Implantable electrical left ventricular assist system: bridge to transplantation and the future

Mechanical circulatory support: 60 years of evolving knowledge

Since the 1950s when the first devices for mechanical circulatory support were developed, there has been an impressive evolution of their technology. The first pioneering pumps were used to rescue acute complications after cardiac surgery. Advances in technology, increased knowledge of flow dynamics, and a more appropriate selection of the patients who actually need this support have contributed to significantly improve the benefits of this therapy. Today, mechanical circulatory support is an essential tool for the treatment of advanced heart failure. This strategy is used either as a bridge to heart transplantation or as a destination therapy for patients who do not meet the transplant criteria. A third indication is the bridge to recovery option for those patients in whom the improvement in cardiac function may be so important that the pump can be removed and the transplantation circumvented. In addition, mechanical circulatory support has fostered marked improvements in several clinical aspects affecting both patient health and quality of life. Despite the improvements in the technology of the devices of the last generation, severe adverse effects are still the Achilles heel of mechanical circulatory support therapy. This review summarizes the history, the technology, the clinical outcomes, and the possible future directions of this therapy.

Management of advanced heart failure: a review

INTRODUCTION

Heart failure (HF) has become a global pandemic. Despite recent developments in both medical and device treatments, HF incidences continues to increase. The current definition of HF restricts itself to stages at which clinical symptoms are apparent. In advanced heart failure (AdHF), it is universally accepted that all patients are refractory to traditional therapies. As the number of HF patients increase, so does the need for additional treatments, with an increased proportion of patients requiring advanced therapies. Areas covered: This review discusses extensive evidence for the effect of medical treatment on HF, although the data on the effect on AdHF is scare. Authors review the relevant literature for treating AdHF patients. Furthermore, mechanical circulatory devices (MCD) have emerged as an alternative to heart transplantation and have been shown to enhance quality of life and reduce mortality therefore authors also review the current literature on the different MCD and technologies. Expert commentary: More patients will need advanced therapies, as the access to heart transplantation is limited by the number of available donors. AdHF patients should be identified timely since the window of opportunities for advanced therapy is narrow as their morbidity is progressive and survival is often short.

The Evolution of Mechanical Circulatory Support

The field of mechanical circulatory support (MCS) has evolved from earlier-generation pulsatile-flow devices that were primarily used to support critically ill patients in the hospital to newer-generation continuous-flow devices that permit hospital discharge and resumption of normal life activities. The technology is used to bridge transplant-eligible patients and can be used for long-term support of patients who are transplant ineligible. Left ventricular assist devices are proved to improve long-term survival and quality of life for patients with advanced heart failure. Adverse events associated with MCS therapy remain the Achilles heel of the field and strategies to improve biocompatibility are ongoing.

Improvement of Survival Rate in Patients with Cardiogenic Shock by Using Nonpulsatile and Pulsatile Ventricular Assist Device

Between January 1988 and January 1992, 65 patients (pts) had a ventricle assist device (VAD) inserted in our clinic. In 24 pts a VAD was applied because of primarily unsuccessful weaning from cardiopulmonary bypass (Group A). In a further 24 pts (Group B) a VAD was installed for the therapy of refractive cardiogenic shock (CS) after initially successful cardiac surgery (n=21) and after acute myocardial infarction (n=3). Twelve pts were bridged to heart transplantation (Group C) and five had a VAD inserted for various other reasons (Group D). In 36 (55.4%) of the total 65 pts a nonpulsatile VAD (Biomedicus® 540) was used: 10 in Group A; 20 in B, 3 in C and 3 in D. In 29 pts (44.6%) a pulsatile VAD (Abiomed® BVS 5000) was used: 14 in Group A, 4 in B, 9 in C and 2 in D. Weaning rate and long-term survival rates were 50% and 46% respectively in Group A and 38% and 42% in Group B. Seven pts from Group C were transplanted and six are long-term survivors. Two pts (40%) in Group D were discharged from hospital. Major postoperative complications were bleeding (46%), thromboembolism (14%), multiple organ failure (11%), renal failure (11%), arterial embolism (4.6%), sepsis (3%). The results indicate that application of a VAD can be recommended in pts with postcardiotomy CS to allow recovery of cardiac function and in pts with irreversible ventricular damage as bridging to HTX.

