HeartMate left ventricular assist devices: a multigeneration of implanted blood pumps

The HeartMate family of implanted left ventricular assist devices (LVADs) developed by Thermo Cardiosystems, Inc. (TCI) span a time frame that goes back to the beginning of clinical use of mechanical circulatory support and will stretch well into the foreseeable future. Associated blood pump technology employed in the HeartMates range from an original pusher plate concept to the most advanced rotary pump devices. Starting initially with a pneumatic actuated pusher plate pump, clinical use of the HeartMate I began in 1986. In 1990, electric motor-actuated versions of the HeartMate I began to be used clinically. Presently, the HeartMate I has been implanted in some 2,300 patients worldwide, and this LVAD is a standard by which all others are currently measured. Following the HeartMate I is TCI's next-generation, the HeartMate II, a rotary-pump-based LVAD that uses an axial flow blood pump having blood immersed mechanical bearings. Clinical trials of the HeartMate II were initiated in 2000. The HeartMate III, representing TCI's next-generation LVAD, is structured around a centrifugal blood pump that uses a magnetically levitated rotating assembly. Compared to the HeartMate II, the HeartMate III has the potential for higher overall efficiency. The pump's operating life is not dependent on bearing wear. Given the significantly advanced LVAD technology represented by HeartMates II and III, coupled with the experience of HeartMate I, TCI is well-poised to keep its LVAD products as industry standards in the future.     

Use of Left Ventricular Assist Device (HeartMate II): A Singapore Experience

Recent advances in medical and device therapies in heart failure have improved the survival of patients with heart failure. However, due to the limited availability of suitable heart donors, left ventricular assist devices (LVADs) have become an important tool as a bridge‐to‐heart transplantation for patients with refractory heart failure in Singapore. We report our experience with the HeartMate II (HMII) LVAD (Thoratec Corporation, Pleasanton, CA, USA) as a bridge‐to‐heart transplant in our center from 2009 to 2012. This was a retrospective review of 23 consecutive patients who underwent HMII LVAD implantation in our center between May 2009 and December 2012. All patients were classified as Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) levels 1 to 3 and underwent LVAD implantation as a bridge‐to‐heart transplant. There were 17 male and 6 female patients. The mean age was 43.6 years old (range 14 to 64). The etiologies of heart failure included ischemic heart disease [8], idiopathic dilated cardiomyopathy [11], viral myocarditis [2], and chemotherapy‐induced cardiomyopathy [2]. Nine patients were INTERMACS level 1, 12 patients level 2, and two patients level 3. All patients successfully underwent HMII LVAD implantation. There was no mortality within the first 30 postoperative days. Postoperative complications included stroke with full neurological recovery (21.7%), mediastinal infection (21.7%), cardiac tamponade or mediastinal collection requiring reopening of the chest (39.1%), cardiac arrhythmia (13.0%), and pump thrombosis with pump replacement (4.3%). All patients were discharged from hospital after LVAD implantation. Three patients experienced driveline infections during outpatient follow‐up. There were 19 readmissions due to the following conditions: sub‐therapeutic anticoagulation (13.0%), gastrointestinal bleeding (13.0%), suspected pump thrombosis (13.0%), transient ischemic attack (8.7%), arrhythmia (8.7%), congestive cardiac failure due to severe aortic regurgitation (8.7%), right ventricular failure (4.3%), rhabdomyolysis (4.3%), and hematuria (4.3%). Post‐LVAD implantation, 20 patients were functionally New York Heart Association (NYHA) class I, while 3 reported NYHA III symptoms. Three patients were successfully bridged to heart transplantation. One patient was successfully explanted 11 months after LVAD implantation. There were two mortalities during the follow‐up period. The average duration of LVAD support was 522 days (range 47 to 1316 days). The HeartMate II LVAD has proven to be effective in our Asian population. Driveline infection rate remains low even in the tropical hot, humid climate in Singapore. With more patients ending up on extended periods of LVAD support, increased emphasis in the detection and management of long‐term complications of ventricular assist devices will be needed.     

