Use of a prosthetic ventricle as a bridge to cardiac transplantation for postinfarction cardiogenic shock

Mechanical assist devices for acute cardiogenic shock

BACKGROUND

Cardiogenic shock (CS) is a state of critical end-organ hypoperfusion due to a primary cardiac disorder. For people with refractory CS despite maximal vasopressors, inotropic support and intra-aortic balloon pump, mortality approaches 100%. Mechanical assist devices provide mechanical circulatory support (MCS) which has the ability to maintain vital organ perfusion, to unload the failing ventricle thus reduce intracardiac filling pressures which reduces pulmonary congestion, myocardial wall stress and myocardial oxygen consumption. This has been hypothesised to allow time for myocardial recovery (bridge to recovery) or allow time to come to a decision as to whether the person is a candidate for a longer-term ventricular assist device (VAD) either as a bridge to heart transplantation or as a destination therapy with a long-term VAD.

OBJECTIVES

To assess whether mechanical assist devices improve survival in people with acute cardiogenic shock.

SEARCH METHODS

We searched CENTRAL, MEDLINE (Ovid), Embase (Ovid) and Web of Science Core Collection in November 2019. In addition, we searched three trials registers in August 2019. We scanned reference lists and contacted experts in the field to obtain further information. There were no language restrictions.

SELECTION CRITERIA

Randomised controlled trials on people with acute CS comparing mechanical assist devices with best current intensive care management, including intra-aortic balloon pump and inotropic support.

DATA COLLECTION AND ANALYSIS

We performed data collection and analysis according to the published protocol. Primary outcomes were survival to discharge, 30 days, 1 year and secondary outcomes included, quality of life, major adverse cardiovascular events (30 days/end of follow-up), dialysis-dependent (30 days/end of follow-up), length of hospital stay and length of intensive care unit stay and major adverse events. We used the five GRADE considerations (study limitations, consistency of effect, imprecision, indirectness, and publication bias) to assess the quality of a body of evidence as it relates to the studies which contribute data to the meta-analyses for the prespecified outcomes Summary statistics for the primary endpoints were risk ratios (RR), hazard ratios (HRs) and odds ratios (ORs) with 95% confidence intervals (CIs).

MAIN RESULTS

The search identified five studies from 4534 original citations reviewed. Two studies included acute CS of all causes randomised to treatment using TandemHeart percutaneous VAD and three studies included people with CS secondary to acute myocardial infarction who were randomised to Impella CP or best medical management. Meta-analysis was performed only to assess the 30-day survival as there were insufficient data to perform any further meta-analyses. The results from the five studies with 162 participants showed mechanical assist devices may have little or no effect on 30-day survival (RR of 1.01 95% CI 0.76 to 1.35) but the evidence is very uncertain. Complications such as sepsis, thromboembolic phenomena, bleeding and major adverse cardiovascular events were not infrequent in both the MAD and control group across the studies, but these could not be pooled due to inconsistencies in adverse event definitions and reporting. We identified four randomised control trials assessing mechanical assist devices in acute CS that are currently ongoing.

AUTHORS' CONCLUSIONS

There is no evidence from this review of a benefit from MCS in improving survival for people with acute CS. Further use of the technology, risk stratification and optimising the use protocols have been highlighted as potential reasons for lack of benefit and are being addressed in the current ongoing clinical trials.

Short-term mechanical circulatory support as bridge to heart transplantation: paracorporeal ventricular assist device as alternative to extracorporeal life support