Acquired coagulopathy in patients with left ventricular assist devices

Chronic heart failure (HF) is a major emerging healthcare problem, associated with a high morbidity and mortality. Left ventricular assist devices (LVADs) have emerged as a successful treatment option for patients with end-stage HF. Despite its great benefit, the use of LVAD is associated with a high risk of complications. Bleeding, pump thrombosis and thromboembolic events are frequently observed complications, with bleeding complications occurring in over a third of the patients. Although the design of the third-generation LVAD has improved greatly, these hemostatic complications still occur. The introduction of an LVAD into the circulatory system results in an altered hematological balance as a consequence of blood-pump interactions, changes in hemodynamics, the rheology, and the concomitant need for anticoagulation while implanted with an LVAD. The majority, if not all, LVAD patients experience a form of platelet dysfunction and impaired von Willebrand factor activity, leading to acquired coagulopathy disorders. Different diagnostic tools and treatment strategies have been reported; however, they require validation in LVAD patients. The present review focuses on acquired coagulopathies, describing the incidence, impact and underlying mechanism of acquired coagulopathy disorders in patients supported by LVADs. In addition, we will discuss diagnostic and management strategies for these acquired coagulopathies.

Right Heart Function during Left Ventricular Assistance in an Open-Chest Porcine Model of Acute Right Heart Failure

Changes in the right ventricular function measured with a thermodilution ejection fraction catheter have been recorded in open-chest normal pigs and pigs with acute right heart failure (RVF) undergoing left ventricular assistance with a pneumatic-sactype device (LVAD). To produce acute right heart failure, 5 pigs underwent ligation of the right ventricular free wall coronary arteries. Compared with normal pigs, cardiac output in ligated pigs fell by 21% (7.5 ± 0.5 vs 9.5 ± 1.2 L/min; p < 0.05) and the right ventricular end diastolic pressure rose (11.4 ± 2.6 vs 5.7 ± 3.6 vs mmHg: p <0.05). With the left ventricular assist device connected, the right atrial pressure was increased to 3, 5, 7, 10 and 12 mmHg by volume loading while maintaining the haematocrit at 35 ± 6%. The right ventricular stroke work index (RVSWI) increased with volume loading in normal pigs. In RVF pigs, RVSWI increased significantly with the LVAD (59.2 ± 5.8 vs 23.5 ± 7.8 mmHg ml/min/kg, p<0.01), approaching that of normal pigs (62.3 ± 4.8 mmHg ml/min/kg). Similar changes were observed in the cardiac output and right ventricular stroke volume. These results show that, in this model of open-chest, mild, acute right heart failure, left ventricular assistance allows right ventricular function to return to normal, despite volume overloading, by decreasing right ventricular after load and increasing right ventricular compliance

Mechanical ventricular support using pulsatile Abiomed BVS 5000 and centrifugal Biomedicus-pump in postcardiotomy shock

Since we started using ventricular assist devices (VAD) in July 1987 up to August 1993, 63 of 15,650 (0.4%) patients (pts) who underwent open heart sugery were supported postoperatively by VAD at out institution. Forty-three were male and 20 female, mean age 55.5 years. In 49 pts coronary artery bypass grafting (CABG), in 8 pts valve surgery, in 3 pts combined CABG and valve surgery and in 3 pts corrective procedures for congenital heart disease were performed. Perioperative myocardial infarction was the most frequent indication (73%). In 37 of the 63 pts (58.7%) a centrifugal (Biomedicus pump (group A) was used and in 26 pts (41.3%) a pulsatile Abiomed BVS 5000 (group B). Fourteen of 37 pts (38%) in group A were weaned from the VAD and all of them were discharged. Twenty-three pts were unable to be weaned and 19 of these pts died. The remaining 4 pts were transplanted successfully and subsequently 3 died and 1 was discharged. In all, 15 pts (39%) were long-term survivors. Sixteen of 26 pts (62%) in group B were weaned from VAD and 13 (50%) of them were discharged of whom 3 died. Ten patients were unable to be weaned and 7 of these died. The remaining 3 pts were transplanted successfully. In all, 16 pts (61.5%) were long-term survivors. The shorter the interval between beginning resuscitation and application of VAD the better the outcome. Younger age, VAD installation in OR, support time between 2 and 7 days and Abiomed pump, influence the survival rate positively. Because of higher recovery and survival rates in patients assisted by Abiomed compared to the Biomedicus pump, we recommend the Abiomed pump in postcardiotomy cardiac failure.

DURABLE MECHANICAL CIRCULATION SUPPORT AS AN ALTERNATIVE TO HEART TRANSPLANTATION

In the review a comparative analysis of the treatment of end-stage chronic heart failure using heart transplantation and durable mechanical circulatory is conducted. It shows the main advantages and limitations of heart transplantation and the prospects of application of durable mechanical circulatory support technology. The main directions of this technology, including two-stage heart transplant (bridge to transplant – BTT), assisted circulation for myocardial recovery (bridge to recovery – BTR) and implantation of an auxiliary pump on a regular basis (destination therapy, DT). 

