifies the molding process. The 
seal member 42 is glued directly to the journal 38, which is made of hard 
plastic, to achieve overall seal stiffness. The process of gluing these 
two components is simple and relies on an inexpensive adhesive. Second, 
this insert 45 had to be machined separately placed in the rubber seal 43. 
As a result, the fabrication process of the seal left metallic sections of 
the insert 45 exposed to fluid contamination and therefore prone to rust. 
Since the seal member 42 of the present invention eliminates the insert, 
no steel is present for potential iron oxidation. 
Further, the overall height, E, of the journal/seal assembly has been 
increased from approximately 0.928 inches to 0.944 inches. This has 
resulted in a tighter seal at the junction between the outer rim 49 of the 
seal member 42 and the top housing 26, decreasing the chance for blood 
stasis and clot formation. As the top housing 26 is tightened down upon 
the lower housing 24 through their threaded connection, it compresses the 
outer rim 49 of the seal 42. The increased journal/seal height allows this 
compression to occur closer to the beginning of the threads. In other 
words, the upper housing does not need to be rotated as far through the 
threads to achieve the same tightness as it would if the journal/seal 
height, E, was not increased. Because of this, there is more room to 
achieve a tighter seal. 
The following are preferred dimensions of the seal constructions shown in 
FIGS. 4a and 4b: 
A=0.273 in. 
B=0.208 in. 
C=0.06 in. 
D=0.192 in. 
E=0.944 in. 
The journal/seal design, as shown in FIG. 4b, has been used in the 
disclosed sheep implantation studies and has functioned superbly. Results 
of the studies have shown inconsequential quantities of thrombus around 
the periphery of the top housing 26 in a few cases and none in the 
majority of the studies. 
As best shown in FIG. 5b, the top edge 50 of the rotor post 46 is 
preferably rounded to allow a better fit under the seal member 42. The 
rotor post 46 is inserted into the journal 38 and fits just beneath the 
seal member 42. The junction between the journal 38 and the seal member 46 
occurs at this point and the two components are affixed with adhesive 
(i.e. Loctite 401). The rounding of the edge 50 on the rotor post 46 
prevents the rotor 36 from rubbing against any excess glue that may be 
present after the seal member 42 and journal 38 are fastened together. 
The surfaces of the rotor 36 are preferably polished to 2.54 .mu.m and 
given a rust-proof coating 58. Results from the sheep studies have 
revealed little evidence of rust and polished surfaces have been shown to 
greatly increase durability between the rotor 36 and journal 38 and 
between the rotor 56 and the lower housing 60. 
As best shown in FIGS. 6a and 6b, the infusion port 62 is preferably 
enlarged from 0.03 inches to 0.062 inches. The housing 24 and port 62 can 
also be cryogenically deburred. Further, a 1/4 28 UNF male luer lock 66 is 
used instead of the prior 1/4 28 UNF threaded hex barb 68 to eliminate the 
male-female junction 64 at this point. 
The port 62 serves as a passageway for pump lubricant, such as water or 
saline, which is delivered to the pump and exits through the rubber seal 
member 42 into the blood stream. The port 62 is enlarged because it 
assists in attaining lower pump lubricant pressures, which diminishes the 
stress on all lubricant system components. Also, a small port is more 
likely to become occluded with debris (e.g. salt deposit from lubricant 
saline solution) and cause increases in lubricant pressures. 
The male-female junction 64 in the previous design (FIG. 6a) was eliminated 
to decrease the chance of foreign debris in the chest cavity from 
infiltrating into the lubricant system. The use of a threaded barb 66 
helps to solve this problem because there is one less junction. The 
threaded end is screwed into the lower housing 60 and chemically sealed 
and the barbed end is inserted directly into the lubricant tubing 69 
creating a mechanical seal. 
The deburring of the housing 60 results in increased durability and 
improved pump performance and lower internal lubricant temperatures. The 
internal lubricant temperature was measured by inserting an Omega, Inc 33 
Gauge hypodermic needle thermocouple directly through the pump baffle 
seal, just below the lip of the seal where the lubricant passes out. It 
was found that rough (undeburred) component surfaces of the prior pump 
resulted in internal lubricant temperatures of 50.degree. C. The lubricant 
temperatures of a pump device 10 with polished, deburred components was 
found to be 42.degree.-43.degree. C., which is significantly less. Since 
heat is thought to be a possible contributor to thrombus formation, this 
may have increased the antithrombogenicity of the pump as well as 
increasing its durability. 
