Ventricular assist device
Encyclopedia
A Ventricular assist device, or VAD, is a mechanical circulatory device
that is used to partially or completely replace the function of a failing heart
. Some VADs are intended for short term use, typically for patients recovering from heart attacks
or heart surgery
, while others are intended for long term use (months to years and in some cases for life), typically for patients suffering from congestive heart failure.
VADs need to be clearly distinguished from artificial heart
s, which are designed to completely take over cardiac function and generally require the removal of the patient's heart.
VADs are designed to assist either the right (RVAD) or left (LVAD) ventricle
, or both at once (BiVAD). Which of these types is used depends primarily on the underlying heart disease
and the pulmonary arterial resistance that determines the load on the right ventricle.
LVADs are most commonly used, but when pulmonary arterial resistance is high, right ventricular assistance becomes necessary. Long term VADs are normally used to keep patients alive with a good quality of life while they wait for a heart transplantation (known as a "bridge to transplantation"). However, LVADs are sometimes used as destination therapy and sometimes as a bridge to recovery.
In the last few years, VADs have improved significantly in terms of providing survival and quality of life among recipients.
s used in VADs can be divided into two main categories - pulsatile pumps, that mimic the natural pulsing action of the heart, and continuous flow pumps.
Pulsatile VADs use positive displacement pumps
. In some of these pumps, the volume occupied by blood varies during the pumping cycle, and if the pump is contained inside the body then a vent tube to the outside air is required.
Continuous flow VADs normally use either centrifugal pump
s or an axial flow pump. Both types have a central rotor containing permanent magnets. Controlled electric currents running through coils contained in the pump housing apply forces to the magnets, which in turn cause the rotors to spin. In the centrifugal pumps, the rotors are shaped to accelerate the blood circumferentially and thereby cause it to move toward the outer rim of the pump, whereas in the axial flow pumps the rotors are more or less cylindrical with blades that are helical, causing the blood to be accelerated in the direction of the rotor's axis.
An important issue with continuous flow pumps is the method used to suspend the rotor. Early versions used solid bearings; however, newer pumps, some of which are approved for use in the EU use either electromagnetic or hydrodynamic suspension. These pumps contain only one moving part.
More recent work has concentrated on continuous flow pumps, which can be roughly categorized as either centrifugal pumps or axial flow
impeller driven pumps. These pumps have the advantage of greater simplicity resulting in smaller size and greater reliability. These devices are referred to as second generation VADs. A side effect is that the user will not have a pulse
, or that the pulse intensity will be seriously reduced, and will need to carry documentation saying that the lack of a pulse does not mean that they are dead.
Third generation VADs suspend the impeller in the pump using either hydrodynamic or electromagnetic suspension, thus removing the need for bearings and reducing the number of moving parts to one.
Another technology undergoing clinical trials is the use of trans cutaneous induction to power and control the device rather than using percutaneous cables. Apart from the obvious cosmetic advantage this reduces the risk of infection and the consequent need to take preventative action. A pulsatile pump using this technology has CE Mark approval and is in clinical trials for US FDA approval.
A very different approach in the early stages of development is the use of an inflatable cuff around the aorta. Inflating the cuff contracts the aorta and deflating the cuff allows the aorta to expand - in effect the aorta becomes a second left ventricle. A proposed refinement is to use the patient's skeletal muscle, driven by a pacemaker, to power this device which would make it truly self contained. However a similar operation (cardiomyoplasty
) was tried in the 1990s with disappointing results. In any case, it has substantial potential advantages in avoiding the need to operate on the heart itself and in avoiding any contact between blood and the device. Interestingly this approach involves a return to a pulsatile flow.
To date, 73% (11 of 15) of patients who underwent the combination therapy regimen demonstrated sufficient recovery to allow explantation and avoid heart transplantation; freedom from recurrent heart failure in surviving patients was 100% and 89% at one and four years after explantation, respectively; average ejection fraction was 64% at 59 months after explantation - all patients were NYHA Class I; and no significant adverse effects were reported with clenbuterol therapy.
The trial demonstrated an 81% improvement in two-year survival among patients receiving HeartMate XVE compared to optimal medical management. In addition, a destination therapy study following the REMATCH trial demonstrated an additional 17% improvement (61% vs. 52%) in one-year survival of patients that were implanted with a VAD (HeartMate XVE), with an implication for the appropriate selection of candidates and timing of VAD implantation.
