The physiopathology of the patent ductus arteriosus.

Patent ductus arteriosus (PDA) remains a frequent problem for the very low birth weight infants. Many questions about the role of PDA, the best method of diagnosing it and the appropriate timing of treatment have been, at time, not completely answered. What we now know is that the left to right shunt appears very soon after birth and, if the ductus remains open, results in a progressively lung over circulation and a left ventricular volume overload. Despite the immature myocardium, the heart is able to increase its cardiac output, mainly through an increase in stroke volume, even in extremely preterm newborns. The increment of stroke volume does not increase or maintain an effective systemic perfusion and with the time it will become unproductive. Both animal and human studies showed a compromise of organ blood flow, with the development of systemic hypotension, steal phenomena, organ hypoperfusion, and ultimately congestive heart failure.