Patent Ductus Arteriosus

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CHAPTER 13 Patent Ductus Arteriosus

Peter B. Manning

Step 1: Surgical Anatomy

♦ Because the dissection performed is typically limited, it is essential to identify key aspects of the juxtaductal anatomy before proceeding with ductal closure.

♦ The ductus arteriosus may be larger than the distal aortic arch, particularly in premature infants, and may be mistaken for the arch itself. Because the aortic arch follows a course in the mediastinum from right to left, the distal arch and isthmus typically lie in a slightly deeper plane, just superior to the ductus arteriosus. As a result of these factors, the ductus may be mistaken for the aortic arch itself, leading to unnecessary additional dissection and injury to other structures, such as the left pulmonary artery, the recurrent laryngeal nerve, or the aorta itself.

♦ With the typical dissection, the left pulmonary artery is not completely exposed, although its location should be appreciated at the superior aspect of the hilum of the lung.

♦ The phrenic nerve should be well anterior of the area of dissection, lying on the thymus in the superior mediastinum and coursing anterior to the pulmonary hilum.

♦ The vagus nerve is typically easily identified just anterior to the descending aorta. The recurrent laryngeal nerve leaves the vagus to loop around the inferior margin of the ductus arteriosus. Its relationship to the ductus arteriosus is the most reliable method of confirming the identity of the ductus, although its location results in its injury being the most common complication of juxtaductal operations.

Step 2: Preoperative Considerations

♦ Indications for ductal closure generally fall into two main categories dictated by the size of the ductus and the age of the child.

Congestive heart failure in the premature infant population is the most common indication for surgical ductal closure. Whereas echocardiography may demonstrate the presence and approximate size of the patent ductus, the decision to intervene should be based on clinical symptoms of congestive heart failure (respiratory compromise caused by excessive pulmonary blood flow, failure to maintain consistent weight gain, compromise of systemic perfusion manifested as renal insufficiency, or necrotizing enterocolitis). Echocardiographic evidence of significant pulmonary volume overload, such as left atrial and left ventricular enlargement, and a chest radiograph showing cardiac enlargement and prominent pulmonary vasculature support the clinical findings.

In older children a medium-sized to large patent ductus may lead to chronic congestive heart failure symptoms, the risk of developing pulmonary hypertension, and ultimately Eisenmenger physiology. In the current era, the incidence of bacterial endarteritis is extremely low, although bacterial endarteritis was responsible for a large portion of the mortality from patent ductus arteriosus (PDA) in the pre-antibiotic era.

♦ Choices for management

Because ductal patency is related to prostaglandin metabolism, medical closure is possible using the prostaglandin synthetase inhibitors indomethacin or other nonsteroidal anti-inflammatory drugs (NSAIDs). Only premature infants in the first week or two of life predictably respond to NSAID therapy, although the use of NSAIDs may be contraindicated because of renal insufficiency or concern about bleeding complications.

Catheter-based therapy using Gianturco coils or the Amplatzer ductal occluder device has become the standard therapy, with few exceptions, for PDA in children beyond the newborn period.

Video-assisted clip occlusion of the patent ductus has been described in premature infants and in older children and is the preferred strategy in some centers. With this technique, the learning curve is often greater and the incidence of complications or incomplete ductal closure is often higher.

Open surgical closure may be performed in patients of any age and can include clip ligation, simple or multiple ligation, or division with oversewing. Choice of closure method depends on surgeon preference, the diameter and length of the ductus, and the patient’s age and size.

Step 3: Operative Steps

♦ Because the premature infant is the patient most commonly requiring surgical closure, the discussion will focus primarily on this population.

♦ Transfer of the patient from bed to bed or transport from site to site within a hospital entails as much risk to the fragile premature neonate as does the operation itself. For this reason, many centers perform PDA closure in the neonatal intensive care unit, even in units unattached to a pediatric hospital. When it is preferred to perform the procedure in the operating room suite, the infant should be maintained in his or her own isolette, preferably one with an overhead warmer. The infant’s head is positioned toward the open end to allow access by the anesthesiologist.

♦ Avoiding hypothermia is essential while operating on premature infants and may be very challenging in the operating room environment. Likewise, ventilation may be difficult because of retraction on the left lung and the underlying lung disease. Proper endotracheal tube position and adequacy of ventilation must be confirmed after positioning in the right lateral decubitus position and before draping for the procedure. Limited, expedient dissection is important in preventing major physiologic compromise in these patients.

♦ A posterolateral left 3rd or 4th interspace thoracotomy gives the best exposure to the juxtaductal region (Fig. 13-1). A muscle-sparing thoracotomy typically provides adequate exposure if it is preferred by the surgeon.

♦ Retracting the left lung anteriorly and inferiorly exposes the posterior mediastinum. Two small malleable retractors (one on the upper lobe above the pulmonary hilum and a smaller one on the lower lobe posteriorly below the pulmonary hilum) can be clamped to the chest retractor and will afford excellent exposure (Fig. 13-2).

♦ Dissection is limited to the region of the ductus at its aortic end and is most easily begun by opening the pleura for 1 to 1.5 cm overlying the descending aorta, staying at least a few millimeters posterior to the vagus nerve. Gentle blunt and electrocautery dissection along the anterior aspect of the aorta should lead first to the ductus itself (Fig. 13-3). Limited dissection superior to the ductus should be carried out to confirm the identity and location of the distal aortic arch, which lies in a slightly deeper plane and is often smaller than the ductus itself, which may lead to confusion.

