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Ann Thorac Surg 1997;64:1764-1769
© 1997 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Quality of Life With an Implanted Left Ventricular Assist Device

Departments of Surgery, and Medicine, and School of Public Health, Columbia University, College of Physicians & Surgeons, and The Presbyterian Hospital, New York, New York

Accepted for publication June 28, 1997.

	Abstract

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Scenarios for... Appendix 2. Three-State Utility... Acknowledgments References

 
Background. With the increasing use of left ventricular assist devices (LVADs) for longer-term support of patients awaiting cardiac transplantation, we must now consider whether to use these devices as alternatives to medical therapy when biologic hearts are needed but not forthcoming. This expansion of use depends as much on quality of life as it does on survival. To draw an inference about long-term quality of life with implanted LVADs, we studied "bridged" patients at our institution.

Methods. We elicited, by standard gamble, the utilities (preferences) of bridged patients at three points in their care: before LVAD implantation, during LVAD support, and after cardiac transplantation.

Results. Utility was 0.548 (±0.276) before implantation, 0.809 (±0.136) during LVAD support, and 0.964 (±0.089) after transplantation. For patients interviewed during all three states of health, the utilities were significantly different (p = 0.0009 by analysis of variance).

Conclusions. The quality of life with an LVAD was substantially better than with medical therapy, on par with renal transplantation (as established by others), and not as good as after cardiac transplantation. These results portend an acceptable quality of life for long-term use of LVADs for patients with end-stage heart failure and contribute to the growing body of evidence supporting a clinical trial to test this new use.

	Introduction

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Scenarios for... Appendix 2. Three-State Utility... Acknowledgments References

 
With a prevalence of nearly 4 million, an annual incidence of 400,000, and a total annual treatment cost of $10 billion (1991), heart failure constitutes a major public health problem in the United States [1–3]. Despite major advances in medical therapy for this clinical entity, existing pharmacologic agents have had only moderate success in patients with end-stage disease (New York Heart Association class IV); the 1-year survival rate for class IV patients is in the range of 40% to 50%, and the expectation for survival at 2 years is around 25% [4]. To date, cardiac transplantation has been the only viable treatment option for these patients. Candidates for this therapy can expect an in-hospital mortality rate of less than 10% and a 5-year survival rate of around 65% [5]. However, this success is mitigated by the complications of long-term immunosuppression, the development of allograft coronary artery disease, and, more importantly, the current serious shortage of donor organs. It has been estimated that at least 16,500 individuals per year in the United States would be suitable candidates to receive donor hearts [6]. Despite major efforts to enhance donor heart procurement, the actual number of donor hearts harvested in the United States over the past few years has remained relatively constant at approximately 2,000 annually [7]. Moreover, mortality for patients on the waiting list has risen, which has further stimulated the interest in alternative treatments to cardiac transplantation [8].

See also 1757.

Over the last 30 years, a variety of circulatory support devices have been developed for temporary support of patients with heart failure. In September 1994, the Food and Drug Administration approved the pneumatically driven left ventricular assist device (LVAD) from Thermo Cardiosystems Inc for bridging such patients to cardiac transplantation. An electrically powered "wearable" version of this device, which has been in "bridge" trials since 1990, was approved for investigation as an alternative to medical therapy by the Food and Drug Administration in December 1995. Although the survival rates of patients who received these devices have been impressive to date (75% to 80% reach transplantation), the potential for their long-term use as an alternative to medical therapy will depend on whether they can offer a desirable quality of life (QoL) as well as whether they are economically feasible, given the large number of potential recipients. Toward this end, we have been studying the QoL experienced by "bridged" patients to draw an inference about the QoL that long-term LVAD recipients might experience. We report here the results of measuring preference values (utilities) in this population and make comparisons concerning QoL with medical therapy, cardiac transplantation, and other chronic illnesses.

	Material and Methods

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Scenarios for... Appendix 2. Three-State Utility... Acknowledgments References

 
This research was approved by the Institutional Review Board of Columbia-Presbyterian Medical Center, and informed consent was obtained from participating patients.

Patient Population
The population comprises all adult patients who underwent LVAD implantation at Columbia-Presbyterian Medical Center during the period December 4, 1993, to June 20, 1995.

Schedule of Interviews
Patients were interviewed at three points during the course of their treatment: immediately preceding LVAD implantation, during LVAD support, and after cardiac transplantation. Interviews were conducted by two of us (A.J.M. and D.L.W.) using a standard script. Table 1 reviews the total number of patients available for interview at each stage of treatment, the number of patients who were actually interviewed, and the reasons why the others were not. Patients who were not interviewed either had an altered state of consciousness, were disoriented to person, place, and time, or had died before they could be interviewed.