Intraperitoneal pocket for left ventricular assist device placement.

BACKGROUND: Implantation of the HeartMate Implanted Pneumatic or Vented Electric Ventricular Assist Device requires that the pump be implanted either in the peritoneal cavity or in the abdominal wall. Both sites have been problematic. METHODS: We describe a new technique in which an intraperitoneal pocket is created, using Gore-Tex Dual Mesh Plus Biomaterial with Holes, to contain the ventricular assist device. This shields the ventricular assist device from the peritoneal contents and avoids abdominal wall dissection. Thirty consecutive patients who underwent implantation using this technique were compared with 16 patients who underwent implantation before this technique was in use. RESULTS: Thirty consecutive patients underwent implantation, and 2 of those patients underwent re-implantation because of device failure (16/30 HeartMate Implanted Pneumatic, 14/30 HeartMate Vented Electric, and 2/14 HeartMate Vented Electric replaced with the HeartMate Implanted Pneumatic). Twenty-five patients have undergone explantation. Pocket infections in patients who have had implanted devices for >1 month decreased from 4 of 13 before the pockets were used to 1 of 25 with the intraperitoneal pockets (Fisher's exact test p = 0.038). Two hernia repairs were required after explantation when the biomaterial pocket was used. A decrease in return to surgery for bleeding was noted after the pocket was used (7/16 without the pocket and 3/32 with the pocket; Fisher's exact test, p = 0.010). CONCLUSIONS: Bleeding complications and pocket infections decreased in this early experience. Further study is necessary to confirm the apparent decrease in complication rate by using this new technique in this small cohort of patients.     

Is it safe to irradiate the newest generation of ventricular assist devices? A case report and systematic literature review

An increasing number of mechanical assist devices, especially left ventricular assist devices (VADs), are being implanted for prolonged periods and as destination therapy. Some VAD patients require radiotherapy due to concomitant oncologic morbidities, including thoracic malignancies. This raises the potential of VAD malfunction via radiation-induced damage. So far, only case reports and small case series on radiotherapy have been published, most of them on HeartMate II (HMII, Abbott, North Chicago, IL, USA). Significantly, the effects of irradiation on the HeartMate 3 (HM3, Abbott) remain undefined, despite the presence of controller components engineered within the pump itself. We report the first case of a patient with a HM3 who successfully underwent stereotactic hypofractionated radiotherapy due to an early-stage non-small-cell lung cancer. The patient did not suffer from any complications, including toxicity or VAD malfunction. Based on this case report and on published literature, we think that performing radiotherapy after VAD implantation with the aid of a multidisciplinary team could be performed, but more in vitro studies and cases series are needed to reinforce this statement.     

HeartMate vented-electric left ventricular assist system: technique for intrathoracic or intraperitoneal implantation via a left thoracotomy.

The HeartMate vented-electric left ventricular assist system (Thoratec Corp., Woburn, MA) has become widely accepted as a temporary bridge to transplantation. We describe a left thoracotomy technique in 3 patients for implanting this pump intrathoracically or intraperitoneally. In all 3 cases, long-term pump function was satisfactory. For HeartMate implantation, the left thoracotomy approach may be particularly useful when previous median sternotomies, coupled with the severe debilitation posed by chronic heart failure and hepatic dysfunction with resultant coagulopathy, would greatly increase the mortality and morbidity of a redo median sternotomy.     

