Comparison of the CardioWest total artificial heart, the novacor left ventricular assist system and the thoratec ventricular assist system in bridge to transplantation

Computational Fluid Dynamics Model of Continuous-Flow Total Artificial Heart: Right Pump Impeller Design Changes to Improve Biocompatibility

Cleveland Clinic is developing a continuous-flow total artificial heart (CFTAH). This novel design operates without valves and is suspended both axially and radially through the balancing of the magnetic and hydrodynamic forces. A series of long-term animal studies with no anticoagulation demonstrated good biocompatibility, without any thromboemboli or infarctions in the organs. However, we observed varying degrees of thrombus attached to the right impeller blades following device explant. No thrombus was found attached to the left impeller blades. The goals for this study were: (1) to use computational fluid dynamics (CFD) to gain insight into the differences in the flow fields surrounding both impellers, and (2) to leverage that knowledge in identifying an improved next-generation right impeller design that could reduce the potential for thrombus formation. Transient CFD simulations of the CFTAH at a blood flow rate and impeller rotational speed mimicking in vivo conditions revealed significant blade tip-induced flow separation and clustered regions of low wall shear stress near the right impeller that were not present for the left impeller. Numerous right impeller design variations were modeled, including changes to the impeller cone angle, number of blades, blade pattern, blade shape, and inlet housing design. The preferred, next-generation right impeller design incorporated a steeper cone angle, a primary/splitter blade design similar to the left impeller, and an increased blade curvature to better align the incoming flow with the impeller blade tips. The next-generation impeller design reduced both the extent of low shear regions near the right impeller surface and flow separation from the blade leading edges, while maintaining the desired hydraulic performance of the original CFTAH design.

"It Works." Every heart transplant program should have one

The total artificial heart (TAH) provides full biventricular cardiac replacement, pulsatile perfusion at flows of 7-9 L/min at low filling pressures. This allows organs that are failing to recover and for the potential cardiac recipient to become a better transplant candidate. Postimplant patients are mobile and able to go through physical rehabilitation in a hospital or at home. The risks are acceptable as shown by the authors. TAH use in more transplant centers could save lives in many transplant candidates.

Hemodynamic Benefits of Counterpulsation, Implantable, Percutaneous, and Intraaortic Rotary Blood Pumps: An In-Silico and In Vitro Study

Mechanical circulatory support (MCS) devices have become a standard therapy for heart failure (HF) patients. MCS device designs may differ by level of support, inflow and/or outflow cannulation sites, and mechanism(s) of cardiac unloading and blood flow delivery. Investigation and direct comparison of hemodynamic parameters that help characterize performance of MCS devices has been limited. We quantified cardiac and vascular hemodynamic responses for different types of MCS devices. Continuous flow (CF) left ventricular (LV) assist devices (LVAD) with LV or left atrial (LA) inlet, counterpulsation devices, percutaneous CF LVAD, and intra-aortic rotary blood pumps (IARBP) were quantified using established computer simulation and mock flow loop models. Hemodynamic data were analyzed on a beat-to-beat basis at baseline HF and over a range of MCS support. Results demonstrated that all LVAD greatly diminished vascular pulsatility (P) and LV external work (LVEW). LVAD with LA inflow provided a greater reduction in LVEW compared to LVAD with LV inflow, but at the potential risk for blood stasis/thrombosis in the LV at high support. Counterpulsation provided greater coronary flow (CoF) augmentation, but had a lower reduction in LVEW compared to partial percutaneous LVAD support. IARBP diminished LVEW, but at the expense of diminished CoF due to coronary steal. The hemodynamic benefits for each type of mechanical circulatory support system are unique and clinical decisions on device selection to maximize end organ perfusion and minimize invasiveness needs to be considered for an individual patients' presentation.

Anesthetic and Perioperative Considerations in Patients Undergoing Placement of Totally Implantable Replacement Hearts

The recent successful implantation of the AbioCor im plantable replacement heart at the Rudd Heart-Lung Institute, Jewish Hospital, Louisville, KY, has renewed clinical interest in the use of the mechanical replace ment heart as therapy for intractable heart failure. Al though the number of orthotopic heart transplants has plateaued in the past decade, the number of patients requiring transplantation continues to increase. This supply/demand discrepancy continues to be the main catalyst for the research and development of other therapies for the failing heart. This review addresses perioperative considerations, monitoring modalities, and perioperative therapeutic interventions that may help guide the cardiac anesthesiologist through the challenges presented by implantation of total replace ment hearts in end-stage cardiac patients.

