Jarvik Heart (United States)

The infant size Jarvik 2000 blood pump is close to a scaled down version of the adult model but redesign of all components was required. Figure 1 - the near complete prototype, and Figure 2 - the impeller (left) compared to a hemopump impeller. The infant pump is designed for flow of .5–1.5 L/min. at 15–25,000 rpm 80 mmHg pressure, 8mm outflow graft, fit in the apex of a newborn, and have a minimum durability >6 months. Bearing analysis predicts hydrodynamic radial support. Prototype motor tests: stall torque .25 oz-in, no load speed 40,000 rpm, peak motor efficiency 54%. Most components have been fabricated. Flow/pressure bench test data on operational prototype will be available prior to June 2006.FigureFigure

A lifetime mechanical solution for advanced heart failure must be reliable, with a low risk of life-threatening complications. After extensive laboratory testing, we began clinical trials with an axial flow pump for long-term treatment of New York Heart Association class IV, transplant-ineligible patients. The Jarvik 2000 is a continuous flow device that is implanted in the apex of the left ventricle with offloading to the descending thoracic aorta. Skull-based percutaneous power delivery was derived from cochlear implant technology. We used this system in 4 patients with end-stage dilated cardiomyopathy. Exercise capacity, quality of life, device parameters, and native heart function were monitored serially. One patient died from right heart failure at 3 months. The other patients were discharged from hospital between 3 and 8 weeks postoperatively and are currently New York Heart Association I or II. Follow-up lasted between 9 and 20 months. There has been no device failure or hemolysis. Native heart function and quality of life were markedly improved. The Jarvik 2000 is a true assist (rather than replacement) device that functions synergistically with the native left ventricle and provides excellent quality of life. Adverse events are infrequent. This blood pump may provide a mechanical solution for end-stage heart failure in the community.

Clinical application of the Jarvik 2000® Heart has begun. The first patient was treated at the Texas Heart Institute in December under medical emergency conditions to replace an infected HeartMate with a torn inflow valve. The Jarvik 2000 flow at 10,000-14,000 RPM was 7.2± 1.9 L/min for 16 days but infection could not be controlled. The patient succumbed to sepsis, MOF & ARDS. Despite positive cultures for MRSA Staph, Serratia, VRE, and Candida, the pump remained extremely clean with only a tiny torus of thrombus < 1/2 mm thick at one bearing, and no evidence of thromboembolism. The clinical Jarvik 2000 utilizes redundant power cables, an all analog manually adjusted control system with alarm and power monitoring functions, and battery power at all times for electrical isolation from the mains. The belt worn Li-ion battery pack weighs ∼1 1/2 lbs. and powers the device for 10–12 hrs. A 15 lb. reserve lead/acid battery with up to 40 hrs of capacity is also provided. The configuration for bridge to recovery and permanent use includes a skull mounted percutaneous power transmission pedistal for an effective barrier to infection. The MDA has granted clinical study approval at the Oxford Heart Centre for patients with dilated cardiomyopathy as bridge to recovery. We expect to implant several patients before June, and also to begin an IDE bridge to transplant study at the Texas Heart Institute in the near future, pending FDA approval.

A belt worn controller and lithium-ion battery pack have been developed for use with the initial clinical trials of the Jarvik 2000 heart. Patient interface considerations, safety, and simplicity were major design inputs for the system. The controller was developed using all analog technology to avoid difficulties with electromagnetic interference (EMI), to minimize susceptibility to electrostatic discharge, and to avoid the need for software validation. Manual control of pump speed is accomplished by a patient operated knob, according to physician instructions for rest and exercise for each individual patient. The system includes alarms and indicators which show the following: the amount of remaining battery charge, if the battery is low and needs replacement, the power in watts being consumed, if the power consumed is above 15 W, if the pump is running below the selected speed setting, and if the pump stops. The control box, curved to be worn on the belt, is only 2.5 inches high for comfort when sitting. The battery pack, also form fitted for patient comfort, weighs just over 1 1/2 pounds and supplies 65 W-h of energy storage, sufficient to run the device for over 8 h at nominal load.

Hydrodynamic blood pumps provide such advantages as not requiring an air vent or compliance chamber as well as a great reduction in mechanical complexity with the potential for very long durability. The detailed design of their bearings is emerging as the single most important determinant of long-term success. Three categories of bearings include remote force, such as magnetic suspension; blood-isolated, which require a shaft seal; and blood-immersed using either mechanical or hydrodynamic support. Blood-immersed bearings permit maximum simplification and miniaturization of the entire system, require no flush fluid, and require no electronics as with magnetic suspension. The Jarvik 2000 heart represents an example of their potential. The intraventricular titanium pump (25 mm diameter, 25 cc, 85 g), uses blood flow through the motor air gap with blood-immersed bearings. The longest in vitro bearing durability test is ongoing at 20,000,000,000 revolutions with minimal wear (3 years at 15,000 rpm). In vivo results include 5-month calf survival, no thromboembolism, plasma Hb 2-5 mg%, and power under 10 W.