A test carried out in 2001 by Dr. Eric A. Rose and REMATCH study group with patients with congestive heart failure that were ineligible for a transplant showed a survival at two years of 23% for those implanted with an LVAD compared with 8% for those who were treated with drugs. The two major complications of VAD implantation were infection and mechanical failure (see below).
According to a retrospective cohort study comparing patients treated with a left ventricular assist device versus inotrope therapy while awaiting heart transplantation, the group treated with LVAD had improved clinical and metabolic function at the time of transplant with better blood pressure, sodium, blood urea nitrogen, and creatinine. After transplant, 57.7% of the inotrope group had renal failure versus 16.6% in the LVAD group; 31.6% of the inotrope group had right heart failure versus 5.6% in the LVAD group; and event-free survival was 15.8% in the inotrope group versus 55.6% in the LVAD group.
, there is need for anticoagulation measures. One device, the HeartMate XVE, is designed with a biologic surface derived from fibrin
and does not require long term anticoagulation (except aspirin); unfortunately, this biologic surface may also predispose the patient to infection through selective reduction of certain types of leukocytes.
New VAD designs which are now approved for use in the European Community and are undergoing trials for FDA approval have all but eliminated mechanical failure.
VAD-related infection
can be caused by a large number of different organisms:
Treatment of VAD-related infection is exceedingly difficult and many patients die of infection despite optimal treatment. Initial treatment should be with broad spectrum antibiotics, but every effort must be made to obtain appropriate samples for culture. A final decision regarding antibiotic therapy must be based on the results of microbiogical cultures.
Other problems include immunosuppression
, clotting with resultant stroke
, and bleeding
secondary to anticoagulation. It is interesting to note that some of the polyurethane
components used in the devices cause the deletion of a subset of immune cells
when blood comes in contact with them. This predisposes the patient to fungal
and some viral
infections necessitating appropriate prophylactic therapy.
As of July 2007, 69 year old Peter Houghton
was the longest surviving recipient of a VAD for permanent use. He received an experimental Jarvik 2000 LVAD in June 2000. Since then, he completed a 91 mile charity walk, published two books, lectured widely, hiked in the Swiss Alps and the American West, flew in an ultra-light aircraft, and traveled extensively around the world. He died of acute renal failure in 2007.
VADs extend the quantity of life. People who have had VADs implanted have had lower rates of depression than those people suffering from cardiac disease that have not undergone implantation surgery.
In a small number of cases left ventricular assist devices, combined with drug therapy, have enabled the heart to recover sufficiently for the device to be able to be removed (explanted).
The majority of VADs on the market today are somewhat bulky. The smallest device approved by the FDA, the HeartMate II, weighs about 1 pound (0.45359237 kg) and measures 3 inches (7.6 cm). This has proven particularly important for women and children, for whom alternatives would have been too large
One device gained CE Mark approval for use in the EU and began clinical trials in the US (VentrAssist). As at June 2007 these pumps had been implanted in over 100 patients including a 10 year old girl. In one case the original heart recovered after the device had been implanted for a year and the device was able to be removed. In 2009, Ventracor was placed into the hands of Administrators due to financial problems and was later that year liquidated. No other companies purchased the technology, so as a result the VentrAssist device was essentially defunct. Around 30-50 patients worldwide remain supported on VentrAssist devices at January 2010.
The Heartware HVAD works very similarly to the VentrAssist - albeit very much smaller and not requiring an abdominal pocket to be implanted into. The device has obtained CE Mark in Europe and is currently in clinical trials in the USA.
Referenced additions are welcome
Machine
A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...
that is used to partially or completely replace the function of a failing heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
. Some VADs are intended for short term use, typically for patients recovering from heart attacks
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
or heart surgery
Cardiac surgery
Cardiovascular surgery is surgery on the heart or great vessels performed by cardiac surgeons. Frequently, it is done to treat complications of ischemic heart disease , correct congenital heart disease, or treat valvular heart disease from various causes including endocarditis, rheumatic heart...
, while others are intended for long term use (months to years and in some cases for life), typically for patients suffering from congestive heart failure.