The total artificial heart

The total artificial heart (TAH) is a form of mechanical circulatory support in which the patient's native ventricles and valves are explanted and replaced by a pneumatically powered artificial heart. Currently, the TAH is approved for use in end-stage biventricular heart failure as a bridge to heart transplantation. However, with an increasing global burden of cardiovascular disease and congestive heart failure, the number of patients with end-stage heart failure awaiting heart transplantation now far exceeds the number of available hearts. As a result, the use of mechanical circulatory support, including the TAH and left ventricular assist device (LVAD), is growing exponentially. The LVAD is already widely used as destination therapy, and destination therapy for the TAH is under investigation. While most patients requiring mechanical circulatory support are effectively treated with LVADs, there is a subset of patients with concurrent right ventricular failure or major structural barriers to LVAD placement in whom TAH may be more appropriate. The history, indications, surgical implantation, post device management, outcomes, complications, and future direction of the TAH are discussed in this review.

An insight into short- and long-term mechanical circulatory support systems

Cardiogenic shock due to acute myocardial infarction, postcardiotomy syndrome following cardiac surgery, or manifestation of heart failure remains a clinical challenge with high mortality rates, despite ongoing advances in surgical techniques, widespread use of primary percutaneous interventions, and medical treatment. Clinicians have, therefore, turned to mechanical means of circulatory support. At present, a broad range of devices are available, which may be extracorporeal, implantable, or percutaneous; temporary or long term. Although counter pulsation provided by intra-aortic balloon pump (IABP) and comprehensive mechanical support for both the systemic and the pulmonary circulation through extracorporeal membrane oxygenation (ECMO) remain a major tool of acute care in patients with cardiogenic shock, both before and after surgical or percutaneous intervention, the development of devices such as the Impella or the Tandemheart allows less invasive forms of temporary support. On the other hand, concerning mid-, or long-term support, left ventricular assist devices have evolved from a last resort life-saving therapy to a well-established viable alternative for thousands of heart failure patients caused by the shortage of donor organs available for transplantation. The optimal selection of the assist device is based on the initial consideration according to hemodynamic situation, comorbidities, intended time of use and therapeutic options. The present article offers an update on currently available mechanical circulatory support systems (MCSS) for short and long-term use as well as an insight into future perspectives.

Total artificial heart in the pediatric patient with biventricular heart failure

Mechanical circulatory support emerged for the pediatric population in the late 1980s as a bridge to cardiac transplantation. The Total Artificial Heart (TAH-t) (SynCardia Systems Inc., Tuscon, AZ) has been approved for compassionate use by the Food and Drug Administration for patients with end-stage biventricular heart failure as a bridge to heart transplantation since 1985 and has had FDA approval since 2004. However, of the 1,061 patients placed on the TAH-t, only 21 (2%) were under the age 18. SynCardia Systems, Inc. recommends a minimum patient body surface area (BSA) of 1.7 m(2), thus, limiting pediatric application of this device. This unique case report shares this pediatric institution's first experience with the TAH-t. A 14-year-old male was admitted with dilated cardiomyopathy and severe biventricular heart failure. The patient rapidly decompensated, requiring extracorporeal life support. An echocardiogram revealed severe biventricular dysfunction and diffuse clot formation in the left ventricle and outflow tract. The decision was made to transition to biventricular assist device. The biventricular failure and clot formation helped guide the team to the TAH-t, in spite of a BSA (1.5 m(2)) below the recommendation of 1.7 m(2). A computed tomography (CT) scan of the thorax, in conjunction with a novel three-dimensional (3D) modeling system and team, assisted in determining appropriate fit. Chest CT and 3D modeling following implantation were utilized to determine all major vascular structures were unobstructed and the bronchi were open. The virtual 3D model confirmed appropriate device fit with no evidence of compression to the left pulmonary veins. The postoperative course was complicated by a left lung opacification. The left lung anomalies proved to be atelectasis and improved with aggressive recruitment maneuvers. The patient was supported for 11 days prior to transplantation. Chest CT and 3D modeling were crucial in assessing whether the device would fit, as well as postoperative complications in this smaller pediatric patient.

The challenge of home discharge with a total artificial heart: the La Pitie Salpetriere experience

OBJECTIVES

The total artificial heart (TAH) helps to counteract the current decrease in heart donors and is likely to bridge patients to transplant under favourable conditions. Today's mobile consoles facilitate home discharge. The aim of this study was to report on the La Pitie Hospital experience with CardioWest TAH recipients, and more particularly, on generally successful outpatient' management.

METHODS

A retrospective analysis was performed on clinical and biological data from patients implanted with a TAH between December 2006 and July 2010 in a single institution. Morbi-mortality during hospital stay, number and causes of rehospitalizations, quality of life during home discharge, bridge to transplant results and survival have all been analysed.

