Novel mapping algorithm during catheter ablation for ventricular parasystole originating from left anterior fascicle

A 17‐year‐old woman presented with frequent palpitations and shortness of breath and was diagnosed with drug‐refractory ventricular parasystole. We predicted that the parasystole originated from the left anterior fascicle (LAF). Detailed activation maps of both conduction systems, including the LAF, during sinus rhythm and ventricular parasystole were obtained using a parallel mapping system. We confirmed the earliest fascicular potential of the parasystole and performed catheter ablation with no complications. This novel mapping algorithm for simultaneous acquisition of multiple maps aided effective treatment of ventricular parasystole originating from the LAF.