A 76-year-old female had undergone implantation of a single chamber pacemaker for sick sinus syndrome 20 years previously. She developed chronic atrial fibrillation and required repeated admission due to congestive heart failure. She had significant mitral and tricuspid regurgitation. Paradoxical movement of the intraventricular septum was severe. Due to right ventricular apical pacing, significant interventricular conduction delay was present with a paced QRS duration of 189 msec. The left ventricular pacing lead was positioned via the coronary sinus. The mode of the previously implanted pacemaker was set at VVT. Biventricular pacing could be achieved even in intrinsic beats by VVT mode. The battery life time was improved. This method is useful in patients with conventional pacemakers.