Extracorporeal life support (ECLS) is generally considered to be the treatment of choice for bridging to heart transplantation (HTx) patients with cardiogenic shock; however, alternative mechanical circulatory support (MCS) devices have been proposed with satisfactory results and, among those, paracorporeal systems have demonstrated to be safe and effective. This technology has been used for decades as bridge to transplant, especially in patients with advanced right ventricular dysfunction or evidence of multiorgan failure (MOF), which could be difficult to manage with an isolated left ventricular support. Paracorporeal systems are defined by having the pump located outside of the body, with inflow and outflow cannulas that traverse the skin connecting the pump with the heart and great vessels. They can be utilised in a uni- or bi-ventricular configuration and can provide pulsatile or continuous flow, depending on the device technology (pneumatic vs. centrifugal). In particular, pneumatic devices allow for patient mobilization and hospital discharge, improving rehabilitation and organ recovery while bridging to transplant. In our institution at the University Hospital of Udine, 34 pneumatic paracorporeal ventricular assist devices (VADs) have been implanted since 1998: in most cases (32 pts), as biventricular support for patients in INTERMACS class I-II. After a median support time of 34 (range, 0-385) days, with 19 patients (56%) supported for more than 1 month, 23 patients (68%) underwent HTx and 3 (9%) were successfully weaned to hospital discharge, resulting in an overall combined 76% survival to HTx or weaning. After transplant, the survival rate was similar to the one of the patients not bridged with MCS. In conclusion, pneumatic VADs can effectively assist patients with severe biventricular failure, especially those with contraindications to ECLS or expected long waiting times for HTx. Moreover, they can potentially result in hospital discharge, optimal organ and patient recovery and donor-recipient matching, resulting in a satisfactory transplant outcome.

Mechanical circulatory support: devices, outcomes and complications

Systolic heart failure is a problem of substantial magnitude worldwide. Over the last 25 years great progress has been made in the medical management of heart failure with the recognition of the benefits of beta-adrenergic blockade, modulation of the renin-angiotensin and mineralocorticoid axes and judicious diuretic therapy. In addition, cardiac resynchronization therapy and prophylactic implantation of cardiac defibrillators have been responsible for measurable benefits in terms of functional status and dysrhythmia-related mortality, respectively. Unfortunately, progressive cardiac dysfunction often results in activity limitation, symptoms at rest, hospital admission, end-organ dysfunction and death despite maximal implementation of standard therapies. Heart transplantation has been a dramatic and effective therapy for end-stage heart failure, but it remains limited by a shortage of donor organs, strict criteria defining acceptable recipients and often unsatisfactory long-term success. Mechanical alternatives to support the failing circulation have been sought for the last 50 years. The history of device development has been marked in general by the slow progress achieved by a few dedicated and persevering pioneers. In the past decade, however, evolving technology has dramatically changed the field and broadened the options for the treatment of advanced heart failure. This review will detail the important milestones and the current state of the art, with an emphasis on implantable devices for intermediate to long term support.

Endoscopic findings and clinical outcomes in ventricular assist device recipients with gastrointestinal bleeding

BACKGROUND

Gastrointestinal bleeding (GIB) is an important clinical problem in recipients of ventricular assist devices (VAD), although data pertaining to the endoscopic evaluation and management of this complication are limited in the medical literature.

AIMS

We sought to identify the most common endoscopic findings in VAD recipients with GIB, and to better define the diagnostic and therapeutic utility of endosopy for this patient population.

METHODS

Twenty-six subjects with VAD and overt GIB were retrospectively identified. Clinical and endoscopic data were abstracted for each subject on to standardized forms in duplicate and independent fashion. Raw data and descriptive statistics were reported.

RESULTS

Non-peptic vascular lesions were the most common cause of GIB. A definitive cause of bleeding was identified by endoscopy in almost 60% of subjects. Endoscopic hemostasis was achieved in 14/15 patients in whom bleeding did not stop spontaneously. Rebleeding occurred in 50% of subjects and was successfully retreated or stopped spontaneously in all cases. Colonoscopy did not establish a definitive diagnosis or deliver hemostatic therapy in any case.

CONCLUSIONS

Vascular malformations account for the overwhelming majority of bleeding lesions in VAD patients with GIB. Endoscopy seems to be a safe and effective tool for diagnosing, risk stratifying, and treating this patient population, although multiple endoscopies may be necessary before therapeutic success, and the incidence of rebleeding is high. A prospective multi-center registry is necessary to establish evidence-based management algorithms for VAD recipients with GIB.

