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Original Articles: Pediatric Cardiac

Costs Associated With Ventricular Assist Device Use in Children

^a Sibley Heart Center Cardiology, Children's Healthcare of Atlanta, Atlanta, Georgia
^b Department of Pediatrics, Division of Cardiothoracic Surgery, Emory University School of Medicine, Atlanta, Georgia
^c Department of Surgery, Division of Cardiothoracic Surgery, Emory University School of Medicine, Atlanta, Georgia

Accepted for publication July 8, 2008.

^_* Address correspondence to Dr Mahle, Children's Healthcare of Atlanta, Emory University School of Medicine, 1405 Clifton Road, NE, Atlanta, GA 30322-1062 (Email: wmahle{at}emory.edu).

Pediatric cardiac surgery: The Annals of Thoracic Surgery CME Program is located online at http://cme.ctsnetjournals.org. To take the CME activity related to this article, you must have either an STS member or an individual non-member subscription to the journal.

 

	Abstract

Top Abstract Introduction Material and Methods Results Comment References

 
Background: Ventricular assist devices (VADs) allow children with severe heart failure to be bridged to successful heart transplantation. Ventricular assist devices are being used with increasing frequency in the pediatric population, and newer devices allow even young infants to be supported. Ventricular assist device implantation and maintenance, however, is quite expensive, and the cost-effectiveness of VAD use in adults has been questioned. To date, an economic analysis of VAD support in children has not been undertaken.

Methods: We used Pediatric Health Information System, an administrative database of the Child Health Corporation of America (a consortium of Children's Hospitals in North America), to determine the outcomes and costs related to VAD use in children. Data on patients younger than 18 years of age from 2002 to 2007 were reviewed. Hospital charges were converted to costs based on cost-to-charge ratios. Projected survival for subjects who were successfully bridged to heart transplant was derived from published data. The model assumed that if a VAD strategy were not used, the majority of subjects would have required extracorporeal membrane oxygenation support as a bridge to transplantation. Cost-utility was expressed as cost per quality-adjusted life years saved. All future costs and benefits were discounted at 3%.

Results: There were 145 children who underwent VAD implantation at 19 centers in North America. The median age at admission was 8.5 years; the range was newborn to 17.7 years. The median duration of VAD support was 43 days (range, 1 to 465 days). Ninety-four patients (65%) survived to heart transplantation. Thirty-nine (27%) patients died during hospitalization. There were 12 patients (8%) who had VAD explantation and survival to hospital discharge. The mean hospital cost was $624,798. When compared with a strategy of extracorporeal membrane oxygenation support, the calculated cost-utility for VAD as a bridge to transplantation was $119,937 per quality-adjusted life year saved. When key assumptions were changed, the cost-utility varied from $88,304 to $282,320 per quality-adjusted life year saved.

Conclusions: Ventricular assist devices allow an effective bridge to heart transplantation in children. Under base-case assumptions, the cost-effectiveness ratios exceed the threshold of $100,000 per quality-adjusted life year saved. The cost-utility of this strategy, however, is comparable to a number of other life-saving technologies.

Heart transplantation represents the definitive therapy for advanced heart failure in children. Historically, a significant number of children awaiting heart transplantation die as a result of progression of heart failure before a donor heart could become available. Extracorporeal membrane oxygenation (ECMO) has been used to bridge children to transplantation [1]. However, this strategy is associated with significant morbidity and mortality and generally can be used for only several weeks before bleeding complications or severe end-organ injury occurs [2]. More recently, ventricular assist devices (VADs) have been used in the management of advanced heart failure [3]. Children bridged to heart transplantation with VAD support appear to have similar survival to those children who receive heart transplantation without needing VAD implantation [4]. Moreover, VAD implantation allows extended support, with some children being managed for more than 12 months with this form of mechanical support [3]. Ventricular assist device implantation also allows reverse remodeling and subsequent recovery of heart failure with device explantation in the minority of patients [5].

