Left atrial thrombus due to transseptal catheterization simulating solid mass of right atrium

BACKGROUND: Transseptal catheterization has been popularized through ongoing advances in percutaneous procedures, but related complications are known to occur. CASE PRESENTATION: A 72 year-old female was admitted with left-sided weakness. In the course of various exams, a rounded and smooth-surfaced solid mass of right atrium was identified. However, a septal aneurysm associated with left atrial mural thrombus was evident intraoperatively. Given that percutaneous transseptal mitral valvotomy had been done 7 years previously, a causal relationship is likely. CONCLUSIONS: Prior cardiac intervention should be considered in patients presenting with mass lesions of interatrial septum.