HeartMate® II continuous-flow left ventricular assist system

Left ventricular assist devices (LVADs) have emerged as a beneficial therapeutic strategy proven to improve the morbidity and mortality of patients with advanced heart failure. Continuous-flow rotary LVADs have been developed in the hopes of delivering circulatory support in a more durable manner with fewer device-related complications. The HeartMate(®) II continuous-flow left ventricular assist system (LVAS; Thoratec Corporation, Pleasanton, CA, USA) has become the standard of care for heart failure patients who require long-term mechanical circulatory support. The efficacy of the HeartMate II has been demonstrated in patients where temporary support with an LVAD is needed until a suitable donor organ can be found for transplant (termed 'bridge to transplantation'), as well as for terminally-ill heart failure patients who are not candidates for transplant ('destination therapy'). When directly compared with a pulsatile LVAD, the implantation of a HeartMate II LVAS resulted in an overall improvement in survival with a reduction in the number of device-related complications and adverse events. The purpose of this article is threefold: to describe the history of the development of continuous-flow LVADs; to describe the technology of the HeartMate II; and, finally, to review the clinical outcomes in patients who have been implanted with the device.

Mechanical circulatory support: a clinical reality

Mechanical circulatory support is becoming an alternative therapeutic option for patients in cardiogenic shock or advanced cardiac failure who cannot be improved by maximal medical therapy. More than 30 years of engineering development and clinical research have led to a level of efficacy and reliability of ventricular assist devices, which allows promotion of this approach for the most difficult patients. Uses include a gaining-time strategy as a bridge to cardiac transplantation or recovery of native cardiac function, as well as permanent support with the device. The large variety of devices permits every cardiac surgical unit, even those not used to cardiac transplantation, to propose this option to the patient. Recent experience with small silent implantable pumps suggests that the pioneering period of mechanical circulatory support is probably over, and the time has come for precise prospective trials to optimize both patient selection and the timing for utilization. In countries where cardiac transplantation has not developed, there is now an easily accessible technique for management of patients with cardiac failure.

Implantation of Cardio West Total Artificial Heart for Irreversible Acute Myocardial Infarction Shock

Patients who develop cardiogenic shock after acute myocardial infarction have a very high mortality rate despite early reperfusion therapy. Hemodynamic stabilization can often only be achieved by implanting a mechanical circulatory support system. When, in cases representing expansive myocardial impairment without any chance of recovery, pharmacological therapy and the use of percutaneous assist devices have failed, the implantation of a total artificial heart is indicated. We report our first experiences with this extensive and innovative method of managing irreversible cardiogenic shock patients. The CardioWest total artificial heart was implanted in 5 patients (male; mean age, 50 years). All patients were in irreversible cardiogenic shock despite maximum dosages of catecholamines, an intra-aortic balloon pump and/or a femoro-femoral bypass. In all patients early reperfusion therapy was performed. After implantation of the Cardio West system, all dysfunctional organ systems rapidly recovered in all patients. Four of 5 patients underwent successful heart transplantation after a mean support time of 156 days. One patient died because of enterocolic necroses caused by an embolic event after termination of dicumarol therapy. In summary, our first experiences justify this extensive management in young patients who would otherwise have died within a few hours.

Mechanical Circulatory Support for Cardiogenic Shock Complicating Acute Myocardial Infarction: An Experimental and Clinical Review

Cardiogenic shock (CS) occurs in 7% to 10% of cases after acute myocardial infarction and remains the most common cause of death in these patients. Despite aggressive treatment regimens such as fibrinolysis and percutaneous transluminal coronary angioplasty, mortality rates from CS remain extremely high. It has been shown that intra-aortic balloon pumping can result in initial hemodynamic stabilization. However, in the majority of studies, death was merely delayed. In recent years, efforts have been made to develop ventricular devices (LVAD) capable of providing complete short-term hemodynamic support. Seventeen major studies of LVAD support for CS complicating acute myocardial infarction are reported in the literature, with a mean weaning and survival rate of 58.5% and 40%, respectively. Patients considered in these studies are difficult to compare in terms of demographic and anatomic data, but taking these considerations into account, LVAD support seems to give no survival improvement in these patients compared with early reperfusion alone or associated with intra-aortic balloon pumping. Data emerging from experimental studies of acute myocardial infarction supported with LVAD are intriguing. In this review, we report the LVAD experience in the CS setting, starting from percutaneous extracorporeal support up to bridge therapy with implantable devices.

