Background: Patent ductus arteriosus (PDA) is normally associated with hyperdynamic status. Given the presence of a vascular shunt between the aorta and pulmonary artery, intrinsic aortic changes occur (aortic stiffness). Arterial stiffness is currently regarded as an independent predictor of cardiovascular morbidity and mortality. There is a close relationship between arterial stiffness and aortic flow propagation velocity (AFPV). Objective: To assess aortic stiffness in patients with isolated PDA using Doppler-derived AFPV, assess shunt magnitude i.e. pulmonary to systemic blood flow ratio (QP/QS) in patients with isolated PDA by echocardiography, compare AFPV values in patients with isolated PDA and apparently healthy individuals, and to correlate AFPV with PDA size and shunt magnitude. Patients and Methods: Our study was performed at Bab EL-Sha'riya Hospital, Al-Azhar University during the period from September 2019 and August 2020, and consisted of twenty-five patients with isolated PDA, and twenty healthy controls. Detailed history, physical examination was performed and conventional two-dimensional echocardiography was done to all cases then echocardiographic assessment of PDA including magnitude of the shunt by measuring QP/QS ratio. Aortic flow propagation velocity (AFPV) was measured in all cases. Results: Patients with PDA exhibited significantly lower AFPV than the control (p < 0.001). AFPV was significantly correlated with systolic blood pressure (r= -0.29 &p= 0.01). Also, there was significant correlation (r=-0.426) between AFPV and PDA size, mainly pulmonary end (p=0.03), and magnitude of the shunt QP/QS (r= 0.723 & p < 0.001). Conclusion: Transthoracic echocardiographic determination of the color M-mode propagation velocity of the descending aorta is a simple, non-invasive practical surrogate method in identifying arterial stiffness in patients with PDA and is related to effective orifice of PDA and magnitude of the shunt.