When Palpitations Unmask Crista Terminalis Hypertrophy: A Case Report and Review of Current Literature

Background: The crista terminalis (CT) is a fibromuscular ridge forming the embryonic boundary between the sinus venosus and the primitive right atrium. While a physio-logical structure, rare cases of CT hypertrophy present a diagnostic challenge, often appearing as a right atrial pseudo-mass on imaging. Given its role as a site of conduction block and its association with two-thirds of right atrial arrhythmias, distinguishing hy-pertrophy from pathological masses is clinically vital. We present a case of a 58-year-old female who was referred to our hospital for rapid, irregular palpitations, accompanied by hypertension. Transthoracic and then transesophageal echocardiography (TEE) revealed an isoechoic right atrial mass, attached to the posterolateral wall of the right atrium, with a broad base of implantation and no intrinsic mobility. To exclude high-risk diagnoses, such as thrombi and myxomas, as well as other common right atrial mass mimics like the Chiari network, cardiac computed tomography angiography (CCTA) was performed. CCTA provided high-resolution tissue characterization, confirming the mass as a hy-pertrophied CT by its lack of contrast enhancement and its precise anatomical orientation. Conclusion: This case reinforces the epidemiological profile of CT hypertrophy, which predominantly affects females in their sixth decade. It highlights the necessity of a multi-modal imaging approach, transitioning from TEE to CCTA or cardiac magnetic resonance imagery (CMR), to prevent unnecessary invasive interventions or anticoag-ulation. Furthermore, this report supports the hypothesis that structural hypertrophy may exacerbate the CT's underlying arrhythmogenic potential, possibly through enhanced conduction anisotropy. Further research is needed to establish the correlation between CT thickness and the severity of atrial tachyarrhythmias.