Objectives: Invasive pulmonary aspergillosis is the most common invasive mycosis in heart transplant recipients. Early clinical recognition of this complication is difficult and laboratory data is not specific. Our aim was to study the characteristics of invasive pulmonary aspergillosis infections in heart transplant recipients.

Materials and Methods: Between 2007 and 2013, there were 82 patients who underwent heart transplant at our institution, including 6 patients who were diagnosed with invasive pulmonary aspergillosis. Medical records of these patients were reviewed for demographic, clinical, and radio­graphic features, microbiology data, serum galactomannan levels, antifungal treatment, and overall outcomes.

Results: The most common species causing the infection was Aspergillus fumigatus. The infection was encountered irrespective of the duration since the transplant. Bronchoalveolar lavage with positive culture for Aspergillus species and/or abnormal serum galactomannan level was suggestive of invasive pulmonary aspergillosis.

Conclusions: In our opinion, empiric antifungal therapy should be commenced as soon as invasive pulmonary aspergillosis is suspected in heart transplant recipients to reduce mortality. Although the duration of antifungal therapy for invasive pulmonary aspergillosis is debatable, heart transplant recipients may require long-term therapy to avoid recurrence.

Key words : Aspergillus fumigatus, Fungus, Galactomannan, Lung infection

Introduction

Invasive fungal infections are an important cause of morbidity and mortality in the recipients of solid-organ transplant.¹ In this population, infection with Aspergillus species can produce several clinical presentations including sinusitis, tracheobronchitis, pneumonia, necrotizing cellulitis, brain abscess, or disseminated disease.² In heart transplant recipients, the fungus Aspergillus most frequently causes pneumonia and is the opportunistic pathogen with the highest attributable mortality.^3-6 Although invasive aspergillosis is a serious disease in this population, little is known about its natural history.

We performed a retrospective chart review of patients who underwent heart transplant at our institution and developed invasive pulmonary aspergillosis (IPA). The objective of our study was to further establish the characteristics of IPA infections in this population.

Materials and Methods

Study population
Patients who underwent heart transplantation at Başkent University School of Medicine between 2007 and 2013 and developed IPA were identified from our transplant database and clinical laboratory information system. Demographic and clinical variables were abstracted onto a data form. These variables included patient age, sex, primary diagnosis, date of transplant, serum galactomannan level, known risk factors for IPA, incidence of rejection, cytomegalovirus infection, immuno­suppressive regimen, radiographic features, prophylactic maneuvers, follow-up, outcomes, bronchoscopy data, and microbiology data. Follow-up information was obtained on all patients for a minimum 2 years after transplant.

Diagnostic criteria
Cases of IPA were identified according to the Clinical Practice Guidelines of the Infectious Diseases Society of America for IPA.⁷ The diagnosis was considered definite when the patient had positive histology and culture of a sample obtained from the same site or negative histology (or none done) and positive culture results of a sample obtained by protocol-specified invasive techniques such as broncho­alveolar lavage (BAL), bronchial washings, brushings, or needle aspiration. The diagnosis was considered probable when the heart transplant recipients with unexplained respiratory symptoms had abnormal chest radiographic findings and an invasive procedure was contraindicated; had 2 positive cultures of either sputum or throat samples or 1 positive culture or smear result of any broncho­scopy specimen; or met criteria for definite invasive aspergillosis in any other organ system. Results are expressed as “galactomannan index,” by comparison to the cutoff control. Galactomannan indexes of 1 or higher are regarded as positive. Positive serum galactomannan level suggested the diagnosis of IPA in which false positive results were excluded. Some antibiotics may cause false-positive results. The greatest problem has been in patients receiving piperacillin-tazobactam, amoxicillin or amoxicillin-clavulanate.

Statistical analyses
Data from case forms were extracted, entered into a central database, and analyzed.

Results

Subjects
We identified 6 patients with IPA in 82 patients who underwent heart transplant between 2007 and 2013 at our institution. The mean age of the entire heart transplant recipient group was 33.8 ± 18 years (range, 2-61 y) and there were 58 males and 24 females. Selection criteria for recipients and donors were as described previously and were constant during the study.⁶ Operative techniques did not markedly change during the study.

Immunosuppression, rejection, and prophylaxis
Each patient received prednisone, either azathioprine or mycophenolate mofetil, and either tacrolimus or cyclosporine as part of the antirejection regimen. All patients were on trimethoprim and sulfamethoxazole prophylaxis for Pneumocystis jiroveci pneumonia.