As shown in FIGS. 7a and 7b, a new mold 70 was designed for stator 
fabrication. New, thermally conductive epoxy material is used for 
fabricating the stator 34. The new mold 70 has two halves 72, 74, a 
removable center stem 76 and handles 78 for quick releasing of the halves 
72, 74. Fastening bolts 80 hold the halves 72, 74 and center stem 76 
together. The mold 70 has significantly increased the quality of the 
stator 34 as indicated by the progressive increases in the survival times 
of sheep in the disclosed blood pump implantation studies. In 
chronological order, the five studies of durations greater than ten days 
were 14, 10, 28, 35, and 154 day durations. The new mold 70 was used in 
the 35 and 154 day studies. 
Thermally conductive epoxy material was used for stator fabrication to help 
carry heat away from the stator 34 and allow it to conduct readily to the 
surrounding tissues. As a result, the present stator 34 with thermally 
conductive epoxy has surface temperatures rarely exceeding 2.5.degree. C. 
above ambient temperature versus 5.degree.-7.degree. C. in the 14 and 10 
day studies. Referring to FIG. 2, environmentally sealed connectors 72 
replace older style connectors used for controller/stator electrical 
connections. Further, the stator 34 can be dip coated in polyurethane 
before potting. 
A commercially available environmentally sealed connector 72 (LEMO USA, 
Inc.) is preferably used to prevent the electrical connections from 
failing in the event of exposure to fluid. The prior art connector was not 
waterproof. To hermetically seal the stator 34, it can be dipped in 
polyurethane several times during the fabrication process. FIGS. 12a and 
12b show the prior art stator and the stator 34 of the present pump device 
10. 
The controller means 80 of the present invention preferably has an output 
82 for actuation of a safety occluder device 83 in the event of motor 
failure. Also, there are standardized outputs for current 84, speed 86, 
and lubricant system pressure 88 (0-1 Volt). The controller 80 uses 
isolated circuitry to cut down on noise by stator commutation. Three 
meters 90 of a display means 89, with both digital and bar graph output 
show the outputs. 
The automated occluder initiation output 82 greatly enhances safety for in 
vivo use of the blood pump. In the event of motor failure, detected by 
back the EMF sensor means 92, the controller 80 will activate the safety 
occluder device 83 to prevent retrograde pump flow through the outlet 
cannula 16. If pump current becomes zero, the controller 80 will attempt 
to restart the pump five times and if it is unsuccessful, it will send a 
signal to actuate the occluder device 83 through output 82. The increased 
reliability allows more time for intervention and troubleshooting. The 
standardized analog outputs for current 84, speed 86, and perfusion 
pressure 88 (0-1 volt) provides enhanced and comprehensive data 
collection. The outputs 84, 86, 88 can be used for trend recording on a 
strip chart recorder 94, as opposed to direct measurements once a day. 
Furthermore, isolated circuitry and display means 89 with three meters 90 
with both digital and bar graph output with .+-.1% accuracy on all 
readings prevent noise caused by stator commutation and provides reliable 
data collection. 
The controller in more detail is shown in FIG. 13. 
The sensorless blood pump controller 80 is preferably used to control the 
motor 888. It is called sensorless because no sensors are disposed in the 
pump 12 itself. Referring to FIG. 14, a block diagram is provided of the 
preferred embodiment of many possible embodiments of the sensorless blood 
pump controller 80. 
A highly integrated control I.C. 170, such as ML4411 available from 
Microlinear, San Jose, Calif., is comprised of the VCO 130 connected to a 
Back-Emf sampler 230 and to a logic and control 140. The control I.C. 170 
also includes gate drivers 240 for connection to power driver 260, linear 
control 901 connected to power driver 260 and I limit 110 and integrator 
101 and R sense 270. The control I.C. 170 additionally includes power fail 
detect 160. The ML4411 I.C. 170 provides commutation for the BLDC motor 
888 utilizing a sensorless technology to determine the proper phase angle 
for the phase locked loop. The function and operation of the specific 
features and elements of the control I.C. 170 itself is well known in the 
art. Motor commutation is detected by the Back-EMF sampler 230. 