Although early experience with VAD support in children has been promising, this therapy is relatively costly [6]. In addition, the currently available VAD products for young children appear to be prone to gradual thrombosis, and a single child may require multiple device implantations [7]. Given the concern about the available resources to care for children with advanced heart failure, we sought to explore trends in the use of pediatric VAD support and the costs associated with this strategy.

	Material and Methods

Top Abstract Introduction Material and Methods Results Comment References

 
Permission to conduct this retrospective cohort study of preexisting de-identified data was obtained from the Children's Healthcare of Atlanta Institutional Review Board. The Pediatric Health Information System (PHIS) is a large inpatient administrative database of 42 participating children's hospitals in the Child Health Corporation of America (CHCA), a children's hospital consortium. Detailed information on demographics, diagnoses, procedures, medications, and outcomes is available on every inpatient since 1997 (all patient-level data are de-identified). The present study was limited to the years 2002 to 2007. Patients were identified by searching for the supply code for VAD (code number 216021) and ICD procedure code 37.65 (insertion of implantable external heart assist system). In addition, we collected length of stay (hospital only; pediatric intensive care unit length of stay was not consistently coded across all hospitals and was not analyzed). Additionally, age and sex were collected. This study was limited to patients younger than 18 years of age at the time of admission.

The PHIS database includes hospital charges that are adjusted by Health Care Financing Administration wage/price index for a hospital's location. In addition, cost-to-charge ratios are available to estimate cost of services provided. Costs included in the PHIS include the costs of per diem inpatient stay, laboratory tests, medications, and medical devices—but does not include physicians' fees. Therefore, to account for physician fees we included estimates of daily intensive care unit and step-down unit care based on CPT codes. These fees were based on Medicare CPT reimbursement rates. Children who are supported with a VAD are generally managed in intensive care units because of the complexity of care. For those patients who underwent device explantation or were transplanted and survived to discharge we assumed that 5 days of the entire stay would occur on a cardiac step-down unit. Hence, we accounted for physician costs by assuming that the physician care was equivalent to CPT code 99291 (critical care 30 to 74 minutes) or CPT code 99254 (inpatient moderate complexity) in the intensive care unit or step-down unit, respectively. We were unable to account for physician consultative services in this model. In addition, we applied CPT codes for device implantation and heart transplantation.

Outpatient charges are not available from the PHIS. Therefore, we incorporated analysis from a previous publication from our institution that reported the costs of pediatric heart transplantation. Costs from the PHIS dataset and from prior publications were adjusted for inflation and reported in 2007 U.S. dollars [8].

Life Expectancy
In this model we assumed that those children with advanced heart failure who were not already on ECMO support and did not receive VAD would likely die within 30 days unless they received a heart transplant. On the basis of published literature we assumed 41% of the subjects placed on ECMO and not receiving VAD support would have survived to heart transplantation [9]. The hospital cost of ECMO support was derived from previous analysis at our institution [10]. To estimate the total costs for the lifetime of a pediatric heart transplant recipient, posttransplant life expectancy was assumed to be 13.2 years with prior VAD support and 8.3 years if the child was receiving ECMO at the time of transplantation [11]. Total cost of heart transplantation was determined by the sum of initial transplant and lifetime follow-up costs.

For patients who had device explantation and were discharged to home, we assumed a total of 10 outpatient visits and 5 limited echocardiograms during a 3-year period and thereafter routine childhood care.

Cost-Utility Analysis
Quality of life after heart transplant was accounted for by determining quality-adjusted life years (QALYs). Quality-adjusted life years were calculated based on previously published assessment of quality of life, Visual Analog Quality of Life Scale (VAQOL), in adolescents [12]. Using the average score on the VAQOL scale (8.7), life expectancies were multiplied by a factor of 0.87 to account for quality of life after transplant. Total costs per QALY saved were then calculated. For subjects with device explantation, a full quality-of-life utility factor 1.0 was assumed.

Discount Rate
All future costs and benefits are discounted at a rate of 3%. Discounting is used to calculate life-years lost [13].

Sensitivity Analysis
For the cost-utility analysis, we evaluated the sensitivity of the model to variations in key assumptions for various ranges. We also varied the utility measure after transplantation from 0.75 to 0.95. Lastly, cost-to-charge ratios were varied ±10%.