Optimal cannula positioning of HeartMate 3 left ventricular assist device

Cannula position in HeartMate II and HeartWare left ventricular assist devices (LVADs) is associated with clinical outcome. This study aimed to investigate the clinical implication of the device positioning in HeartMate 3 LVAD cohort. Consecutive patients who underwent HeartMate 3 LVAD implantation were followed for one year from index discharge. At index discharge, chest X-ray parameters were measured: (a) cannula coronal angle, (b) height of pump bottom, (c) cannula sagittal angle, and (d) cannula lumen area. The association of each measurement of cannula position with one-year clinical outcomes was investigated. Sixty-four HeartMate 3 LVAD patients (58 years old, 64% male) were enrolled. In the multivariable Cox regression model, the cannula coronal angle was a significant predictor of death or heart failure readmission (hazard ratio 1.27 [1.01-1.60], P = .045). Patients with a cannula coronal angle ≤28° had lower central venous pressure (P = .030), lower pulmonary capillary wedge pressure (P = .027), and smaller left ventricular size (P = .019) compared to those with the angle >28°. Right ventricular size and parameters of right ventricular function were also better in the narrow angle group, as was one-year cumulative incidence of death or heart failure readmission (10% vs. 50%, P = .008). Narrow cannula coronal angle in patients with HeartMate 3 LVADs was associated with improved cardiac unloading and lower incidence of death or heart failure readmission. Larger studies to confirm the implication of optimal device positioning are warranted.     

Over 870 days of successful antibiotic suppression therapy for VRE-infected left ventricular assist device

Left ventricular assist devices (LVADs) are used in patients with advanced heart failure. Infections are common complications following device placement; however, the efficacy of chronic antimicrobial suppression therapy for deep-seated infections is not well characterized. We report the case of a 49-year-old male with a HeartMate II LVAD who presented with a methicillin-sensitive Staphylococcus aureus pump pocket infection that was subsequently treated with antibiotics and HeartMate III pump exchange. A vancomycin-resistant Enterococcus faecium (VRE) pump pocket infection then developed and responded to surgical drainage followed by long-term suppression with daptomycin then linezolid for over 870 days. A second pump exchange was not required. To our knowledge, this represents the longest reported use of daptomycin (341 days) without symptomatic adverse events. Managing infections caused by multidrug-resistant pathogens presents a clinical challenge. This case demonstrates the potential for antimicrobial suppression therapy to allow for successful retention of a VRE-infected LVAD.     

Numerical and In Vitro Investigation of a Novel Mechanical Circulatory Support Device Installed in the Descending Aorta

Traditional implantation techniques of assist devices from the apex of left ventricle to the ascending or descending aorta are highly invasive and carry substantial complications for end‐stage heart failure patients. This study has shown that the descending aorta can be a promising location to install an implantable mechanical circulatory support with minimally invasive surgery. Herein, the hemodynamic effect of an in‐house prototyped pump implanted in the descending aorta was investigated numerically as well as experimentally. The objective of the experimental study is met by using the in‐house simulator of the cardiovascular loop replicating congestive heart failure conditions. The objective of the numerical study was met by using the modified version of the concentrated lumped parameter model developed by the same team. The results show that the pump placement in the descending aorta can lead to an improvement in pulsatility. The pressure drop, generated at the upstream of the pump, facilitates the cardiac output as a result of after‐load reduction, but at the same time, it induces a slight drop in the carotid as well as the coronary perfusion. The pressure rise, generated at the downstream of the pump, improves the blood perfusion in the renal circulation.     

Successful replacement of malfunctioning TCI HeartMate LVAD with DeBakey LVAD as a bridge to heart transplantation

Congestive heart failure is the leading cause of hospitalization and death in the developed world and affects about 0.4-2% of the adult population [Ann Thorac Surg 1999;68:637-40]. Heart transplantation remains the most effective therapy for end-stage heart disease, but the shortage of donors has led to increasing interest in other surgical options, especially ventricular assist devices (VAD). Several VADs are available to bridge patients to transplantation [N Engl J Med 2001;345:1435-43], including pulsatile devices like the HeartMate (HeartMate, Thoratec, Pleasanton, CA) and Novacor (World Heart, Netherlands), and the DeBakey VAD (MicroMed Technology, Inc., Houston, TX), which is an electromagnetically driven implantable titanium axial flow blood pump designed for left ventricular support. Despite technical improvements, VADs still are associated with serious complications. We reporte a successfull case where we replaced a TCI HeartMate with a DeBakey VAD because of a serious pocket infection, deterioration and failure of the inflow valve.     