For closed loop control, loop filter 900, connected to VCO 130 and 
amplifier 290, charges on late commutation, discharges on early 
commutation and is buffered by a non-inverting amplifier 290, model LM324 
available from National Semiconductor, Santa Clara, Calif.. The buffered 
output provides feedback to the integrator 101 that includes an inverting 
amplifier, model LM324. Preferably, non-inverting amplifier 290 and 
integrator 101 with an inverting amplifier are disposed on one chip. The 
speed control 120 uses a 20K ohm dailpot, model 3600S-001-203 available 
from BOURNS, Riverside, Calif. The speed control 120 in conjunction with 
summer 700 provides the set point for integrator 101. The output from the 
integrator 101 is used in conjunction with the input from R Sense 270, 
0.05 ohms, part number MP821-.05, available from Caddock Electronics, 
Riverside, Calif., to the linear control 901 to modulate gate drivers 240. 
The power drivers 260 consists of six N- channel field effect transistors, 
part number RFP70N03, available from Harris Semiconductor, Melbourne, Fla. 
The power drivers 260, connected to the gate drivers 240, drive the BLDC 
motor 888. 
The integrator 101 receives the desired speed control from the speed 
control 120 and also receives a feedback signal from the control I.C. 170 
through its Back-EMF sampler 230 which passes the speed of the rotor 36 in 
the BLDC motor 888. The output signal from the integrator 101, which 
essentially is an error correction signal corresponding to the difference 
between the speed control set point signal and the sensed velocity of the 
rotor mechanism 36 of the BLDC motor 888, is provided to the linear 
control 901. The linear control 901, with the error correction voltage 
signal from the integrator 101 and the voltage signal from the R sense 
270, which corresponds to the stator mechanism 34 current, modulates the 
gate drivers 240 to ultimately control the current to the stator mechanism 
34 of the DC motor 888. The R sense 270 is in series with the power 
drivers 260 to detect the current flowing through the power drivers 260 to 
the stator mechanism 34 windings of the BLDC motor 888. 
Power fail detect 160, an open collector output from the ML4411 control 
I.C. 170, is active when the +12VDC or the +5VDC from the power supply 180 
is under-voltage. The power fail detect 160, alerts the microcomputer 880 
that a fault condition exists. 
Referring to FIG. 15, external power supply 144 provides 12 VDC for the 
sensorless controller 80. Switching the external power supply 144 on or 
off is accomplished by the on/off control entry microcomputer 800. A logic 
`1` gates the external power supply 1 off and vice-versa. Battery back-Up 
is accomplished by solid state relay 777, P.N. AQV210, available from 
AROMAT, New Providence, N.J. When external power is lost, the internal 
power supply 180, P.N V1-J01-CY, available from Vicor, Andover, Mass. is 
enabled. The internal power supply 180 which derives power from the 
battery 490 P.N. V1-J01-CY, available from Vicor, Andover, Mass. is 
enabled. The internal power supply 180 derives power from the battery 490 
P.N. 642-78002-003, available from GATES, Gainsville, Fla. Charge relay 
333, P.N. 81H5D312-12, available from Potter and Brumfield, Princeton, IN 
switches out the external battery charger 214 when the control entry 
microcomputer 800 is `ON`. Schottky diode 134, P.N. MBR1545, available 
from International Rectifier, Segundo, Calif., performs a logic `OR` on 
the External Power 144 or Internal power supply 180 to the 12V Buss 250. 
Referring to FIG. 16, power is derived from the 12V Buss 250 and feeds DC 
to DC converter 410, P.N. NME1212S, available from International Power 
Sources, Ashland, Mass. and provides +12, -12V for the Analog circuitry. 
The DC/DC converter 820, P.N. 78SR105 available from Power Trends, 
Batavia, Ill. provides +5 VDC power for the DVM's and the control I.C. 
170. The DC/DC converter 122, P.N. 11450, available from Toko America, 
Prospect, Ill. provides +5 VDC to the microcomputer 880. 
Referring to FIG. 17, depression of the "ON" switch, p/o of switch assembly 
of the control entry device 190, P.N. 15.502, available from Solico/MEC, 
Hartford, Conn., discharges capacitor (RC) p/o external reset circuit 660 
initiating a reset signal to the Control Entry microcomputer 800, P.N. 