[The results of the artificial heart]

The artificial heart is no more a dream but a reality. Over the last 40 years, many circulatory assist devices have been developed. First were the pneumatic devices, external or implantable, providing uni- or biventricular support; next were the partially implantable electromecanical devices. We went from the first generation of devices with all components (pump, energy power, control system) outside of the body to the second generation of devices with the pump and the motor implanted inside the body. Recently, the third generation of artificial hearts appeared with all components implanted inside the body allowing better mobility and quality of life. Results depend on the indication and on the kind of artificial heart implanted: partial (native heart still in place) or total (native heart removed). Essentially developped as a bridge to transplant, the artificial heart is now allowed as destination therapy.

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.

Clinical outcomes in pediatric patients implanted with Thoratec ventricular assist device

Most mechanical circulatory support devices are designed for adult patients; however, some can be successfully applied to pediatric patients. The rates of complications and patient survival to transplant or native heart recovery after implantation of the Thoratec ventricular assist device (VAD) (Thoratec Corp, Pleasanton, CA) in children and adolescents were determined from the company's voluntary registry. As of January 2005, 209 patients (mean age 14.5 years; range 5 to 18 years) have been supported with the Thoratec VAD. Mean patient weight was 57 kg (range, 17 to 118 kg), and patients had a mean body surface area of 1.6 m2 (range, 0.73 to 2.3 m2). The major etiologies necessitating VAD support included cardiomyopathy (55.0%), acute myocarditis (25.4%), and end-stage congenital heart disease (5.8%). Mean duration of VAD support was 44 days (range, 0 to 434 days). Patient survival to transplantation or native heart recovery was 68.4%. Patients with cardiomyopathy and acute myocarditis had 74.1% and 86.0% survival, respectively, with only 27.3% survival in patients having congenital heart disease. The overall survival rate in smaller children (body surface area, <1.3 m2) was similar at 51.7%, although the incidence of congenital heart disease was higher.

Short-term bridge to heart transplant using the BVS 5000 external ventricular assist device

From January 1995 to April 2001, 71 patients with cardiogenic shock using the BVS 5000 were treated or accepted in transfer. Of the 24 transplanted, nine had dilated cardiomyopathy, ischemic cardiomyopathy, acute myocardial infarction, giant cell myocarditis and previous Fontan procedure (group I, n = 13). The others had postcardiotomy shock (group II, n = 11); seven were transferred to our center after device implantation. Age ranged from 8 to 67 years. Ten (77%) patients in group I were implanted without cardiopulmonary bypass. The mean duration of support was 6.7 (2-24) d. Twelve patients were extubated before transplantation and 13 (five in group I, eight in group II) received nonstandard donor organs. Survival to discharge and 1-year actuarial survival was 85 and 77% for group I and 73 and 64% for group II, respectively. Patients with post-implant serum bilirubin levels > 10 mg/dL had a tendency to expire from multiple systemic organ failure. Patients not ventilator-dependent at the time of transplant had the best outcomes. Short-term bridge to transplantation using the BVS 5000 is feasible in selected patients. Caution is recommended when directing such patients to transplant if they need ventilator support and have high serum bilirubin levels.

The thoratec ventricular assist device: a paracorporeal pump for treating acute and chronic heart failure

The Thoratec Ventricular Assist Device (VAD) System (Thoratec Laboratories, Pleasanton, CA) is a paracorporeal pump that can provide univentricular or biventricular assistance for patients with heart failure. The system consists of a prosthetic ventricle that has a blood-pumping chamber of Thoralon (Thoratec Laboratories) polyurethane, cannulas for univentricular or biventricular support, and either a hospital-based pneumatic drive console or a portable battery-powered drive unit. For biventricular assistance, 2 pumps are used. The Thoratec voluntary registry indicates that, as of May 2000, this system had been implanted in 1,376 patients, mainly for bridging to transplantation (828 patients) or postcardiotomy support (195 patients); the remaining 353 patients received a hybrid configuration of the device or had incomplete information, so they are not included in this analysis. In the 828 bridge-to-transplant patients, the Thoratec system provided biventricular assistance in 472 cases, left ventricular assistance in 326 cases, and right ventricular assistance in 30 cases for up to 515 days. During the support period, the cardiac index increased significantly from 1.4 +/- 0.8 L/min/m2 to 3.0 +/- 0.5 L/min/m2 (with biventricular assistance and left ventricular cannulation). Sixty percent of the 828 patients underwent transplantation, and the posttransplant survival rate was 86%. In the 195 patients who needed postcardiotomy support, VADs were used for up to 80 days for cardiac recovery. Thirty-eight percent of the patients were weaned from the VAD, and 59% of the weaned group were discharged from the hospital. In addition, 49 postcardiotomy patients were considered for transplantation; of these, 32 received a transplant and 23 were discharged. Patient mobility is being improved by the use of a portable driver. The Thoratec VAD is suitable for a wide range of applications, and efforts are underway to facilitate patient mobility and allow hospital discharge. An intracorporeal version of the VAD, which is currently under development, will help achieve these goals.

