(Circulation. 2001;103:231.)
© 2001 American Heart Association, Inc.
Clinical Investigation and Reports |
Mechanical Circulatory Support for Advanced Heart Failure
Effect of Patient Selection on Outcome
From the Cardiothoracic Surgery and Transplant Center (M.C.D.), Westfalian Wilhelms University Münster, Münster, Germany; the German Heart Institute (M.L.), Berlin, Germany; Heartcenter North Rhine Westfalia (A.E.-B.), Bad Oeynhausen, Germany; Hospital Niguarda Ca’ Granda Milano (E.G., E.V.), Milan, Italy; World Heart Corporation (P.G.M.J., D.R.W.), Oakland, Calif; IRCCS Policlinico S. Matteo (M.V.), University of Pavia, Pavia, Italy; Cardiothoracic Surgery (G.M.W.), University of Vienna, Vienna, Austria; Cardiothoracic Surgery (B.R.), Hospital Großhadern, Munich, Germany; Cardiothoracic Surgery (A.P.), Hospital La Pitié Salpétrière, Paris, France; Cardiothoracic Surgery (T.M.), Hospital La Timone, Marseilles, France; Thoracic and Cardiovascular Surgery (D.Y.L.), Hospital Henri Mondor, Créteil, France; and Stanford University School of Medicine (P.M.P.), Stanford, Calif.
Correspondence to Mario C. Deng, MD, FESC, FACC, Director of Cardiac Transplantation Research, The Heart Failure Center & Division of Circulatory Physiology, Columbia University College of Physicians & Surgeons, New York Presbyterian Hospital, Milstein Hospital Building, Room 5-435, 177 Fort Washington Ave, New York, NY 10032. E-mail md785{at}columbia.edu
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Abstract |
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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.
Key Words: heart-assist device • heart failure • patients
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Introduction |
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TopAbstractIntroductionMethodsResultsDiscussionAppendix 1References |
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Despite considerable advances in the diagnosis and medical treatment of heart failure, this condition remains the most common "malignant" disease in western society today.1 2 The Working Group on Heart Failure of the European Society of Cardiology has promoted a number of initiatives aimed at improving the treatment of heart failure.3 However, even the best combination of ACE inhibition, ß-blockade, and diuretics is able to confer only up to a 16% survival benefit at 1 year, and this benefit disappears by year 5.4 How to treat the >50 000 patients per year worldwide who are aged <60 years and who develop advanced heart failure despite optimal medical therapy has not been resolved.5 The available donor supply limits cardiac transplantation to
3500 patients per
year worldwide, and of these, <60% will survive >10 years, many with
increasing morbidity. All the available evidence suggests that the
donor supply is declining, implying an increasing gap between the
supply and demand for heart replacement
therapies.6 There is also
evidence of a decreased survival benefit from transplantation compared
with other forms of heart failure
therapy.7 Xenografting, as a
potential solution to this problem, has received widespread yet
critical attention in recent
years,8 whereas the more
realistic solution of using mechanical circulatory support (MCS)
systems has yet to be seriously considered. There is a lack of
prognostic data of patients supported by MCS systems. Therefore, the
aim of the present study was to identify prognostic indicators of
survival from a consecutive unselected cohort of 464 European
recipients of the Novacor left ventricular assist system
(LVAS). |
Methods |
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LVAS Configuration
The Novacor LVAS was developed by Portner et al,9 in collaboration with Stanford University, and was used in the first successful LVAS bridge-to-transplant application in 1984. The pump drive unit is implanted below the diaphragm, anterior to the posterior rectus sheath, and connected in parallel to the natural circulation, taking blood from the left ventricle and returning it to the ascending aorta (Figure 1
). Initially, the pump takes over the entire
workload of the left ventricle, but usually some degree of native
ventricular recovery and of ventricular ejection via the aortic valve
occurs during exercise. Internal sensors allow the pump to track the
output of the natural heart, providing automatic control, a degree of
redundancy, and the possibility of removal should native ventricular
recovery occur. Although early systems required a large console, a
wearable version that is supported by a small electronic controller and
by batteries worn on a belt was introduced in
1993.10
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In March 1998, a new inflow conduit was introduced, consisting of a knitted, gelatin-sealed, integrally supported, uncrimped polyester graft, replacing the previous inflow graft, which explant analysis had shown to be vulnerable to distortion and to have unfavorable flow characteristics. Comparative studies have demonstrated that this change has been associated with a significant reduction in embolic complications.11
Patients and Definitions
Between March 1993 and May 1999, 464 patients were
implanted with the Novacor LVAS in 22 European centers, of which 11
centers have performed >10 implants each.
