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

Background and Clinical Significance: The crista terminalis (CT) is a physiological fibromuscular ridge in the right atrium. While benign, rare cases of CT hypertrophy present a diagnostic challenge, as it can mimic a pathological right atrial mass on cardiac imaging. The CT also presents arrhythmogenic potential and is known to be associated with right atrial tachyarrhythmias. Case Presentation: We present the case of a 58-year-old female that presented with rapid, irregular palpitations, accompanied by hypertension. Holter electrocardiography (ECG) confirmed self-limiting episodes of atrial tachycardia (max heart rate 170 bpm). Initial transthoracic echocardiography (TTE) identified an echogenic, non-mobile mass on the posterolateral right atrial wall. Transesophageal echocardiography (TEE) confirmed a 12 × 9 mm homogenous structure with a broad base of implantation and no intrinsic mobility, initially raising the suspicion of an atrial lipoma. Subsequent cardiac computed tomography angiography (CCTA) provided high-resolution tissue characterization, identifying the mass as a hypertrophied CT due to its precise anatomical orientation and its lack of contrast enhancement, also ruling out neoplastic and thrombotic aetiologies. Conclusions: CT hypertrophy is a key differential diagnosis for right atrial masses, particularly in females in their sixth decade. A multimodal imaging approach, transitioning from TTE to TEE and finally CCTA or Cardiac Magnetic Resonance Imaging (CMR), is advantageous in preventing unnecessary invasive interventions or anticoagulation.