VADs need to be clearly distinguished from artificial heart
Artificial heart
An artificial heart is a mechanical device that replaces the heart. Artificial hearts are typically used in order to bridge the time to heart transplantation, or to permanently replace the heart in case transplantation is impossible...
s, which are designed to completely take over cardiac function and generally require the removal of the patient's heart.
VADs are designed to assist either the right (RVAD) or left (LVAD) ventricle
Ventricle (heart)
In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...
, or both at once (BiVAD). Which of these types is used depends primarily on the underlying heart disease
Heart disease
Heart disease, cardiac disease or cardiopathy is an umbrella term for a variety of diseases affecting the heart. , it is the leading cause of death in the United States, England, Canada and Wales, accounting for 25.4% of the total deaths in the United States.-Types:-Coronary heart disease:Coronary...
and the pulmonary arterial resistance that determines the load on the right ventricle.
LVADs are most commonly used, but when pulmonary arterial resistance is high, right ventricular assistance becomes necessary. Long term VADs are normally used to keep patients alive with a good quality of life while they wait for a heart transplantation (known as a "bridge to transplantation"). However, LVADs are sometimes used as destination therapy and sometimes as a bridge to recovery.
In the last few years, VADs have improved significantly in terms of providing survival and quality of life among recipients.
Pumps
The pumpPump
A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...
s used in VADs can be divided into two main categories - pulsatile pumps, that mimic the natural pulsing action of the heart, and continuous flow pumps.
Pulsatile VADs use positive displacement pumps
Pump
A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...
. In some of these pumps, the volume occupied by blood varies during the pumping cycle, and if the pump is contained inside the body then a vent tube to the outside air is required.
Continuous flow VADs normally use either centrifugal pump
Centrifugal pump
A centrifugal pump is a rotodynamic pump that uses a rotating impeller to create flow by the addition of energy to a fluid. Centrifugal pumps are commonly used to move liquids through piping...
s or an axial flow pump. Both types have a central rotor containing permanent magnets. Controlled electric currents running through coils contained in the pump housing apply forces to the magnets, which in turn cause the rotors to spin. In the centrifugal pumps, the rotors are shaped to accelerate the blood circumferentially and thereby cause it to move toward the outer rim of the pump, whereas in the axial flow pumps the rotors are more or less cylindrical with blades that are helical, causing the blood to be accelerated in the direction of the rotor's axis.
An important issue with continuous flow pumps is the method used to suspend the rotor. Early versions used solid bearings; however, newer pumps, some of which are approved for use in the EU use either electromagnetic or hydrodynamic suspension. These pumps contain only one moving part.
History
The early VADs emulated the heart by using a "pulsatile" action where blood is alternately sucked into the pump from the left ventricle then forced out into the aorta. Devices of this kind include the HeartMate IP LVAS, which was approved for use in the US by the FDA in October 1994. These devices are commonly referred to as first generation VADs.More recent work has concentrated on continuous flow pumps, which can be roughly categorized as either centrifugal pumps or axial flow
Axial flow pump
An axial flow pump, or AFP, is a common type of pump that essentially consists of a propeller in a pipe. The propeller can be driven directly by a sealed motor in the pipe or mounted to the pipe from the outside or by a right-angle drive shaft that pierces the pipe.The main advantage of an AFP is...
impeller driven pumps. These pumps have the advantage of greater simplicity resulting in smaller size and greater reliability. These devices are referred to as second generation VADs. A side effect is that the user will not have a pulse
Pulse
In medicine, one's pulse represents the tactile arterial palpation of the heartbeat by trained fingertips. The pulse may be palpated in any place that allows an artery to be compressed against a bone, such as at the neck , at the wrist , behind the knee , on the inside of the elbow , and near the...
, or that the pulse intensity will be seriously reduced, and will need to carry documentation saying that the lack of a pulse does not mean that they are dead.
Third generation VADs suspend the impeller in the pump using either hydrodynamic or electromagnetic suspension, thus removing the need for bearings and reducing the number of moving parts to one.
Another technology undergoing clinical trials is the use of trans cutaneous induction to power and control the device rather than using percutaneous cables. Apart from the obvious cosmetic advantage this reduces the risk of infection and the consequent need to take preventative action. A pulsatile pump using this technology has CE Mark approval and is in clinical trials for US FDA approval.
