Usefulness of routine surveillance endomyocardial biopsy 6 months after heart transplantation

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Usefulness of routine surveillance endomyocardial biopsy 6 months after heart transplantation Carlos M. Orrego, MD,a Andrea M. Cordero-Reyes, MD,a Jerry D. Estep, MD,a Matthias Loebe, MD, PhD,a and Guillermo Torre-Amione, MD, PhDa,b From the aThe Methodist DeBakey Heart and Vascular Center, Houston, Texas; and bCatedra de Cardiologia y Medicina Vascular, Escuela de Medicina, Tecnologico de Monterrey, Monterrey, Nuevo León, Mexico.

KEYWORDS: endomyocardial biopsy; transplant; rejection

BACKGROUND: Endomyocardial biopsy (EMB) remains the gold standard for detecting rejection episodes in orthotopic heart transplant (OTH) patients. Follow-up protocols vary widely between transplant centers. At our center, we have implemented a conservative strategy protocol and here we report our outcomes. METHODS: Patients from 2 cohorts were used for comparison analysis. OHT recipients from 1990 to 1995 comprised the standard strategy group, and those from 2004 to 2009 comprised the conservative strategy group. Survival outcomes and rejection episodes were compared between groups. RESULTS: Mean age at OHT was 56 ⫾ 10 years in the standard strategy group and 53 ⫾ 10 years in the conservative strategy group. Both groups were predominantly composed of white men. The etiology of congestive heart failure was ischemic cardiomyopathy in more than 50% of the patients in both groups. From 6 to 12 months after OHT, we found that the number of episodes of rejection/total number of EMBs was 4.9% (8/163) in the standard group vs 2.0% (1/50) in the conservative group. From 12 to 24 months after transplant, the rate was 2.5% (8/320) in the standard group vs 11.9% (5/42) in the conservative group (p ⬍ 0.05). CONCLUSIONS: Surveillance EMB after 6 months post-OHT in patients receiving contemporary immunosuppression is associated with a low yield of EMB-confirmed rejection in the absence of a clinical indication or echocardiographic findings that support clinical rejection. Most episodes of cellular rejection are mild and do not warrant treatment or a change in immunosuppression. The frequency of EMBs did not correlate with an increased risk of cardiac allograft vasculopathy or death. J Heart Lung Transplant 2012;31:845–9 © 2012 International Society for Heart and Lung Transplantation. All rights reserved.

Endomyocardial biopsy (EMB) is the gold standard method for detecting episodes of acute cellular rejection in patients after orthotopic heart transplantation (OHT). Although other noninvasive methods, such as echocardiography, magnetic resonance imaging, and analysis of serum biomarkers,1 have been suggested as promising alternatives to EMB, none of these methods have been shown to be useful clinically. Therefore, analysis of EMB specimens is still the standard method for detecting cellular rejection during the first 5 years after OHT in many transplant centers worldwide. With the advent of novel immunosuppressive therapies, including calcineurin inhibitors and mycophenolate mofetil Reprint requests: Guillermo Torre-Amione, MD, PhD, 6550 Fannin St, Houston, TX 77030. Telephone: 713-441-2761. E-mail address: [email protected]

(MMF), the risk of significant rejection has decreased from 70% to 20% to 40%,2–5 with most rejection episodes occurring during the first 6 months after OHT. As a result, the overall benefit of routine surveillance EMB after 12 months post-OHT has become controversial. The estimated risk of cellular rejection after 12 months post-OHT is about 1%. The risk of EMB-related complications, which include pericardial tamponade and severe tricuspid regurgitation,6 – 8 as well as the patient’s discomfort and anxiety, are between 0.2% and 3%. Recently, the Invasive Monitoring Attenuation Through Gene Expression (IMAGE) group9 demonstrated that gene expression profiling is as good as EMB for surveillance in selected patients after 6 months post-OHT, which raises the question of when to discontinue routine surveillance EMBs. In the late 1990s, our group found that the risk of acute cellular rejection was low and, as a consequence, instituted

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a protocol in which routine surveillance EMB was performed only during the first 6 months after OHT (conservative strategy) or as clinically indicated after that period. Because the survival rate of our center is similar to other transplant centers, despite using a different surveillance protocol, we aimed to demonstrate that the conservative EMB strategy is equally effective as the standard EMB strategy in patient outcomes and survival.

