Background: Postcardiac injury syndrome (PCIS) is a complication of a variety of cardiac injuries, of which small heart perforation is the etiology that is often unrecognized. We reported a series of patients with PCIS secondary to cardiac perforation during catheter ablation procedures. Methods and results: Out of 1728 radiofrequency catheter ablation procedures, 21 patients (1.2%) were complicated by echo-defined cardiac perforation not requiring surgical intervention. Among them, 6 patients (6/21, 28.6%) were diagnosed with PCIS secondary to cardiac perforation because they also developed pleural effusions (6/6, 100%) and fever (4/6, 66.7%) in addition to pericardial effusion/tamponade. Four patients with PCIS (4/6, 66.7%) and four patients without PCIS (4/15, 26.7%) underwent pericardial drainage but the drainage volume during the first 24 h was not significantly different (441.3 +/- 343.9 mL vs. 182.5 +/- 151.3 mL, P = 0.248). In the 6 PCIS patients, pleural effusion was detected from 3 h to 4 days (median: 2 days) after ablation procedure, predominantly bilateral (66.7%) or left-sided if unilateral. Patients with PCIS were older (64.8 +/- 7.3 years vs. 45.9 +/- 14.8 years, P = 0.0078), were more likely accompanied by hypertension (66.7% vs. 6.7%, P = 0.0114) and had a prolonged hospital stay (34.2 +/- 15.8 days). Conclusions: More than 25% of patients with small cardiac perforation during catheter ablation may develop PCIS which can be masked by pericardial effusion/tamponade. This kind of PCIS is more likely associated with elder or hypertensive patients and is usually characterized by early onset of pleural effusion. (C) 2013 Elsevier Ireland Ltd. All rights reserved.