Invasive pulmonary aspergillosis cases
All IPA cases were male patients with a mean age of 52.5 ± 9.7 years (range, 38-61 y). The most common indication for heart transplant was dilated cardiomyopathy (83.3%) (Table 1). The most common symptoms of IPA were fever (n = 4) and cough (n = 3). Serum galactomannan level was abnormally high in 4 of 6 patients (Table 1). Aspergillus fumigatus grew in 50% cases on BAL culture. The onset of IPA varied between 30 days to 3 years after heart transplant. Each patient had abnormalities on chest radiography and thoracic computed tomography (Table 2). Multiple nodular consolidations were observed in all patients. A cavity was detected only in 1 patient. Voriconazole was prescribed in all patients for treatment (range, 1-12 mo) (Table 2). Only 1 patient (case 4) required the addition of intravenous amphotericin B due to resistant fever. Only 1 patient died because of the IPA infection.

Discussion

Since the introduction of heart transplantation as a therapeutic modality for end-stage congestive heart failure in 1968, Aspergillus has been recognized as a major opportunistic pathogen after transplant.8 During the past 30 years, major improvements have been introduced in immunosuppressive protocols, treatment of rejection, and prophylaxis against opportunistic infections. Since the introduction of cyclosporine in 1980, several immunosuppressive protocols have been suggested for heart transplant recipients. Initially, most patients who underwent heart transplant received prednisone, azathioprine, and cyclosporine as part of their immunosuppressive regimen. Subsequently, other immunosuppressive agents were added including muromonab-CD3 in June 1987 and mycophenolate mofetil and tacrolimus in February 1994. Ganciclovir was added as prophylaxis against cytomegalovirus in January 1987, and inhaled amphotericin B against fungi was added in July 1993. It is very likely that these pharmacologic modifications decreased the incidence of invasive aspergillosis in heart transplant recipients.⁵

Before the introduction of cyclosporine, the overall incidence of IPA was 27% and mortality from IPA was 60%.⁸ More recently, these numbers have decreased to 8% and 36%.⁵ It also has been suggested that the incidence of IPA has decreased markedly in heart transplant recipients receiving prophylactic inhaled amphotericin B.^5,9 However, inhaled ampho­tericin B prophylaxis has not been implemented at our institution.

The IPA remains a major cause of morbidity and mortality in heart transplant recipients. Patients with IPA more frequently present with fever with or without cough, usually within 3 months after transplant.¹⁰ Most of our patients also presented with these symptoms. These symptoms are vague and nonspecific but might be of value in interpreting a positive culture result for Aspergillus species, particularly within 3 months after transplant. In the present study, 50% cases were diagnosed during the first 90 days after heart transplant.

Risk factors for invasive aspergillosis include prolonged neutropenia, neutrophil function deficits, corticosteroid therapy, graft-versus-host disease, and cytomegalovirus infection.^11-14 In contrast with patients who have hematologic malignancies, neutropenia is not a risk factor for IPA in heart transplant recipients. None of our patients with IPA were neutropenic (absolute neutrophil count < 500 cells/mm³) at the time of diagnosis.

The radiographic findings of IPA in our patients were similar to those described in the literature. Multiple pulmonary nodules are the most common radiographic manifestation and were present in all our patients.^15-17 A cavitating nodule was present in only 1 of our patients but has been described to occur more frequently in this group of patients. Cavitation either may be present either at the time of detection of the nodule or may develop during the infection.^16,17 Although the computed tomographic halo sign has been proposed as a useful sign in the early diagnosis of IPA, we did not encounter this finding in our patients. This could be due to the small number of patients in our study. Cytomegalovirus infection is a risk factor for the development of IPA in solid-organ transplant recipients, but we did not observe this organism in our patients.^18,19

In conclusion, the incidence, morbidity, and mortality of IPA have steadily declined during the past 20 years. This is due most likely to the introduction of newer antirejection regimens and antifungal prophylaxis including inhaled amphotericin B. It also appears that these modifications have led to delayed appearance of IPA in this group. Patients with IPA usually present with respiratory symptoms and fever within the first 90 days after transplant. The most common radiographic findings include single or multiple pulmonary nodules. Cavitation or the halo sign may not always be present. Presence of neutropenia is not essential for the development of IPA. The advent of 2 new antifungal drugs with marked activity against Aspergillus species, voriconazole and caspofungin, may improve the outcomes of patients with IPA.²⁰ Although the duration of antifungal therapy for IPA is controversial, some patients may require therapy for a long duration to prevent recurrent IPA infection.^7,20 The development of IPA should be suspected in heart transplant recipients who present with fever and respiratory symptoms during the first 3 months after transplant, have a positive culture result for Aspergillus species, and have abnormal radiographic findings, especially nodules, even in the absence of neutropenia.

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