Methods This study was done in accordance with a protocol approved by The Methodist Hospital Research Institute Institutional Review Board.

Data collection Data were collected from the Cardiac Transplant Database at The Methodist Hospital, and hospital records were reviewed for pathology reports. We collected each right heart catheterization report and included each pathology report in which adequate samples were obtained to determine a rejection score.

Patient population Data from adult patients in the Cardiac Transplant Database who underwent OHT during the years 1990 to 1995 and 2004 to 2009 were reviewed. The study included 256 patients. The 2 patient cohorts, with 128 patients each, were defined as the standard strategy group and the conservative strategy group. The patients in the standard group underwent OHT from 1990 to 1995 and had surveillance EMB per protocol at 1, 2, 3, 4, 6, 8, 10, 12, 16, 20, and 24 weeks, at 9, 12, 18, 24, and 30 months, and at 3 and 5 years. The conservative group underwent OHT from 2004 to 2009 and had surveillance EMB at 1, 2, 3, 4, 6, 8, 10, 12, 16, 20, and 24 weeks. In both groups, additional EMB specimens obtained for clinical indication were counted as EMBs after 6 months post-OHT. In the conservative group, EMBs for protocol per se were not performed unless there was a clinical indication, such as symptoms and signs associated with acute cellular rejection, instances in which graft function could be compromised (ie, infection), or a decrease in left ventricular ejection fraction (LVEF) of more than 10 points.

Definitions A positive EMB specimen was defined as grade 2R (moderate) and/or grade 3R (severe) according to the 2004 International Society for Heart and Lung Transplantation (ISHLT) classification. Previous EMB specimens that were classified by the 1990 ISHLT or the Texas Heart classifications were reviewed by a pathologist and converted to the current classification system. Cardiac allograft vasculopathy (CAV) was defined according to the recommended 2010 ISHLT classification.10

Table 1

Demographics of Heart Transplant Population Biopsy strategy

Variablesa Diagnosis Cardiomyopathy Ischemic Idiopathic dilated Other Age at transplant, years Sex Male Female Race White Black or African American Hispanic or Latin American Other Comorbidities Diabetes mellitus COPD Peripheral vascular disease Hyperlipidemia BUN, mg/dL Creatinine, mg/dL Immunosuppressive regimen Cyclosporine Tacrolimus Azathioprine MMF Azathioprine or MMF Prednisone

Standard (n ⫽ 128)

Conservative (n ⫽ 128)

72 (56.3) 38 (28.1) 12 (15.6) 56.5 ⫾ 10.4

85 (66.4) 25 (19.5) 18 (14) 55.3 ⫾ 10.7

107 (84) 21 (16)

100 (78) 28 (22)

106 6 7 9

(84) (4) (6) (7)

79 23 21 5

(62)b (18)b (16)b (4)

12 (9.1) 2 (1.6) 3 (2.4) 30 (23.6) 23.7 ⫾ 12.8 1.3 ⫾ 0.4

46 (36)b 8 (6) 10 (8) 61 (48)b 25.9 ⫾ 12.4 1.3 ⫾ 0.7

113 0 91 ... 12 113

70a 58a ... 120 ... 125

BUN, blood urea nitrogen; COPD, chronic obstructive pulmonary disease; MMF, mycophenolate mofetil. a Categoric data are presented as number (%) and continuous data as mean ⫾ standard deviation. b p ⬍ 0.05.