Left ventricular assist device bridge therapy for acute myocardial infarction

BACKGROUND

Patients with acute myocardial infarction (AMI) complicated by cardiogenic shock have a high mortality rate. Current treatment modalities remain suboptimal for these patients.

METHODS

From April 1995 to March 1998, 7 patients were identified as having AMI associated with cardiogenic shock. All received intraaortic balloon pump assistance, in addition to maximal inotropic support.

RESULTS

The mean preoperative cardiac index was 2.0+/-0.3 L/min/m2 and pulmonary capillary wedge pressure was 23+/-6 mm Hg. Three patients received thrombolytic therapy and 4 patients underwent percutaneous transluminal coronary angioplasty without success. Left ventricular assist devices (LVADs) were implanted as bridge therapy to heart transplantation. One patient died from recurrence of a ventricular septal defect during LVAD support. Six patients were transplanted successfully after mean LVAD support of 59+/-33 days. Five patients are alive and well at a mean follow-up of 898+/-447 days. One patient died 3 days after transplantation from acute allograft dysfunction.

CONCLUSIONS

Timely application of LVADs as bridge therapy to heart transplantation in these critically ill patients can be lifesaving, and should be investigated further.

The need for artificial hearts

Chronic immunosuppression, allograft coronary disease, and restricted availability of donor organs continue to limit the scope of cardiac transplantation. Meanwhile increasingly favourable experience with implantable blood pumps used as a bridge to transplant has reintroduced the concept of permanent mechanical cardiac support. Existing models (for example, the Thermo Cardiosystems Heartmate device) are now used for such support in patients who are not candidates for transplantation. Miniaturised axial flow pumps such as the Jarvik 2000 fit within the failed left ventricle and provide an exciting prospect for the treatment of heart failure in the future. Preliminary experience suggests that the "offloaded" left ventricle may recover. Mechanical blood pumps can be used before the onset of multisystem failure and removed if the myocardium recovers. This "bridge to recovery" concept should be tested in patients with recoverable cardiomyopathy and those with coronary disease and poor left ventricular function where an implantable pump can be used in conjunction with myocardial revascularisation.

Mechanical circulatory support: lessons from a single centre

Over recent years, a number of different mechanical circulatory support (MCS) products have been developed to a stage where they are no longer investigational devices. Registry data provide some information, but this is limited by the mix of historical and contemporary data and the voluntary nature of the contributions. As yet, there are no clear guidelines for patient selection, the differential application of generically different devices or for optimal patient management. Ours is a busy centre offering a comprehensive cardiovascular service. This review details our experience since 1987 and 189 patients supported with five different types of device, used in all of the common applications. Our experience has permitted the formulation of some general principles and guidelines. Data published by registries and by individual manufacturers are, as yet, not standardized. We hope that our experience will be of interest to those centres wishing to establish a mechanical assist service.

Improved mortality and rehabilitation of transplant candidates treated with a long-term implantable left ventricular assist system

OBJECTIVE

This nonrandomized study using concurrent controls was performed to determine whether the HeartMate implantable pneumatic (IP) left ventricular assist system (LVAS) could provide sufficient hemodynamic support to allow rehabilitation of severely debilitated transplant candidates and to evaluate whether such support reduced mortality before and after transplantation.

METHODS

Outcomes of 75 LVAS patients were compared with outcomes of 33 control patients (not treated with an LVAS) at 17 centers in the United States. All patients were transplant candidates who met the following hemodynamic criteria: pulmonary capillary wedge pressure > or = 20 mm Hg with a systolic blood pressure < or = 80 mm Hg or a cardiac index < or = 2.0 L/minute/m2. In addition, none of the patients met predetermined exclusion criteria.