Left ventricular assist devices: current controversies and future directions

Advanced heart failure is a growing epidemic that leads to significant suffering and economic losses. The development of left ventricular assist devices (LVADs) has led to improved quality of life and long-term survival for patients diagnosed with this devastating condition. This review briefly summarizes the short history and clinical outcomes of LVADs and focuses on the current controversies and issues facing LVAD therapy. Finally, the future directions for the role of LVADs in the treatment of end-stage heart failure are discussed.

Biocompatibility of Ricinus communis polymer with addition of calcium carbonate compared to titanium. Experimental study in guinea pigs

OBJECTIVE

The aim of the present investigation was to determine whether the difference in inflammatory tissue reaction between the Riccinus communis (castor) polymer with calcium carbonate and the titanium implant is statistically significant.

METHODS

Thirty-two Cavia porcellus were allocated into four groups of eight animals each. We implanted the two types of materials in the retroperitoneal space of all the animals. They were euthanized at 7, 20, 30 and 40 days after surgery, and an histological study of the samples was conducted.

RESULTS

All implants showed characteristics of chronic inflammation regardless of the material and timepoint of evaluation. There was no statistically significant difference between Pm+CaCO3 and Ti with regard to the presence of granulation tissue, tissue congestion, histiocytes, lymphocytes, neutrophils, giant cells, and fibrosis (P> 0.05).

CONCLUSION

The castor oil polymer plus calcium carbonate implant was not statistically different from the titanium implant regarding inflammatory tissue reaction.

A history of devices as an alternative to heart transplantation

The rapid evolution of mechanical circulatory support (MCS) has extended survival and improved quality of life for patients suffering from the most advanced heart failure (HF). Survival at one year after placement of a left ventricular assist device exceeds 80%. MCS and transplant have developed in counterpoint to each other. Patients with HF now have a meaningful option for lifelong support even if they are not candidates for heart transplant. As the profiles of MCS recipients change and the next generation of devices emerges, new challenges and opportunities await physicians caring for patients with cardiac failure.

Left ventricular assist devices: from the bench to the clinic

The development of ventricular assist devices (VADs) over the past 5 decades as therapy for advanced heart failure (HF) has been extraordinary. Since the original VAD design by Michael DeBakey in the early 1960s, numerous devices for mechanical circulatory support have been engineered, assessed in preclinical studies, applied to human patients in large multicenter clinical trials, and now, select devices are Food and Drug Administration-approved therapy for advanced HF patients. This review highlights select examples of durable VADs from the engineering aspect of design and conception to experimental studies and clinical application underscoring the remarkable progression of such technology to now becoming the standard of care for many advanced HF patients.

Devices in the management of advanced, chronic heart failure

Heart failure (HF) is a global phenomenon, and the overall incidence and prevalence of the condition are steadily increasing. Medical therapies have proven efficacious, but only a small number of pharmacological options are in development. When patients cease to respond adequately to optimal medical therapy, cardiac resynchronization therapy has been shown to improve symptoms, reduce hospitalizations, promote reverse remodelling, and decrease mortality. However, challenges remain in identifying the ideal recipients for this therapy. The field of mechanical circulatory support has seen immense growth since the early 2000s, and left ventricular assist devices (LVADs) have transitioned over the past decade from large, pulsatile devices to smaller, more-compact, continuous-flow devices. Infections and haematological issues are still important areas that need to be addressed. Whereas LVADs were once approved only for 'bridge to transplantation', these devices are now used as destination therapy for critically ill patients with HF, allowing these individuals to return to the community. A host of novel strategies, including cardiac contractility modulation, implantable haemodynamic-monitoring devices, and phrenic and vagus nerve stimulation, are under investigation and might have an impact on the future care of patients with chronic HF.

[Left ventricular assist devices in the catheterisation laboratory]

Mechanical cardiac support represents a large spectrum of devices. The duration of assistance may vary from a few hours in the cath lab to several weeks. The goals for a temporary support by percutaneus assistance are: improve end-organ perfusion; decrease pulmonary capillary wedge pressure; decrease myocardial oxygen consumption. The potential indications are: acute left ventricular dysfunction; "bridge to recovery": acute myocarditis, acute myocardial infarction, valve disease bridge to surgery; "bridge to implantable LVAD"; "bridge to transplant"; high risk PCI and surgery.