♦ The superior and inferior aspects of the ductus itself are dissected at the aortic end of the ductus, which will result in the recurrent laryngeal nerve being pushed out of harm’s way toward the pulmonary end of the ductus. The ductus need not be circumferentially dissected if clip occlusion is the planned method of closure, but enough dissection is needed to be able to see well the tip of the clip close beyond the deep edge of the ductus to avoid ductal injury during clip application. Retraction of the proximal descending aorta anteriorly will allow posterior dissection of the back wall of the ductus if this is needed for methods that use circumferential dissection.

♦ Management of the PDA itself

Division of the ductus between vascular clamps with oversewing of the ends is the only method that can confidently be predicted to result in a 100% closure rate, but this technique is appropriate only for larger children with relatively longer ductal lengths.

Closure by Ligaclip may be used with open or thoracoscopic techniques. It is the simplest and most appropriate method in the premature infant. It is important to recognize that clips close first at their tips and then in the middle. It is essential to be able to dissect enough of the ductus to see that the tip does not close on the ductal wall itself and perforate it; rather, it must come together beyond the ductal wall. This may result in the need to use a larger clip size than expected from the initial exposure. Positioning the legs of the clip applier along the superior and inferior aspect of the ductus and then pushing the applier against the descending aorta while lifting the latter structure posteriorly and upward will allow good visualization of clip closure and also will minimize the risk of injury to the recurrent laryngeal nerve, which will tend to stay near the pulmonary end of the ductus.

Simple ligation of a large ductus in a premature infant may be more difficult because of the need to perform circumferential dissection and the inability to feel when the suture is tied down securely without tearing through the fragile ductal wall, potentially resulting in a higher rate of incomplete closure.

In older children, a multiple ligation technique may be performed using simple ligatures along the length of the ductus or ligatures secured by taking fine adventitial bites in the ductal wall to prevent slipping toward the center (Fig. 13-4).

♦ In the absence of injury to the lung during exposure, a chest tube typically does not need to be left following the procedure. In older children, this improves postoperative comfort and typically allows for more expedient discharge from the hospital.

Figure 13-1

Figure 13-2

Figure 13-3

Figure 13-4

Step 4: Postoperative Care

♦ Older children should be able to be discharged from the hospital within 24 to 48 hours following ductal closure. Resumption of a normal diet and adequate pain control are the typical driving factors.

♦ Ligation of a hemodynamically important ductus in a premature infant typically results in a rise in diastolic and mean arterial pressures noted immediately. Studies have demonstrated improvements in pulmonary mechanics soon after ductal occlusion and a variable response in left ventricular performance with an acute increase in ventricular afterload. The need for initiation or escalation of inotropic support is observed in up to a third of these patients. Chronic lung disease is frequent in this population even after ductal ligation, leading some to suggest using this therapy earlier given its demonstrated safety even in very-low-birth-weight neonates.

Step 5: Pearls and Pitfalls

♦ It is critical to understand the anatomy of the juxtaductal aorta and the pulmonary hilum and the distortion that may be caused with a large patent ductus. Dissection should be minimized for expedient conduct of the procedure, but definitive identification of the pertinent anatomy cannot be compromised. Confusion has led to such complications as ductal injury, left pulmonary artery ligation, or aortic ligation.

♦ Recurrent laryngeal nerve injury is best prevented by limiting dissection to the aortic end of the ductus and by avoiding handling the anterior flap of pleura where the vagus nerve could be grasped above the level of recurrent laryngeal nerve exit.

♦ The risk of postoperative chylothorax may be lessened by limiting dissection to the periadventitial plane of the vascular structures and the use of low-energy cautery during much of the dissection.

Gould DS, Montenegro LM, Gaynor JW, et al. A comparison of on-site and off-site patent ductus arteriosus ligation in premature infants. Pediatrics. 2003;112(6 Pt 1):1298-1301.

Hillman ND, Mavroudis C, Backer CL. Patent ductus arteriosus. In: Mavroudis C, Backer CL, editors. Pediatric cardiac surgery. 3rd ed. Philadelphia: Mosby; 2003:223-233.

Jacobs JP, Giroud JM, Quintessenza JA, et al. The modern approach to patent ductus arteriosus treatment: complementary roles of video-assisted thoracoscopic surgery and interventional cardiology coil occlusion. Ann Thorac Surg. 2003;76(5):1421-1427.

Moin F, Kennedy KA, Moya FR. Risk factors predicting vasopressor use after patent ductus arteriosus ligation. Am J Perinatol. 2003;20(6):313-320.

Rao PS. Percutaneous closure of patent ductus arteriosus: state of the art. J Invasive Cardiol. 2007;19(7):299-330.

Raval MV, Laughon MM, Bose CL, Phillips JD. Patent ductus arteriosus ligation in premature infants: who really benefits, and at what cost? J Pediatr Surg. 2007;42(1):69-75.

Schneider DJ, Moore JW. Patent ductus arteriosus. Circulation. 2006;114(17):1873-1882.

Zbar RI, Chen AH, Behrendt DM, et al. Incidence of vocal fold paralysis in infants undergoing ligation of patent ductus arteriosus. Ann Thorac Surg. 1996;61(3):814-816.

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