Abstract: Our aim was to compare the Cardiac Output (CO), Filling Time (FT) and Myocardial Performance Index (MPI) derived optimal atrioventricular delay (AVD) and to analyze systolic and diastolic performance at every optimal AVD. We studied 32 patients with implanted DDD pacemaker, from implantation time to 6 months following PM implantation, in Tabriz Shahid Madani Heart Center. The evaluation was performed during AV sequential pacing with different programmed AVDS ranged from 100-200 ms by steps of 20-30 ms. At every AVD, the following parameters were measured: FT, mitral VTI, ET, aortic VTI, ICT and IRT. CO and FT derived optimal AVDs were significantly different (146�37 and 126�35 ms, respectively), but their difference with MPI derived optimal AVDs was not significant (130�28 ms). ICT/ET was similar at CO, FT and MPI derived optimal AVD (0.24�0.10, 0.22�0.05 and 0.20�0.07, respectively). IRT/ET ratio was similar at CO, FT and MPI derived optimal AVDs (0.46�0.14, 0.45�0.10 and 0.42�0.10, respectively).