Clinical experience with long-term use of implantable left ventricular assist devices: indications, implantation, and outcomes

We describe our clinical experience with 205 implantable left ventricular assist devices at the Cleveland Clinic between December 1991 and January 2000, along with manufacturers' data submitted to the Food and Drug Administration. In patients with end-stage cardiac failure who are suitable candidates for transplantation, these devices serve as excellent bridges to transplantation. Recent modifications have increased pump reliability and reduced thromboembolic rates. The vented electric HeartMate (Thermocardiosystems Inc, Woburn, MA) and the Novacor (Baxter-Novacor, Oakland, CA) left ventricular assist systems allow patients to be discharged from the hospital while awaiting a donor heart. Experience with long-term support is providing insights into permanent implantation of these devices as destination therapy. Although infection remains a major impediment to long-term support, patient-pump interactions leading to changes in the coagulation and immune systems are being recognized, and these interactions may have important implications with respect to thromboembolism, infection, and sensitization to human leukocyte antigens (HLAs). Better understanding of these factors may eventually lead to the development of permanently implantable pumps as an alternative to transplantation.     

Bridging to transplant with the HeartMate left ventricular assist device: The Columbia Presbyterian 12-year experience

OBJECTIVE: Implantation of a left ventricular assist device as a bridge to transplantation has become an acceptable approach for patients with end-stage heart failure. Our long-term results with 3 Thoratec HeartMate devices are presented to outline improvements in successful bridging to transplantation and post-transplant survival. METHODS: From August 1990 through January 2003, 243 patients underwent implantation of Thoratec HeartMate devices as a bridge to transplantation. This included 52 (21.4%) pneumatic devices, 17 (7.0%) dual-lead vented electric devices, and 174 (71.6%) single-lead vented electric devices. RESULTS: Mean age was 49.7 +/- 13.7 years. Mean support time was 78.1 +/- 82.9 days (0-541). Bridging success increased from 63.5% (n = 33) for pneumatic devices to 64.7% (n = 11) for dual-lead vented electric devices and 72.4% (n = 126) for single-lead vented electric devices (P =.005). Posttransplant 1-, 3-, and 5-year actuarial survival increased from 87.5%, 78.1%, and 71.9% in patients with pneumatic devices to 91.5%, 86.9%, and 81.3%, respectively, for patients with single-lead vented electric devices. Device infection and malfunction occurred in 17.7% (n = 43) and 12.8% (n = 31) of patients, respectively. CONCLUSIONS: Successful bridging to transplantation and posttransplant survival has improved over time. Left ventricular assist devices have become increasingly more effective in bridging patients with end-stage heart failure to transplantation. This is likely due to a combination of better patient selection, improvements in clinical practice, and evolution in device design.     

HeartMate 3 pump exchange via sternal-sparing bilateral minithoracotomies

As median survival for left ventricular assist device (LVAD) patients increases, the incidence of adverse events requiring device exchange is likely to increase as well. Less invasive surgical approaches for device exchange of older generation pumps have demonstrated multiple potential benefits compared with median sternotomy. However, there remains a paucity of data in regard to less invasive surgical techniques for the exchange of the newest generation intrapericardial devices. In this report we describe a complete sternal-sparing technique for the LVAD exchange of a HeartMate 3 via bilateral minithoracotomies.     

Control of perigraft bleeding during ventricular assist device implantation

This report describes a surgical technique devised to reduce perigraft bleeding in left ventricular assist devices, which has yielded excellent results in our institution. The technique may be applied during implantation of the Novacor N100, HeartMate 1000 VE, and Thoratec systems.     

Incidence and clinical management of life-threatening left ventricular assist device failure.