RESULTS

Twenty-seven patients were implanted with the CardioWest. Fifteen patients (55.5%) died during support. Prior to home discharge, the most frequent cause of death was multi-organ failure (46.6%). Twelve patients were discharged home from hospital within a median of 88 days [range 35-152, interquartile range 57] postimplantation. Mean rehospitalization rate was 1.2 by patient, on account of device infection (n = 7), technical problems with the console (n = 3) and other causes (n = 4). Between discharge and transplant, patients spent 87% of their support time out of hospital. All patients who returned home with the TAH were subsequently transplanted, and 1 died in post-transplant.

CONCLUSION

Despite the morbidity and mortality occurring during the postimplantation period, home discharge with a TAH is possible. Portables drivers allow for a safe return home. Aside from some remaining weak points such as infectious complications or noise, CardioWest TAH allows for successful rehabilitation of graft candidates, and assures highly satisfactory transplant results.

Past and present of cardiocirculatory assist devices: a comprehensive critical review

During the last 20 years, the management of heart failure has significantly improved by means of new pharmacotherapies, more timely invasive treatments and device assisted therapies. Indeed, advances in mechanical support, namely with the development of more efficient left ventricular assist devices (LVADs), and the total artificial heart have reduced mortality and morbidity in patients awaiting transplantation, so much so, that LVADs are now approved of as a strategy for destination therapy. In this review, the authors describe in detail the current basic indications, functioning modalities, main limitations of surgical LAVDs, total artificial heart development, and percutaneous assist devices, trying to clarify this complex, but fascinating topic.

A review of clinical ventricular assist devices

Given the limited availability of donor hearts, ventricular assist device (VAD) therapy is fast becoming an accepted alternative treatment strategy to treat end-stage heart failure. The field of mechanical ventricular assistance is littered with novel and unique ideas either based on volume displacement or rotary pump technology, which aim to sufficiently restore cardiac output. However, only a select few have made the transition to the clinical arena. Clinical implants were initially dominated by the FDA approved volume displacement Thoratec HeartMate I, IVAD, and PVAD, whilst Berlin Heart's EXCOR, and Abiomed's BVS5000 and AB5000 offered suitable alternatives. However, limitations associated with an inherently large size and reduced lifetime of these devices stimulated the development and subsequent implantation of rotary blood pump (RBP) technology. Almost all of the reviewed RBPs are clinically available in Europe, whilst many are still undergoing clinical trial in the USA. Thoratec's HeartMate II is currently the only rotary device approved by the FDA, and has supported the highest number of patients to date. This pump is joined by MicroMed Cardiovascular's Heart Assist 5 Adult VAD, Jarvik Heart's Jarvik 2000 FlowMaker and Berlin Heart's InCOR as the axial flow devices under investigation in the USA. More recently developed radial flow devices such as WorldHeart's Levacor, Terumo's DuraHeart, and HeartWare's HVAD are increasing in their clinical trial patient numbers. Finally CircuLite's Synergy and Abiomed's Impella are two mixed flow type devices designed to offer partial cardiac support to less sick patients. This review provides a brief overview of the volume displacement and rotary devices which are either clinically available, or undergoing the advanced stages of human clinical trials.

Results of mechanical circulatory support in France

OBJECTIVE

To present the analyzed results on mechanical circulatory support (MCS) collected over a 7-year period, from 2000 to 2006, in France.

METHODS

A cohort of 520 patients was analyzed. Mean age was 43.7 ± 13.6 years. The main causes of cardiac failure were ischemic cardiomyopathy (39%), idiopathic dilated cardiomyopathy (41.3%), or myocarditis (6.4%). Bridge to transplantation was indicated in 87.8% of patients, bridge to recovery in 9%, while destination therapy was proposed in 3.2% of patients.

RESULTS

For patients in cardiogenic shock or advanced heart failure undergoing device implantation as bridge to transplantation or recovery (n=458), overall mortality was 39% (n=179). The main causes of mortality under MCS were multi-organ failure (MOF) (57.4%), neurological events (14.1%), or infections (11.9%). Heart transplantation was performed in 249 (54.3%) patients. The main causes of death following heart transplantation were primary graft failure (22.4%), MOF (14.3%), neurological event (14.3%), or infection (10.2%). Long-term survival in transplanted patients was 75 ± 2.8% at 1 year and 66 ± 3.4% at 5 years.

CONCLUSIONS

MCS is an essential therapeutic tool to save the life of young patients with cardiogenic shock or advanced cardiac failure. Early MCS implantation and the availability of a device that is adapted to the patient's clinical status are prerequisites for reducing overall mortality rates.