Statistical analysis Results are reported as mean and standard deviation, with p ⬍ 0.05 considered significant. A Kaplan-Meier curve was constructed to compare survival at 1 and 2 years in the 2 strategy groups. Patients who died before 6 months after OHT were not included in the analysis. Results are reported as episodes of rejection per total number of biopsies for 2 time periods, from 6 to 12 months and 12 to 24 months after OHT. To evaluate the correlation between the number of episodes of rejection and the development of CAV, a Pearson correlation analysis was performed in the group that underwent OHT from 1990 to 1995.

Results End points The primary end point assessed was death at 6 months and at 1 and 2 years after OHT. Secondary end points included the number of episodes of moderate and severe rejection per biopsy and per year with scheduled biopsies.

The patient demographics for both groups are summarized in Table 1. Mean age at transplant was 56 ⫾ 10 years in the standard strategy group and 53 ⫾ 10 years in the conservative strategy group. Both groups were predominantly composed of white men. The etiology of chronic heart failure was ischemic

Orrego et al. Table 2

Utility of Routine EMB After OHT

847

Biopsies and Rejection Episodes in Conservative and Standard Strategy Groups Over Time 0–6 months

Variable Biopsies, No. Patients, No. Average biopsies/patient Rejection episodes 1R 2R 2R rejection episodes/ total biopsies Rejections/total biopsies, %

ⱖ12 months

6–12 months

Conservative

Standard

Conservative

Standard

1,063 128 8.3

1,121 128 8.8

50 115 0.4

163 102 1.6

... ... ...

... ... ...

49 1 1/50

155 8 8/163

...

...

2

4.90

cardiomyopathy in more than 50% of the patients in both groups. More comorbidities, including diabetes mellitus, peripheral vascular disease, and dyslipidemia, were observed in the conservative strategy group. The immunosuppressive therapy for this group included cyclosporine A (CsA) or tacrolimus, MMF, and prednisone. In the standard group, all patients were taking CsA and prednisone, as well as azathioprine or MMF. During the first 6 months after OHT, 1,063 EMBs were performed in 128 conservative group patients, an average of 8.3 EMBs per patient (Table 2), and 1,121 EMBs were performed in 128 standard group patients, an average of 8.8 EMBs per patient. In contrast, between 6 and 12 months after OHT, only 50 EMBs were obtained in 115 patients in the conservative group, for an average of 0.4 biopsies per patient, whereas 163 biopsies were obtained in 102 patients in the standard group, for an average of 1.6 biopsies per patient (p ⫽ 0.04). Finally, after 12 months post-OHT, 42 EMBs were performed in 110 patients in the conservative group, for an average of 0.3, and 320 EMBs were performed in 98 patients the standard group, for an average of 3.2 (p ⫽ 0.001). During the 6 to 12 months after OHT, there were 155 grade 1R and 8 grade 2R rejections in the standard group compared with 49 grade 1R and 1 grade 2R rejections in the conservative group. After 12 months post-OHT, there were 312 grade 1R and 8 grade 2R rejections in the standard group compared with 37 grade 1R and 5 grade 2R rejections in the conservative group.

