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Guide to Collections Relating to the History of Artificial Internal Organs


Thoratec Corporation (formerly Nimbus Inc.)


2945 Kilgore Road, Rancho Cordova, CA 95670


(916) 852-2833

Fax Number

(916) 638-3216


Contact Person

Thomas Rintoul, Senior Engineer


Access and Services

Appointment required.


Thoratec Corporation's "Nimbus Group" is a research and development organization specializing in blood pump devices. The company has expertise in precision, high tolerance and high performance fluid flow systems. The Nimbus group has developed miniature, precision hydraulic gear pumps, pulsatile blood pumps, as well as centrifugal and axial-flow non-pulsatile blood pumps. The intended use of these systems range from the 6-hour life of a disposable pump for surgical support, to permanent implantation of left ventricular assist and total artificial heart (TAH) systems. The Nimbus group also has considerable expertise at motor control technology, having developed brushless DC motor drive circuits to run each pump. Past products include Plutonium Left Ventricular Assist System (LVAS energy converter) Aerojet; Thermal LVAS; Electrical LVAS; Electrical TAH; Hemopump; "Bard" Centrifugal Pump; IVAS/HeartMate II Axial Pump. Miscellaneous projects include PortaJet (High Frequency Jet Ventilator); Integrated Blood Pump/Oxygenator; Centrifugal Pump for Pediatric Use; Cardiac Preservation/Transportation Device.



Thoratec Corporation (Nimbus Group Collection), 1968 to present.

Collection ID



Biographical Note

The first company employees were involved in the development of artificial heart energy converter devices under NIH contract while employed by Aerojet Liquid Rocket Company. In 1982, the 13 founders formed Nimbus Inc. to continue the NIH development work when Aerojet declined to pursue contract follow-on. The name Nimbus was selected because of the region, at one time called Nimbus, and because of its nondescript nature. The intent was to select a name to avoid typecasting the company as being solely medical in nature, leaving open the possibility for other avenues of commerce including private development projects. Nimbus self-funded the initial development of the Hemopump, first conceived by Nimbus employees and co-founder, Dr. Richard Wampler. Nimbus later obtained venture capital and the company grew as it simultaneously pursued development and commercialization of the Hemopump along with the government funded electrical and thermal LVAS contracts. In 1990 the Hemopump technology was sold to Johnson and Johnson, with half the employees joining J & J and the other half returning to NIH contract development work. Spin-off technology from the Hemopump was further developed under NHLBI contract in their innovative ventricular assist system (IVAS) initiative that started in 1995. On the strength of that technology, Nimbus was purchased by former competitor Thermo Cardiosystems Inc. at the end of 1996. The IVAS technology was given the working name "HeartMate II" as a so-called "second generation" LVAS. It was first used clinically in July 2000 in Israel. On February 14, 2001 Thermo Cardiosystems Inc., and its wholly-owned subsidiary Nimbus Inc. were sold to Thoratec Laboratories Corporation, with the combined entity renaming itself, "Thoratec Corporation."

Collection Description

Prototypes of all energy converters and blood pumps developed by Nimbus, including materials related to the Plutonium Left Ventricular Assist System (LVAS energy converter) Aerojet, Thermal LVAS, Electrical TAH, Electrical LVAS, Hemopump, "Bard" pump, IVAS/HeartMate II. Other projects include PortaJet (High Frequency Jet Ventilator), Integrated Blood Pump/Oxygenator, Centrifugal Pump for Pediatric Use, Cardiac Preservation/Transportation Device. Additional material, such as all supporting documentation for these prototypes, is available as well. Since 1977, Nimbus has mounted exhibits for the "Contractor's Conference" and this material has been preserved.

Finding Aid


Some proprietary material may be restricted.

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