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Left ventricular assist devices (LVADs) for end stage heart failure |
Christopher F, Clegg A |
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Authors' objectives To assess the effectiveness, cost and utility of the use of left ventricular assist devices (LVADs) for end-stage heart failure.
Searching The following electronic databases were searched: Cochrane Systematic Reviews Database, Cochrane Controlled Trials Register (both 1999 Issue 1), DARE, NHS EED (searched 7/6/1999), MEDLINE (1966 to Feb 1999), PREMEDLINE, EMBASE (1980 to Jan 1999), BIOSIS Previews (1993 to 1999), Inspec (1969 to 1999), Index to Scientific and Technical Proceedings (1969 to 1999), Science Citation Index (1981 to 1999), Getting Easier Access to Reviews (GEARS) (searched on 5/3/1999), and National Research Register (searched 23/3/1999). Search terms were not provided. Searches were limited to English language articles only. Bibliographies of related papers were assessed for relevant studies. UK LVAD manufacturers, experts in the field, and Finance Departments of NHS Trusts were contacted.
Study selection Study designs of evaluations included in the reviewSystematic reviews, randomised controlled trials (RCTs), controlled clinical trials, and cohort studies were eligible for inclusion. Studies were considered to be of cohort design rather than case series if they defined, a priori, their inclusion criteria for patients, use of the intervention, outcomes, follow-up, and analysis.
Specific interventions included in the reviewLVADs available within the UK, used as either a bridge to heart transplant or a bridge to myocardial recovery.
Participants included in the reviewPeople diagnosed with end-stage heart failure.
Outcomes assessed in the reviewStudies had to report patient-related outcomes such as survival or quality of life in order to be included. Outcomes relating to functional capacity such as haemodynamic function and end organ function (i.e. effects upon renal and hepatic functioning), defined according to the New York Heart Association (NYHA) classification of heart failure, were also extracted. Other outcomes of interest included distance walked in 6 minutes, device-related complications, peri-operative mortality, and length of hospital stay post-transplant.
How were decisions on the relevance of primary studies made?The inclusion criteria were applied by one reviewer and checked by a second reviewer. Any disagreements were resolved through discussion.
Assessment of study quality Cohort studies were assessed according to the following criteria: patient characteristics and co-morbidity; use of co-interventions; statistical power; statistical methods; presence and type of control group (concurrent or historical); and baseline comparability of groups. The assessment tool used was based on a published checklist (see Other Publications of Related Interest no.1). Quality criteria were applied by one reviewer and checked by a second reviewer, with disagreements resolved through discussion.
Data extraction Data were extracted on the following: study type; intervention; participants; outcome measures; results; and methodological quality. Data were extracted by one reviewer and checked by a second reviewer, with any disagreements resolved through discussion.
Methods of synthesis How were the studies combined?The studies were combined in a narrative summary.
How were differences between studies investigated?Heterogeneity was not formally assessed. The characteristics of each study were presented separately in tables and in the text. In the section on LVADs used as a bridge to heart transplantation, the review authors distinguished between controlled and uncontrolled cohort studies.
Results of the review Ten cohort studies of LVADs used as bridge to transplant (619 participants), and one cohort study of LVADs used as bridge to myocardial recovery (17 participants).
All of the included studies were of poor methodological quality.
LVADs used as bridge to heart transplant (10 cohort studies).
Results from three out of four controlled studies suggested increased survival with LVADs. In four out of six studies assessing changes in NYHA functional class as a result of LVAD implantation, results indicated improvement. However, the statistical significance of the observed changes was not reported. Results of one study suggested that submaximal exercise capacity of patients with LVADs was comparable to that of patients with moderate heart failure, and significantly better than that of dobutramine dependent patients.
LVADs used as bridge to myocardial recovery (one cohort study).
In a single uncontrolled study, of 17 patients with idiopathic dilated cardiomyopathy, five demonstrated significant recovery of their natural heart function and were weaned from the device after 160-794 days.