p-value

Conservative

Standard

0.04

42 110 0.3

320 98 3.2

37 5 5/42

312 8 8/320

11.9

2.5

⬍0.05

p-value

0.001

⬍0.05

From 6 to 12 months post-OHT, the number of episodes of rejection/total number of biopsies was 4.9% (8/163) in the standard group vs 2.0% (1/50) in the conservative group. From 12 to 24 months post-OHT, the rate was 2.5% (8/320) in the standard group vs 11.9% (5/42) in the conservative group (p ⬍ 0.05). In the conservative strategy group, 5 of 6 patients who had grade 2R rejection after 6 months post-OHT presented with symptoms resembling heart failure (dyspnea, orthopnea, fatigue) and depressed LVEF on echocardiogram (LVEF ⬍ 30%). These patients were treated appropriately, with excellent outcomes (Table 3). During the period of 6 months to 2 years after OHF, 12 patients died in the standard group: 5 of cardiovascular causes and 7 of non-cardiovascular causes such as sepsis and multiorgan failure (Table 4). In the conservative group, 9 patients died: 2 of cardiovascular causes and 7 of noncardiovascular causes such as cancer, sepsis, and multiorgan failure. Similar mortality rates were observed in both groups, without significant differences in survival (p ⫽ 0.49) after up to 2 years follow-up (Figure 1). In the standard strategy group, CAV developed in 17 of 33 patients (in a 15-year cohort), of whom 12 had CAV grade 1, 3 had CAV grade 2, and 2 had CAV grade 3. The major vessel affected was the left anterior descending artery. In the conservative strategy cohort, 3 of 39 patients developed CAV grade 1 (mild) at 5-year follow-up angiography. To evaluate whether a correlation existed between

Table 3 Patients in the Conservative Strategy Group With One Rejection Episode During the Period of 6 to 24 Months After Orthotopic Heart Transplantationa Pt

Rejection (No.)

Class

Clinical presentation

Echo EF (%)

Immunosuppression

1 2 3 4 5 6

1 1 1 1 1 1

2R 2R 2R 2R 2R 2R

CHF CHF CHF CS CHF CS

30 30 22 20 22 20

Cyclosporine Cyclosporine Cyclosporine Cyclosporine Cyclosporine Cyclosporine

CHF, congestive heart failure; CS, cardiogenic shock; EF, ejection fraction.

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Table 4 Cause of Death After 6 Months Post-orthotopic Heart Transplantation Group

No. (%)

Standard strategy Non-cardiovascular Sepsis Multiorgan failure Cardiovascular Acute rejection Cardiac allograft vasculopathy Conservative strategy Non-cardiovascular Sepsis Shock Cancer Cardiovascular Cardiac allograft vasculopathy

12 (100) 3 (25) 4 (33) 3 (25) 2 (17) 9 (100) 4 (44) 1 (11) 2 (22) 2 (22)

the number of episodes of rejection and the development of CAV (1, 2, or 3), we performed a Pearson correlation analysis between the number of episodes of rejection (⬍ 3 and ⬎ 3 EMBs per total years lived) and the development of CAV. No correlation was found between episodes of rejection and CAV (p ⬎ 0.05).

Discussion The use of routine EMB for monitoring cardiac allograft rejection was introduced by the Stanford group in 1972. Since then, nearly all heart transplant centers worldwide have used similar surveillance protocols. However, in the era of improved immunosuppressive therapy, lower rejection rates, and reduced rejection-related mortality,11 the significance of using the EMB surveillance strategy several years after OHT may be questionable. The number of cellular rejection episodes after OHT requiring intensification of immunosuppression is low, ranging from 1.2 to 1.8 episodes per patient during the first year after OHT.12 In addition, between 60% and 85% of moderate rejection episodes can have spontaneous resolution, and those that progress to higher rejection scores usually occur during the first 6 months after OHT.13,14 Therefore, intensive routine EMB may not have a significant effect on clinical decision making, and less invasive strategies to identify rejection episodes, especially after the first year after OHT, are advocated. In this study, we found that during the period of 6 to 24 months after OHT, most patients in the standard and conservative groups had mild rejection (1R) that did not require any adjustment in immunosuppression (Table 2). In addition, the incidence of significant rejection (⬎ 2R) between 6 and 12 months after OHT was significantly lower in the conservative group than in the standard group (2% vs 4.9%). These results confirm the previous observation of a low incidence of significant, biopsy-detected rejection in patients receiving triple immunosuppression (CsA, MMF or azathioprine, and prednisone) within the first year after OHT.15 In our cohort, however, the total incidence of

