Jarvik 2000 Ventricular Assist Device
Overview
The Jarvik 2000 Heart Pump
Like the artificial heart, the first ventricular assist devices (VADs) developed 25 years ago were meant to sideline the failing biological heart of a heart failure patient. These pumps were heavy, bulky things that drew blood from the left ventricle through an intake valve and moved it into the aorta at as much as 10 liters per minute — the full output of a healthy heart.
Some of the VADs made today take into account the fact that even severe heart failure patients retain partial functioning of the left ventricle: from as little as 10 percent to as much as 50 percent of its normal capacity. The tiny, valveless Jarvik 2000 FlowMaker®, developed by artificial heart pioneer Dr. Robert Jarvik, is one such design.
Held in the hand, the Jarvik 2000 pump is about the size of a C battery. Within its welded titanium shell sits a direct-current motor, a rotor supported by two ceramic bearings, and a single moving part: a small, spinning titanium impeller that pumps blood from the heart at up to 7 liters per minute. Rather than take over for the biological heart, the Jarvik 2000 augments the weakened heart's blood output to help restore a normal blood flow throughout the body.
By utilizing the heart's remaining strength, the Jarvik 2000 takes a simple, unobtrusive approach to circulatory support. Any muscle that gets too little exercise becomes "out of shape," and the heart is no exception. The Jarvik 2000 allows the patient's heart to continue to exercise as it recovers after surgery. The pump is designed to minimize patient reliance on mechanical support, avoid risk and redundancy in its function, and give the patient the best chances of recovery.
How It Works
Unlike the natural heart, the Jarvik 2000 pump does not "beat." Instead, it uses a spinning rotor to propel blood from the left ventricle into the aorta. But the natural heart continues to contract and relax, and the volume of blood moved by the spinning rotor rhythmically increases and decreases in synchrony with those contractions.
Jarvik 2000 patients do, therefore, retain a pulse. The Jarvik 2000 magnifies the blood output of the heart, effectively producing a pulsatile blood flow in concert with it. The device truly assists the patient's own heart without hindering it. With both the biological heart and the mechanical pump moving blood into the aorta, the congestion of fluids brought on by heart failure can quickly subside.
Miniaturized technology has allowed the Jarvik 2000 pump to be made small — so small that it is implanted inside the left ventricle of the biological heart. The pump is inserted through a circular incision in the heart wall and secured with a polyester sewing cuff. A fabric tube from the outflow end of the pump connects it to the aorta.
This type of device is sometimes called a "booster" pump. By supplying some — but not all — of the blood flow to the aorta, the pump boosts the performance of the natural heart to stabilize blood pressure, normalize blood flow to the body, and relieve fluid congestion in the body, all the while allowing the natural heart to fill with and eject blood.
Manual control
Control of the Jarvik 2000 FlowMaker® is placed in the hands of the patient. Jarvik 2000 patients must therefore monitor both themselves and the device to some degree. Unlike the natural heart, mechanical devices do not "know" with certainty when patients exert themselves and need more oxygen-rich blood to the muscles; neither do they know when patients are sleeping and need less. Depending on the heart's condition and the patient's level of activity, the output (i.e. rotor speed) of the Jarvik 2000 can be adjusted to accommodate patient needs using a small, external controller.
We believe that the manual-control approach of the Jarvik 2000 FlowMaker® remains the safest approach to regulating a VAD. Some other heart rotary assist devices have automatic control systems in which a computer determines the speed of the pump. This works in some circumstances, but there can be situations in which the computer can make a mistake and run the device at a dangerous speed because it does not have enough information about the patient's condition.
With the Jarvik 2000, Patients receive guidelines for making adjustments to the pump's speed, but over time, they learn to adapt the settings to their individual health conditions. Improvement in heart function, for example, can prompt gradual changes to their settings. Most patients need only to adjust the pump speed occasionally, and they often "feel" the need to turn the pump up when exercising or down when at rest or going to sleep. The five speeds of the Jarvik 2000 FlowMaker® afford the patient a considerable range for rest and exercise but does not permit unsafe extremes.
System Components
While the innovative design of the Jarvik 2000 pump is typically the focus of discussion in news and medical forums, the complete Jarvik 2000 system consists of several components, including external components that patients come to know far more intimately than the pump itself.