A very different approach in the early stages of development is the use of an inflatable cuff around the aorta. Inflating the cuff contracts the aorta and deflating the cuff allows the aorta to expand - in effect the aorta becomes a second left ventricle. A proposed refinement is to use the patient's skeletal muscle, driven by a pacemaker, to power this device which would make it truly self contained. However a similar operation (cardiomyoplasty
Cardiomyoplasty
Cardiomyoplasty is a surgical procedure in which healthy muscle from another part of the body is wrapped around the heart to provide support for the failing heart. Most often the latissimus dorsi muscle is used for this purpose. A special pacemaker is implanted to make the skeletal muscle contract....
) was tried in the 1990s with disappointing results. In any case, it has substantial potential advantages in avoiding the need to operate on the heart itself and in avoiding any contact between blood and the device. Interestingly this approach involves a return to a pulsatile flow.
Recent developments
- In July 2009 in England, surgeons removed a donor heart that had been implanted in a toddler next to her native heart, after her native heart had recovered. This technique suggests mechanical assist device, such as an LVAD, can take some or all the work away from the native heart and allow it time to heal.
- In July 2009, 18-month follow-up results from the HeartMate II Clinical Trial concluded that continuous-flow LVAD provides effective hemodynamic support for at least 18 months in patients awaiting transplantation, with improved functional status and quality of life. (see below).
- Heidelberg University Hospital reported in July 2009 that the first HeartAssist5, known as the modern version of the DeBakey VAD, was implanted there. The HeartAssist5 weighs 92 grams, is made of titanium and plastic, and serves to pump blood from the left ventricle into the aorta.
- A phase 1 clinical trial is underway (as of August 2009), consisting of patients with coronary artery bypass grafting and patients in end-stage heart failure who have a left ventricular assist device. The trial involves testing a patch, called Anginera(TM) that contains cells that secrete hormone-like growth factors that stimulate other cells to grow. The patches are seeded with heart muscle cells and then implanted onto the heart with the goal of getting the muscle cells to start communicating with native tissues in a way that allows for regular contractions.
- In September 2009, a New Zealand news outlet, Stuff, reported that in another 18 months to two years, a new wireless device will be ready for clinical trial that will power VADs without direct contact. If successful, this may reduce the chance of infection as a result of the power cable through the skin.
- The National Institutes of Health (NIH) awarded a $2.8 million grant to develop a "pulse-less" total artificial heart using two VADS by Micromed, initially created by Michael DeBakey and George Noon. The grant was renewed for a second year of research in August 2009. The Total Artificial Heart was created using two HeartAssist5 VADs, whereby one VAD pumps blood throughout the body and the other circulates blood to and from the lungs.
- HeartWare International announced in August 2009 that it had surpassed 50 implants of their HeartWare Ventricular Assist System in their ADVANCE Clinical Trial, an FDA-approved IDE study. The study is to asses the system as bridge-to-transplantation system for patients with end-stage heart failure. The study, Evaluation of the HeartWare LVAD System for the Treatment of Advance Heart Failure, is a multi-center study that started in May 2009.
HeartMate II LVAS Pivotal Study
A series of studies involving the use of the of HeartMate II LVAD have proven useful in establishing the viability and risks of using LVADs for bridge-to-transplantation and destination therapy.- The pilot trial for the HeartMate II LVAS began in November 2003 and consisted of 46 study patients at 15 centers. Results included 11 patients supported for more than one year and three patients supported for more than two years.
- The HeartMate II pivotal trial began in 2005 and included the evaluation of HeartMate II for two indications: Bridge to transplantation (BTT) and destination therapy (DT), or long-term, permanent support. Thoratec Corp. announced that this was the first time the FDA had approved a clinical trial to include both indications in one protocol.
- A multicenter study in the United States from 2005 to 2007 with 113 patients (of which 100 reported principal outcomes) showed that significant improvements in function were prevalent after three months, and a survival rate of 68% after twelve months.
- Based on one-year follow up data from the first 194 patients enrolled in the trial, the FDA approved HeartMate II for bridge-to-transplantation. The trial provided clinical evidence of improved survival rates and quality of life for a broad range of patients.