BACKGROUND: Mechanical device failure can be life-threatening and is becoming increasingly important as left ventricular assist devices (LVADs) are being used for longer periods as a bridge to transplantation (period lengthening due to donor shortage) or recovery, or as destination therapy. However, its incidence and clinical management have not been widely studied. METHODS: We investigated the incidence and management of major device failure for a total of 102 Thoratec/TCI HeartMate and Thoratec PVAD devices implanted at our institution since 1995. RESULTS: The cumulative probability of device failure was 6%, 12%, 27% and 64% at 6 months, 1 year, 18 months and 2 years, respectively. Major failure occurred in 8 (7.8%) patients. Four patients presented as emergency cases with vented electric (VE) failure, and 3, with failure due to a seized motor, were supported on the pneumatic driver to explantation, transplantation or device change. Another patient had a ruptured pump diaphragm and was maintained for 12 hours, but died of a Type B aortic dissection. Four patients underwent elective device change, including 2 of a VE pump, 1 with inlet valve regurgitation and fractured power cable at 414 days, and 1 with inlet valve regurgitation at 656 days, all of whom underwent transplantation or explantation. One patient with VE failure was maintained on the pneumatic driver, then underwent Thoratec paracorporeal ventricular assist device (PVAD) implantation and was transplanted. One Thoratec PVAD patient developed LVAD thrombus, underwent pump replacement, and was transplanted. A further patient on the implantable pneumatic (IP) HeartMate developed a pneumoperitoneum due to a leak at the junction of the pneumatic driveline, which was repaired by inserting a new driveline, and underwent heart/kidney transplantation. CONCLUSIONS: Life-threatening mechanical device failure is not uncommon and increases with time, but can be managed successfully in most patients. Improvements in design and manufacture should further enhance outcome with LVADs.     

Treatment of end-stage heart disease with outpatient ventricular assist devices

BACKGROUND: Initiating outpatient therapy with ventricular assist devices (VAD) was important in the progress of mechanical circulatory support. This article reviews our experience with VAD therapy from the start of our outpatient program until the present. METHODS: Medical records of patients who received a Thoratec para-corporeal VAD, HeartMate vented electrical VAD, or HeartMate pneumatic VAD between 12/1/97 and 9/1/01 were reviewed. Variables included age, type of devices, total duration of VAD support, discharge status, duration of outpatient support, outcome (transplanted, died on support, ongoing), in-hospital length of stay after transplantation, and complications during VAD support. RESULTS: There were 53 device implants in 46 patients. The cumulative patient-days of VAD support was 7,468 (mean duration of support, 138 +/- 195 days; median, 95 days; range, 2 to 948 days). Twenty of the 46 patients were discharged with a VAD. The cumulative outpatient days was 3,600 (mean outpatient duration, 157 +/- 164 days; median, 83 days; maximum, 560 days). Of the 20 outpatients, 11 received cardiac transplantation, 5 died, and 4 are ongoing as of 9/1/01. Major complications that occurred in the outpatient setting included 5 deaths after hospital readmission (1 sepsis, 1 conduit tear, 3 neurologic events); 4 device infections (3 sepsis, 1 pouch infection); and 3 device malfunctions that required reoperation for pump replacement (1 HeartMate pneumatic and 2 HeartMate vented electrical). No deaths occurred in an outpatient setting. CONCLUSIONS: Ventricular assist devices effectively support outpatients for months to years. The anticipated time for postoperative recovery and VAD training before discharge is approximately 14 to 21 days, although shorter times may be possible in the future. Establishing a successful outpatient VAD program is a crucial step toward VAD as definitive therapy for end-stage heart disease.     

