Pulsatile aortopulmonary pressure-flow dynamics of patent ductus arteriosus in patients with various hemodynamic states

Abstract

This paper considers the pulsatile pressure-flow relationships in patients with a patent ductus arteriosus (PDA). The emphasis is on the patterns that occurred with variable hemodynamic states, extending from the continuous left-to-right (L→R) PDA shunt with low pulmonary vascular resistance to the opposite extreme where the systemic circulation depended entirely on the right-to-left (R→L) PDA flow. Pressure gradients were determined from pressures measured simultaneously with matched catheter systems, and flow was evaluated by biplane cineangiography. In all of the hemodynamic states there was flow from the aorta to the pulmonary artery during diastole, even with aortic atresia. With bidirectional shunts, the R→L pressure gradient and flow occurred during the initial systolic rise of the pulse pressure in association with an earlier rise of the pulmonary artery pressure than the aortic pressure at the PDA site. With bidirectional shunts the LD[R diastolic flow across the PDA originated preferentially from backflow in the descending thoracic aorta distal to the PDA. Because the aortic backflow appeared to be considerable and occurred over large distances in some patients, the authors suggest that this may result in a 'diastolic steal' of blood from the abdominal organs to the pulmonary artery. The diastolic steal raises questions about a potential interaction of this steal and necrotizing enterocolitis in infants with a large PDA. Since the patterns found could not be explained using the concept of vascular resistance, especially the marked L→R PDA diastolic flow in aortic atresia, they relate the preferential L→R diastolic flow from the descending aorta to existing analyses of the effects of geometry on the impedance of the systemic arterial system.