CardioWest temporary total artificial heart

BACKGROUND

The CardioWest temporary total artificial heart (TAH-t) replaces both native ventricles of the heart and is more beneficial for a select group of patients than most other typical ventricular assist devices (VADs). This review will expand on the current literature and highlight the chronology of this device. The CardioWest TAH-t has been implanted in over 715 patients at 30 multiple institutional centers worldwide as a bridge-to-transplant (BTT) since 1993. The mechanical flow dynamics of the device are manufactured and designed differently from other traditional VADs, allowing increased outputs and normal filling pressures, allowing for sufficient organ and tissue perfusion and dramatic recoveries, allowing patients to return to an almost normal quality of life.

RESULTS

There was a 79% survival to transplant achievement in the protocol group who received the TAH-t versus a 46% in the control group (P < 0.001). Furthermore, there was a 70% survival rate at one year in the protocol group versus 31% in the control group (P < 0.001). The one- and five-year survival rates after transplantation were 69% and 34%, respectively, in the control group and 86% and 64%, respectively, in the protocol group.

CONCLUSION

It is evident that the advancement of modern engineering and medicine has made way for a reliable and durable device that provides a promising future in the field of end-stage heart failure.

Total artificial heart--concepts and clinical use

End-stage congestive heart failure remains the leading cause of death in the United States. Despite advances in medical treatment, it also remains the most common reason for admission to the hospital. The gold standard of treatment for the failing heart, orthotopic heart transplantation, is limited by a shortage of donor hearts. There are also a significant number of patients who are not transplant candidates due to comorbid conditions and/or inability to tolerate immunosuppressive therapy. To meet the need for this latter group, the medical field has embraced ventricular assist device (VAD) therapy to extend survival and improve quality-of-life for the end-stage cardiac patient. This therapy, however, has been currently limited to the failing left ventricle and is still fraught with complications that limit long-term and widespread use. The total artificial heart, as currently available with two devices, is rapidly becoming the treatment of choice for biventricular failure.

Cerebrovascular accidents in patients with a ventricular assist device

OBJECTIVE

A cerebrovascular accident is a devastating adverse event in a patient with a ventricular assist device. The goal was to clarify the risk factors for cerebrovascular accident.

METHODS

Prospectively collected data, including medical history, ventricular assist device type, white blood cell count, thrombelastogram, and infection, were reviewed retrospectively in 124 patients.

RESULTS

Thirty-one patients (25%) had 48 cerebrovascular accidents. The mean ventricular assist device support period was 228 and 89 days in patients with and without cerebrovascular accidents, respectively (P < .0001). Sixty-six percent of cerebrovascular accidents occurred within 4 months after implantation. Actuarial freedom from cerebrovascular accident at 6 months was 75%, 64%, 63%, and 33% with the HeartMate device (Thoratec Corp, Pleasanton, Calif), Thoratec biventricular ventricular assist device (Thoratec Corp), Thoratec left ventricular assist device (Thoratec), and Novacor device (WorldHeart, Oakland, Calif), respectively. Twenty cerebrovascular accidents (42%) occurred in patients with infections. The mean white blood cell count at the cerebrovascular accident was greater than the normal range in patients with infection (12,900/mm3) and without infection (9500/mm3). The mean maximum amplitude of the thrombelastogram in the presence of infection (63.6 mm) was higher than that in the absence of infection (60.7 mm) (P = .0309).

CONCLUSIONS

The risk of cerebrovascular accident increases with a longer ventricular assist device support period. Infection may activate platelet function and predispose the patient to a cerebrovascular accident. An elevation of the white blood cell count may also exacerbate the risk of cerebrovascular accident even in patients without infection. Selection of device type, prevention of infection, and meticulous control of anticoagulation are key to preventing cerebrovascular accident.

Does total implantability reduce infection with the use of a left ventricular assist device? The LionHeart experience in Europe

BACKGROUND

Infection is the leading cause of death for left ventricular assist device (LVAD) patients with end-stage heart failure. Decreased infection may be possible with fully implantable LVADs such as the LionHeart, which lacks percutaneous conduits (PCs), a common source of device-related infection (DRI). This sub-study reports infections with the LionHeart and compares these results with historic data from the REMATCH trial, bridge to recovery (BTR) and bridge-to-transplantation (BTT) studies.

METHODS

Twenty-three patients were implanted with the LionHeart LVAD and followed until death or heart transplant during a non-randomized, multicenter, European trial from October 1999 to April 2004. The nature and incidence of infection were analyzed and adjudicated to definitions similar to, or the same as, the REMATCH definitions.

RESULTS

The combined number of implant days was 7,980, with a mean of 347 days (median 112, range 17 to 1,259 days). Survival at 1 year was 39%, with 2-year survival at 22%. Seventy-four percent of patients developed one or more infections, with 30% developing sepsis, and 35% developing pump-pocket infections (PSIs). No patients developed pump-housing or inflow- or outflow-tract infections (PI). For comparison, the prevalence rates of sepsis, PSI and PI in REMATCH were 51%, 35% and 19%, respectively.