Omental Transposition Flap for Salvage of Ventricular Assist Devices

BACKGROUND

The use of ventricular assist devices for patients with end-stage cardiac failure awaiting heart transplantation has become increasingly common. Ventricular assist devices improve the longevity and the quality of life for these patients. In addition, they serve as a bridge to cardiac allograft transplantation until a donor heart is found. However, ventricular assist device-related infections remain a major problem complicating their long-term use. Clinical infection and sepsis can critically threaten these patients with ventricular assist devices. Infection can delay immediate transplantation and potentially require the removal of the device for definitive treatment of the problem.

METHODS

Patients who underwent insertion of a ventricular assist device at the University of Pittsburgh Medical Center were identified through accessing the medical records archives of the hospital. Review of patients' medical records was conducted to obtain patient demographics, preoperative diagnosis and disease state, type of ventricular assist device inserted, postoperative day of ventricular assist device infection onset, infectious organism identified, timing of omental flap procedure after the initial insertion, duration of ventricular assist device support before cardiac transplantation, and patient follow-up.

RESULTS

There were 76 patients who underwent a ventricular assist device insertion procedure during the 4-year period between January of 2000 and January of 2004. Of the 76 patients who received a device, 11 (14 percent) had evidence of clinical infection secondary to insertion. Two of these 11 patients died before surgical intervention, four had their devices explanted, and the remaining five underwent omental flap transposition with bilateral pectoralis major advancement flaps in surgically addressing their infections. Of the five patients with infections who received omental transposition flaps, two went on to undergo successful transplantation, two continue to await cardiac allograft transplantation, and one died as a result of an unknown cause.

CONCLUSIONS

The authors present their experience with five patients who received omental transposition flaps to cover infected ventricular assist device pumps and the associated tubing in large, open sternoabdominal wounds. Treatment included the direct application of an omental transposition flap over the infected device with use of a bilateral pectoralis advancement flap to aid in complete sternal and skin closure of the sternal wound defect. In each of these cases, the use of the omental flap was followed by resolution of the mediastinal infection. In addition, the treatment with an omental flap prevented the removal of infected devices in patients who were otherwise pump dependent during their waiting periods for transplantation. The use of omental transposition flaps can be an effective technique in salvaging infected ventricular assist devices and preserving this valuable device for patients awaiting a cardiac transplant.

Development of mechanical heart devices

BACKGROUND

A succinct, historical review of developments in mechanical devices to assist the failing heart is provided.

METHODS

A number of methods of mechanical devices to assist the failing heart are briefly assessed. Personal experimental and clinical studies of devices developed over several decades are presented.

RESULTS

Findings and data of devices used in assisting the failing heart, including those developed by the author, are analyzed.

CONCLUSIONS

On the basis of this review, the left ventricular assist device is believed to be the most effective. There is also reason to believe that the axial flow system has considerable advantages. This form of therapy has potentially great value for permanent use in some patients with intractable heart failure.

Heart transplant and left ventricular assist device costs

BACKGROUND

With the increasing clinical success of left ventricular assist devices (LVADs), physicians need to measure device cost efficacy to determine the societal value of this technology. Today's large clinical volume allows comparison of the costs of this innovation as compared with orthotopic heart transplant (OHT).

METHODS

We evaluated hospital cost and reimbursement for patients who were discharged after LVAD implantation and returned to the hospital for OHT. To control for patient-specific variables, LVAD therapy and OHT therapy were compared in the same patient; that is, only those patients who received an LVAD were discharged, and returned for OHT were studied. Length of stay (LOS), re-admissions and outpatient services were analyzed, including their respective total actual hospital cost (TAHC) and net revenue (NR). Time periods analyzed were the same for LVAD and OHT.

RESULTS

From the LVAD population at Columbia-Presbyterian Medical Center, 36 patients were discharged following HeartMate vented electric (VE) implantation and re-admitted for OHT between December 1996 and June 2000. Mean pre-LVAD implantation LOS was 21.3 +/- 24.1 days. Post-LVAD LOS was 36.8 +/- 22.2 days vs 18.2 +/- 12.2 days post-OHT (p < 0.001). Mean length of LVAD support was 123.4 +/- 77.7 days. Overall total costs for LVADs exceeded that of OHT, whereas revenue was relatively lower. TAHC post-LVAD averaged $197,957 +/- 77,291, whereas TAHC post-OHT averaged $151,646 +/-53,909 (p = 0.005). NR averaged $144,756 +/- 96,656 post-LVAD vs $178,562 +/- 68,571 post-OHT (p = 0.09). LVAD patients had more re-admissions compared with OHT: 1.2/123 days (+/- 1.7) vs 0.3/123 days (+/- 0.6), respectively (p = 0.005). The average LOS during a re-admission was similar between the 2 groups (LVAD 5.6 days [+/- 10.6] vs OHT 9.6 days [+/- 8.2]; p = 0.18). OHT was associated with a significantly greater number of outpatient services compared with LVAD (9.7 [+/- 6.1] vs 3.0 [+/- 4.7]; p < 0.001). In contrast to OHT, revenues did not match the costs of LVAD therapy.

