Dilated cardiomyopathy following right ventricular pacing for AV block in young patients: resolution after upgrading to biventricular pacing systems.

INTRODUCTION: Cardiac resynchronization therapy (CRT) has been demonstrated to result in clinical improvement in older adult patients with dilated cardiomyopathy (DCM), specifically those with left bundle branch block and prolonged QRS duration. We sought to demonstrate the benefits of CRT on improvement in cardiac function and clinical outcome in young patients that developed congestive heart failure (CHF) and DCM following cardiac pacing for AV block. METHODS AND RESULTS: We reviewed the charts of six patients who developed CHF or low cardiac output symptoms and DCM following implantation of right ventricular (RV)-based pacing systems for AV block, and subsequently underwent CRT. Patients ranged in age from 6 months to 23.7 years (mean: 11.3 +/- 3.6 years). AV block was congenital (3), post-surgery (2), and acquired (1). Pacing had been performed for 0.1-14.5 (7.6 +/- 2.4) years prior to development of DCM. Two patients required listing for cardiac transplantation. Following CRT: (1) QRS duration shortened from 204 +/- 15 to 138 +/- 10 msec, P = 0.002, (2) left ventricular ejection fraction improved from 34 +/- 6 to 60 +/- 2%, P = 0.003, and (3) left ventricular end diastolic dimension shortened from 5.5 +/- 0.8 to 4.3 +/- 0.5 cm, P = 0.03. All patients demonstrated clinical improvement and have been weaned from CHF medications and listing for cardiac transplantation. CONCLUSIONS: CRT can benefit young patients that develop CHF and DCM following RV pacing for AV block. Upgrading to biventricular pacing systems should be considered early in the management of these patients prior to listing for cardiac transplantation.

Thymic expression of peripheral tissue antigens in humans: a remarkable variability among individuals.

The majority of maturing T lymphocytes that recognize self-antigens is eliminated in the thymus upon exposure to their target antigens. This physiological process of negative selection requires that tissue-specific antigens be expressed by thymic cells, a phenomenon that has been well studied in experimental animals. Here, we have examined the expression in human thymi of four retinal antigens, that are capable of inducing autoimmune ocular disease retinal S-antigen (S-Ag), recoverin, RPE65 and inter-photoreceptor retinoid-binding protein (IRBP)], as well as four melanocyte-specific antigens, two of which are used as targets for melanoma immunotherapy [gp100, melanoma antigen recognized by T cells 1, tyrosinase-related protein (TRP)-1 and TRP-2]. Using reverse transcription (RT)-PCR, we found that all thymic samples from the 18 donors expressed mRNA transcripts of most or all the eight tested tissue antigens. Yet, the expression of the transcripts varied remarkably among the individual thymic samples. In addition, S-Ag, RPE65 and IRBP were detected by immunostaining in rare cells in sections of human thymi by antibodies against these proteins. Quantitative real-time RT-PCR analysis revealed that the retinal antigen transcripts in the human thymus are present at trace levels, that are lower by approximately five orders of magnitude than those in the retina. Our observations thus support the notions that thymic expression is a common feature for all tissue-specific antigens and that the levels of expression play a role in determining the susceptibility to autoimmunity against these molecules.