CONCLUSIONS

The patients in the European LionHeart Clinical Utility Baseline Study (CUBS) trial had less sepsis and less overall DRI compared with the REMATCH LVAD group. Therefore, the fully implanted device may cause less infection than PC devices during destination therapy (DT). Although lower for DT, these rates are still higher than for some BTT experiences. Areas for future improvement include miniaturization of controller/battery components to reduce wound complications related to pocket size, and installation of more modern lithium-ion batteries to decrease the need for re-operations due to battery end-of-life.

Neurologic Events With a Totally Implantable Left Ventricular Assist Device: European LionHeart Clinical Utility Baseline Study (CUBS)

BACKGROUND

Neurologic events such as thromboembolic and hemorrhagic strokes are common complications of mechanical circulatory support. We report the neurologic events observed in patients treated for end-stage heart failure with the implantable, pulsatile LionHeart left ventricular assist device (LVAD). This sub-study was part of the LionHeart European Clinical Utility Baseline Study (CUBS).

METHODS

Twenty-three male patients were implanted with the LionHeart LVAD in a non-randomized, observational study. Neurologic events were classified into three categories: (1) transient ischemic attacks (TIAs); (2) strokes, including cerebrovascular accidents (CVAs) and intracranial bleeding (ICB); and (3) "other," including hypoperfusion, coma and brain death. Neurologic injuries were also categorized as transient/reversible or permanent/disabling.

RESULTS

Thirteen of 23 patients (57%) had a total of 30 neurologic events. Eight patients (35%) had 18 TIAs. Eight patients (35%) also had a stroke, either CVA (n = 5, 22%) or ICB (n = 3, 13%), and 5 of these patients (22%) also had 12 TIAs. Three patients (13%) had 4 "other" neurologic events. Ten patients (43%) had transient/reversible neurologic deficits and 10 (43%) had permanent/disabling events. One patient (4%) had intracranial bleeding as a primary cause of death (anti-coagulation-related hemorrhage). The combined incidence of neurologic events was 1.37 events/patient-year. The incidences of transient and permanent events were 0.91 and 0.46 event/patient-year, respectively.

CONCLUSIONS

Neurologic events caused morbidity in the CUBS trial, with infrequent mortality. These results are similar to previous experiences with destination therapy and underscore the need for improvements in LVAD design, patient selection and patient management to reduce the incidence of neurologic events.

CardioWest Total Artificial Heart in a Moribund Adolescent With Left Ventricular Thrombi

Bridge to transplant is a well-known strategy to enable patients with congestive heart failure to live until transplant. A 15-year-old boy with Beckers' muscular dystrophy and cardiomyopathy was accepted for heart transplantation. He suffered a cardiac arrest and was placed on extracorporeal membrane oxygenator. A paracorporeal biventricular assist device and a total artificial heart were considered for bridge to transplant. A CardioWest total artificial heart was chosen because of the patient's size. Multiple left ventricular thrombi were identified at the time of the ventriculectomy. The patient did well with the total artificial heart was transplanted and discharged home. The unknown presence of significant left ventricular thrombi raises the question of outcome with a paracorporeal ventricular assist device.

Patients With a Body Surface Area Less Than 1.7 m2 Have a Good Outcome With the CardioWest Total Artificial Heart

BACKGROUND

A body surface area (BSA) of 1.7 m2 was considered as the lower limit to implant a CardioWest Total Artificial Heart (TAH). We reviewed our experience with the TAH in patients with a BSA of less than 1.7 m2.

METHODS

From April 1986 to May 2003, among 149 patients implanted with a TAH in our institution, 30 had a BSA of less than 1.7 m2 (Group I). Results were compared with the remaining 119 patients (Group II).

RESULTS

One patient in Group I experienced a fitting problem and was left with the chest open. Otherwise, in this group, the Day 1 cardiac index averaged 3.6 +/- 0.6 liter/min/m2, which was significantly higher than the 2.8 +/- 0.36 liter/min/m2 observed in Group II. Post-implantation central venous pressure and mean arterial pressure were similar in both groups: 14.7 +/- 3.8 mm Hg vs 14.5 +/- 4 mm Hg and 87 +/- 23 mm Hg vs 88 +/- 19 mm Hg, respectively. In Group I, survival on the device dramatically increased from 9% before 1992, to 36% between 1992 and 1997 and finally reached 75% after then. In the meantime, for the same time periods, global survival to hospital discharge increased from 9% to 36% and reached 50% after 1997. In Group II, global survival to hospital discharge was 25.5% before 1992, 34.6% between 1993 and 1997, and reached 52% thereafter.

CONCLUSION

The CardioWest TAH can be used in patients with a BSA between 1.5 m2 and 1.7 m2 with few fitting problems. In this group of patients, results are similar to those obtained in patients with a BSA greater than 1.8 m2.