significant rejection between 6 and 24 months was 3.3% (16 of 465) in the standard group compared with 6.4% (6 of 92) in the conservative group. The explanation for the higher incidence in the conservative group is that EMB was performed only as clinically indicated by symptoms or echocardiographic findings, resulting in a higher yield of EMB-detected rejections (Table 2). Interestingly, the patients in the conservative strategy group who experienced episodes of biopsy-proven cellular rejection after 6 months were taking CsA and all presented with signs and symptoms of heart failure and LV dysfunction confirmed by echocardiography (Table 3) for which the EMB was obtained. Levi et al16 reported that the EMB yield in the pediatric population depends on which calcineurin inhibitor is used and whether the patient has symptoms. The incidence of cellular rejection in their study was 0.85% in the tacrolimus group vs 4.1% in the CsA group, and the yield of EMB-detected rejections for patients taking tacrolimus was only 0.26% in asymptomatic vs 9.1% in symptomatic patients. These findings suggest that surveillance EMB is useful only when there is a high probability of acute cellular rejection based on clinical or echocardiographic findings, and routine surveillance EMB after 6 months postOHT would not be necessary if tacrolimus is used as part of the triple immunosuppressive therapy. In a study similar to ours in pediatric OHT patients, Braunlin et al17 demonstrated that the use of surveillance EMB after 6 months was unlikely to show rejection in the absence of symptoms or abnormal test results.17 In addition, the IMAGE study, in which gene expression profiling was compared with EMB, only 6 of 34 treated rejection episodes were detected using gene-expression analysis. The remaining 28 rejections were detected due to the presence of heart failure symptoms or echocardiographic evidence of graft dysfunction.18 Taken together, these data raise the question of whether surveillance EMB or gene-expression profiling are really necessary after 6 months after OHT.19 An additional reason for performing surveillance EMB lies in the potential benefit of treating unsuspected cellular

Figure 1 Kaplan-Meier curve shows that survival rates for the standard strategy and conservative strategy groups are similar up to 2 years after heart transplant (day 0 represents 6 months after transplant).

Orrego et al.

Utility of Routine EMB After OHT

rejection that could have a significant effect in overall survival as well as decrease in the progression of CAV. A multi-institutional analysis to observe the influence of longterm surveillance EMB demonstrated that patient age at transplant, recipient ethnic origin (especially African American), and recipient rejection and infection history were predictors of late rejection with an effect in survival benefit.20 However, our data and recent data from the ISHLT registry demonstrate that acute cellular rejection represented less than 2% of the incidence of cause-specific death from 1992 to 2008.21 In our study, the causes of death after 6 months post-OHT in the conservative strategy group were not related to acute cellular rejection, and the number of patients who died of CAV in the standard and conservative groups was similar (Table 4). In addition, we did not see a correlation between the number of episodes of rejection and the development of CAV. Therefore, our study demonstrates that stopping surveillance EMB after 6 months is safe and is not associated with an increase in serious adverse outcomes. Performing fewer EMBs would have a significant effect on complications associated with this procedure, such as tricuspid regurgitation and patient discomfort. This study has similar limitations inherent to any retrospective analysis. EMB reports in the standard group were graded according to the 1990 ISHLT grading system and then converted by an experienced pathologist to the 2004 ISHLT grading system, which could have some interobserver and intraobserver variability. Different immunosuppression regimens were used in both groups; therefore, the risk of rejection was probably higher in the standard group. However, the overall risk for rejection in the conservative group was higher based on risk factors for acute cellular rejection. In conclusion, we demonstrate that surveillance EMB after 6 months post-OHT in patients receiving contemporary immunosuppression is associated with a low yield of EMB-confirmed rejection in the absence of a clinical indication or echocardiographic finding that supports clinical rejection. Most episodes of cellular rejection are mild and do not warrant treatment or a change in immunosuppression. In addition, the frequency of EMBs did not correlate with an increased risk of CAV or death. Further prospective studies are needed to confirm our findings.

Disclosure statement None of the authors has a financial relationship with a commercial entity that has an interest in the subject of the presented manuscript or other conflicts of interest to disclose.

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