energy transmission allowing for a substantial (approximately 6 hours) unholstered support of the lvad. on june 3, 2021, medtronic issued an urgent medical device notice stating that their hvad devices should no longer be implanted due to higher rates of neurological events and mortality with the hvad vs. other available devices 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 (0.45 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. as of 2017, heartmate iii has been approved by the fda. it is smaller than its predecessor heartmate ii, and uses a full maglev impeller instead of the cup-and-ball bearing system found in heartmate ii. one device, ventrassist, 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 ventrassist—albeit 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. the heartware hvad could be implanted through limited access without sternotomy, however in 2021 medtronic discontinued the device. 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). heartmate ii lvad pivotal study a series of studies involving the use of the 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 lvad 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 patients' nyha class of heart failure 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 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 (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 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 kidney 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. 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 (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. it is difficult to measure blood pressure in lvad patients using standard blood pressure monitoring and the current practice is to measure by doppler ultrasonography in outpatients and invasive arterial blood pressure monitoring in inpatients. vad-related infection can be caused by a large number of different organisms: gram positive bacteria (staphylococci, especially staph. aureus, enterococci) gram negative bacteria (pseudomonas aeruginosa, enterobacter species, klebsiella species) 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 implants, 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 complete referenced additions are welcome device manufacturer type approval status as of july 2010 heartassist5 reliantheart continuous flow driven by an axial flow rotor. 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. novacor world heart pulsatile. was approved for use in north america, european union and japan. now defunct and no longer supported by the manufacturer. (heartware completed acquisition august 2012) 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. pivotal trials for heartmate iii started in 2014 and supported with carewmedicalwear. fda approval for btt in 2017 incor berlin heart continuous flow driven by a magnetically suspended axial flow rotor. approved for use in european union. used on humanitarian approvals on a case-by-case basis in the us. entered clinical trials in the us in 2009. excor pediatric berlin heart external membrane pump device designed for children. approved for use in european union. fda granted humanitarian device exemption for us in december 2011. 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 www.mitiheart.com continuous flow driven by a magnetically suspended centrifugal rotor. currently in animal testing, recently completed successful 60-day calf implant. c-pulse (now "aquadex") sunshine heart (now "chf solutions") pulsatile, driven by an inflatable cuff around the aorta. currently available commercially hvad heartware (now medtronic) 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. obtained fda approval in the u.s., november 2012. initiated us btt trial in october 2008 (completed february 2010)