CardioWest Total Artificial Heart: Bad Oeynhausen Experience

BACKGROUND

The use of ventricular assist devices (VAD) has become a widely accepted therapeutic option. However, there are still limitations to the patient collective eligible for VAD placement, who might therefore benefit from the implantation of a total artificial heart. We present the first German single-center experience with the CardioWest total artificial heart (TAH) (SynCardia Systems, Tucson, AZ) in 42 patients.

METHODS

Between February 2001 and December 2003, 42 patients (37 men, 5 women, mean age 51 +/- 13 years) received a TAH at our Center. Their body surface area ranged between 1.5 and 2.4 (mean, 1.9 +/- 0.19) m2. All patients were in persistent cardiogenic shock in spite of maximum inotropic support and had numerous preoperative risk factors (intraaortic balloon pumping, mechanical ventilation, acute renal failure, previous cardiac surgery, recent cardiopulmonary resuscitation).

RESULTS

Duration of support was 1 to 291 days. Eleven patients (26%) underwent successful transplantation; 9 of them could be discharged home. Twenty-two patients died under support, 21 of them from multiple organ failure and 1 patient from a technical problem. Nine patients are still on the device, 4 of them at home after the original CardioWest console was replaced by the Berlin Heart EXCOR driver (Berlin Heart, Berlin, Germany). Exceptional results were achieved in patients with cardiogenic shock after cardiac surgery or after acute myocardial infarction.

CONCLUSIONS

Against the background of the extremely poor preoperative situation of our patients, the overall survival rate of 48% can be considered as favorable. A prospective, randomized study is planned to find out whether patients with idiopathic dilated or ischemic cardiomyopathy are more likely to benefit from a biventricular assist device or a total artificial heart.

Left ventricular apical infection and rupture complicating left ventricular assist device explantation in 2 women with postpartum cardiomyopathy

Postpartum cardiomyopathy is rare form of cardiac failure, with the potential for cardiac function to recover to normal. When medical therapy fails to control symptoms or haemodynamic stability, circulatory support with a ventricular assist device may be considered as a bridge to cardiac transplantation. We describe 2 patients with severe postpartum cardiomyopathy, in whom cardiac function recovered sufficiently during mechanical circulatory assistance to enable device explantation. Bacteremia during device support was treated with chronic suppressive antibiotics, yet after cannula explantation and ventricular repair, residual infection led to destruction of the primary repair, with formation of a left ventricular pseudoaneurysm. This is a complication of device support not previously reported. Surgery was necessary to repair the infected ventricular cannula site. Both patients recovered; however one patient developed recurrent cardiomyopathy 4 months later.

Left ventricular assist devices for the treatment of congestive heart failure

The mainstay of heart failure therapy is aggressive medical management with consideration of resynchronization therapy and automatic implantable cardioverter-defibrillator. This is best done with the support of a multidisciplinary team. Transplantation, when possible, remains the therapy of choice for patients who are refractory to medical therapy. Other options short of left ventricular assist device (LVAD) that should be considered include revascularization, mitral valve repair, and left ventricular remodeling procedures. LVAD therapy as a bridge to transplantation should be considered in patients with heart failure who are clinically deteriorating while on the transplant waiting list. This should be initiated prior to the onset of irreversible end-organ damage. In nontransplant candidates, an LVAD can be considered as an alternative to transplantation (destination therapy). However, cost and the availability of expertise continue to limit this therapy to quaternary care and research institutions.

Intercontinental LVAS Patient Transport

Mechanical circulatory support is currently indicated for patients with cardiac insufficiency as a bridge to transplantation or as a bridge to recovery. These systems continue to evolve and improve, and many patients (after they are stabilized) are now able to be discharged from the hospital. This article reports our experience with the intercontinental transportation of a patient while being supported with a Novacor left ventricular assist system (WorldHeart Corp, Ottawa, Canada). While in Japan, the Canadian patient suffered a myocardial infarction and despite coronary artery bypass grafting, the patient remained in a low cardiac output state. After implantation of the left ventricular assist system in Japan, the patient was stabilized and transported by a commercial airline to Canada where he underwent successful heart transplantation.

Total artificial heart bridge to transplantation: a 9-year experience with 62 patients

BACKGROUND

The SynCardia CardioWest total artificial heart (CardioWest TAH) is a biventricular, orthotopic, pneumatic, pulsatile blood pump driven by an external console. For each ventricle, the length of the blood-flow path is shorter and the inflow and outflow valves are larger than in any other bridge-to-transplant device, resulting in greater blood flow at smaller pre-load. Such a device should be optimal for bridging transplant candidates who have biventricular failure and for whom all other therapies have failed.