PIC16C54, available from Microchip, San Jose, Calif. The control entry 
computer 800 toggles an I/O line to signal the External Power Supply 144 
to power up and to turn status indicator 222 on. The START, RESET, and 
MUTE lines from 190 are connected to resistor pack 480 P.N. R-9103-10K, 
available from Panasonic, Secacus, N.J. The control entry microcomputer 
800, sends control lines including START, RESET, and MUTE to the control 
microcomputer 880, P.N. PIC16C71, available from Microchip, San Jose, 
Calif. and to the Status Indicators 222, P.N. 16.921-08, available from 
Solic/MEC, Hartford, Conn. Depressing the START on control entry device 
190 causes the Control Entry microcomputer 800, to assert the START signal 
to Control microcomputer 880. The Control microcomputer 880 initiates the 
sequence to start the motor 888. Refer to FIG. 18. Upon successful 
completion of the START routine, referring to FIG. 19, the control 
microcomputer 880, digitizes three analog inputs including current 
conditioner 460 connected to the motor 888, Infusion Pressure conditioner 
280 and the internal battery voltage 490. The Control I.C. 170 is 
connected to the RPM conditioner 380. The control microcomputer 880 is 
connected to the RPM conditioner 380. Referring to FIG. 18, the control 
microcomputer 880 measures the period of the RPM input and calculates the 
RPM. Referring to FIG. 19, the control microcomputer 880 updates the LCD 
Display 603, P.N. 97-20947-0, available from EPSON, Terrance, Calif. and 
downloads the data including RPM, current, infusion pressure, and battery 
voltage to the external connection connecting the SBPC to the IBM printer 
port 604. The control microcomputer 880 is connected to the alarm 602, 
P.N. P9923, available from Panasonic, Secaucus, N.J. and is activated when 
the infusion pressure is low. See FIG. 20. Upon an error detected with the 
retrograde flow, the control microprocessor 880 of FIG. 19, outputs ramped 
voltage to the digital to analog converter 500, P.N. MAX531, available 
from Maxim, Sunnyvale, Calif. The D/A converter 500 is connected to an 
analog summer 700. The speed control 120 is connected to the analog summer 
700, which is part of four amplifiers in a package. P.N. LM324, available 
from national semiconductor, Santa Clara, Calif. The summer 700 is 
connected to the integrator 101. The integrator 101 is connected to the 
control I.C. 170. 
Referring to FIG. 20, the control microcontroller 880, upon detecting an 
error that RPM is less than 2000 or zero motor current tries to restart 
the motor 888 five times. After five times, if the motor 888 does not 
start, then the SBPC activates an external occluder. See U.S. patent 
application Ser. No. 08/228,150, titled "Occluder Device and Method of 
Making", by John J. Pacella and Richard E. Clark, having attorney docket 
number AHS-3, incorporated by reference herein, filed contemporaneously 
with this application for a description of the occluder. 
An implantable centrifugal blood pump for short and medium-term (1-6 
months), left ventricular assist is disclosed in "Modified Fabrication 
Techniques Lead to Improved Centrifugal Blood Pump Performance", John J. 
Pacella et al., presented at the 40th Anniversary Meeting of the American 
Society for Artificial Internal Organs, San Francisco, Calif., April 1994. 
Pump operation such as durability and resistance to clot formation was 
studied. The antithrombogenic character of the pump 10 is superior to 
prior art pumps due to the coating 18 at the cannula-housing interfaces 
and at the baffle seal. Also, the impeller blade material has been changed 
from polysulfone to pyrolytic carbon. The electronic components of the 
pump have been sealed for implantable use through specialized processes of 
dipping, potting, and ultraviolet-assisted sealing. The surfaces of the 
internal pump components have been treated in order to minimize friction. 
These treatments include polishing, ion deposition, and cryogenic 
deburring. The pump device 10 has demonstrated efficacy in five chronic 
sheep implantation studies of 10, 14, 28, 35 and 113+ day durations. 
Post-mortem findings of the 14-day experiment revealed stable fibrin 
entangled around the impeller shaft and blades. Following pump 
modification with refined coating techniques and advanced impeller 
materials, autopsy findings of the ten-day study showed no evidence of 
clot. Additionally, the results of the 28-day experiment showed only a 
small (2.0 mm) ring of fibrin at the shaft-seal interface. In this study, 
however, the pump failed on day 28 due to erosion of the stator epoxy. 
