An Implantable Centrifugal Blood Pump with a Recirculating Purge System (Cool‐Seal System)

Abstract

A compact centrifugal blood pump has been developed as an implantable left ventricular assist system. The impeller diameter is 40 mm, and pump dimensions are 55 x 64 mm. This first prototype, fabricated from titanium alloy, resulted in a pump weight of 400 g including a brushless DC motor. The weight of a second prototype pump was reduced to 280 g. The entire blood contacting surface is coated with diamond like carbon (DLC) to improve blood compatibility. Flow rates of over 7 L/min against 100 mm Hg pressure at 2,500 rpm with 9 W total power consumption have been measured. A newly designed mechanical seal with a recirculating purge system (Cool-Seal) is used for the shaft seal. In this seal system, the seal temperature is kept under 40 degrees C to prevent heat denaturation of blood proteins. Purge fluid also cools the pump motor coil and journal bearing. Purge fluid is continuously purified and sterilized by an ultrafiltration unit which is incorporated in the paracorporeal drive console. In vitro experiments with bovine blood demonstrated an acceptably low hemolysis rate (normalized index of hemolysis = 0.005 +/- 0.002 g/100 L). In vivo experiments are currently ongoing using calves. Via left thoracotomy, left ventricular (LV) apex descending aorta bypass was performed utilizing an expanded polytetrafluoroethylene (ePTFE) vascular graft with the pump placed in the left thoracic cavity. In 2 in vivo experiments, the pump flow rate was maintained at 5-9 L/min, and pump power consumption remained stable at 9-10 W. All plasma free Hb levels were measured at less than 15 mg/dl. The seal system has demonstrated good seal capability with negligible purge fluid consumption (<0.5 ml/day). In both calves, the pumps demonstrated trouble free continuous function over 6 month (200 days and 222 days).

Electrochemical and antimicrobial properties of diamondlike carbon-metal composite films

“…For example, diamondlike carbon has been considered for use in a coronary artery stents, synthetic heart valves, left ventricular assist devices, and artificial hearts, because platelet activation and platelet adhesion occur less often on diamondlike carbon-coated surfaces than on conventional (titanium, titanium carbide, titanium nitride, or stainless steel) surfaces [31][32][33][34][35][36][37][38]. Another medical application for diamondlike carbon thin films is use on hip joint prostheses and knee joint prostheses.…”

Completely pulsatile high flow circulatory support with a constant-speed centrifugal blood pump: mechanisms and early clinical observations

“…1, 2), an implantable centrifugal blood pump, has been developed by Sun Medical Technology Research Corporation (Nagano, Japan). 1,2 The pump is made of pure titanium and weighs 420 g. A 40-mm diameter impeller is directly driven by a sensorless, brushless direct-current motor. The pump draws the blood from the left ventricle through the apical infl ow cannula and propels it to the ascending aorta via the outfl ow vascular graft.…”

Laser Processing of Advanced Bioceramics

“…[40±48] Diamondlike carbon films exhibit diminished platelet activation and lower thrombus formation rates than many conventional vascular prosthesis materials. [49] Figure 3 contains a scanning electron micrograph of a hydrogen-free diamondlike carbon film placed in platelet rich plasma. Unlike many conventional metallic or polymeric medical device surfaces, diamondlike carbon coated surfaces do not readily adsorb proteins.…”