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J Thorac Cardiovasc Surg 2003;125:49-59
© 2003 The American Association for Thoracic Surgery
Cardiothoracic Transplantation (TX) |
From the Heart Transplant Program, University of California, Los Angeles, Calif.
Presented in part at the annual meeting of the International Society of Heart and Lung Transplantation, Osaka, Japan, April 2000.
Received for publication Jan 24, 2002. Revisions requested April 18, 2002; revisions received June 4, 2002. Accepted for publication July 8, 2002. Address for reprints: Hillel Laks, MD, UCLA School of Medicine, 10833 Le Conte Ave, 62-182 CHS, Box 951741, Los Angeles, CA 90095-1741 (E-mail: Llaks{at}mednet.ucla.edu).
| Abstract |
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| Introduction |
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As wait times for heart transplant recipients increase, nonstandard donor hearts are being used for higher risk recipients and for status I (critically ill) patients, while older recipients are potentially not listed.
1-6 In such cases the risk/benefit ratio justifies such a donor while expanding the pool of available hearts. Despite this, as many as 40% of organs remain unused, prompting our program to create an alternate recipient list in 1992. Borderline recipients who otherwise would be excluded from transplantation were considered for the alternate list and, once accepted, were educated as to the possible risk factors associated with the donor hearts that would be assigned to them.
| Patients and methods |
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Comparison group
Alternates who underwent transplantation (group I) were compared with 401 consecutive patients (
12 years old) who could have accepted the donor hearts by virtue of size (group II). This contemporaneous cohort underwent heart transplantation according to the criteria delineated in the 24th Bethesda Conference.
7 Urgent priority (status I) was not offered to alternate recipients so that they would not be competing for organs with regularly listed patients. Outpatient assist device placement was, however, permitted.
Donor heart allocation
Donor hearts were considered nonstandard as outlined in Appendix Table 1.
8 These were first offered by third-party organ procurement organizations to regularly listed patients according to United Network for Organ Sharing geographic allocation guidelines. Nonstandard hearts were used by us or others for regularly listed patients, usually waiting as status I. If the heart was refused by us (for example, if it was hepatitis C seropositive and the recipient was young or refused such a donor), then we instructed the organ procurement organization to call us back if the heart remained unused. We then considered the organ for alternate recipients.
3
Preservation
Preservation solution consisted of University of Wisconsin solution.
9 Reperfusion consisted of leukocyte-depleted, aspartate- and glutamate-enriched, warm blood cardioplegia (Buckberg solution) for 3 to 4 minutes, followed by leukocyte-depleted blood (8 minutes). Separate anastomoses of the superior and inferior venae cavae were used for the right atrium.
10
Immunosuppression and prevention of infection
Methylprednisolone (7 mg/kg) was given on reperfusion, on separation from cardiopulmonary bypass, and at a dose of 125 mg every 12 hours for three doses. Cyclosporine was administered with the aim of achieving a level of 250 ng/mL. Azathioprine was administered at 2 mg/kg and at half dose for older recipients (unusually >65 years old) not exhibiting rejection. Prednisone was initiated at 1 mg/(kg x d) and tapered to 0.1 mg/(kg x d) during the course of 3 months.
11 For those patients with few rejections, complete weaning from steroids was attempted. Since July 1994, all patients have received pravastatin after the operation. Older recipients (>65 years old) showing absence of rejection were targeted for lower cyclosporine levels (by 10%-20%).
In case of cytomegalovirus positivity in either the donor or recipient, ganciclovir was administered intravenously for 2 weeks at a dose of 2.5 to 5.0 mg/(kg x d), adjusted for renal function. This was followed by per os administration for 3 months at a dose of 1 to 3 g/d. This was extended for an additional 3 months if rejection (and treatment) or chronic illness occurred. Double-strength trimethoprim-sulfamethoxazole tablets (160-800 mg) were administered twice daily 2 days per week for 6 months. An additional 6-months course was repeated if patients had been treated for rejection during the 6 months before planned cessation. Clotrimazole (10 mg) was administered as a lozenge three times daily for 3 months and extended in the case of treatment for rejection. Beyond 6 months after the operation, influenza vaccination was recommended for patients who exhibited a low risk of rejection.