The next step in the interview process established the relative values of the QoL before, during, and after LVAD support compared with full health and dead. We accomplished this using the standard gamble, a technique based directly on the fundamental axioms of rational behavior, delineated by von Neumann and Morgenstern [9] 50 years ago [10, 11]. Preference values for each state of health are determined by the risk of treatment-related mortality the patient would be willing to accept to improve health in that state. Presumably, the better the patient felt, the less risk of dying he or she would be willing to assume to improve health. This part of the interview started with a hypothetical scenario designed to put the patient into the position of having to choose between remaining in current health or trying a new hypothetical therapy in an attempt to improve health (Appendix 1). When successful, the hypothetical therapy is supposed to return the patient to full health for the remainder of his or her life. When unsuccessful, it is supposed to result in the patient's worst perceived outcome, usually immediate death.

After the scenario, the patient was asked a series of questions in which he or she was to choose between taking the new therapy and remaining in current health. We systematically varied the chances of the best and worst outcome of the new therapy for each iteration of the question and stopped the exercise when the patient was indifferent between trying the new therapy and remaining in current health. At that point, the value of current health equaled the expected value of the gamble. When full health is assigned a value of 1 and dead a value of 0, the expected value of the gamble, ie, the value of current health, can be mapped on a 0 to 1 scale. Negative values were possible if the patient perceived current health to be worse than being dead. The interview used a probability wheel as a visual aid and a variety of techniques designed to avert interviewer-imposed bias [10].

Statistical Analysis
The utility values for the three states of health were each normally distributed, and the 95% confidence interval for the means was determined assuming a t distribution. Differences between the means were not normally distributed, and therefore, paired testing was done using the nonparametric Wilcoxon signed rank-sum test. Analysis of variance was used to compare utilities of all three health states. Data were analyzed using SAS System software (SAS Institute, Inc, Cary, NC).

	Results

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Scenarios for... Appendix 2. Three-State Utility... Acknowledgments References

 
The characteristics of the patients who were interviewed and those who were not are presented in Table 2. At the time of evaluation for implantation, all patients were in the intensive care unit on a minimum of two inotropic agents, with resting heart rates greater than 100 bpm and cardiac indices less than 2.5 L^-1 • min^-1 • m^-2. The median duration of heart disease for the entire implantation group was 3.3 years (mean duration, 6.5 years; standard deviation [SD], 8.4 years; range, 0.1 to 40.9 years). Approximately a third of these patients had urine outputs of less than 30 mL/h, and a fourth required mechanical ventilatory support.

The initial interviews (before LVAD implantation) occurred an average of 1.93 days (SD, 2.19 days; range, 0 to 7 days) before the implantation procedure. Interviews during LVAD support, which were all conducted while patients were hospitalized, were performed a mean of 47.3 days (SD, 21.3 days; range, 14 to 91 days) after the implantation procedure. Posttransplantation interviews, which were conducted both during and after hospitalization, were performed a mean of 117 days (SD, 105 days; range, 6 to 377 days) after the transplantation procedure. The interviews ranged from 25 to 50 minutes in duration. Initial interviews, especially those in the intensive care unit, required the greatest amount of time to complete.

The average utilities associated with the three states of health were as follows: end-stage heart failure immediately before LVAD implantation, 0.548; during LVAD support, 0.809; and after cardiac transplantation, 0.964 (Table 3). As expected, scores before implantation were the worst. At that point, patients were willing to take up to a 45.2% chance of dying to return to full health. Scores improved substantially after LVAD implantation and again after transplantation, where the willingness to assume a mortality risk to improve health was reduced significantly (threshold mortality risks of 19.1% and 3.6%, respectively).

Ten patients were interviewed both during LVAD support and after transplantation and were found to have mean scores of 0.826 (SD, 0.149) and 0.990 (SD, 0.015), respectively. The difference, 0.164, was significantly different from 0 even after correcting for multiple comparisons (p = 0.0039).

Three-Way Comparison
Six patients were interviewed sequentially during all three periods. Group mean scores assessed during the three periods were significantly different (analysis of variance). Binary contrasts performed after that analysis, which lacked conventional power to avoid a type II error, demonstrated a significant difference between transplantation and time preceding implantation only (Appendix 2).

