key: cord-0723753-f9c78qew
authors: Mai, Xingchen; Alvarez, Paulino A.; Rodriguez, E. Rene; Tan, Carmela D.; Boyle, Gerard J.
title: Microvesicular Steatosis and Severe Cardiac Allograft Dysfunction
date: 2022-02-10
journal: Transplant Direct
DOI: 10.1097/txd.0000000000001290
sha: a956d25765ad9a183b1dc77d13eb7a021d1f9a45
doc_id: 723753
cord_uid: f9c78qew

nan

Cardiac allograft dysfunction due to rejection is a potentially fatal phenomenon that requires rapid evaluation and treatment. Myocardial steatosis refers to the accumulation of lipids in the myocardium and can be defined as macrovesicular or microvesicular depending on the lipid droplet size.

We report on 3 patients who presented with acute severe cardiac allograft dysfunction and microvesicular steatosis.

A 16-mo-old girl with a history of restrictive cardiomyopathy probably associated with MHY7 mutation presented with cardiogenic shock 1 mo after heart transplantation because of severe biventricular dysfunction. The patient had preexisting donor-specific antibodies (DSAs)‚ but repeat DSA testing on admission revealed de novo DSAs and increased mean fluorescence intensity of preexisting DSAs (Table 1) . She was started on intravenous milrinone and treated with high-dose corticosteroids for presumed acute allograft rejection. Endomyocardial biopsy (EMB) showed mild acute cellular rejection (ACR) (International Society for Heart and Lung Transplantation [ISHLT] grade 1R) with negative immunofluorescence staining for markers of antibody-mediated rejection (AMR)-C3d and C4d; however, the myocytes showed numerous small vacuoles in the sarcoplasm on hematoxylin and eosin that stained positive for fat on oil red O (ORO) stain in frozen sections. The initial working diagnosis was microvesicular steatosis, probably related to an adverse drug reaction. Her medications included mycophenolate, tacrolimus, sulfamethoxazole-trimethoprim, valganciclovir, Nystatin, melatonin, furosemide, and famotidine. Given previous reports of calcineurin inhibitors (CNIs) associated with hepatic steatosis after liver transplant, tacrolimus was held. 1 There were no rash or eosinophilia on admission. Notably, the patient was not on steroids per standard pediatric transplant protocol. Laboratory findings were not consistent with carnitine deficiency. Liver enzymes were normal, and ultrasound and liver biopsy did not reveal hepatic steatosis. Over the next few days, cardiac function and hemodynamics improved, and immunosuppressants were restarted. On hospital day 9, she progressed to worsening cardiogenic shock. Repeat cardiac biopsy still exhibited microvesicular steatosis but was less extensive; however, immunofluorescence for C3d and C4d were now positive, and DSAs continued to rise. Plasmapheresis and intravenous immunoglobulin (IVIG) were administered. Hemodynamics recovered, DSA values stabilized, and a third cardiac biopsy showed resolution of microvesicular steatosis. She was discharged on hospital day 33. The patient has been doing well with no recurrent allograft dysfunction or pathologic findings of microvesicular steatosis in the subsequent 6 y. There has been no evidence of cardiac allograft vasculopathy in recent follow-up coronary angiograms.

An 8-y-old girl with dilated cardiomyopathy presented with dyspnea, epigastric discomfort, and emesis 4 mo after her second heart transplant with cardiogenic shock because of severe biventricular dysfunction.

The patient received high-dose corticosteroids and intravenous milrinone. EMB performed on day 1 of hospitalization revealed moderate ACR (ISHLT grade 2R) and no histopathological or immunopathological evidence of AMR. DSA testing on admission did not show de novo DSAs or increased intensity of preexisting DSAs (Table 1) The patient's hemodynamics deteriorated, requiring multiple inotropic and vasopressor agents. Although the biopsy did not suggest AMR, she was started on plasmapheresis, IVIG, and rituximab in the setting of refractory shock. Despite aggressive therapy, the patient progressed into multisystem organ failure and expired on hospital day 27. Postmortem tissue analysis found extensive vacuolization of the cardiomyocytes, hepatocytes, and renal tubular epithelial cells. ORO staining confirmed microvesicular steatosis in these cells. The donor's heart showed mild cellular rejection, negative C3d and C4d staining, and no evidence of allograft vasculopathy. Previous heart allograft did not show evidence of microsteatosis.