Because this model (N100 PC) was released in Europe as a commercial product, clinicians in participating centers were not bound by the constraints of an investigational protocol and predefined implantation criteria; thus, selection practices between centers varied greatly, with a large percentage of patients moribund at the time of implantation.12 One of the major purposes of the present study is to examine the consequences of a less rigorous patient selection.
Data were obtained from the Novacor European Registry. This Registry was instituted in 1997 at the instigation of a number of clinicians (European Advisory Board) who were active in the use of MCS in an endeavor to promote an evidence-based perspective in mechanically supported advanced heart failure patients. The format for data collection and definitions of complications were a result of an expert consensus process, and the system was refined over the subsequent years.
As yet, there are no internationally agreed on definitions for complications in the field of mechanical circulatory assistance. Therefore, the European Advisory Board developed a set of definitions; the most important of which are listed here. Bleeding was defined as perioperative, related to the surgical procedure, and requiring reoperation or originating from anticoagulation imbalance occurring as digestive tract bleeding, late pump pocket bleeding, dental bleeding, or cerebral hemorrhage. Right heart failure was defined as cardiac index <2.0 L · min-1 · m-2 with central venous pressure >18 mm Hg and with normovolemia, requiring intravenous dobitamine/dopamine >10 µg · kg-1 · min-1 or support by a right ventricular assist device. Renal failure was defined as abnormal kidney function requiring replacement therapy (hemodialysis or filtration). Stroke was defined as a central nervous system deficit with sudden onset, persisting for >24 hours and confirmed by either conventional diagnostic methods (eg, CT scan) and/or at autopsy. Transient ischemic attacks (neurological events resolving within 24 hours) were excluded from the analysis because of the high degree of variability of diagnostic accuracy by clinical examination. Infection was defined as any positive culture for pathogenic organisms requiring antimicrobial therapy.
Data Analysis
Data were analyzed with SPSS (SPSS for Windows
Release 9.0, SPSS Inc). Survival after LVAS implantation was defined as
follows: currently supported, alive after transplantation, or alive
after weaning from the LVAS. Continuous variables were expressed as
medians with range. Binary variables were described by frequency
distributions. In a subset of patients, for whom a more complete set of
data was available (n=366), univariate analysis (Fisher exact test) and
multivariate analysis (Cox proportional hazards regression analysis)
were used to identify preimplant risk factors for mortality after LVAS
implantation. Kaplan-Meier analysis was used to estimate survival
probability over time. The incidence of clinical complications was
analyzed in 4 time frames after LVAS implantation: (1) occurring in the
first 30 days, (2) occurring from 1 to 3 months, (3) occurring from 3
to 6 months, and (4) occurring after 6
months.
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Results |
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At the time of implantation, median age was 49 (16 to 75) years, with 5% of recipients aged >65 years. The majority of recipients were male (89%); body surface area was 1.92 (1.39 to 2.68) m2. Diagnoses were dilated cardiomyopathy in 221 (60%) patients, ischemic heart disease in 100 (27%), acute myocardial infarction in 24 (7%), acute myocarditis in 19 (5%), and other causes in 2 (1%). Sixty-four (18%) patients had undergone prior thoracic surgical procedures. Preimplant hemodynamic, renal, and hepatic data showed a pattern of cardiac decompensation despite maximal medical therapy: pulmonary capillary wedge pressure was 25 (2 to 45) mm Hg, and the cardiac index was 1.9 (0.6 to 3.7) L · min-1 · m-2. Serum creatinine levels were 1.3 (0.6 to 10.3) mg/dL, serum sodium was 135 (109 to 165) mmol/L, and total bilirubin was 1.7 (0.3 to 6.7) mg/dL. The intention to treat was as follows: bridge to transplant in the majority (321 recipients, 88%), followed by bridge to recovery (33 of 366 recipients, 9%), and definitive therapy (contraindication to transplant, 12 of 366 recipients, 3%).