In the experiments of 35 and 113+ day durations, the stators were 
re-designed, and the results of both experiments have shown no evidence of 
motor failure. Furthermore, the 35-day study revealed a small deposit of 
fibrin 0.5 mm wide at the lip of the seal. Based on these studies, it can 
be ascertained that these new pump constructions have significantly 
contributed to the improvements in durability and resistance to clot 
formation. In this study, the pump device 10 was implanted in five sheep 
for a minimum of 10 days. Prior to surgery, the sheep were fasted for 24 
hours, but were allowed unlimited access to water. The pump device 10 was 
implanted through a left thoracotomy and arranged in a left 
atrial-to-descending aortic cannulation scheme. Two percutaneous tubes 
were required for pump operation: one was used to jacket the conductors 
that supply power to the stator 34 and the other provided a conduit for 
pump lubricant infusion. The animals were infused at a constant rate with 
either 0.9% saline or sterile water as the pump lubricant. Daily 
measurements of pump speed, current, voltage, flow, animal body 
temperature, and stator surface temperature were obtained. The animals 
were free to ambulate within a 4-foot by 6-foot pen and were tethered to a 
custom-made swivel tether device as disclosed in U.S. Pat. No. 5,305,712. 
Weekly blood draws consisted of blood counts, electrolytes, coagulation 
profiles, hepatic and renal function, and hemolysis. Blood cultures were 
obtained as needed. The autopsy included complete histopathologic studies 
and a microscopic analysis of the pump 10. 
Various modifications in the pump configuration throughout the course of 
the five studies were made to improve the antithrombogenicity, corrosion 
resistance, and durability of the pump. Antithrombogenicity was addressed 
by applying polyurethane coatings to the cannulae housing interface and 
the seal and substituting pyrolytic carbon for polysulfone as the impeller 
blade material. In addition, alterations in the lubricant infusion rate 
and the anticoagulation scheme were incorporated. The rotor surfaces 46 
were conditioned through polishing and passivating procedures with the 
goal of increasing pump durability, and the lower housing rotor bearing 
surface was cryogenically deburred for the same purpose. Finally, the pump 
stator 34 was dip-coated in polyurethane and potted in a larger sized mold 
to provide more material coverage of the stator to increase the resistance 
of the pump to fluid corrosion. 
Pump modifications were made continuously throughout the five studies, 
depending on the results of each preceding study, as shown below in Table 
I: 
TALBE I 
______________________________________ 
Result Dependent Modifications 
Experiment Duration (Days) 
Modification 
14 10 28 35 154 
______________________________________ 
Lower Housing X X 
Conditioning 
Rotor Conditioning X X 
Re-designed Stator X X 
Seal Coating 
X X X X 
Cannula/Housing 
X X X X X 
Coating 
Impeller P C C.sup.1 
C.sup.1 
C.sup.1 
Material 
Perfusion Flow 
2 4 10 10 10 
Rate (ml/hr) 
Anticoagulation 
N H,S A,H,C,S 
A,H,C,S 
A,H,C,S,U 
______________________________________ 
N = none; A = aspirin; H = heparin; C = coumadin; S = streptokinase; U = 
urokinase; P = polysulfone; C.sup.1 = pyroltic carbon 
The 14-day study incorporated a prior art rotor and lower housing, a 
polysulfone impeller, and a polyurethane coating applied to the 
cannulae/housing interfaces. The lubricant flow rate was 2 ml/hr and no 
anticoagulants were used. Autopsy findings revealed a massive clot 
entangled within the impeller blades and fixed to the impeller shaft at 
the shaft/seal junction, as shown in FIG. 10a. The cannulae/housing 
interfaces were free to clot due to the sealing material 18. Rust was 
present on the rotor, as shown in FIG. 11a. 
The second study of 10 days duration included pump alterations consisting 
of a polyurethane coating (Biomer, Ethicon, Inc.) applied to the seal 42, 
a pyrolytic carbon impeller 40, a 0.9% saline lubricant flow rate of 4 
ml/hr, and the use of heparin in the saline lubricant. Streptokinase was 
administered every third day with the lubricant. The explanted pump was 
found completely devoid of thrombus, as shown in FIG. 10b. 
In a third study of 28 days duration, the pump was arranged similarly to 
the 10-day study. However, the lubricant flow rate was increased to 10 
ml/hr and 325 mg aspirin and 5-20 mg coumadin were given daily by mouth to 
broaden the anticoagulant regimen. A 2 mm ring thrombus was found at the 
impeller shaft/seal interface, as shown in FIG. 10c, and the motor was 
found to be contaminated by chest cavity fluid as indicated by chemical 
corrosion of select stator windings. 
