Pacemaker-associated bigeminy

BACKGROUND: Pacemaker-associated bigeminy is an electrocardiographic pattern characterized by a regular alternation of two distinct cardiac events. It can arise from normal operation of device algorithms or indicate underlying dysfunction, such as sensing abnormalities. Accurate differentiation is crucial to avoid misdiagnosis and inappropriate clinical intervention. OBJECTIVE: To systematically elucidate the mechanisms underlying pacemaker-associated bigeminy and establish a practical diagnostic framework. METHODS: We conducted a retrospective analysis of six patients exhibiting pacemaker-associated bigeminy on ambulatory electrocardiograms (ECGs). The patients were identified from the databases of the Children's Hospital of Soochow University and the First Affiliated Hospital of Chongqing Medical University between March 2020 and December 2025. RESULTS: We delineate six distinct mechanisms: 1) Non-competitive atrial pacing (NCAP) triggered by sinus tachycardia; 2) Fusion beat exclusion due to evoked response (ER) undersensing; 3) Auto capture (AC) operation with start-stop pattern constrained by maximum tracking rate (MTR); 4) Window of atrial rate acceleration detection (WARAD) activation by non-conducted atrial premature complexes; 5) A Pace on Premature Ventricular Contraction (A Pace on PVC) triggered by PVCs; and 6) Dynamic atrioventricular (AV) delay operation following atrial premature beats. CONCLUSIONS: Pacemaker-associated bigeminy represents a spectrum of phenomena driven by specific "algorithm-rhythm interactions." Recognition of these characteristic patterns is essential for correctly distinguishing normal device function from malfunction, thereby guiding appropriate clinical management and optimizing patient outcomes.