- Eighteen-month follow up data on 281 patients who had either reached the study end-point or completed 18 months of post-operative follow-up showed improved survival, less frequent adverse events and greater reliability with continuous flow LVADS compared to pulsatile flow devices. Of the 281 patients, 157 patients had undergone transplant, 58 patients were continuing with LVADs in their body and seven patients had the LVAD removed because their heart recovered; the remaining 56 had died. The results showed that the NYHA Class of heart failure the patients had been designated had significantly improved after six months of LVAD support compared to the pre-LVAD baseline. Although this trial involved bridge-to-transplant indication, the results provide early evidence that continuous flow LVADs have advantages in terms of durability and reliability for patients receiving mechanical support for destination therapy.
- Following the FDA approval of HeartMate II LVAD for bridge-to-transplantation purposes, a post-approval ("registry") study was undertaken to assess the efficacy of the device in a commercial setting. The study found that the device improved outcomes, both compared to other LVAD treatments and baseline patients. Specifically, HeartMate II patients showed lower creatinine levels, 30-day survival rates were considerably higher at 96%, and 93% reached successful outcomes (transplant, cardiac recovery, or long-term LVAD).
HARPS
The Harefield Recovery Protocol Study (HARPS) is a clinical trial to evaluate whether advanced heart failure patients requiring VAD support can recover sufficient myocardial function to allow device removal (known as explantation). HARPS combines an LVAD (the HeartMate XVE) with conventional oral heart failure medications, followed by the novel β2 agonist clenbuterol. This opens the possibility that some advanced heart failure patients may forgo heart transplantation.To date, 73% (11 of 15) of patients who underwent the combination therapy regimen demonstrated sufficient recovery to allow explantation and avoid heart transplantation; freedom from recurrent heart failure in surviving patients was 100% and 89% at one and four years after explantation, respectively; average ejection fraction was 64% at 59 months after explantation - all patients were NYHA Class I; and no significant adverse effects were reported with clenbuterol therapy.
REMATCH
The REMATCH (Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure) clinical trial began in May 1998 and ran through July 2001 in 20 cardiac transplant centers around the country. The trial was designed to compare long-term implantation of left ventricular assist devices with optimal medical management for patients with end-stage heart failure who require, but do not qualify to receive cardiac transplantation. As a result of the clinical outcomes, the device received FDA approval for both indications, in 2001 and 2003, respectively.The trial demonstrated an 81% improvement in two-year survival among patients receiving HeartMate XVE compared to optimal medical management. In addition, a destination therapy study following the REMATCH trial demonstrated an additional 17% improvement (61% vs. 52%) in one-year survival of patients that were implanted with a VAD (HeartMate XVE), with an implication for the appropriate selection of candidates and timing of VAD implantation.
A test carried out in 2001 by Dr. Eric A. Rose and REMATCH study group with patients with congestive heart failure that were ineligible for a transplant showed a survival at two years of 23% for those implanted with an LVAD compared with 8% for those who were treated with drugs. The two major complications of VAD implantation were infection and mechanical failure (see below).
According to a retrospective cohort study comparing patients treated with a left ventricular assist device versus inotrope therapy while awaiting heart transplantation, the group treated with LVAD had improved clinical and metabolic function at the time of transplant with better blood pressure, sodium, blood urea nitrogen, and creatinine. After transplant, 57.7% of the inotrope group had renal failure versus 16.6% in the LVAD group; 31.6% of the inotrope group had right heart failure versus 5.6% in the LVAD group; and event-free survival was 15.8% in the inotrope group versus 55.6% in the LVAD group.
Complications and side effects
Because the devices generally result in blood flowing over a non biologic surface, predisposing the blood to clottingCoagulation
Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...
, there is need for anticoagulation measures. One device, the HeartMate XVE, is designed with a biologic surface derived from fibrin
Fibrin
Fibrin is a fibrous, non-globular protein involved in the clotting of blood. It is a fibrillar protein that is polymerised to form a "mesh" that forms a hemostatic plug or clot over a wound site....
and does not require long term anticoagulation (except aspirin); unfortunately, this biologic surface may also predispose the patient to infection through selective reduction of certain types of leukocytes.
New VAD designs which are now approved for use in the European Community and are undergoing trials for FDA approval have all but eliminated mechanical failure.
VAD-related infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
can be caused by a large number of different organisms:
- Gram positive bacteria (Staphylococci especially Staph. aureusStaphylococcus aureusStaphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...
, Enterococci) - Gram negative bacteria (Pseudomonas aeruginosaPseudomonas aeruginosaPseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...