Statistical methods
Analysis was performed with Excel 97 (Microsoft Corp, Redmond, Wash), SPSS 8.0 (SPSS Inc, Chicago, Ill), and STATA (Stata Corporation, College Station, Tex). Averages were compared with the Student t test, and proportions were compared with the Pearson
2. Kaplan-Meier analysis with log rank test was used for survival and freedom from graft coronary artery disease (CAD). P values were calculated with the Wilcoxon rank-sum test for continuous variables and the Fisher exact test for categoric variables.
Regression models were used to study covariates (Appendix Table 2A), including the designation of alternate recipient. Early and late mortality and graft CAD-free survival for all patients (n = 463) were analyzed; 95% confidence intervals (CIs) are shown when available. A separate analysis was used to study early mortality among alternate list patients only (n = 62). Selection models were used on a backward-stepping algorithm with Premove of .15 and Penter of .10. The global test of proportional hazard assumptions (for Cox regression analysis of long-term outcome) was based on Schoenfeld residuals. Plots of natural log of survival for categories of the selected independent variables versus natural log of time did not show gross violations regarding proportionality assumptions.
| Results |
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Median follow-up time for all 463 patients in this study was 3.25 years. As of June 2001, a total of 13 alternates had follow-up beyond 4 years; 12 are still alive. Death rates per 1000 person-mo were 9.0 for alternate recipients and 5.8 for the comparison group. Overall 4-year survival was 68% (vs 77%, relative risk 1.55, 95% CI 0.96-2.48, P = .11; Figure 2, left). Beyond 90 days, death rate per 1000 person-mo was 4.3 for alternates (vs 3.6, relative risk 1.2; 95% CI 0.62-2.36, P = .77; Figure 2
, right).
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Multivariable analyses
Survival at less than 90 days (groups I and II combined, n = 463)
Recipient previous cardiac surgery and poor renal function were risk factors for early mortality. Odds ratios were 2.74 (95% CI 1.37-5.48) and 1.39 (95% CI 1.10-1.76). Donor death from aICB was also found to be a risk factor (odds ratio 2.84, 95% CI 1.51-5.34). Goodness-of-fit
2 in the selection model had a P value of .54. Odds ratio for alternate listing was 1.36 (95% CI 0.53-3.5; Appendix Table 2B).
Late survival longer than 90 days (groups I and II combined, n = 463)
Donor age and long graft ischemia time were slight but significant risks. Hazard ratios for these were 1.30 (95% CI 1.02-1.65) and 1.28 (95% CI 1.05-1.55). Global test of proportional hazards in this selection model had a P value of .84. Hazard ratio for alternate listing was 0.85 (95% CI 0.35-2.03). P value for the selection model was .003 (Appendix Table 2C).
Graft coronary artery disease (groups I and II combined, n = 463)
The only significant predictor of graft CAD was donor age both by linear (hazard ratio 1.58, 95% CI 1.23-2.04) and quadratic analyses (hazard ratio 1.43, 95% CI 1.15-1.77). P value for the global test of proportional hazards for this late-occurring event was .10. P value for the selection model was < .001 (Appendix Table 2D).
Early mortality among alternate list patients (group I only, n = 62)
Only donor cause of death as aICB was predictive of early mortality for alternate recipients (odds ratio 9.68; 95% CI 1.59-58.9). Goodness-of-fit
2 P value for this model was .24. None of the recipient risk factors tested were found to be significant (Appendix Table 2E).
| Discussion |
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Increasing supply involves extending the margins of what is considered acceptable and has led to the widely used term marginal donor.
5,6 Many extracardiac and cardiac factors may qualify a donor as marginal; this is constantly being updated. The term nonstandard seems appropriate, because the only donor criteria on which the transplant community generally agree are the ideal criteria. These are age of 45 to 55 years, normal cardiac anatomy and function, and negative results of serologic studies. Ischemia times longer than 300 minutes are also generally accepted, but few opportunities exist to go up to the 500-minute mark.
12
Central to the use of nonstandard donors is allocation, defined as to apportion for a specific purpose or to particular persons.
13 United Network for Organ Sharing guidelines have acknowledged the fact that not all needs are the same. Some recipients are listed on a more urgent basis than others, and this can change. Given the choice between an assist device and a hepatitis C-seropositive nonstandard donor, one might allocate such a potentially higher risk donor heart to a patient in whom the excess risk is justified (for example, an older patient with previous cardiac surgery). Nonstandard organs would not necessarily be allocated to a much younger recipient who is not in extremis.
14 This also depends on the circumstances leading to the organs being nonstandard. Thus the concept of matching donor and recipient risk remains fluid and is adjusted for each individual.
