Heart Transplant Pathology - Introduction

Heart transplantation is still the most effective therapy for end-stage heart disease when medical therapy, surgical therapy and other devices have failed. This applies whether the heart failure it is secondary to coronary artery disease, or myocardial disease. There has been a continued improvement in survival over the years. In adults; 85% of cases are roughly equally divided between coronary heart disease and non-ischemic cardiomyopathies. In the pediatric age group, congenital heart disease is the leading diagnosis for recipients <1 year of age. Cardiomyopathy and congenital heart disease are the two most common indications for transplantation in children.  

The heart transplant surgery consists of removal of the diseased heart and replacement of it with a donor heart.  There are two main surgical techniques for implanting the donor heart: 1. Is a bi-atrial anastomosis and 2. a bicaval anastomosis.

The survival rate after ten year post-cardiac transplantation currently approaches 50% and better in high-volume centers. The success of heart transplantation, for the most part, has been achieved through better understanding of the immunology of transplant rejection and application of strategies for the recognition, treatment and prevention of rejection. In the early years of cardiac transplantation, failure resulted from a high incidence of acute cellular rejection that limited graft survival. The signs and symptoms of acute cellular rejection are often vague and there are no serological markers of cardiac allograft rejection. The treatment of rejection, in turn, was often complicated by infection, malignancy and drug toxicities that result from the difficulty in titrating immunosuppression to the desired endpoint according to the severity of rejection. The introduction of percutaneous transvenous endomyocardial biopsy by Caves et al in 1973 provided an objective means of diagnosing rejection and allowed for careful monitoring and prompt treatment of cardiac allograft rejection. Tan CD, Baldwin WM, Rodriguez ER: Update on Cardiac Transplantation Pathology. Arch Pathol Lab Med 2007: 131; 1169-1191

The survival of patients depends on accurate monitoring of the rejection process.   Rejection is monitored by means of an endomyocardial biopsy.  Three main types or rejection can occur and harm the transplanted heart.   Hyperacute rejection is a devastating process that occurs at the time or transplantation due to massive activation of the complement system because of pre-existing antibodies.  Fortunatelly this type of rejection is nowdays extremely rare.  The two more common types of rejection reflect which arm of the immune response is most active in the process.  Thus they are named accordingly cellular rejection and humoral rejection (or antibody mediated rejection (AMR) which is the preferred term). Although, historically AMR has also been called vascular rejection and microvascular rejection. 

The endomyocardial biopsy interpretation requires knowledge of other lesions present in the spectrum of heart transplant pathology such as Endocardial Lymphocitic Infiltrates (ELI) also know as Quilty effect lesions, peritransplant ischemia, late ischemia, previous biopsy sites, recurrent primary diseases and opportunistic infectious processes