STATE-OF-THE-ART Spectral Doppler waveforms in systemic arteries and physiological significance of a patent ductus arteriosus A Sehgal 1,2 , P Coombs 3 , K Tan 1,2 and PJ McNamara 4,5 1 Monash Newborn, Monash Children’s, Monash Medical Centre, Melbourne, VIC, Australia; 2 Monash University, Melbourne, VIC, Australia; 3 Department of Diagnostic Imaging, Monash Medical Centre, Melbourne, VIC, Australia; 4 Physiology and Experimental Medicine Program, SickKids Research Institute, Department of Paediatrics Toronto, Toronto, ON, Canada and 5 Division of Neonatology, Department of Paediatrics Toronto, Toronto, ON, Canada Patent ductus arteriosus in extremely premature babies is associated with major neonatal morbidities, such as necrotizing enterocolitis and intraventricular hemorrhage. This may be attributable, at least in part, to systemic hypoperfusion secondary to ductal steal. A hemodynamically significant ductus arteriosus (HSDA) is known to be associated with altered systemic blood flow and end-organ hypoperfusion. Although descending aorta blood flow profiles may show abnormal diastolic retrograde flow, Doppler studies of blood flow in the systemic arteries may help improve our understanding of the relationship of a HSDA with these morbidities. In this article, we discuss aspects of diastolic blood flow reversal in the systemic arteries in premature infants with a hemodynamically significant duct. Whether these hemodynamic effects are significant enough to form the basis for initiating treatment is still unclear; these should form the basis for prospective studies. Journal of Perinatology (2011) 31, 150–156; doi:10.1038/jp.2010.83; published online 22 July 2010 Keywords: ductal steal; hemodynamically significant ductus arteriosus; Doppler Introduction The presence of a hemodynamically significant ductus arteriosus (HSDA) is observed in B40% infants born with <1000 g birth weight 1 and has been considered as a risk factor for the development of necrotizing enterocolitis (NEC) and renal failure. 2 A HSDA has been previously defined by a transductal diameter >1.5 mm with echocardiographic findings of a significant transductal shunt (for example, left atria:aorta ratio >1.4, unrestrictive transductal flow on pulse-wave Doppler with velocity <1.5 m per s). 3 This may be accompanied by clinical features of pulmonary overcirculation (for example, increased oxygen or ventilation requirements) and/or systemic hypoperfusion (for example, hypotension and metabolic acidosis). The lack of consensus regarding therapeutic intervention, related in part to inadequately designed clinical trials, has led to medical uncertainty. The common practice is to intervene and assess outcome based on ductal size and the clinical consequences of excessive pulmonary blood flow (for example, increased ventilatory requirements and chronic lung disease). This may relate to the lack of a more comprehensive hemodynamic evaluation (for example, cardiac output, arterial Doppler), which serves as an indirect evaluation of the magnitude of transductal flow. The concept of ‘ductal steal’ is defined by an absence or retrograde flow in the major arteries (such as the renal and mesenteric arteries) during diastole. It could potentially be an important contributor to neonatal morbidity as it is a surrogate of a generalized systemic hypoperfusion state, as it compromises renal and/or gastrointestinal diastolic blood flow. 4,5 In this paper, we discuss the nature and relevance of ductal steal and compromised systemic blood flow in neonates with a HSDA. There are no conflicts of interest or disclosures. Physiology of ductal steal The phenomenon of ductal steal in premature infants with a patent ductus arteriosus (PDA) was first described by Cassell 6 more than 30 years ago. He demonstrated that at the time of duct ligation surgery, regurgitant flow from the descending aorta during diastole accounted for a considerable amount of the total left-to- right shunt. This was estimated by comparing the ascending aortic flow before and after duct ligation. It is well recognized that blood flow profiles in the descending aorta show abnormal diastolic retrograde flow in infants with PDA. Meyers et al. 7 showed that a PDA produced a significant decrease in intestinal blood flow. McCurnin and Clyman 8 recently showed that in preterm baboons, a moderate-sized ductus arteriosus shunt limits the ability to increase postprandial mesenteric blood flow velocity. It was speculated that this may lead to compromised bowel perfusion Received 18 February 2010; revised 11 April 2010; accepted 29 April 2010; published online 22 July 2010 Correspondence: Dr A Sehgal, Neonatologist, Monash Newborn, Monash Children’s, Monash University, 246, Clayton Road, Clayton, VIC 3168, Australia. E-mail: Arvind.Sehgal@southernhealth.org.au Journal of Perinatology (2011) 31, 150–156 r 2011 Nature America, Inc. All rights reserved. 0743-8346/11 www.nature.com/jp