Fluid Dynamics in the HeartMate 3: Influence of the Artificial Pulse Feature and Residual Cardiac Pulsation

Ventricular assist devices (VADs), among which the HeartMate 3 (HM3) is the latest clinically approved representative, are often the therapy of choice for patients with end‐stage heart failure. Despite advances in the prevention of pump thrombosis, rates of stroke and bleeding remain high. These complications are attributed to the flow field within the VAD, among other factors. One of the HM3’s characteristic features is an artificial pulse that changes the rotor speed periodically by 4000 rpm, which is meant to reduce zones of recirculation and stasis. In this study, we investigated the effect of this speed modulation on the flow fields and stresses using high‐resolution computational fluid dynamics. To this end, we compared Eulerian and Lagrangian features of the flow fields during constant pump operation, during operation with the artificial pulse feature, and with the effect of the residual native cardiac cycle. We observed good washout in all investigated situations, which may explain the low incidence rates of pump thrombosis. The artificial pulse had no additional benefit on scalar washout performance, but it induced rapid variations in the flow velocity and its gradients. This may be relevant for the removal of deposits in the pump. Overall, we found that viscous stresses in the HM3 were lower than in other current VADs. However, the artificial pulse substantially increased turbulence, and thereby also total stresses, which may contribute to clinically observed issues related to hemocompatibility.     

Do left ventricular assist device (LVAD) bridge-to-transplantation outcomes predict the results of permanent LVAD implantation?

BACKGROUND: Implantable left ventricular assist devices (LVADs) were designed for permanent implant, but we began their use for bridge-to-transplant (BTTx) to study their safety and effectiveness. We review our experience in order to compare the BTTx lessons learned with the outcomes and goals of permanent implants. METHODS: From December 1991 until January 2002, 264 patients received 277 LVADs for BTTx. We analyzed temporal trends in pre-LVAD patient factors and device-specific time-related complications. RESULTS: Survival to transplant was 69%. Adverse event analysis demonstrated a high risk of infections (0.56, 1.28, and 1.88 per patient at 30 days and 3 and 6 months). HeartMate devices were more prone to infection than Novacor devices (p < 0.0001). Cerebral infarctions occurred less commonly than infections (0.15, 0.25, 0.30 at 30 days and 3 and 6 months), were more common in Novacor than HeartMate (p = 0.0001), and were decreased by the new Novacor Vascutek conduit (p = 0.07), but these were still slightly higher than the HeartMate (p = 0.04). Device failures occurred in 21 instances (all but one were in HeartMate devices [p = 0.04 vs Novacor]), but have significantly decreased (p < 0.0001) in HeartMate since 1998. CONCLUSIONS: Infections and device durability limit the chronic use of the HeartMate device, but device failures are decreasing. Novacor has fewer problems with infection and durability, and the new Vascutek conduit will reduce, but not eliminate, strokes.     

Computational fluid dynamics analysis of a maglev centrifugal left ventricular assist device

The fluid dynamics of the Thoratec HeartMate III (Thoratec Corp., Pleasanton, CA, U.S.A.) left ventricular assist device are analyzed over a range of physiological operating conditions. The HeartMate III is a centrifugal flow pump with a magnetically suspended rotor. The complete pump was analyzed using computational fluid dynamics (CFD) analysis and experimental particle imaging flow visualization (PIFV). A comparison of CFD predictions to experimental imaging shows good agreement. Both CFD and experimental PIFV confirmed well-behaved flow fields in the main components of the HeartMate III pump: inlet, volute, and outlet. The HeartMate III is shown to exhibit clean flow features and good surface washing across its entire operating range.     

Minimally Invasive Ventricular Assist Device Surgery

The use of mechanical circulatory support to treat patients with congestive heart failure has grown enormously, recently surpassing the number of annual heart transplants worldwide. The current generation of left ventricular assist devices (LVADs), as compared with older devices, is characterized by improved technologies and reduced size. The result is that minimally invasive surgery is now possible for the implantation, explantation, and exchange of LVADs. Minimally invasive procedures improve surgical outcome; for example, they lower the rates of operative complications (such as bleeding or wound infection). The miniaturization of LVADs will continue, so that minimally invasive techniques will be used for most implantations in the future. In this article, we summarize and describe minimally invasive state‐of‐the‐art implantation techniques, with a focus on the most common LVAD systems in adults.