Cost information A cost-utility analysis was carried out for LVADs used as a bridge to heart transplant, using evidence from the cohort study deemed to be of highest methodological quality. Based on total treatment costs of both LVAD support and heart transplantation, the cost per QALY discounted at 1.5% was estimated as £39,790. The range estimated from one-way sensitivity analysis was £28,510 - £74,000 (over a 20 year time period). Sensitivity analysis in the form of threshold analysis suggested that, in order to bring down the cost per QALY to a more widely acceptable cost-utility ratio (i.e. less than £20,000), the costs of the LVAD device and procedure combined would have to fall to approximately £19,300 per person (current estimated cost per person £62,480). A cost-utility analysis was not carried out for the bridge to recovery setting as it was considered that this would be too speculative. Authors' conclusions In the bridge to transplant setting, the evidence suggests that the use of LVADs may increase survival to transplant, whilst at the same time improving functional capacity, haemodynamic status and end-organ function. However, results are based on largely poor quality cohort studies, mainly carried out in the USA, and conducted on small numbers of patients. In the bridge to recovery setting, one cohort study provided limited evidence that the use of LVADs may enable a small number of patients to recover their natural heart function, although this study is also subject to many methodological limitations.
CRD commentary Clear selection criteria were provided for the primary studies in terms of participant characteristics, interventions, and outcomes. However, the criteria for study design were less clear, and more information about the validity-related criteria used for excluding studies would have been useful. A number of sources were accessed to locate both published and unpublished studies. However, relevant articles may have been omitted due to the decision to limit the search to English language papers only. Although it was possible to deduce the criteria used to assess study validity from descriptions in the text and tables, a clear presentation of this in the methods section of the review would have been helpful. Adequate study details were shown in tables. The decision to provide a narrative summary was appropriate given the clinical heterogeneity across the studies, and the methodological problems involved in each primary study. Adequate details were provided relating to the review process. The cautious conclusions expressed by the authors are appropriate given the nature of the evidence in this field.
Implications of the review for practice and research Practice: The Development and Evaluation Committee reached the following conclusion '...although there was some suggestion of potential benefits, particularly from haemodynamic studies, the evidence was not of sufficient quality to reach a decision'.
Research: The authors stated the following. 'Further good quality research is needed to address the uncertainties highlighted in this report, particularly regarding the magnitude of possible benefits gained from the use of LVADs, and the associated costs. Research from a UK perspective is particularly important, as there is currently no published evidence from the UK. It is therefore not known how UK results with these devices will compare to those of the published studies considered in this report, although there is some suggestion that UK results may be worse than in the US at the present time. In the case of bridge to transplant, although there is some evidence that LVADs can improve quality of life and physiological functioning for those with severe heart failure awaiting transplantation, the cost per QALY range is high and so further research is needed to provide better estimates of the increased proportion that survive to transplant, and evidence of the extra possible benefits that LVAD patient may gain after heart transplant. Within the bridge to recovery setting, there is little evidence at present from which to draw conclusions. With the introduction to smaller, more manageable pumps, there is a need for further well designed research to determine clinical effectiveness and criteria for use. In the case of LVADs as a long term alternative to transplantation, there is as yet no good evidence of effectiveness in this setting. However, as smaller, more manageable devices become available and the number of patients with severe heart failure continues to increase, a formal evaluation of LVADs as an alternative to transplant may be justified.'
Bibliographic details Christopher F, Clegg A. Left ventricular assist devices (LVADs) for end stage heart failure. Southampton: Wessex Institute for Health Research and Development. Development and Evaluation Committee Report; 103. 1999 Other publications of related interest 1. NHS Centre for Reviews and Dissemination. Undertaking systematic reviews of research on effectiveness. CRD's guidance for those carrying out or commissioning reviews. York: University of York, NHS Centre for Reviews and Dissemination; 1996. Report No.: CRD report 4.
Indexing Status Subject indexing assigned by CRD MeSH Heart Failure /surgery; Heart-Assist Devices AccessionNumber 12000008096 Date bibliographic record published 31/08/2001 Date abstract record published 31/08/2001 Record Status This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn. |
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