CONCLUSIONS

LVAD implantation is associated with longer LOS and higher cost for initial hospitalization compared with OHT. LVAD patients have higher re-admission rates compared with OHT but similar costs and LOS. OHT is associated with a greater number of outpatient services. Reimbursements for LVAD therapy are relatively low, resulting in significant lost revenue. If LVAD therapy is to become a viable alternative, improvements in both cost-effectiveness and reimbursement will be necessary.

Cost-effectiveness of Pediatric Heart Transplantation

BACKGROUND

Survival after pediatric heart transplantation has continued to improve. Nonetheless, graft survival is generally <15 years and the costs of transplantation and subsequent immunosuppression are substantial. In the present study, we sought to examine the cost-effectiveness of pediatric heart transplantation.

METHODS

Data from 95 pediatric subjects undergoing transplantation at our institution from 1997 through 2004 were reviewed to determine the costs of pediatric heart transplantation. Costs included pre-transplant care, organ procurement, initial hospitalization and follow-up care. Life expectancy was derived from the United Network of Organ Sharing data set. Data were reported as cost per quality-adjusted life-years (QALYs) gained, which were discounted at 3%. Cost-effectiveness was stratified by primary transplantation vs re-transplantation.

RESULTS

The mean cost of initial hospitalization and organ procurement was $221,897 per patient for primary transplant and $285,296 per patient for re-transplant. Annual follow-up costs were estimated to be $18,141 in the first year (excluding the first 90 days post-transplant) and $18,480 per year thereafter. Under base-case assumptions, costs per QALY gained were $49,679 for primary transplantation and $87,883 for re-transplantation. Sensitivity analysis yielded a cost-utility range of $44,943 to $57,628 per QALY gained for primary transplantation and $70,834 to $103,661 per QALY gained for re-transplantation.

CONCLUSIONS

Costs of primary pediatric heart transplantation are within the accepted range of cost effectiveness. Pediatric heart re-transplantation has higher costs relative to benefits gained owing to shorter graft survival.

Different clinical scenarios for circulatory mechanical support in acute and chronic heart failure

Chronic heart failure (HF) is a leading cause of death in developed countries. Over the last 2 decades, mechanical circulatory support (MCS) devices have steadily evolved in the clinical management of end-stage HF and have emerged as a standard of care for the treatment of acute and chronic HF refractory to conventional medical therapy. Possible indications for using MCS are acute cardiogenic shock, as a bridge to transplantation, as a bridge to recovery, and more recently, as destination therapy in dilated cardiomyopathy, of either ischemic or idiopathic etiology. We reviewed the different clinical scenarios in which we think there are currently indications to implant different kinds of MCS systems.

Japanese multicenter clinical evaluation of the HeartMate vented electric left ventricular assist system

Implantable left ventricular assist device systems (LVAS) are increasingly being used to bridge patients to heart transplantation because of the limited number of available donor hearts. This prospective, multicenter trial was designed to evaluate the usefulness of the HeartMate vented electric (VE) LVAS as a bridge to transplantation in Japan. Between November 2001 and June 2003, six patients with end-stage heart failure [New York Heart Association (NYHA) class IV] were supported with the LVAS and five of the six were able to implement the evaluation (one dropped out). The five were men with an average age of 38.6 years and were supported for 2390 cumulative days (6.6 years). Average preimplant cardiac index improved from 1.93 l/min/m(2) to a 3.79 l/min/m(2) VAD flow index at the end of the clinical trial. All five patients improved to NYHA class I or II, survived more than 1 year, and one patient was discharged from the hospital. Mean LVAS support duration was 478 days (range 390-575 days) and four patients remain supported. One patient died from cardiac failure and sepsis. Device-related complications included: infections (four patients), thromboembolism (one patient), hemolysis (two patients), and repeat operation for bleeding (two patients). There was one case of inflow valve incompetence and two pump motor malfunctions. We conclude that the LVAS can effectively support patients as they await cardiac transplantation and offers improvement to the patient's quality of life.

Left ventricular assist devices as destination therapy: A new look at survival

OBJECTIVE

The REMATCH trial compared the use of left ventricular assist devices with optimal medical management for patients with end-stage heart failure. When the trial met its primary end point criteria in July 2001, left ventricular assist device therapy was shown to significantly improve survival and quality of life. With extended follow-up, 2 critical questions emerge: (1) Did these benefits persist, and (2) did outcomes improve over the course of the trial, given the evolving nature of the technology?

