Introduction: The hemodynamic advantage of maintaining AV synchrony through AV synchronous pacing is widely known as compared to single chamber pacing. DDD pacemaker implantation entails higher cost and is technically more challenging than the VDD pacemaker. However, chronotropic competence of sinus node and appropriate sensing of sinus activity are crucial to maintain AV synchrony in patients with VDD pacemaker. Methods and Results: One hundred seventy nine patients underwent VDD pacemaker implantation since 1995 through subclavian or axillary vein route for second degree and complete AV block. Among them, 123 patients (50 males, 63짹12 years) were followed up regularly for more than 6 months (42짹33 months) for ventricular capture threshold and ventricular, atrial sensing amplitude. Patients with sinus bradycardia (<60 BPM) or atrial tachyarrhythmia at the time of implantation were excluded. All pacemakers were initially programmed to default sensing value (0.25 mV for atrium) and minimum ventricular pacing rate (50 BPM). Pacemaker follow up was performed 4-6 weeks after implantation, and then at 6 month intervals. Amplitude of sensed atrial activity changed from 1.8짹2.2 mV at implantation to 1.1짹1.4 mV at the final follow up. Even though high atrial sensitivity below than 0.5 mV was programmed in 31 patients (25.2%), atrial sensing failure developed in 7 (5.7%). Sinus node dysfunction (sinus rate <50 BPM) developed in 6 patients (4.9%) and atrial fibrillation in 2 patients (1.6%). Decrease of sensed atrial activity less than 0.5 mV during follow up was associated with higher BMI (25짹3 to 23짹2, p=0.048), older age (66짹10 to 62짹13 years, p=0.041), long abdominal circumference (90짹5 to 76짹7 cm, p=0.001). Conclusion: Atrial sensing failure and sinus node dysfunction in patients receiving VDD pacemaker are not rare during long term follow up. DDD pacemaker implantation may be considered in elderly or obese to avoid atrial sensing failure.