	Comment

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Scenarios for... Appendix 2. Three-State Utility... Acknowledgments References

 
With the coming of age of implantable LVADs for longer-term hemodynamic support of patients awaiting cardiac transplantation, we must now consider whether to use these same devices as an alternative to medical therapy for those who need but will not be fortunate enough to receive a biologic heart. Although survival to transplantation for patients bridged long term has been very impressive to date, the potential for the long-term use of LVADs as an alternative to medical therapy will also depend on whether these devices offer a better QoL than the alternative and whether this QoL is desirable enough to be worth the risks associated with achieving it (ie, the risks associated with implantation). Although best addressed through a formal clinical trial, much can be learned about QoL from prospective studies of patients bridged for a longer term.

Published reports on the health-related QoL of patients bridged for a longer term are sparse. One such study [12] measured the QoL of 2 patients supported on a Novacor device who were discharged to a halfway-house setting. The QoL in the physical, emotional, and social domains more closely resembled that experienced by transplant recipients than transplant candidates. Another study [13] of 11 patients receiving pneumatically driven LVAD support found that the Nottingham Health Profile scores were moderately high compared with scores for patients with peripheral vascular disease. Both studies used health profiling to characterize QoL that can provide useful information about the specific aspects of QoL affected by therapy. However, such profiles are scored on ordinal scales with arbitrary magnitudes (ie, they express rank order only), and this does not facilitate quantitative comparisons. Moreover, these profiles do not use a common set of domains, which hinders interstudy comparisons. Finally, these profiles do not facilitate pragmatic interpretation, as they often do not summarize the multiple domains measured into a single, overall numeric score. Thus, in a therapeutic comparison, where the task is to select the therapy that offers the best "overall" QoL, such profiles would be helpful only if, fortuitously, one therapy consistently scored higher in every domain then the other therapies under consideration.

Some of these limitations are addressed by utility measures, which express the quantitative preferences of patients for the QoL experienced in given health states relative to full health and death. Thus, they are valuations of QoL experiences that are elicited in a decision-making framework. These measures have interval rather than ordinal properties, meaning that differences between successive values in the scale are of uniform magnitude. One can, then, evaluate the magnitude of differences between measured values. The fact that utilities are expressible as single global values on a common scale facilitates the comparison of overall changes in QoL, which is necessary for pragmatic interpretation. Utilities are particularly useful in cost-effectiveness analysis because they can be used as quality adjustment factors for calculating quality-adjusted life years, a composite measure of health effectiveness that collates survival and QoL experiences [11, 14].

Value measures, such as utilities, also have their limitations in conveying QoL information. The valuation process itself involves a subjective self-assessment with internal standards. Thus, the same physical limitation may be held at different levels of importance by different individuals and consequently result in different utility scores. Beyond the health state experience itself, utilities that are elicited by the standard gamble technique also capture patient attitudes toward taking risks. Thus, respondents who are highly risk averse may assign a higher value to a given state of health than those who are less risk averse, even though they may have experienced the state of health equivalently. These factors may account for some of the within-group variation found in the present study. However, because this study compares the same group of patients at different points in time, albeit in different health states, these factors should have less of an impact, ie, it is likely that each patient will hold roughly the same internal values and nearly the same risk attitude at each of the utility elicitations.

Problematic to the interpretation of QoL studies of seriously ill patients are the biases that can be introduced when data collection is incomplete. For example, being able to capture only the QoL of survivors of a high-risk procedure will fail to consider the lost QoL of the nonsurvivors. The same is true when individuals are too impaired to be interviewed after a procedure. The resultant group differences (before and after the procedure) can, therefore, bias in favor of finding a benefit to performing the procedure. In the present study, statistical comparisons between different states of health were done by paired-data analysis. This analysis eliminated from consideration any unpaired data and thus controlled for the bias just described. However, the analysis did not use all of the data that were collected and thereby can itself introduce a bias.

In regard to our preimplantation and postimplantation comparison, this raises the question of whether the difference that we observed would exist if all of the implantation interview data obtained before and after implantation were considered in the analysis. To draw an inference about this, we inputted values for the missing data that would deliberately underestimate the improvement in QoL after implantation. If, after introducing a bias against detecting a favorable difference, one continues to exist, confidence in there being a true favorable difference should increase. Three of the patients whom we evaluated before LVAD use were not interviewed during LVAD support, and 9 patients interviewed during LVAD support were not evaluated before LVAD insertion. To bias against finding a difference, we inputted 0, equivalent to being dead, for the missing interview scores during LVAD support and 0.534 (the preimplantation mean) for the missing interview scores before LVAD use. The recalculated LVAD support score is 0.699 (SD, 0.056), down from 0.809 but still substantially better than the score before implantation (0.534) (p = 0.0096).