RESULTS

More LVAS patients than control patients survived to transplantation: 53 (71%) versus 12 (36%) (p = 0.001); and more LVAS patients were alive at 1 year: 48 (91%) versus 8 (67%) (p = 0.0001). The time to transplantation was longer in the group supported with the LVAS (average, 76 days; range, < 1-344 days) than in the control group (average, 12 days; range, 1-72 days). In the LVAS group, the average pump index (2.77 L/minute/m2) throughout support was 50% greater than the corresponding cardiac index (1.86 L/minute/m2) at implantation (p = 0.0001). In addition, 58% of LVAS patients with renal dysfunction survived, compared with 16% of the control patients (p < 0.001).

CONCLUSIONS

The LVAS provided adequate hemodynamic support and was effective in rehabilitating patients based on improved renal, hepatic, and physical capacity assessments over time. In the LVAS group, pretransplant mortality decreased by 55%, and the probability of surviving 1 year after transplant was significantly greater than in the control group (90% vs. 67%, p = 0.03). Thus, the HeartMate IP LVAS proved safe and effective as a bridge to transplant and decreased the risk of death for patients waiting for transplantation.

Advanced technology within the cardiac transplant process

The field of cardiac transplantation is still undergoing changes in every sphere from donor management to long-term care of the recipients as research-based experience highlights new and exciting boundaries. This paper contains discussion of one aspect of the pretransplant support that some patients may require, including examples of the impact of technology on nursing care with specific reference to 'bridges to transplantation', and some dilemmas faced by transplant teams. Consideration of some effects of bridging is followed by suggestions for transplant nursing teams' ongoing development within this changing field in order to provide optimum nursing care.

Mechanical circulatory support: the Bad Oeynhausen experience

From September 1987 to February 1994, we treated 147 patients ranging between 11 and 82 years old with different mechanical circulatory support systems. The applied devices were the Bio-Medicus centrifugal pump in 61 patients, the Abiomed BVS System 5000 in 49 patients, the Thoratec ventricular assist device in 42 patients, and the Novacor left ventricular assist device in 7 patients. On the basis of indication for mechanical circulatory support, the patients were divided into three groups: group 1 consisted of 72 patients with postcardiotomy cardiogenic shock; group 2, 50 patients in whom mechanical support was used as a bridge to cardiac transplantation; and group 3 (miscellaneous), 25 patients in cardiogenic shock resulting from acute myocardial infarction (n = 14), acute fulminant myocarditis (n = 3), primary graft failure (n = 2), right heart failure after heart transplantation (n = 3), and acute rejection (n = 3). Time of support ranged from 1 hour to 97 days (mean duration, 10.8 days). Seventy-five patients (51%) were discharged from the hospital. The best survival rate was achieved in group 2 with 72%, followed by group 1 with 44% and then group 3 with 28%. The most frequent complications in group 1 were bleeding (44%), multiple-organ failure (24%), neurologic disorders (18%), and acute renal failure (15%). In group 2, the major complications were bleeding (34%) and cerebrovascular disorders (22%) and in group 3, multiple-organ failure and sepsis (60%) and bleeding (32%).

Circulatory support with shock due to acute myocardial infarction

Cardiogenic shock after acute myocardial infarction develops according to the amount of lost myocardium, function of remote myocardium, and the phenomenon of infarct expansion. Patients treated with mechanical support alone, without additional measures, have a mortality rate of 80%, the same as patients treated medically. Emergency angioplasty and emergency coronary artery bypass grafting can reduce mortality in certain subsets of patients to 40%. Patients with more severe shock and secondary organ dysfunction may be treated with mechanical bridging to transplantation with survival rates varying between 45% and 76%. Percutaneous support systems may be used to resuscitate a patient or to temporize, allowing time to perform diagnostic studies to determine if the patient is suitable for revascularization or heart transplantation. Intravenous enoximone may improve cardiac function as well and thus allow better decision making for further therapy.