METHODS

We analyzed survival in this randomized trial by using the product-limit method of Kaplan and Meier. Changes in the benefits of therapy were analyzed by examining the effect of the enrollment period.

RESULTS

The survival rates for patients receiving left ventricular assist devices (n = 68) versus patients receiving optimal medical management (n = 61) were 52% versus 28% at 1 year and 29% versus 13% at 2 years ( P = .008, log-rank test). As of July 2003, 11 patients were alive on left ventricular assist device support out of a total 16 survivors (including 3 patients receiving optimal medical management who crossed over to left ventricular assist device therapy). There was a significant improvement in survival for left ventricular assist device-supported patients who enrolled during the second half of the trial compared with the first half ( P = .03). The Minnesota Living with Heart Failure scores improved significantly over the course of the trial.

CONCLUSION

The extended follow-up confirms the initial observation that left ventricular assist device therapy renders significant survival and quality-of-life benefits compared with optimal medical management for patients with end-stage heart failure. Furthermore, we observed an improvement in the survival of patients receiving left ventricular assist devices over the course of the trial, suggesting the effect of greater clinical experience.

Doppler microembolic load predicts risk of thromboembolic complications in Novacor patients

OBJECTIVE

Left ventricular assist devices have become an established method to bridge patients with end-stage cardiac failure to heart transplantation. Besides infection and bleeding, thromboembolism represents one of the most serious complications. We evaluated the value of microembolic signals in predicting thromboembolic events for individual patients and distinctive left ventricular assist device periods.

METHODS

Twenty patients (14 male) aged 23-57 years supported with the Novacor N100 left ventricular assist device were enrolled in this study. All patients were on effective anticoagulation, 12 patients additionally received antiplatelet therapy. Unilateral detection of microembolic signals was performed once weekly by insonation of the middle cerebral artery using transcranial Doppler sonography for 30 minutes duration. Evidence of clinically manifest thromboembolic events was based on regular questionnaires, clinical examinations, and results of diagnostic procedures.

RESULTS

During a cumulative follow-up of 3876 left ventricular assist device days, 44 thromboembolic complications occurred (incidence, 1.1%) in 15 out of 20 patients. A total of 360 transcranial Doppler sonography monitorings (range, 5-34 per patient) were performed with an overall microembolic signals prevalence of 35.3% and a microembolic signal mean of 2.3 +/- 9.2 per examination. There was a highly significant correlation between the individual microembolic signal activity and the respective incidence of clinical thromboembolism (r = 0.61-0.9; P <.01). Patients with additional antiplatelet treatment had significantly less thromboembolic complications (0.7%) and lower microembolic signal prevalence (18.3%) than those without (2.8% and 65.4%, respectively). Individual patients and left ventricular assist device months with clinical thromboembolization could be identified using the microembolic signal activity with moderate positive (0.37-0.7) and high negative predictive values (0.82-1.0).

CONCLUSIONS

The amount of microembolic signals, serially detected in patients with the Novacor left ventricular assist device, is significantly associated with their incidence of embolic complications. The high negative predictive value of microembolic signals enables to identify those patients and left ventricular assist device periods with particularly low risk of clinical thromboembolization.

The future of mechanical circulatory support

Heart failure is one of the most important causes of morbidity and mortality in adults and the elderly. In the United States, an estimated 5 million persons already have heart failure, and more than 500,000 new cases are being diagnosed each year [ 1]. Today, cardiovascular physicians can choose from a wide range of mechanical circulatory systems, depending on the desired degree of support, length of support, extent of postoperative mobility and other factors. This article describes the growing problem of heart failure and the future prospects for patients with heart disease. It discusses current mechanical circulatory support devices and their changing applications, newer devices still in the experimental stages, and some hurdles to the use of mechanical circulatory support.

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.