Risk Factors
The clinical status of recipients at the time of
implant
(Table 1) illustrates their advanced condition.
Univariate analysis of the preimplant clinical status showed that acute
postcardiotomy status, respiratory failure, and right heart failure had
a significant impact on 1-year survival. Subsequent multivariate
analysis revealed that age at implant >65 years, preimplant acute
myocardial infarction, preexisting right heart failure, acute
postcardiotomy, and preimplant sepsis with concomitant respiratory
failure were independent risk factors for survival after LVAS
implantation
(Table 2).
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Survival Analysis
On the basis of this analysis, the recipient population
was divided into 2 subgroups: 1 group included recipients without any
of these risk factors (low-risk group, n=276, 75.4% of study
population), and the other included those recipients with at least 1 of
these risk factors (high-risk group, n=90, 24.6% of study population).
The median LVAS support time was 100 (0 to 1477) days. Thirty-three
recipients (9%) had been supported for at least 1 year; of these, 8
were supported >2 years, 2 were supported >3 years, and 1 was
supported >4 years
(Figure 2). In the high-risk group, 46 (51%) of 90
recipients were supported on LVAS for <30 days. The survival
probability of each group is shown in Kaplan-Meier curves
(Figure 3).
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Table 3 shows the LVAS support duration related to
outcomes. The median time to transplantation was 139 days in the
low-risk group and 88 days in the high-risk group
(P=0.133, not
significant).
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Morbidity
Of the recipients who received LVAS implants from 1996
to 1997, 23% were in the high-risk group. This percentage increased to
31% in the more contemporary (1998 to 1999) group. However, despite
the selection of sicker patients, there was a reduction in morbidity
due to bleeding, right heart failure, bacteremia, and cerebral embolism
(Figure 4). In the case of stroke, this reduction was
associated with the introduction of a new inflow
conduit.11 The temporal
distribution of major complications experienced by this group of
recipients is shown in
Figure 5. Early bleeding complications were mainly
perioperative and related to the surgical procedure and hepatic
dysfunction. Bleeding complications after the first month were
secondary to problems with coagulation management and were manifested
as digestive tract bleeding, late pump pocket bleeding, dental
bleeding, and cerebral hemorrhage. During the chronic phase of support,
from 3 months on, infections of the driveline exit site, device pocket,
and bacteremia occurred in 5% to 10% of patients. The predominant
organisms cultured from driveline exit site and device pocket were
Staphylococcus (46%) and
Enterococcus (18%). In blood
cultures, the predominant organisms were
Staphylococcus (36%),
Enterococcus (20%), and
Candida (15%). Four patients
with device valve endocarditis were successfully treated by replacement
of the inflow and outflow valved conduits on postimplant day 6, 114,
490, and 1123, respectively. A fifth patient with valve endocarditis
received a donor heart on day 464, 23 days after the
diagnosis.
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Mortality
The primary causes of death were sepsis (21%),
multiple organ failure (18%), bleeding (15%), stroke (15%), and
other (16%).
No mechanical failure was encountered during the study period, which constituted 179 patient years. One pump was replaced electively after 1342 days because of impending deterioration of the pump drive. When the device was predicted to wear out within the following 2 months, 2 patients underwent cardiac transplantation at day 664 and 1297, respectively.
Outpatients
Of the recipients who were supported for at least 30
days, 49% were discharged from the hospital with their LVAS. This
increased from 25% of the recipients in 1994 to 55% in 1999. The
median time in the hospital until first discharge was 65 days, and the
median time spent outside the hospital was 152 days, giving a
cumulative out-of-hospital experience of 73.8 patient years. In total,
75% of the time on LVAS was spent outside the hospital environment,
where the majority of recipients resumed their normal daily
activities.