In the present study, we found that the average utility for patients on the precipice of receiving an LVAD was 0.548, whereas for those receiving LVAD support, it was 0.809. To put these values into a broader perspective, patients requiring renal transplantation have rated their QoL in the range of 0.80, patients requiring hospital hemodialysis have rated their QoL in the range of 0.57, and patients with severe rheumatoid arthritis have rated their QoL in the range of 0.7 without treatment and 0.77 with oral gold treatment (Table 4) [15, 16]. By comparison, the QoL of our small group of LVAD patients was surprisingly high, especially considering that they were all inpatients at the time.

We conclude that the QoL with an LVAD is substantially better than that experienced just before LVAD support, on par with that of patients with renal transplantation, and not as good as that after cardiac transplantation. These results portend an acceptable QoL for the long-term use of LVADs as an alternative to medical therapy for patients in need of cardiac transplantation but who will not receive it. These results contribute to the growing body of evidence that supports conducting a randomized, controlled trial for this new use. Such a trial should facilitate full collection of preoperative data and would need to extend the observation period well into the outpatient setting, when the novelties of improved health have had a chance to wear off and the realities of life with an implanted device have set in.

	Appendix 1. Scenarios for Standard Gamble

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Scenarios for... Appendix 2. Three-State Utility... Acknowledgments References

 
Before Implantation
Imagine that you have been told that you are no longer a candidate for cardiac transplantation or for a mechanical assist device to support your own heart. Along with this news you are told that a new treatment for your heart disease is available. This new treatment is a pill that would need to be taken only once. When successful, it will immediately and permanently eliminate all symptoms of heart disease and return you to full health for the remainder of your life, with no further need of any medication. It will not increase the length of your life over what you currently can expect. When this treatment is unsuccessful, you will die within days of taking the pill, in a painless manner, during sleep. There are no other complications or side effects from taking this imaginary pill. If you choose not to take the pill, you will remain the way you are now for the rest of your life.

During LVAD Support
Imagine that you are told that you are no longer a candidate for cardiac transplantation. You are also told that a new treatment for your heart disease is now available. The treatment is a pill that would need to be taken just once, and the effects are permanent. When this treatment is successful, it returns you to full health, with a normally functioning heart, in a matter of days. You will no longer require the LVAD or experience any further discomfort or limitation related to the device. This pill will not increase the length of your life over what you can now expect with LVAD treatment, but it can return you to full health for the remainder of your life with no further need for medication. When the treatment is unsuccessful, you will die within days of taking the pill, in a painless manner, during sleep. There are no other complications or side effects from taking this imaginary pill. Should you choose not to take it, you can remain on LVAD support for the remainder of your life and can return home with your device when you are ready for hospital discharge. (Those with pneumatic LVADs were told, in addition, that the external portion of their device could be switched to a portable unit before hospital discharge.)

After Cardiac Transplantation
Imagine that your doctor has told you that a new therapy is available that can permanently return you to full health, without any limitations or symptoms that you may now have with your transplanted heart. The treatment is a pill that would need to be taken just once and, when successful, would return you to full health, permanently, within days of taking it, without the need for any medication or any follow-up medical examinations. It would not increase the length of your life over what you can now expect with a transplanted heart. When treatment is not successful, you will die within days of taking the pill, in a painless manner, during sleep. There are no other complications or side effects from taking this imaginary pill. Should you choose not to take it, you will continue with your transplant on the treatments that you are now receiving for the remainder of your life.

	Appendix 2. Three-State Utility Comparison

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Scenarios for... Appendix 2. Three-State Utility... Acknowledgments References

 

	Acknowledgments

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Scenarios for... Appendix 2. Three-State Utility... Acknowledgments References

Doctor Oz was supported, in part, by an award from the Irving Center for Clinical Research at Columbia-Presbyterian Medical Center and holds the Irving Assistant Professorship of Surgery.

	Footnotes

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Scenarios for... Appendix 2. Three-State Utility... Acknowledgments References

 
Address reprint requests to Dr Moskowitz, International Center for Health Outcomes and Innovation Research, Columbia University, Harkness Pavilion (Room 756), 180 Fort Washington Ave, New York, NY 10032. (e-mail: ajm4{at}columbia.edu).

	References

Top Footnotes Abstract Introduction Material and Methods Results Comment Appendix 1. Scenarios for... Appendix 2. Three-State Utility... Acknowledgments References

 

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