A 61-y-old woman with a history of heart transplant 2 y prior for advanced heart failure due to nonischemic cardiomyopathy presented to the Emergency Department with cardiogenic shock. Five weeks before presentation, she was diagnosed with COVID-19 by polymerase chain reaction test via nasopharyngeal swab and reported mild symptoms. Left ventricular ejection fraction was 15%. Repeat SARS-CoV-2 nasopharyngeal swab polymerase chain reaction test was negative. She was given high-dose corticosteroids, antithymocyte globulin, dobutamine, and an intra-aortic balloon pump was placed. Mechanical circulatory support was exchanged for an axillary Impella 5.5 due to refractory shock. EMB on the first day of her hospitalization showed ACR ISHLT grade 1R and no AMR. There was focal mild myocyte vacuolization positive for ORO staining, consistent with microvesicular steatosis.

Admission DSA testing revealed de novo DSAs with significantly elevated mean fluorescence intensity (Table 1) . She had no DSAs and no history of AMR before this admission. After initial therapies, the patient improved allograft function to left ventricular ejection fraction 35%, and hemodynamics allowed mechanical and inotropic support removal. Repeat biopsy on hospital day 9 revealed more extensive microvesicular steatosis, markedly increased from the previous biopsy, with stable ACR and no AMR ( Figure 1A and B) . Cardiogenic shock recurred, requiring inotrope and intra-aortic balloon pump. She underwent plasmapheresis and IVIG. Additional EMB on hospital day 16 did not show any change in ACR and still no AMR, but there was a significant reduction in microvesicular steatosis ( Figure 1C ). Electron microscopy did not reveal viral particles ( Figure 1D ). The patient developed intracranial hemorrhage on hospital day 21 and multisystem organ failure, and she expired on hospital day 29. An angiogram performed 12 mo before admission showed no evidence of cardiac allograft vasculopathy.

To our knowledge, this is the first report describing the presence of myocardial microvesicular steatosis in patients presenting with severe cardiac allograft dysfunction. In humans, myocardial steatosis has been reported in coronary artery disease and aortic stenosis. 2,3 Decreased fatty acid utilization, reduced energy production by a reduction in the respiratory chain and adenosine triphosphatase activity, and decreased availability of high energy phosphates are among the metabolic abnormalities described in heart failure. 4 Animal models have shown that cardiac-restricted long-chain acyl CoA synthase overexpression, administration of pyruvate kinase inhibitors, and inactivation of pituitary adenylate cyclase-activating polypeptide can all disrupt mitochondrial fatty acid metabolism and lead to lipid vacuolization in multiple tissues, including the heart, liver, and skeletal muscle. [5] [6] [7] Microvesicular fat accumulation in multiple organs is a hallmark of Reye syndrome. [8] [9] [10] This disorder is characterized by rapidly progressive encephalopathy, usually occurring after recovery from a viral illness, such as influenza and varicella, and is strongly associated with salicylate use. 11 Neither of the pediatric patients in our cohort had known salicylate exposure.

In patient 1, CNI were placed on hold because of their potential relationship with microsteatosis in liver transplantation. 12 The adverse metabolic effects of CNI have been well described. Still, their link to the development of steatosis is uncertain. 1 Drugs that have been associated with microvesicular steatosis include amiodarone, aspirin, steroids, and ibuprofen. Our patient was not exposed to any other potential medication. Holding the CNI leads to the expression of graft rejection as the possible mechanism of allograft dysfunction. The relationship of microsteatosis as an initial marker of metabolic stress in the context of early rejection cannot be ruled out.