Statistical Analysis
Continuous variables are reported as mean ± standard deviation as well as median and range, as appropriate.

	Results

Top Abstract Introduction Material and Methods Results Comment References

 
Between January 1, 2002, and June 20, 2007, there were 145 patients who had VAD implantation in the institutions included in the PHIS database. The median age at admission was 8.5 years; the range was newborn to 17.7 years. There were 72 boys and 73 girls. The most common indications included primary cardiomyopathy (n = 59), myocarditis (n = 15), congenital heart disease (n = 29), and unspecified congestive heart failure (n = 62). Ninety-four patients (65%) survived to transplantation, of which 86 survived to hospital discharge. Thirty-nine patients (27%) did not receive a transplant and died before hospital discharge. There were 12 patients (8%) who had explantation of VAD and were discharged from the hospital.

The median length of hospital stay was 50 days (range, 1 to 470 days). The median length of VAD support was 43 days. Twenty patients were supported with ECMO before receiving a VAD. The mean cost of hospitalization for the entire cohort based on reported cost-to-charge ratios was $624,798. The highest cost of hospitalization was incurred by those children who went on to receive a heart transplant (Table 1). Follow-up costs exceeded $250,000 for those who underwent transplantation. And the mean number of QALYs for the pediatric transplant recipients was 9.4 years (Table 2).

View larger version (10K): [in this window] [in a new window]   Fig 1. Sensitivity analysis of cost-effectiveness ratio varying the health utility of patients after transplantation and varying the cost-to-charge ratios (, baseline; , –10%; *, +10%) of institutions in the Pediatric Health Information System database. (QALY = quality-adjusted life year.)

View larger version (11K): [in this window] [in a new window]   Fig 2. Sensitivity analysis of cost-effectiveness ratio varying the health utility of patients after transplantation and varying the probability of successful ventricular assist device explantation (, baseline; , 0%; , 5%; *, 10%) and discharge to home. (QALY = quality-adjusted life year.)

	Comment

Top Abstract Introduction Material and Methods Results Comment References

The cost of VAD support in adults has been intensely studied. Investigators have examined both VAD as a bridge to transplantation and VAD as destination. A detailed analysis from the United Kingdom suggested that the cost-utility of VAD as a bridge to transplantation was not cost-effective [14]. These investigators calculated a base case of $159,203/QALY, well above the threshold for reasonable health-care expenditure in that country. Analyzing VAD as a destination therapy appears somewhat more favorable [15]. A cost-effectiveness study of data from the REMATCH trial suggested the incremental cost-effectiveness ratio of VAD as destination was reported as $89,790 [16]. Moreover, there seemed to be increased efficiencies in the post-REMATCH trial period, with subjects having a shorter length of stay as institutions became more familiar with the devices and developed protocols to reduce morbidities.

Importantly, our analysis suggests that the hospital cost of VAD implantation in children is higher than that reported from the adult series. There are a number of factors that could explain this difference. The pediatric experience to date has been to use VADs as a bridge to transplantation. Therefore, the length of hospitalization is longer and the accrued costs of intensive care unit care increase proportionally. The cost of VAD equipment is for the most part similar to that used in adults. Neither the Berlin EXCOR nor the DeBakey Micromed, two devices designed specifically for children, is available as biventricular VADs. Two separate devices can be used in series, but this adds significantly to the overall cost. Approximately 40% of all children receive biventricular VAD support, and some centers had adopted a strategy of biventricular VAD support in nearly all of the infants [4]. In addition, the Berlin EXCOR has been thought to have an increased disposition to thrombus formation owing in part to the small size and design [17]. Not uncommonly, once a significant thrombus is detected the device is exchanged for a new device. In one study 60% of infants had device changes for thrombus formation or VAD malfunction. This adds considerable additional cost to VAD support.