, Enterobacter species, KlebsiellaKlebsiellaKlebsiella is a genus of non-motile, Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule. It is named after the German microbiologist Edwin Klebs...
species) - Fungi especially Candida sp.
Treatment of VAD-related infection is exceedingly difficult and many patients die of infection despite optimal treatment. Initial treatment should be with broad spectrum antibiotics, but every effort must be made to obtain appropriate samples for culture. A final decision regarding antibiotic therapy must be based on the results of microbiogical cultures.
Other problems include immunosuppression
Immunosuppression
Immunosuppression involves an act that reduces the activation or efficacy of the immune system. Some portions of the immune system itself have immuno-suppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other...
, clotting with resultant stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
, and bleeding
Bleeding
Bleeding, technically known as hemorrhaging or haemorrhaging is the loss of blood or blood escape from the circulatory system...
secondary to anticoagulation. It is interesting to note that some of the polyurethane
Polyurethane
A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...
components used in the devices cause the deletion of a subset of immune cells
White blood cell
White blood cells, or leukocytes , are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five different and diverse types of leukocytes exist, but they are all produced and derived from a multipotent cell in the bone marrow known as a...
when blood comes in contact with them. This predisposes the patient to fungal
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
and some viral
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
infections necessitating appropriate prophylactic therapy.
As of July 2007, 69 year old Peter Houghton
Peter Houghton
Peter Houghton , was the longest surviving artificial heart transplant patient in the UK.Houghton was implanted with a Jarvik 2000 heart pump at the John Radcliffe Hospital, Oxford, England, by professor Stephen Westaby, on 20 June 2000 owing to severe heart failure...
was the longest surviving recipient of a VAD for permanent use. He received an experimental Jarvik 2000 LVAD in June 2000. Since then, he completed a 91 mile charity walk, published two books, lectured widely, hiked in the Swiss Alps and the American West, flew in an ultra-light aircraft, and traveled extensively around the world. He died of acute renal failure in 2007.
VADs extend the quantity of life. People who have had VADs implanted have had lower rates of depression than those people suffering from cardiac disease that have not undergone implantation surgery.
In a small number of cases left ventricular assist devices, combined with drug therapy, have enabled the heart to recover sufficiently for the device to be able to be removed (explanted).
The majority of VADs on the market today are somewhat bulky. The smallest device approved by the FDA, the HeartMate II, weighs about 1 pound (0.45359237 kg) and measures 3 inches (7.6 cm). This has proven particularly important for women and children, for whom alternatives would have been too large
One device gained CE Mark approval for use in the EU and began clinical trials in the US (VentrAssist). As at June 2007 these pumps had been implanted in over 100 patients including a 10 year old girl. In one case the original heart recovered after the device had been implanted for a year and the device was able to be removed. In 2009, Ventracor was placed into the hands of Administrators due to financial problems and was later that year liquidated. No other companies purchased the technology, so as a result the VentrAssist device was essentially defunct. Around 30-50 patients worldwide remain supported on VentrAssist devices at January 2010.
The Heartware HVAD works very similarly to the VentrAssist - albeit very much smaller and not requiring an abdominal pocket to be implanted into. The device has obtained CE Mark in Europe and is currently in clinical trials in the USA.
