Ectopic discharge originating from the ostium of the inferior vena cava that is likely to cause atrial fibrillation.

It has been established that the initiation of paroxysmal atrial fibrillation (AF) is frequently associated with ectopic beats inside the thoracic veins, including the pulmonary veins, superior vena cava, coronary sinus, and/or vein of Marshall. However, similar arrhythmogenic ectopic discharge or premature atrial contractions (PACs) originating from the inferior vena cava (IVC) have been rarely described. We present the case of a 51-year-old man with paroxysmal AF undergoing electrophysiological study. Twelve-lead electrocardiography demonstrated PACs with negative P waves in the inferior leads. Ectopic beats originating from the ostium of the IVC, which were likely to initiate AF, were observed. Furthermore, the origin of the PAC was visualized using an electroanatomical local activation timing (LAT) map and located close to the fibrotic tissue of the vasculature. Radiofrequency catheter ablation was performed at the earliest activation site, and ectopic beats were not observed after the procedure. This is the first report to demonstrate a LAT contact map of ectopic discharge arising from the IVC. If PACs with negative P waves in the inferior leads are found in a patient with AF, the IVC should be investigated for possible focal ectopic discharges. Learning objective: Non-pulmonary vein foci play a significant role in the pathogenesis of atrial fibrillation (AF). However, inferior vena cava (IVC) triggers that initiate AF have rarely been described. Premature atrial contractions with negative P waves in the inferior leads may be associated with ectopic discharges originating from the IVC, which contribute to the initiation of AF.