This equipment includes the external controller, two different types of batteries, and various cables and connectors. Depending on whether the pump is implanted for temporary or permanent use, the power cable exits the patient's body either through the abdominal wall or through a connector mounted on the head, behind the ear. The power cable connects the implanted pump to its wearable battery and controls. Because the pump requires an external battery to function, patients are connected to a battery at all times. A small half-size AA battery powers the Jarvik 2000's alarm system, which alerts the patient if the battery that powers the pump has become completely discharged or disconnected.
The Jarvik 2000 FlowMaker® can run for 8-10 hours on a single, portable Lithium-ion battery pack, similar to those used for high-end video cameras and laptops. These batteries are small and light, so patients can carry extras to extend their time untethered to a stationary power source. The total weight of the battery pack, controller, and cables is less than three pounds. Patients also keep a complete set of backup equipment close at hand in case of damage to their primary equipment.
Though rugged, the external components of the Jarvik 2000 are not indestructible. Like all electronics, they should be handled with care. The components ought not be dropped or subjected to extremes of heat and cold. The cables, when not protected, can suffer significant damage.
Still, damage to the Jarvik 2000 equipment rarely causes harm to the patient. One Jarvik 2000 patient broke a cable connector when he slammed it in a car door; another accidentally cut his cable with a scissors while changing his bandage; yet another patient lost connection to his battery and controller when a purse snatcher grabbed his shoulder bag and ran off with it. Fortunately, in each of these situations, the patient suffered no harm. Their own natural hearts were able to sustain them until they could connect their backup equipment.
External Controller
The FlowMaker® external controller delivers power to the heart pump, provides the interface for patient control of the pump speed, and monitors system function to alert the patient to potential problems, such as low power or underspeed operation.
The only user-controllable feature of the Jarvik 2000 is the pump speed, set by a dial within the range of 1 to 5. Speed setting 1 is slowest, driving the impeller at 8,000 RPM and producing blood flow of 1-2 liters per minute. Speed setting 5 is fastest, driving the impeller at 12,000 RPM and producing blood flow of 5-7 liters per minute.
Batteries
Portable batteries and charger
Two wearable, gray Lithium-ion battery packs are provided for tether-free operation of the Jarvik 2000 FlowMaker®. Each fully-charged battery delivers about 8-10 hours of pump operation under normal conditions, and each has its own indicator lights to show how much power remains. A tongue-and-groove mechanism allows the controller to be mounted to the battery for easy handling, and both the battery and the controller can be worn in a waist-belt or shoulder bag. The portable Li-ion batteries are rechargeable, and come with a separate charger and power supply that plugs into any wall outlet.
Reserve batteries
Two lead-acid batteries are provided for use while sleeping or during any unusual event, such as a local power outage. These batteries are heavy (15 lbs.) and come in a red carrying case with skid-proof material on the bottom. Each reserve battery will power the Jarvik 2000 for more than 30 hours under normal conditions and is rechargeable. Each lead-acid battery has a charger built-in and can be plugged directly into the wall to recharge.
(Note: The Jarvik 2000 cannot be run from wall power. Even when connected to a battery that is plugged into a wall outlet, the Jarvik 2000 pump draws power only from the battery, and the controller will not draw power from the wall.)
Other Items
Cables and connectors
Connector cables are supplied with the Jarvik 2000 FlowMaker® to link the components together: the battery to the controller, the controller to the pump. The cables are color-coded and keyed to ensure that they cannot be connected the wrong way. A latch mechanism allows the cables to "click" together securely, making connections hold up against sudden tugs or strain. A retractable extension cord for connecting the controller and the pump allows the external equipment to be kept at a distance while sleeping or bathing. A "Y" cable is also provided to allow the patient to seamlessly change batteries without stopping the pump.
Patient instruction manual
A patient manual gives detailed guidelines on how to use the external components of the Jarvik 2000 FlowMaker® to ensure maximum safety. Patients also carry an identification card with important contact and technical information, which may be necessary in emergency situations. Patients and family members receive detailed instruction and can be a good resource for information regarding operation and pump controls.
Risks
The biggest risks related to VAD surgery are bleeding, infection, and the failure of other organs, such as the kidneys, liver, or lungs. Since an LVAD supports only the left side of the heart, failure of the right side can occur and become a serious complication. The use of a mechanical circulatory device introduces inherent risks, however small, of events such as air entering the arteries during device implant or failure of the device itself.
Although risk is inevitable in the application of any medical technology, the Jarvik 2000 FlowMaker® has been developed and tested over 16 years to minimize complications. Perhaps the Jarvik 2000's most important attributes in this regard are the simplicity and economy of its design.
