BACKGROUND Damage of tricuspid valve (TV) with resultant tricuspid regurgitation (TR) induced by endomyocardial biopsy (EMB) following heart transplantation has been reported in several studies. This study tried to determine the prevalence of EMB-related iatrogenic damage over tricuspid apparatus following orthotopic heart transplantation and to evaluate its impact on the patients. METHODS Fifty patients received orthotopic heart transplantation between July 1987 and March 2005. Eleven patients were excluded from the study due to early postoperative mortality or inadequate follow-up. The medical records of the remaining 39 patients were reviewed retrospectively for basic characteristics as well as each attempted EMB. The iatrogenic damage of tricuspid apparatus and serial change of TR were accessed with 2-D and Doppler echocardiography. The obtained data were analyzed for their statistical significance with SPSS (version 12.0). RESULTS A total of 373 biopsies were performed on the 39 patients between 1987 and 2005. The follow-up duration was 42.9+/-26.7 months. The prevalence of TR immediately following heart transplantation was 84.6%, with only 25.6% of patients having moderate or severe TR. At the end of the follow-up, the prevalence of TR increased to 92.3% and 61.5% of patients having moderate or severe TR, respectively. Eight patients (20.5%) had small chordae rupture (SCR) noted after 6.6+/-3.2 biopsies, and 10 patients (25.6%) had flail tricuspid valve (FTV) after 5.7+/-5.1 biopsies. Of patients with SCR, 62.5% had progression of TR, and 70% of patients with FTV showed significant TR change. CONCLUSIONS The prevalence of iatrogenic tricuspid apparatus damage was high in this study. It contributed to the progression of TR significantly regardless of the damage severity. Measurements should be taken for prevention of iatrogenic tricuspid apparatus damage induced by EMB.