In patient 2, moderate cellular rejection and allograft dysfunction were the presenting features and clinical course worsening despite aggressive immunosuppression. Microvesicular steatosis in cardiac allograft, liver, and kidneys makes the case of immunological mediated injury unlikely. Interestingly, acylcarnitine serum levels were low despite normal serum concentrations 6 y prior. The link between hemodynamic stress, multiorgan failure, and acquired carnitine deficiency leading to multiorgan microsteatosis has not been described but is biologically plausible. 13 Patient 3 presented with severe allograft dysfunction and microsteatosis that resolved with antirejection therapy. Whether hemodynamic stress or biopsy-negative rejection were the causes leading to steatosis is unknown. 14 Patient 3 was on daily aspirin 81 mg, but there is no known evidence suggesting adult salicylate use is a risk factor for Reye syndrome. Patient 3 did acquire a viral illness with COVID-19 5 wk antecedent to her admission. COVID-19 myocarditis has led to cases of cardiogenic shock, and viral particles of SARS-CoV-2 have been identified within the myocardium 15 ; however, no viral particles were discovered on the electron microscopy of patient 3. Myocardial microvesicular lipid infiltration has been reported in a case of toxic shock syndrome, but none of our patients met the criteria for this condition. 16 Gene expression profiling studies have shown that myocardial samples obtained during an episode of rejection have decreased activity of mitochondrial-related genes and increased activity of immune response genes. 17 Chronic tumour necrosis factor-alpha exposure alters mitochondrial function through the activation of nuclear factor-kappa B. 18 Anticardiac antibodies directed against ATP synthase have been reported in end-stage heart failure. 19 A potential diagnostic and therapeutic approach to microsteatosis in an EMB includes: (1) rule out potential medications associated with steatosis; (2) evaluate the presence of metabolic disorders related to steatosis; (3) evaluate and treat causes of metabolic stress such as allograft rejection and cardiogenic shock.

Magnetic resonance spectroscopy can measure myocardial triglyceride content and correlates well with histological quantification providing a potential tool for the noninvasive diagnosis of myocardial steatosis. 3 In conclusion, we reported 3 cases of microsteatosis detected in the EMB sample obtained in the context of cardiac allograft dysfunction. Further research is needed to understand the significance and potential links between microvesicular steatosis and cardiac allograft dysfunction and whether these findings may be a response to injury or treatments.

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Heart fat infiltration in subjects with and without coronary artery disease

Myocardial steatosis and left ventricular contractile dysfunction in patients with severe aortic stenosis

The failing heart-an engine out of fuel

Hyperleptinemia prevents lipotoxic cardiomyopathy in acyl CoA synthase transgenic mice

Myocardial steatosis and necrosis in atria and ventricles of rats given pyruvate dehydrogenase kinase inhibitors

Immunometabolic cross-talk in the inflamed heart

Pathologic changes in a rabbit model of Reye's syndrome

Pathology of the heart in Reye's syndrome (encephalopathy and fatty degeneration of the viscera)

Reye's syndrome associated with acute myocarditis and fatal circulatory failure

Reye's and Reye's-like syndromes

Ischemic stroke after heart transplantation

Role of carnitine in disease

Biopsy-negative cardiac transplant rejection: etiology, diagnosis, and therapy

The enemy within: sudden-onset reversible cardiogenic shock with biopsy-proven cardiac myocyte infection by severe acute respiratory syndrome coronavirus 2

A variant of toxic shock syndrome. Clinical, microbiologic, and autopsy findings in a fatal case

Rejection-associated mitochondrial impairment after heart transplantation

Targeted disruption of the pituitary adenylate cyclase-activating polypeptide gene results in early postnatal death associated with dysfunction of lipid and carbohydrate metabolism

High proportion of patients with end-stage heart failure regardless of aetiology demonstrates anti-cardiac antibody deposition in failing myocardium: humoral activation, a potential contributor of disease progression