Andersons pediatric cardiology 1076

Historical Considerations When Siegal1 reexamined the original second century Greek text of Galen, he pointed out that Galen was familiar with many aspects of the fetal circulation even though he did not realize that blood circulated Galen understood that fetal blood was aerated in the placenta and that blood was diverted away from the liver by a short vessel connecting the portal to the inferior caval vein He also knew that blood passed through the oval foramen to bypass the right ventricle and reach the left side of the heart directly He realized that some blood still entered the right ventricle and pulmonary trunk, from whence it was shunted into the aorta through a special fetal channel, thereby bypassing the lungs The quotation at the beginning of this chapter, taken from Siegal,1 provides a clear indication of Galen's understanding of the dramatic readjustment of the circulation at birth Nevertheless, Botallo is the name we usually associate the persistently patent arterial duct In fact, Botallo described postnatal patency of the oval foramen! It was by a series of misinterpretations and careless translations that his name became quite unjustifiably attached to the arterial duct2; the attribution of the discovery should more accurately be called an independent rediscovery.3 William Harvey, who was a pupil of Fabrizi d'Acquapendente in Padova for 2 years, synthesized previous detailed descriptions of fetal cardiac anatomy from his mentor in his own writings His genius resided in proposing the concept of active circulation of the blood He was well aware of the large size of the arterial duct prior to birth and the fact that blood flowed through it from right to left during fetal life.4 Harvey4 was incorrect only in his belief that flow of blood to the lungs was completely lacking in the fetus Subsequently, Highmore, a friend of Harvey, described closure of both the oval foramen and the arterial duct as occurring with the onset of respiration, believing the arterial duct to collapse as a consequence of blood being diverted to the lungs.5 Since then, several ingenious theories have been put forward to explain closure of the duct, all being based on postmortem appearances and all invoking mechanical factors.6 Virchow7 first suggested that the closure results from contraction of its mural smooth muscle, and Gerard8 introduced the concept of two-stage closure, in which functional constriction is followed by anatomic obliteration Thanks to Huggett,9 we came to understand the role of oxygen in causing functional closure by muscular contraction As early as 1907, in an address to the Philadelphia Academy of Surgery, John Munro had suggested surgical ligation of the persistently patent arterial duct.10 After an interval of 31 years, the first attempt at surgical closure was made in a 22-year-old woman with bacterial endocarditis.11 Unfortunately, although the patient survived the surgery, she died a few days later from complications of the infection As a result, Robert Gross of Boston first successfully ligated a patent duct in a 7-year-old child with intractable heart failure.12 He thereby introduced an amazing era of progress in the surgery of congenital malformations of the heart No historical review of the arterial duct, however brief, would be complete without recognizing the importance of Gibson's exquisite description of the murmur that typifies its persistence,13 notwithstanding the fashion in which Gibson's initial account has subsequently been misquoted.14 Nomenclature From time to time, authors have argued that the terms “patent” or “persistent” are redundancies that should be avoided when describing the arterial duct In our view, this oversimplifies the situation, and both terms retain their value Persistence implies that the duct is present after the time of its expected closure and therefore distinguishes a pathologic from a physiologic state The concept of patency remains useful in the perinatal period, especially in the premature infant in whom the term can be used to signify a duct that is functionally open, as opposed to one that is functionally closed but retains the potential to reopen