Infection and Clots
With no inflow or outflow valves and no air vent tube to the outside of the body, the Jarvik 2000 eliminates the risk of problems associated with these components. The very small size of the Jarvik 2000 makes it the only blood pump to be implanted inside the natural heart's left ventricle. Its positioning inside the heart eliminates the risk of infection in a "tissue capsule" around the outside of the device because no such capsule forms. Capsule infection and air vent tube infection still occur at high rates in some VADs, while complications due to infections of all types remain much lower in Jarvik 2000, as reported in the scientific literature.
Stroke from blood clots has not yet been eliminated with the Jarvik 2000 and has occurred in 8-12% of all patients treated to date. Most have recovered significantly, and some have recovered completely. Better surgical technique and better anticoagulation management can further reduce the rate of blood clots associated with the Jarvik 2000. Additionally, a pump design improvement tested in animals but not yet introduced in patients appears promising. The risk of stroke with the Jarvik 2000 is about the same as the risk with the HeartMate and Novacor devices.
Device Reliability
As a device that must operate safely inside the human body for long periods of time, the Jarvik 2000 has shown itself to be highly reliable, with no mechanical failures of the implanted blood pump in more than 100 cases to date. The titanium, blood-contacting surfaces are highly polished, biocompatible and remain corrosion free in the harsh environment that blood creates. The small, spinning impeller responsible for generating the bloodflow through the pump causes no clinically significant damage to blood cells.
EMS Concerns
In the event of an emergency, such as cardiac arrest, the Jarvik patient is to be treated just as any other patient. All ACLS protocols apply. Chest compressions are used when indicated and defibrillation is appropriate. It is not necessary to disconnect any of the Jarvik equipment when defibrillating the patient. It is important to keep these patients in a normal sinus rhythm. However, many of these patients are long standing heart failure patients and have Pacer/AICD's already in place. If a patient does present with V-tach/V-fib, they are often conscious, but very weak and upon assessment have the classic low output signs. It is appropriate to increase the pump speed during a cardiac emergency. However, remember not to go above 4, and if you do turn a patient up to a setting of 4, don't leave the patient at that setting for more than 5 minutes.
Contact Situations
Recipient patients and families are instructed by the implanting facility and physicians to contact them and / or EMS when certain situations arise. Here’s the criteria they use;
The hospital VAD Coordinator should be called when:
- A battery issue occurs other than low battery
- A controller issue/alarm requiring replacement of controller
The hospital medical staff should be called for any of the following situations:
- Complaint of numbness, tingling or weakness in any limb
- Blurred vision, speech problems
- Seizure/convulsions
- Shortness or breath, dizziness
- Complaint of any pain
- Oral temperature > 38C
- Any redness, swelling, or drainage around driveline exit site
- Unusual bleeding or bruising
- Any condition where the recipient feels "unwell"
- If emergency medical services/paramedics have been called
Emergency medical services/paramedics should be called when:
- The recipient is unconscious
- The recipient is awake but non-responsive
- The recipient falls or suddenly collapses
- The recipient experiences a severe neurological deficit (sensory or motor)
- The recipient experiences a severe arrhythmia or cardiac arrest (ventricular tachycardia or ventricular fibrillation) The pump stops and cannot be restarted within three minutes
Warnings and Restrictions
- Patients should not engage in contact sports or jumping activities.
- No MRI.
- Do not immerse in water.
- Do not allow fluid (of any kind) to come in contact with the abdominal cable/ driveline. Fluid can be sucked into the motor and cause a pump failure.
- If the battery is disconnected from the controller the pump will STOP!!
- Plug all charging equipment into grounded (3 prong) outlets.
- Do not run the pump off of a battery that is plugged into the wall.
- Rotate use of all portable and reserve batteries.
- Perform CPR as usual
- Follow ACLS guidelines, there are no restrictions
- Contact hospital LVAS team during all emergent situations
- Take all Jarvik equipment with you to the hospital.
Emergency Contact
Example Emergency Contacts
UNC Hospitals
101 Manning Drive
Chapel Hill, NC 27514
Date of Implant: 11/21/2005
Your Surgeon is: Craig Selzman, MD
Your Coordinator is: Tracy Vernon-Platt
***PAGER: (919) 216-2095***
Office phone number: (919) 966-1207
Only use this number if you plan on leaving a message and DO NOT have an urgent matter to discuss.
Or you may call the:
HOSPITAL OPERATOR:
(919) 966-4131
ASK FOR Cardiac SURGERY RESIDENT ON CALL
Or call CTICU
(919) 966-5246