Non-invasive approaches for the diagnosis of acute cardiac allograft rejection

Despite modern immunosuppressive regimes, acute rejection remains a leading cause of morbidity and mortality in heart transplant recipients. Clinical features are unreliable, and therefore, screening is performed in order to detect rejection, and hence, augment immunosuppressive therapy, at an early stage, with the aim of reducing short- and long-term sequelae. Histological analysis of right ventricular myocardial tissue obtained at endomyocardial biopsy remains the 'gold standard' surveillance technique; however 'biopsynegative' rejection occurs in up to 20% of patients, the procedure is associated with uncommon but potentially serious complications and it is expensive. Non-invasive screening would, conceivably, be safer, more tolerable and cheaper, and could potentially allow more comprehensive monitoring. The evidence for non-invasive methods of diagnosing acute rejection, including assessment of myocardial deformation, myocardial tissue characterisation, electrophysiological monitoring, visualisation of cellular and molecular components of rejection and peripheral monitoring of immune activation, is reviewed.