The present study made a number of important assumptions that influence the incremental cost-effectiveness ratio. The study assumes that the quality of life after transplant for children who received VAD support is similar to that of other transplant recipients. However, the occurrence of acute neurologic events such as stroke for children supported with VAD may impact later quality of life. In adults stroke occurs in 25% of patients supported for 6 months or longer [18]. Limited data from children would suggest that the risk of stroke is the same if not higher than in adults [19]. Stroke appears to impair children's social ability along with their neurologic function [20]. Therefore, the health utility score for this patient population may be lower than the base assumption of 0.87 used in our model. The use of pretransplant VAD has been identified with poorer neurologic function in adults after transplantation [21]. In addition, it is assumed that children who undergo VAD implantation have equivalent posttransplant survival to those not receiving VAD support. One report from the Pediatric Heart Transplant Study did not find that VAD support was a risk factor for death after transplant [4].

Importantly, the PHIS data would suggest that VAD explantation occurred more commonly than was described in the PHTS series. This may be a result of increased familiarity with these devices and the emerging literature in adults of ventricular reverse remodeling with VADs. In addition, there may be significant variability among institutions regarding the indications for VAD implantation. In fact, two institutions accounted for almost half of the cases resulting in explantation and recovery. If one were to apply our present cost variables to the PHTS outcomes (77% transplanted, 17% death while waiting, and 5% weaned from VAD support), the calculated cost-effectiveness ratio would be $117,073/QALY saved. The reason that VAD as a bridge to transplantation is such an expensive strategy is that these subjects may have extended wait times and the median survival following heart transplantation is only approximately 13 years. Follow-up medical costs are substantial, adding to the overall costs.

The costliness of VAD support has been a concern for health-policy officials, engendering much debate. The Canadian government initially limited the use of VAD support, concerned that the cost-effectiveness was unfavorable [22]. The cost-effectiveness of pediatric health interventions in the United States have been considered, although the health system has generally not denied clinically efficacious procedures on the basis of cost alone. Moreover, it should be recognized that there are a number of endorsed pediatric interventions that have a less favorable cost-effectiveness ratio than pediatric VAD support. Use of Palivizumab (Syangis) prophylaxis in preterm infants costs $200,000 per QALY saved and enzyme replacement therapy for Gaucher's disease exceeds $850,000 per QALY saved [23, 24]. Nonetheless, it is worth considering that there are a number of potential changes that might lower the cost of VAD implantation and support. First and foremost, lowering the cost of the VAD can improve the cost-effectiveness ratio favorably. There have been efforts to design VAD devices less expensively [25]. The costs of postoperative care will be difficult to modify. One strategy might be to discharge a significant number of children from the hospital so that they might be able to wait at home for an available organ. Certainly, adult centers now have a wealth of experience with home VAD management [26]. Previous investigators have shown that home inotropic medication can be administered safely and inexpensively to children awaiting transplantation [27]. A shorter waiting time would also reduce overall costs. However, the increasing use of VADs in children might have the paradoxic effect of prolonging waiting and worsen the shortage of donors [28].

There are a number of limitations to this study. The PHIS is an administrative database and is designed primarily for benchmarking and quality improvement among children's hospitals. Although efforts are made to ensure the fidelity of data, previous studies have identified the challenges of using administrative databases. In addition, the PHIS database lacks many important clinical variables that might improve the model. Clearly some children's hospitals are more likely to institute VAD therapy than others. It is possible that many children who received VAD therapy in this series might have been effectively managed without mechanical support. In the absence of such data, our model assumed that nearly all patients would have died had they not received VAD support. Lastly, the neurodevelopmental outcome of survivors is largely unknown. Children with VAD support before transplantation may have a significantly poorer quality of life than other pediatric transplant recipients. Prospective data from the INTERMACS registry will hopefully provide valuable data regarding neurodevelopmental outcome after pediatric VAD support [29].

In summary, using VAD support for children with advanced heart failure permits the majority of children to be bridged to heart transplantation. The costs associated with this strategy are relatively high and—by some standards—exceed the threshold for acceptable cost-effectiveness. In light of the rapid pace of evolution in VAD technology one hopes that novel approaches can both improve the outcomes and lower the costs associated with VAD support in children.

	References

Top Abstract Introduction Material and Methods Results Comment References

 

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