Multicenter clinical evaluation of the HeartMate 1000 IP left ventricular assist device

The Thermo Cardiosystems Inc (Woburn, MA) HeartMate 1000 IP left ventricular assist device (LVAD) has been evaluated as a bridge to transplantation in 34 patients for up to 324 days at seven clinical centers in the United States. Sixty-five percent of the patients underwent transplantation, 80% of whom were discharged from the hospital. Six additional control patients, transplant candidates who met the entrance criteria but who did not receive the device, were also included in the study. Although 3 (50%) of the control patients received transplants, all 6 died within 77 days of having met the LVAD inclusion criteria (100% mortality). Complications resulting from use of the device were comparable with those previously reported for all ventricular assist devices, except for thromboembolic events: bleeding, 39%; infection, 25%; and right heart failure, 21%. No device-related thromboembolic events occurred, although 1 patient experienced an event related to a mechanical aortic valve in the native heart. None of the complications had a significant negative association with outcome of the patient except for right heart failure. All survivors had a significant improvement in hepatic function before transplantation. Total bilirubin values were reduced by 60% during LVAD support. No significant differences were observed when total bilirubin values were compared at 30 and 60 days after LVAD support and at 30 and 60 days after transplantation in a cohort of 15 patients (p greater than 0.05). The improvement in renal function was less predictable than that of hepatic function. Creatinine values decreased significantly before transplantation; however, the values measured at 30 and 60 days after transplantation were higher than those measured at the same intervals after LVAD support had been initiated, and this increase is presumably related to the immunosuppressive drugs. In conclusion, the HeartMate 1000 IP LVAD has been shown to be effective in supporting end-stage cardiomyopathy patients to transplantation. Thromboembolism, previously regarded as a serious complication with such devices, has not been a problem with this device. Additional patients are being enrolled into the study to further document the safety and effectiveness of this technology.

Surgical complications in bridging to transplantation: the Thermo Cardiosystems LVAD

Left ventricular assistance with a number of different devices has been used to successfully bridge patients to cardiac transplantation. Surgical complications or complications related to the device itself, however, may preclude transplantation or lead to death. We report our recent experience with the Thermo Cardiosystems model 14 "HeartMate" left ventricular assist device in 3 patients. The device was implanted for 15 to 95 days. Complications included mediastinitis and peritonitis associated with the device in place before transplantation, and colonic perforation, and a late diaphragmatic hernia after transplantation. Despite these and other minor complications, all 3 patients underwent successful cardiac transplantation. Mechanical support for the right ventricle was not necessary. The Thermo Cardiosystems left ventricular assist device provided excellent support in a range of physiological conditions with no mechanical malfunction despite the surgical complications.

Evolving experience with mechanical circulatory support

Since 1985 total mechanical circulatory support for mortally ill transplant candidates has been progressively integrated into the authors' program. During this period 379 patients underwent transplantation. Of this group of patients, 62 required some form of mechanical support other than the intra-aortic balloon pump. Because intra-aortic balloon pump assist was limited in therapeutic effect and was associated with patient immobility and line-related sepsis, the next logical step toward support was the artificial heart. Of 20 patients implanted with the Jarvik heart, 17 underwent transplantation, but only 9 of these survived to discharge. In 1988, the authors abandoned the preferential use of the total artificial heart because of excessive cumulative probability of death from wound infection. They began to use the Novacor electrical assist device with the percutaneous power cord because they believed that univentricular support would be adequate for most patients, because its heterotopic position would reduce the likelihood of infection, and because it had the potential for chronic implantation. Twenty-three patients with biventricular failure (right ventricular ejection fraction less than 20%, 18/23) received the electrical assist device for an average of 50.4 days (range 1-193 days). All 17 transplanted patients survived until discharge. Only one of the five deaths that occurred after implantation, but without transplantation, was due to infection (candidiasis). Remarkably, all patients who survived the perioperative period ultimately survived with univentricular support alone. Based on this experience, survival of mechanically supported patients is now comparable to that of those less mortally ill.

Directions in cardiac assistance

The use of mechanical circulatory support devices came to prominence with the use of the Jarvik 7 total artificial heart, both as a permanent implant and as a bridge to transplantation. Over the past decade, however, interest in the use of left ventricular assist devices has overshadowed that of the total artificial heart and great strides have been made, both in the use of such devices as temporary support, and towards the ultimate goal of permanent implantation. A variety of devices are available to support either or both ventricles with a great range of complexity and expense. This test discusses the use of ventricular assist devices and briefly describes the options available. The era is rapidly approaching when the use of implantable circulatory support devices will become commonplace and may outpace, and possibly outperform, the results currently obtained with cardiac transplantation.