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionAppendix 1References |
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Heart failure is now acknowledged to be the most common malignant disease in industrialized countries, with advanced heart failure having a worse prognosis than most forms of cancer.1 Transplantation provides the most effective therapy for this condition, but the shortage of donor organs results in <10% of potential recipients actually receiving a transplant. The Registry of the International Society of Heart and Lung Transplantation reports that 1-year posttransplant survival has remained
80% over the past 5 years,
with a 5-year survival of 60% and thereafter a steady attrition
rate of 4% per year.6
Furthermore, recent research suggests that the benefit from heart
transplantation may be even lower than
expected.7 In addition,
long-term morbidity is not insignificant even at 1 year after
transplant, with 70% of recipients encountering hypertension, 21%
with renal dysfunction, 39% with hyperlipemia, 19% with diabetes, and
4% with malignancies.6 All
of these complications show increasing prevalence with
time. The current generation of MCS devices has evolved from a program initiated by the US National Heart, Lung, and Blood Institute in the 1970s to develop long-term artificial heart devices.13 Two electrically powered pumps have emerged from this initiative; trials sponsored by the Food and Drug Administration for evaluating their safety and efficacy have recently been completed, and these pumps have received certification for commercial application in 1998. The pumps are the HeartMate 1205 VE (ThermoCardio Systems)14 and the Novacor N100 PC (World Heart Corp).9 15 Basic pump design has remained little changed over this development period, but power delivery and control have moved from large bedside consoles to wearable components, enabling patient autonomy in an outpatient setting.16 17 18 This has brought about substantial improvement in patient quality of life19 and a reduction in resource use.20 Compared with medical treatment in a control group of patients, the Novacor was shown to confer a survival benefit of >80% two months after enrollment and >30% survival benefit 30 days after transplant in the same group of patients.21 A recent single-center report of a large cohort of transplant patients shows that the bridged transplant recipients demonstrated a survival benefit of >10%.22
The Novacor N100PC LVAS received CE marking in Europe in 1993. This allowed unrestrained use with regard to application and patient selection. Initial use was as a rescue therapy for transplant-eligible patients, and selection and management varied widely between centers.12 Therefore, the results from this early experience represent the learning phase of LVAS therapy. The present report illustrates that an acceptable 1-year survival and reduced morbidity is achievable with careful patient selection and optimal implant timing, consistent with findings from a previous single-center report.23 The preponderance of early complications, such as right heart failure, renal failure, stroke, and respiratory infections, suggests the strong influence of patient selection and reflects the preimplant morbidity. Extended utilization of intensive care is, besides its impact on resources, associated with an increased incidence of infection, with more problematic organisms and a spiral of negative sequelae. This has been independently studied by Gracin et al,24 who showed that MCS patients with a preimplant APACHE (Acute Physiology and Chronic Health Evaluation) score in the mid range (APACHE 11 to 20) had a larger survival benefit (40%) than either the very sick (APACHE >20, benefit 20%) or the minimally compromised (APACHE <10, 0% benefit). It is now well established that advanced heart failure is associated with a systemic inflammatory response25 that is interactive with both LVAS therapy and transplantation, compounding the already considerable challenges of recipient management.
Major morbidity has been declining as centers have gained wider experience with recipient management, despite the enrollment of sicker patients. The advantages of aprotinin26 and simpler surgical implant techniques have reduced surgical bleeding.27 28 More careful perioperative hemodynamic management and the use of inhaled nitric oxide have markedly reduced the incidence of right heart failure.29 Infection (in particular, driveline infection) rates are diminishing as a result of better prophylaxis and management of the exit site. However, infection has not proven to be a contraindication to thoracic transplantation.30 Replacement of valved-conduits for endocarditis has been straightforward because of the modular design of the system.
Design changes can have a major impact, as demonstrated by changing the inflow conduit to an uncrimped, integrally supported, and gelatin-coated graft, resulting in a 50% reduction in embolic complications.11 This experience illustrates that it has been possible to effect major improvements in outcomes by attention to detailed aspects of the therapy, and there is the potential for further improvement in the near future.
Mancini et al31 have recently demonstrated that LVAS patients can achieve a near-normal exercise response, equivalent to patients with mild heart failure, and Dew et al19 have shown that patients with a left ventricular assist device enjoy a quality of life that is comparable to that of transplant recipients.