List of implantable VAD devices
This is a partial list and may never be completeReferenced additions are welcome
| Device | Manufacturer | Type | Approval Status as of July 2009 |
|---|---|---|---|
| Novacor | World Heart | Pulsatile. | Was approved for use in North America, European Union and Japan. Now defunct and no longer supported by the manufacturer. |
| HeartMate XVE | Thoratec | Pulsatile. | FDA approval for BTT in 2001 and DT in 2003. CE Mark Authorized. Rarely used anymore due to reliability concerns. |
| HeartMate II | Thoratec | Rotor driven continuous axial flow, ball and cup bearings. | Approved for use in North America and EU. CE Mark Authorized. FDA approval for BTT in April 2008. Recently approved by FDA in the US for Destination Therapy (as at January 2010). |
| HeartMate III | Thoratec | Continuous flow driven by a magnetically suspended axial flow rotor. | Clinical trials yet to start, uncertain future. |
| Incor | Berlin Heart | Continuous flow driven by a magnetically suspended axial flow rotor. | Approved for use in European Union. Used on humanitarian approvals on case by case basis in the US. Entered clinical trials in the US in 2009. |
| Jarvik 2000 | Jarvik Heart | Continuous flow, axial rotor supported by ceramic bearings. | Currently used in the United States as a bridge to heart transplant under an FDA-approved clinical investigation. In Europe, the Jarvik 2000 has earned CE Mark certification for both bridge-to-transplant and lifetime use. Child version currently being developed. |
| MicroMed DeBakey VAD | MicroMed | Continuous flow driven by axial rotor supported by ceramic bearings. | Approved for use in the European Union. The child version is approved by the FDA for use in children in USA. Undergoing clinical trials in USA for FDA approval. |
| VentrAssist | Ventracor | Continuous flow driven by a hydrodynamically suspended centrifugal rotor. | Approved for use in European Union and Australia. Company declared bankrupt while clinical trials for FDA approval were underway in 2009. Company now dissolved and intellectual property sold to Thoratec. |
| MTIHeartLVAD | MiTiHeart Corporation MiTiHeart Corporation MiTiHeart Corporation is a product technology company specializing in ventricular assist devices for patients suffering from congestive heart failure... |
Continuous flow driven by a magnetically suspended centrifugal rotor. | Yet to start clinical trials. |
| C-Pulse | Sunshine Heart | Pulsatile, driven by an inflatable cuff around the aorta. | Currently in clinical trials in the US and Australia. |
| HVAD | HeartWare | Miniature "third generation" device with centrifugal blood path and hydromagnetically suspended rotor that may be placed in the pericardial space. | Obtained CE Mark for distribution in Europe, January 2009. Initiated US BTT trial in October 2008 (completed February 2010) and US DT trial in August 2010. |
| DuraHeart | Terumo Terumo was founded in 1921 by Dr. Kitasato Shibasaburō. The company's first product was thermometers and it has since expanded into a global largest medical devices manufacturer, producing a wide variety of products ranging from medical disposables, cardiovascular systems and diabetes care products.In... |
Magnetically levitated centrifugal pump. | CE approved, US FDA trials underway as at January 2010. |
| Thoratec PVAD (Paracorporeal Ventricular Assist Device) | Thoratec | Pulsatile system includes three major components: Blood pump, cannulae and pneumatic driver (dual drive console or portable VAD driver). | CE Mark Authorized. Received FDA approval for BTT in 1995 and for post-cardiotomy recovery (open heart surgery) in 1998. |
| IVAD - Implantable Ventricular Assist Device | Thoratec | Pulsatile system includes three major components: Blood pump, cannulae and pneumatic driver (dual drive console or portable VAD driver). | CE Mark Authorized. Received FDA approval for BTT in 2004. Authorized only for internal implant, not for paracorporeal implant due to reliability issues. |
External links
- LifeFlow LVAD at the University of Virginia
- Nader Moazami, Patrick M. McCarthy Temporary Circulatory Support
- Eugene L. Kukuy, Mehmet C. Oz, Yoshifumi Naka Long-Term Mechanical Circulatory Support - a review of the subject as at 2003.
- Mechanical Circulatory Support Resource Center
- Health Center Online VAD
- Mayo Clinic VAD
- Life without a pulse — news story about Canadian man with VAD
- Heart Pump Design Could Give Patients New Hope — A new counter-flow heart pump developed by Queensland University of TechnologyQueensland University of TechnologyQueensland University of Technology is an Australian university with an applied emphasis in courses and research. Based in Brisbane, it has 40,000 students, including 6,000 international students, over 4,000 staff members, and an annual budget of more than A$750 million.QUT is marketed as "A...
- Heart pump improves quality of life in congestive heart failure patients A rapid review of the medical literature and specialist opinion as at December 2005
- NATIONAL INSTITUTE FOR HEALTH AND CLINICAL EXCELLENCE (UK) Interventional procedures overview - short-term circulatory support with left ventricular assist devices as a bridge to cardiac transplantation or recovery A rapid review of the medical literature and specialist opinion as at December 2005
- Courtney J. Gemmato,Matthew D. Forrester,Timothy J. Myers,O.H. Frazier,Denton A. Cooley Thirty-Five Years of Mechanical Circulatory Support at the Texas Heart Institute Tex Heart Inst J 2005;32:168-77
- MyLVAD.com Non branded site with video, news, and community discussions on VAD's.