The fourth study of 35 days used several of the new pump components. These 
comprised a stator 34 with several polyurethane coatings and an increased 
epoxy potting thickness to prevent fluid corrosion, as shown in FIG. 12b. 
Also, a thin layer of titanium ion-coating was used to passivate the rotor 
surfaces 46 and reduce the opportunity for rust formation. Furthermore, 
the lower housing bearing surface was deburred to decrease wear on the 
rotor 36. The perfusion flow rate and anticoagulation scheme remained 
unaltered in this study. The explanted pump had a small irregular ring 
clot of 0.5 mm at its widest point surrounding the impeller shaft/seal 
junction. The pump lubricant system became completely occluded due to 
precipitation of salt from the saline solution. As a result, significant 
seepage of blood products below the seal caused increased friction between 
the rotor 36 and its bearing surfaces and eventually caused pump stoppage. 
However, there were no emboli at autopsy. 
The last study of 154 days duration included variations from the previous 
study. For instance, thin layer chromium ion-coating was used in place of 
titanium coating to passivate the rotor 36 because it was available and 
cheaper. The lubricant was changed from 0.9% saline to sterile water on 
post-operative day (POD) 86 in order to reduce the chance of lubricant 
system occlusion due to salt precipitation. Next, based on published 
reports and preliminary studies of various antithrombotic drugs in sheep, 
urokinase was used as an alternative to streptokinase beginning on POD 130 
because of its suspected superior thrombolytic effect. This study revealed 
a pump devoid of thrombus and free of measurable wear based on light 
microscopic and dimensional analysis, as shown in FIG. 10d. Furthermore, 
no evidence of rust was found on the rotor surface, as shown in FIG. 11b. 
However, the pump stator 34 completely failed due to fluid corrosion. 
The lubricant rate was increased from 2 to 10 ml/hr over the course of the 
five studies. The intention was to increase fluid washing of the 
seal/impeller shaft interface to prevent blood stasis and thrombus 
formation. Precipitated salt was identified as a potential source of 
lubricant blockage in the 35-day study. As a result, the 154-day study 
underwent a change in lubricant from 0.9% saline to sterile water. The 
hematocrit and serum free hemoglobin measures were unaffected by this 
change. 
Efficiency was calculated for each study by applying interpolation 
techniques to bench data of hydraulic performance and using pump input 
power as the product of pump voltage and current. Table II, shown below, 
shows stator temperature, animal body temperature, and their difference 
for each experiment. The average difference between the stator surface 
temperature and the animal core temperature decreased from 
5.5.degree.-7.degree. C. in the 14 and 10 day studies to approximately 
1.degree.-3.degree. C. in the 28, 35, and 154-day studies: 
TABLE II 
__________________________________________________________________________ 
Average Values of Pump Efficiency, Stator Temperature, Animal 
Temperature, 
and Temperature Difference for Each Study 
Study Duration (days) 
14 10 28 35 154 
__________________________________________________________________________ 
Pump Efficiency (%) 
13.6 .+-. 2.1 
16.3 .+-. 4.7 
20.5 .+-. 2.6 
15.0 .+-. 1.6 
13.2 .+-. 2.2 
Stator Temperature (.degree.C.) 
45.4 .+-. 1.4 
44.8 .+-. 1.4 
41.5 .+-. 0.7 
41.5 .+-. 0.7 
41.6 .+-. 1.0 
Animal Temperature (.degree.C.) 
39.2 .+-. 0.3 
39.0.sup.1 
40.6 .+-. 0.7 
39.0 .+-. 0.7 
39.1 .+-. 0.6 
Temperature Difference.sup.2 (.degree.C.) 
6.8 .+-. 1.5 
5.8 .+-. 1.4 
1.3 .+-. 0.7 
2.4 .+-. 0.5 
2.6 .+-. 0.6 
__________________________________________________________________________ 
Note: 
All values are averages over the course of each study 
.sup.1 Measurement taken on first postoperative day only. 
.sup.2 Temperature Difference = Stator TemperatureAnimal Temperature 
The novel construction of the pump device 10 contributed to overall 
improved pump performance as compared to previous pump devices. 
