Backgroud : The synchrony of pacing heart may be affected by RV pacing site and important in pacemaker patients for cardiac function. The mechanism of dyssynchrony includes regional delays of both ventricular contraction and relaxation. Dyssynchrony may be inter- or intraventricular, and echocardiography may evaluate both types through several techniques. We evaluated the difference of LV synchrony according to RV pacing sites (RV apex, mid-septum and RVOT) in normal systolic functioned patients with narrow QRS. Methods : We performed in 18 patients (8 men, 10 women; age, 49.5 짹 13.7 years) paing at RV apex, interventricular mid-septum and RVOT. Transthoracic echocardiography at rest and during pacing were performed in all patients. Pacing rate was 600msec. We measured both interventricular and intraventricular dyssynchrony by echocardiography. Interventricular dyssynchrony was performed by measuring the time between ventricular ejections (the time interval between the beginning of the systolic wave of pulmonary and aortic ejection) and by measuring the time between septal contraction and posterior wall contraction though the M-mode. Intraventricular dyssynchrony was performed by measuring the time between the beginning of the QRS complex and the peak systolic wave of tissue Doppler (between the septal and lateral basal wall). Results : Results are presented in Table 1. Conclusion : The RVA pacing is superior to mid-septum and RVOT pacing for intraventricular synchrony in normal systolic functioned patients with narrow QRS.