What if there are no available recipients for a nonstandard donor? About a third of such donor organs offered to our program cannot be allocated, and therefore a strategy to offer these unused organs to patients who would otherwise not be offered transplantation (mostly because of age) was developed. The current single list system for adult recipients does not formalize this concept. We informed these patients about the risks involved in using such donor organs and explained that they are usually turned down or used only for certain status I patients. We observed that we could decrease the number of unallocated organs and use them for a specific group of the potential recipient pool. Median age for alternate recipients was 67 years, compared with 54 years for regular list patients. The comparison group comprised all patients that could have potentially used the donor hearts allocated to the alternates by virtue of size.
We found that between 1992 and 1999 a third of nonstandard organs accepted by our program went to alternates. This demonstrates that most are being used selectively in regularly listed recipients in whom the added risk is justified.
8,15,16 Older donors allocated for the alternate list in this study were always associated with another risk, including no coronary angiogram available, CAD, or long distance. Among the 62 alternates, 6 received hearts from donors older than 45 years old. In this study older donor age slightly influenced late mortality, as did longer ischemia. The quadratic effect of donor age on graft CAD may be explained by a previous observation that early mortality is increased for the donor age range of 35 to 55 years, reflecting a more cautious selection bias when using older donors.
17
Our preservation method was adapted to retrieve higher risk hearts from outside our local area. Alternate recipients had longer mean graft ischemia times. We also observed that the hearts used for alternates came from donors who more often had died of aICB. This was a risk factor on multivariable analysis of groups I and II combined and an even stronger risk when only the alternates were analyzed. This has been noted to be a sensitive but not specific marker for both short- and long-term mortalities and is probably a surrogate for undetected left ventricular hypertrophy.
18
Alternates who underwent transplantation were older than regular list recipients and more frequently had ischemic cardiomyopathy. These findings suggest less end-organ reserve and higher risk. The significantly increased 90-day mortality for alternates was explained by the observation that the risk factors for early mortality in this study were previous cardiac surgery, poor renal function, and donor death from aICB. This increased risk (18% vs 9%) supports keeping these patients on a separate list with consent in advance. Alternates were able to benefit from the shorter waiting times relative to status II patients on the regular list (median 107 vs 158 days).
On the basis of our early results, the age for alternate listing was raised from 65 to 70 years in 1998, according to the reasoning that heart transplants in those older than 65 years was feasible and should not be withheld. The number of alternates newly listed and undergoing transplantation decreased, perhaps reflecting the fact that the current number of patients older than 70 years who require heart transplantation and are acceptable surgical candidates is low. Shorter waiting times were also noted. This led to our current policy of offering both alternate and regular listing for patients older than 65 years. Alternate listing only is offered to those older than 70 years.
Three of the early deaths were associated with donor CAD, LVH, and long distance from the center; we no longer consider organs with such a triple combination of risk factors. Individually, donor hearts with these risk factors are allocated to status I or alternate recipients (CAD) and to smaller size status I or alternates (LVH). Long distance aggravates LVH.
8 Other deaths were from multisystem organ failure related to recipient risk factors in combination with generally higher risk donors. Three had renal insufficiency as well as representing retransplantation. One patient who died of volvulus illustrates the pathologic features specific to aging. Multivariable analysis of the factors affecting early mortality specifically in alternates alone did not show any recipient trends. After 90 days the death rates for both groups were comparable. On the basis of preoperative maximal oxygen consumption, this current survival is better than that which would be expected if these patients did not undergo transplantation.
19 A separate report on quality of life among these generally older recipients is needed to better define this benefit.
Freedom from rejection for alternates within the first year was 90%, versus 70% for those on the regular list. This lower rejection rate was probably due to immunosenescence in older patients, which permits a reduced immunosuppression in these patients. All recipients in our institution are started on cholesterol-lowering therapy.
20,21 Alternate recipients did not have increased graft CAD, after those receiving hearts with preexisting disease were excluded. To date, the longest survival of a revascularized donor heart is more than 7 years. Donor CAD appeared to be a risk factor for early graft failure when combined with other factors that aggravated ischemic insult but not independently when selectively used.
Alternate recipients currently account for about 10% of our program's yearly transplants. This model may provide a partial solution for the current increased waiting times for heart transplantation and the growing number of older recipients. Such a strategy might be complemented by destination therapy with mechanical devices should these alternately listed patients require continuous inotropic support.
| Members of the heart transplant program, University of California, Los Angeles |
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| Appendix: |
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| Footnotes |
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| References |
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