Costs and insurance coverage associated with permanent mechanical cardiac assist/replacement devices in the United States

Each year over 50,000 persons in the United States could potentially benefit from some form of permanent cardiac replacement or assistance. Approximately 7000 of these persons get on the waiting list for a transplant, and 2300 are transplanted. About 2000 patients are reportedly exposed to a mechanical cardiac assist device, most often as a bridge to transplant. The majority of persons who might benefit from cardiac replacement are never referred for treatment and, thus, the number of deaths on the waiting list is a misleading indicator of access to transplantation and overall patient mortality. The total economic burden associated with coronary artery disease and congestive heart failure now exceeds $140 billion each year, with approximately $700 million directly spent on heart transplant procedures alone. If a viable total artificial heart is devised to replace a failed heart, or a ventricular assist system to permanently assist a failing heart, direct aggregate expenditures alone are likely to be somewhere between $5.4 and $24.0 billion annually. Based on individual patient care costs, as well as aggregate national expenditures, insurers will be reluctant to pay for the permanent use of such devices, even though cost is reportedly not a consideration in coverage decisions. Today, medical benefits and added value are concepts that will shape the coverage determination process, as will increasingly liberal policies regarding payment for treatment costs in relationship to clinical trials. Nonetheless, resource allocation and rationing decisions loom large as strange "characters at play" on an international economic "stage," while being "directed" by worldwide health care needs.

Long-term use of a left ventricular assist device for end-stage heart failure

BACKGROUND

Implantable left ventricular assist devices have benefited patients with end-stage heart failure as a bridge to cardiac transplantation, but their long-term use for the purpose of enhancing survival and the quality of life has not been evaluated.

METHODS

We randomly assigned 129 patients with end-stage heart failure who were ineligible for cardiac transplantation to receive a left ventricular assist device (68 patients) or optimal medical management (61). All patients had symptoms of New York Heart Association class IV heart failure.

RESULTS

Kaplan-Meier survival analysis showed a reduction of 48 percent in the risk of death from any cause in the group that received left ventricular assist devices as compared with the medical-therapy group (relative risk, 0.52; 95 percent confidence interval, 0.34 to 0.78; P=0.001). The rates of survival at one year were 52 percent in the device group and 25 percent in the medical-therapy group (P=0.002), and the rates at two years were 23 percent and 8 percent (P=0.09), respectively. The frequency of serious adverse events in the device group was 2.35 (95 percent confidence interval, 1.86 to 2.95) times that in the medical-therapy group, with a predominance of infection, bleeding, and malfunction of the device. The quality of life was significantly improved at one year in the device group.

CONCLUSIONS

The use of a left ventricular assist device in patients with advanced heart failure resulted in a clinically meaningful survival benefit and an improved quality of life. A left ventricular assist device is an acceptable alternative therapy in selected patients who are not candidates for cardiac transplantation.

The Batista procedure: fact, fiction and its role in the management of heart failure

End-stage heart failure is associated with high rates of mortality. Obviously, heart transplantation is the ultimate surgical intervention for its treatment. However, this surgical option is severely limited by immunosuppressive drug morbidity and inadequate donor organ availability. Partial left ventriculectomy, the so called Batista procedure, has been proposed for the treatment of dilated cardiomyopathy and other end-stage heart failure. Although initial reports lacked significant information on the safety and efficacy of this procedure, overall clinical impression from the reports is that the operation may serve as a relatively inexpensive bridge to transplantation especially in the patients with idiopathic dilated cardiomyopathy. In order to select an exact procedure to resect appropriate amount of scar tissue, dobutamine echocardiographic study, intraoperative volume reduction test using cardiopulmonary bypass, positron emission tomography, or magnetic resonance imaging scans can be used. To avoid the late deterioration related to the development of significant mitral valve regurgitation, definitive mitral valve repair or replacement at the time of the partial left ventriculectomy may be advised. Further study is required to determine the procedure's exact role in the treatment of congestive heart failure. This would have to be a multicenter, randomized, and long-term follow-up study.

Initial hydrodynamic study on a new intraaortic axial flow pump: Dynamic aortic valve

Rotary blood pumps have been researched as implantable ventricular assist devices for years. To further reduce the complex of implanted axial pumps, the authors proposed a new concept of intraaortic axial pump, termed previously as "dynamic aortic valve (DAV)". Instead of being driven by an intraaortic micro-electric motor, it was powered by a magnetic field from outside of body. To ensure the perfusion of coronary artery, the axial flow pump is to be implanted in the position of aortic valve. It could serve as either a blood pump or a mechanical valve depending on the power input. This research tested the feasibility of the new concept in model study. A column, made from permanent magnet, is jointed to an impeller in a concentric way to form a "rotor-impeller". Supported by a hanging shaft cantilevered in the center of a rigid cage, the rotor-impeller can be turned by the magnetic field in the surrounding space. In the present prototype, the rotor is 8 mm in diameter and 15 mm in length, the impeller has 3 vanes with an outer diameter of 18 mm. The supporting cage is 22 mm in outer diameter and 20 mm in length. When tested, the DAV prototype is inserted into the tube of a mock circuit. The alternative magnetic field is produced by a rotating magnet placed side by side with the rotor-impeller at a distance of 30 mm. Once the alternative magnetic field is presented in the surrounding space, the DAV starts to turn, leading to a pressure difference and liquid flow in the tube. The flow rate or pressure difference is proportioned to rotary speed. At the maximal output of hydraulic power, the flow rate reached 5 L/min against an afterload of 100 mmHg. The maximal pressure difference generated by DAV at a rotation rate of 12600 r/min was 147 mmHg. The preliminary results demonstrated the feasibility of "DAV", further research on this concept is justifiable.