METHODS

From January 1, 1993, to April 1, 2002, we prospectively studied 62 consecutive CardioWest TAH implant recipients to document safety and efficacy in bridge to transplantation. We used multisystem monitoring and multidrug therapy for anti-coagulation in 58 patients starting September 1, 1994.

RESULTS

Before implantation, patients were critically ill with biventricular heart failure. Mortality in this group from the time of implantation until transplantation was 23%. Causes of death during device support included multi-organ failure (6), sepsis (3), and valve entrapment (2). Forty-eight patients underwent transplantation (77%). Forty-two survived to hospital discharge (68% of the total, 88% of those undergoing transplantation). Adverse events included bleeding (20%), device malfunction (5%), fit complications (3%), mediastinal infections (5%), visceral embolus (1.6%), and stroke during support (1.6%). The linearized stroke rate was 0.068 events per patient-year.

CONCLUSIONS

Sixty-eight percent of critically ill transplant candidates for whom medical therapy failed were bridged to transplantation with the CardioWest TAH and survived long-term. Most deaths that occurred during device support were related to pre-implant problems. Infection and stroke were rare events. Therefore, we recommend the CardioWest TAH as the biventricular bridge-to-transplant device of choice.

Biventricular mechanical replacement

The role of biventricular mechanical support (assist or replacement) is important for the management of severe biventricular cardiac failure. One only has to look at the role of cardiac transplantation to realize the benefit of a natural therapy to end-stage heart disease. Although the technology today is not that different from the technology that existed a decade ago (ie, BioMedicus, BVS 5000, Thoratec, CardioWest), the application of it and the experience gained by it have allowed surgeons to improve the chances of a positive outcome. In terms of new technologies for biventricular mechanical support, the totally implantable versions of a VAD (eg, Thoratec IVAD) or the totally implantable TAH (eg, AbioCor) are promising technologies that add to the spectrum of devices as destination therapy or alternatives to transplantation. And lastly, the role of the Berlin Heart as a tool for the management of biventricular failure in pediatric patients may be realized in the United States in the near future. In conclusion, the treatment of biventricular failure (acute or chronic) with assist or replacement technologies has gained widespread acceptance in the medical and surgical communities. It is now time to use these technologies wisely in an effort to treat the worldwide epidemic of congestive heart failure.

Improved Early Survival with the Total Artificial Heart

We report our experience with the total artificial heart (TAH) to determine if outcomes have improved. Thirty-one patients received the TAH as a bridge to transplant and were divided into the two groups A (eighteen implanted in the first eight years) and B (thirteen implanted in the last eight years). Changes in management included immediate sternal closure, early extubation, delayed transplant listing, early rehabilitation, and measurement of preformed antibodies. The infection rate in B was lower than in A, both during support (31% versus 39%) and following transplant (38% versus 72%), and rejection was lower in B than in A (0% versus 44%). There was no difference in neurological events between groups; however, reopening was more frequent in B (61% versus 28%). Hospital survival increased from 61% in A to 85% in B; however, this was not statistically significant. We hypothesize that this improvement was likely due to changes in patient management.

Ventricular Assist Devices as a Bridge to Cardiac Transplantation: The Ottawa Experience

This article reports our experience with ventricular assist devices (VADs) as a bridge to cardiac transplantation. From 1991 to 2003, a total of 42 patients received a Thoratec VAD (Thoratec Laboratories Corporation Inc., Pleasanton, CA, U.S.A.) (Group T) and 12 patients received a Novacor VAD (WorldHeart Corporation, Ottawa, Canada) (Group N). Thirty Thoratec patients were transplanted compared to six in the Novacor group. Four more Novacor patients are still supported. Of the transplanted patients, 87% survived to hospital discharge in Group T and 67% in Group N. Infections affected 29% and 50% of Group T patients during support and post-transplantation, respectively, compared to 25% and 0%, respectively, in Group N. Neurologic complications affected 33% of patients in each group during support. Reopening rates for bleeding during support were 45% and 42% in Groups T and N, respectively. There were no significant differences in outcomes between the two groups. Our study demonstrated the effectiveness of VADs in bridging mortally ill cardiac patients to successful heart transplantation.