A new technique for bridging to heart transplantation: feasibility of monoventricularization of bilateral ventricles with LVAD

Because the prognosis of ventricular septal perforation (VSP) and mitral regurgitation (MR) after acute myocardial infarction (MI) is remarkably poor, heart transplantation would be necessary for many of those patients. A new bridging technique was examined in canine models. The bilateral ventricles communicating through VSP were monoventricularized with mitral valve closure and maintained the pulmonary circulation, which had low vascular resistance. The systemic circulation was maintained by a left ventricular assist device (LVAD) placed between the left atrium and the aorta. VSP and MR were made in eight mongrel dogs (pulmonary to systemic flow ratio = 2.24 +/- 0.90). They were then monoventricularized and equipped with LVADs. The hemodynamic state was evaluated (a) in intact hearts, (b) after VSP and MR were made, and (c) after monoventricularization and assisted circulation by LVAD. Cardiac output was (a) 90.60 +/- 23.16, (b) 42.23 +/- 15.76, and (c) 73.43 +/- 15.14 ml/min/kg (a vs. c: not significant; a vs. b and b vs. c: p less than 0.001); mean aortic pressure was (a) 96.75 +/- 24.69, (b) 30.25 +/- 11.08, and (c) 66.50 +/- 18.40 mm Hg (a vs. b: p less than 0.01, a vs. c and b vs. c: p less than 0.05); central venous pressure was (a) 4.76 +/- 1.68, (b) 8.94 +/- 2.17, and (c) 10.68 +/- 2.43 mm Hg (a vs. c: p less than 0.01, a vs. b: p less than 0.05, and b vs. c: not significant). Mean pulmonary arterial pressure and mean left atrial pressure did not show any significant difference among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged extracorporeal life support of pediatric and adolescent cardiac transplant patients

Options for mechanical support of pediatric patients with severe heart failure who are awaiting transplantation or have undergone transplantation are limited. This report examines 3 patients placed on extracorporeal life support (ECLS) while awaiting transplantation and 3 patients who underwent transplantation and suffered subsequent heart failure due to rejection or postoperative myocardial dysfunction. The overall survival rate was 2 of 6. The 2 surviving patients had a failing transplanted heart. There were no survivors among the patients placed on ECLS as a bridge to transplantation. In each case a contraindication to transplantation developed before a donor heart could be obtained. The mean time of ECLS support was 147.5 hours (range, 70 to 370 hours). The ECLS circuit did not affect cyclosporin levels or antirejection therapy. Extracorporeal life support can be used to support pediatric cardiac transplant patients with biventricular failure due to acute rejection or postoperative dysfunction. Although the results have been discouraging, ECLS may still have a role as a bridge to transplantation. However, complications can develop during ECLS that may preclude transplantation.

Transesophageal echocardiographic evaluation of mechanical biventricular assist device

The usefulness of transesophageal echocardiography in the assessment of mechanical biventricular assist devices is described.

Measurement of cardiac reserve in cardiogenic shock: implications for prognosis and management

The hypothesis that the prognosis of cardiogenic shock patients is primarily dependent on cardiac pumping reserve was tested in a prospective study of 28 consecutive patients clinically diagnosed to be in cardiogenic shock and treated medically. Haemodynamic function was assessed by thermodilution Swan-Ganz catheters and arterial cannulas. The cardiac pumping reserve was evaluated by the response of the failing heart to graded incremental dobutamine infusion (2.5 to 40 micrograms/kg/min) after optimalising the left ventricular preload. Eleven of the patients survived for more than the one year of follow up and the rest died. Haemodynamic evaluation during the basal resting state was only able to identify unambiguously non-survivors whose cardiac function was most severely compromised. Survivors and non-survivors with higher values were indistinguishable by basal haemodynamic criteria. The response to dobutamine stimulation clearly separated the cardiac pump function of survivors and those who died. All patients with peak cardiac power output of less than 1.0 W or peak left ventricular stroke work index of less than 0.25 J/m2 died whereas all those with higher values lived for more than a year. Thus this study showed that haemodynamic evaluation of cardiac reserve can provide objective criteria for predicting outcome in individual patients with cardiogenic shock. The availability of such a prognostic indicator will be invaluable in formulating management plans for these patients.