Mechanical circulatory support for advanced heart failure: effect of patient selection on outcome

BACKGROUND

Use of wearable left ventricular assist systems (LVAS) in the treatment of advanced heart failure has steadily increased since 1993, when these devices became generally available in Europe. The aim of this study was to identify in an unselected cohort of LVAS recipients those aspects of patient selection that have an impact on postimplant survival.

METHODS AND RESULTS

Data were obtained from the Novacor European Registry. Between 1993 and 1999, 464 patients were implanted with the Novacor LVAS. The majority had idiopathic (60%) or ischemic (27%) cardiomyopathy; the median age at implant was 49 (16 to 75) years. The median support time was 100 days (4.1 years maximum). Forty-nine percent of the recipients were discharged from the hospital on LVAS; they spent 75% of their time out of the hospital. For a subset of 366 recipients, for whom a complete set of data was available, multivariate analysis revealed that the following preimplant conditions were independent risk factors for survival after LVAS implantation: respiratory failure associated with septicemia (odds ratio 11.2), right heart failure (odds ratio 3.2), age >65 years (odds ratio 3.01), acute postcardiotomy (odds ratio 1.8), and acute infarction (odds ratio 1.7). For patients without any of these factors, the 1-year survival after LVAS implantation including the posttransplantation period was 60%; for the combined group with at least 1 risk factor, it was 24%.

CONCLUSIONS

Careful selection, specifically implantation before patients become moribund, and improvement of management may result in improved outcomes of LVAS treatment for advanced heart failure.

Partial aortic valve fusion induced by left ventricular assist device

BACKGROUND

Left ventricular assist devices (LVADs) may be used (1) as a bridging device to cardiac transplantation, (2) for permanent replacement of left ventricular function, and (3) as a bridge to recovery of ventricular function, for example, in recoverable myocardial disease. In this third group of patients, it is important that the LVAD does not produce changes in the heart that will have a deleterious effect on cardiac function once the device is removed. Furthermore, if the LVAD fails, survival depends on optimal function of the diseased heart.

METHODS

All hearts with LVADs encountered as surgical specimens following heart transplantation or at autopsy at the Fairview-University of Minnesota Medical Center during the 5-month period August 1998 to January 1999 were examined for native valvular heart disease. The nature and extent of commissural fusion was noted and measured. Light microscopy was performed on any valve lesions.

RESULTS

Four of 6 patients with HeartMate (Thermo Cardiosystems, Inc, Woburn, MA) LVADs showed evidence of commissural fusion (acquired aortic stenosis). In 1 patient, this condition was caused by an organizing thrombus uniting a 14-mm length of the commissural region of the right coronary and noncoronary cusps of the aortic valve. Fibrous commissural fusion due to totally organized thrombus in the other 3 patients affected one aortic commissure (2 patients, 2 mm and 4 mm, respectively) and two commissures (1 patient, 2 mm and 5 mm). Partial cuspal fusion in each case was due to permanent closure of the native aortic valve induced by the LVAD's operating in its automatic setting. Mean length of commissural fusion was 5.4 mm (range, 2 to 14 mm; standard deviation [SDI = +/-5.0 mm). Mean duration of implantation of the six LVADs was 180.3 days (range, 26 to 689 days; SD = +/-253.8 days). The LVADs of the 3 patients with fibrous fusion of the commissures had been implanted for an average of 252.3 days (range, 26 to 689 days; SD = +/-378.2 days).

CONCLUSIONS

Normal function of the LVAD produces permanent closure of the native aortic valve. Stasis on the ventricular aspect of the aortic valve, combined with a low level of anticoagulation, favors thrombosis at this site. Thrombus organization leads to aortic stenosis of variable severity. This previously unsuspected complication was not detected clinically in any of our patients. Aortic stenosis may hold serious implications for patients in whom the LVAD acts as a bridge to recovery or in those in whom the LVAD fails. Prevention may be achieved by intermittently reducing LVAD pumping action. A built-in venting cycle would be of value in long-term implants. Thrombi on the aortic valve may also predispose patients to infective endocarditis, because bloodstream infection is common in patients with LVADs.