Although the majority of Novacor applications have been as a bridge to transplant, a growing number of patients are now implanted with a view to recovery of native left ventricular function. A recent single-center publication has demonstrated that as many as 24% of supported patients may recover sufficient ventricular function to allow weaning from the LVAS.32 This has obvious implications for resource use and quality of life and could make a significant impact on the treatment of advanced heart failure, once the appropriate target population has been identified and optimal management regimes have been established. The process of reverse remodeling of the unloaded left ventricle has to be studied in prospective multicenter trials.
The Novacor N100 LVAS has demonstrated a very high level of reliability and durability in the laboratory33 and in a wide variety of clinical settings, with no device-related failures in the study cohort. During routine surveillance of long-term support, 2 pumps were explanted because of the normal wearing out after >3 years, and 1 pump was explanted because of abnormal wear at nearly 2 years. In all cases, impending wearing out was diagnosed at least 2 months before anticipated potential failure.
Smaller, inexpensive, and less obtrusive blood pumps are undergoing development, and some are just entering clinical trials.34 35 However, although the potential benefits are encouraging, these designs still have to prove their durability, reliability, and physiological suitability for chronic applications. Transplantation is able to meet <10% of the need for cardiac replacement therapy, and outcomes have not improved over the past decade. Xenografting is also unlikely to provide a clinical solution within the next 10 years. The present study provides evidence for the efficacy of current LVAS therapy when applied to carefully selected and managed recipients. LVAS therapy provides the only practical alternative to heart transplantation today, and future device refinements promise to make a significant impact.
The data for this publication were extracted from the Novacor Registry, established in 1993. This registry was set up to provide data to facilitate clinical decision-making with respect to patient selection and management before and after device implantation, and it highlights aspects of the therapy that require attention. The potential value of an international registry of the entire spectrum of devices designed for prolonged (>30-day) MCS has been recognized by the Scientific Council on MCS of the International Society for Heart and Lung Transplantation. The council is currently working on establishing an international MCS registry and has adopted the data forms of the Novacor Registry as a template. This international registry would provide the additional benefit of enabling comparative assessments of efficacy between generic therapies and between individual devices, because definitions of outcomes and complications could be standardized. These data are critical to advancing our knowledge and our ability to provide an effective therapy for one of the most difficult and costly problems facing 21st century medicine, the treatment of the malignant syndrome of advanced heart failure.
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Appendix 1 |
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TopAbstractIntroductionMethodsResultsDiscussionAppendix 1References |
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The following are contributing centers (in alphabetic country order): University Hospital Vienna, Vienna, Austria; University Hospital Saint Luc, Brussels, Belgium; Helsinki University Hospital, Helsinki, Finland; Hospital La Pitié Salpétrière, Paris, France; Hospital Henri Mondor, Créteil, France; Hospital Laennec, Nantes, France; Hospital Brabois, Nancy, France; Hospital La Timone, Marseilles, France; Hospital Trousseau, Chambray les Tours, France; Hospital Rangueil, Toulouse, France; Hospital Broussais, Paris, France; German Heart Center, Berlin, Germany; Heart Center Nordrhein Westfalen, Bad Oeynhausen, Germany; Westfalian Wilhelms University Hospital Münster, Münster, Germany; Hospital Großhadern, Munich, Germany; Hospital Ruprecht-Karls, Heidelberg, Germany; University Hospital, Freiburg, Germany; Hospital San Matteo, Pavia, Italy; Hospital Niguarda Ca’ Granda Milano, Milan, Italy; Hospital Padova, Padova, Italy; University Hospital Uppsala, Uppsala, Sweden; and Papworth Hospital, Cambridge, UK.
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Footnotes |
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Drs Jansen and Wheeldon are employees of World Heart Corporation. In addition, Dr Portner serves as Chairman Emeritus for Edwards LifeSciences, Novacor Division.
Received July 20, 2000; revision received August 23, 2000; accepted August 23, 2000.
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References |
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TopAbstractIntroductionMethodsResultsDiscussionAppendix 1References |
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