Conditioning of both the rotor 36 and lower housing surfaces has included 
polishing and passivating and cryogenic deburring, respectively. These 
techniques provide even distribution of lubricant over the moving 
components, smoother surfaces for direct contact in the event of lubricant 
system failure, and resistance to the oxidation of iron. These studies 
show that passivation of the rotor surfaces caused elimination of rotor 
rust, as evidenced by a comparison of the prior art rotor used in the 
14-day study (FIG. 11a) with the chromium-coated rotor used in the 154-day 
study (FIG. 11b). The decreases in temperature difference between the 
stator and ambient can be related to increases in lubricant flow rate from 
2 to 10 ml/hr (Table II). Based on these five studies, the implications 
are that the temperature difference between the stator surface and ambient 
decreased by means of increased convective heat loss through higher 
lubricant infusion rates. 
Also, since this pump relies on a fluid bearing between the rotor and its 
adjacent surfaces, no correlation between efficiency and pump surface 
modification should necessarily be expected. That is, regardless of the 
coefficient of static and dynamic friction between the rotor and journal 
or rotor and lower housing, the no-slip condition for the lubricant holds 
at the solid surfaces, and the frictional losses are viscous in nature. 
The polyurethane coatings have contributed significantly to the 
antithrombogenicity of the pump. Specifically, the application of 
polyurethane material 18 to the cannulae/housing interface has had 
striking results: no clots have been found in any of the five studies at 
this juncture, nor have they been found in 39 other accumulated 
implantation studies. This has been a major improvement of the present 
pump device 10 based on prior studies (Goldstein, A. H., Pacella, J. J., 
Trumble, D. R., et al.: Development of an implantable centrifugal blood 
pump. ASAIO Trans 38:M362-M365, 1992). In addition, the polyurethane 
coating of the seal and the use of pyrolytic carbon impeller blades have 
been associated with decreased thrombus formation, as shown in comparisons 
of the first study of 14 days duration and all four subsequent studies 
(10, 28, 35, and 154-day lengths). 
The prevention of thoracic cavity fluid leakage into the electronic 
components of the pump stator 34 through various environmental sealing 
techniques has been of utmost importance. Developed methods involve 
coating the stator windings in polyurethane and increasing the size of the 
stator mold to allow thicker epoxy coverage. As a result, the occurrence 
of fluid-based corrosion has been significantly reduced. No evidence of 
motor failure was found in the 35-day study; however, the 154-day study 
was ended due to corrosion of the stator by chest fluid. In this study, 
the time to catastrophic motor failure secondary to corrosion was 
increased significantly from the 28-day study. 
The use of anticoagulation administered in all experiments following the 
first 14-day study appears to have contributed to a significant reduction 
in pump thrombosis. However, the role of specific anticoagulant drugs as 
antithrombotic agents in sheep will be addressed separately. 
The change from 0.9% saline lubricant to sterile water in the 154-day study 
on POD 86 was made based on the findings from the 35-day experiment. This 
change appears to have reduced the occurrence of salt deposition within 
the occlusion system as indicated by decreased variation in the perfusion 
system pressures and flows and more reliable delivery of lubricant to the 
pump. 
Thus, with the present pump device, modifications in blood surface 
materials, blood surface coatings, and electronic component fabrication 
and environmental sealing have had a positive impact on pump performance 
as indicated by increased survival times, decreased pump clot formation, 
less pump component wear, lower pump stator surface temperatures, and 
increased in fluid corrosion resistance. Moreover, both the expense and 
the learning curve associated with these long-term implantation studies 
have prompted changes from one study to the next. For example, in the 
35-day study, salt thought to be was precipitating from saline solution 
due to low lubricant flow rates, blocking the lubricant conduit, and 
preventing lubricant from reaching the pump. Eventually, pump failure 
occurred. This knowledge was applied in an ongoing study of 154 days by 
substituting sterile water for saline. The result was increased 
reliability of pump lubricant delivery and elimination of episodes of flow 
blockage. 
The myriad of device-centered modifications in these studies were made with 
the goals of achieving longer survival times, increasing pump reliability, 
and proving feasibility of the device as a VAD. As a result, the 
centrifugal pump has evolved through multiple intermediate forms, with 
increasing improvements in its performance. 
Although the invention has been described in detail in the foregoing 
embodiments for the purpose of illustration, it is to be understood that 
such detail is solely for that purpose and that variations can be made 
therein by those skilled in the art without departing from the spirit and 
scope of the invention except as it may be described by the following 
claims.