Total artificial hearts: bridge to transplantation

The CardioWest TAH was created and initially tested at the same time as the Thoratec, Novacor, and HeartMate devices. It was designed as a permanent artificial heart and was the first-ever mechanical circulatory device to be used as destination therapy. Twenty years have passed since that early experience. Pneumatic technology is still current and being developed as in existing or new implantable Thoratec VADs the pneumatic HeartMate, and the Abiomed BVS 5000 pumps. Portable pneumatic drivers have been available since 1982, and in recent times have allowed discharge to home of substantial numbers of patients, thus reducing the length of hospital stays and making mechanical device support less expensive to society and more tolerable to patients. Within months, a portable driver for the CardioWest will be available. The documented benefits of the CardioWest TAH include rescue of: critically ill patients with advanced heart failure; patients with biventricular failure especially those with significant right heart failure, elevated pulmonary vascular resistance, or pulmonary edema; patients with renal or hepatic failure secondary to low cardiac output; patients with massive myocardial damage such as those with post-\infarction VSD or irreversible cardiac graft rejection; patients with mechanical valves or native valve disease; and patients with intractable arrhythmias and heart failure. High device outputs with restoration of normal filling pressures result in high perfusion pressures that have led to dramatic recoveries, convalescence, and return to levels of activity compatible with normal life. The average device output with the CardioWest TAH is higher than any other approved or investigational device. The reason for this resides in design simplicity this device has the shortest and largest inflow pathway. Stroke, in the authors' own series, is rare with a linearized rate of 0.068 events per patient year. If the experiences of La Pitie and the University of Arizona are combined, there has been one stroke in 25 patient years (0.04 events/patient year). Serious infections have been rare (12% of patients). No clinical mediastinitis has occurred. Drivelines have healed in tightly and never caused an "ascending" infection. There has not been a case of device endocarditis. Using a broad definition of bleeding, including takeback reoperation for bleeding, bleeding more than 8 units in the first postoperative 24 hours or 5 units over any other 48-hour period, a 25% to 36% incidence has been documented. No cases of fatal exsanguination have resulted, as there have been with the HeartMate. The incidence of bleeding as an adverse event is about 17% lower than the rate reported for the HeartMate VE LVAD, and it is about the same as that reported for Novacor and for Thoratec. Implantation of this device is relatively easy and often done (with attending help) by the authors' residents. If one follows the guidelines for fitting the device, and takes the recommended advice for implantation, hemostasis is excellent and restoration of immediate cardiac function with high flows is nearly automatic. Use of a neopericardium of 0.1 mm EPTFE at the time of implantation assures atraumatic and relatively quick re-entry for transplantation and prevents the normal inflammatory mediastinal reaction that might be desirable in a destination application. In selected patients the CardioWest TAH is the device of choice for bridge to transplantation. When a portable driver becomes available, out of hospital management of CardioWest TAH patients will be feasible and consideration of use of this device for longer term applications, (e.g., "destination therapy,") will be reasonable. A wearable driver, even smaller than a portable, will improve quality of life and expand the patient population that may be therapeutically served with this system. In short, the CardioWest TAH has come nearly full circle. It was first used as a destination device. It has since been used as a bridge to transplantation in nearly 200 patients as the Jarvik-7/Symbion TAH and, since 1993, in over 225 patients as CardioWest. The results have improved with time. Thromboembolism and infection rates have been competitive with currently available devices. Device reliability and durability have been excellent. Survival rates have been very high in a group of perhaps the sickest patients to be supported with any pulsatile device. Pneumatic technology has improved with portability and miniaturization, and there is reason to believe that it will become even better. Application of modern manufacturing techniques to this very simple device raises the possibility of significant manufacturing cost reduction, in an era of prohibitive cost for other devices. All of this establishes the CardioWest as a valuable device for any program that is seriously interested in end-stage heart disease and a likely device for permanent use in appropriately selected patients.

The left ventricular assist device

Of the 400,000 people in the United States who develop end-stage heart failure each year, 60,000 are unresponsive to medical therapy and 2,500 undergo heart transplantation. Surgically implanted pumps, called LVADs, are extending many lives.

Implantation of biventricular assist devices for chronic heart transplant rejection

Mechanical circulatory support has been used to treat graft failure caused by rejection after heart transplantation, but the prognosis remains bleak. Organ failure induced by the addition of or an increase in immunosuppressive medication is known to be a cause of the poor outcomes. Thus we tried a new therapeutic technique that allows complete withdrawal of immunosuppressive medication, as the donor heart is removed and circulatory support is maintained with a biventricular assist device.

Current options for mechanical heart technology

Heart transplantation remains the treatment of choice for end-stage heart failure despite limited donor availability and allograft durability. Artificial heart technology was initially developed as a replacement for transplantation but the initial experience with these technologies was disappointing. The quest for a total artificial heart has largely been abandoned in favor of ventricular assist devices (VADs). VADs have gained widespread acceptance as bridge to transplant and bridge to recovery therapy. After more than a decade of clinical use, several FDA approved device designs have proved effective in treating patients with various causes of heart failure. This review describes the current, clinically available ventricular replacement and assist devices and defines the adult patient populations in which they are useful. The next generation of these devices will soon become available and their clinical utility will likely shape the future direction of heart failure therapy. Ultimately the concept of a long-term total artificial heart may be revisited.