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  • A ventricular assist device is an electromechanical circulatory device

  • that is used to partially or completely replace the function of a failing heart.

  • The function of VADs differs from that of artificial cardiac pacemakers. 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,

  • typically for patients suffering from advanced congestive heart failure.

  • VADs are distinct from artificial hearts, 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 or left ventricle, or

  • both at once. The type that 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 may become

  • necessary. Long term VADs are normally used to keep patients alive with a good

  • quality of life while they wait for a heart transplantation. However, LVADs

  • are sometimes used as destination therapy, meaning they will never undergo

  • heart transplant, 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.

  • Design = Pumps=

  • The pumps used in VADs can be divided into two main categoriespulsatile

  • 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 are smaller and

  • have proven to be more durable than pulsatile VADs. They normally use either

  • a centrifugal pump 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 suspension or

  • hydrodynamic suspension. These pumps contain only one moving part.

  • History The first successful implantation of a

  • left ventricular assist device was completed in 1966 by Dr. Michael E.

  • DeBakey to a 37-year-old woman. A paracorporeal circuit was able to

  • provide mechanical support for 10 days after the surgery. The first successful

  • long-term implantation of an artificial LVAD was conducted in 1988 by Dr.

  • William F. Bernhard of Boston Children's Hospital Medical Center and Thermedics,

  • Inc of Woburn, MA under a National Institutes of Health research contract

  • which developed Heart-mate, an electronically controlled assist device.

  • This was funded by a three year $6.2 million contract to Thermedics and

  • Children's Hospital, Boston MA from the National Heart and Lung and Blood

  • Institute, a program of NIH. 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 Food

  • and Drug Administration 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 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. 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 expandin 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 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. This approach involves a return to a

  • pulsatile flow. 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 at the age of 69.

  • Studies and outcomes = 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..

  • 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, 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

  • 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 assess 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. On June 27, 2014 Hannover Medical School

  • in Hannover, Germany performed the first human implant of HeartMate III under the

  • direction of Professor Axel Haverich M.D., chief of the Cardiothoracic,

  • Transplantation and Vascular Surgery Department and surgeon Jan Schmitto,

  • M.D., Ph.D. On January 21, 2015 a study was

  • published in Journal of American College of Cardiology suggesting that long-term

  • use of LVAD may induce heart regeneration. This may explain the

  • bridge to recovery phenomenon first described by the Yacoub group in NEJM in

  • 2009. 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 and measures 3 inches. 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. As of June 2007 these pumps

  • had been implanted in over 100 patients. 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 as of January 2010.

  • The Heartware HVAD works similarly to the VentrAssistalbeit much smaller

  • and not requiring an abdominal pocket to be implanted into. The device has

  • obtained CE Mark in Europe, and FDA approval in the U.S. Recently, it was

  • shown that the Heartware HVAD can be implanted through limited access without

  • sternotomy. 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.

  • = HeartMate II LVAD 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 and destination

  • therapy, 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 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 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.

  • = HARPS= The Harefield Recovery Protocol Study is

  • a clinical trial to evaluate whether advanced heart failure patients

  • requiring VAD support can recover sufficient myocardial function to allow

  • device removal. HARPS combines an LVAD 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% 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 explantationall patients were NYHA Class I; and no significant adverse

  • effects were reported with clenbuterol therapy.

  • = REMATCH= The REMATCH clinical trial began in May

  • 1998 and ran through July 2001 in 20 cardiac transplant centers around the

  • USA. 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 in one-year survival of patients that were

  • implanted with a VAD, 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.

  • 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 Bleeding is the most common

  • postoperative early complication after implantation or explantation of LVADs,

  • necessitating reoperation in up to 60% of recipients. The implications of

  • massive blood transfusions are great and include infection, pulmonary

  • insufficiency, increased costs, right heart failure, allosensitization, and

  • viral transmission, some of which can prove fatal or preclude transplantation.

  • When bleeding occurs, it impacts the one year Kaplan-Meier mortality. In addition

  • to complexity of the patient population and the complexity of these procedures

  • contributing to bleeding, the devices themselves may contribute to the severe

  • coagulopathy that can ensue when these devices are implanted. Critical in the

  • management of bleeding in the early hours after implantation or explantation

  • is to adequately evacuate the post-surgical blood from around the

  • heart and lungs to prevent retained blood from contributing to the need for

  • reoperation to wash out clot that can compress the device features and

  • contribute to post operative shock. Preventing chest tube clogging during

  • this period is critical to recovery. Because the devices generally result in

  • blood flowing over a non-biologic surface, predisposing the blood to

  • clotting, 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; 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: Gram positive bacteria

  • Gram negative bacteria Fungi. especially Candida species

  • 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. 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. Considering the multitude of risks and

  • lifestyle modifications associated with ventricular assist device implant, it is

  • important for prospective patients to be informed prior to decision making. In

  • addition to physician consult, various Internet-based patient directed

  • resources are available to assist in patient education.

  • List of implantable VAD devices This is a partial list and may never be

  • completeReferenced additions are welcome See also

  • Intra-aortic balloon pump Gus Rosenberg

  • References 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 pulsenews 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 Technology

  • 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 Interventional procedures overviewshort-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. Ventricular Assist Device Center for

  • Heart FailureNorthwestern Memorial Hospital

  • [1] Website Hannover Medical School. LVAD FAQ.

A ventricular assist device is an electromechanical circulatory device

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