Persistent patent ductus arteriosus (PDA) occurs in anywhere from 1 in 2500 to 1 in 5000 live births, with higher rates being found in premature infants(1). Patients are typically then treated medically with a COX inhibitor unless contraindicated. In these instances, in addition to the failure of medical treatment, surgical options are then explored. Thoracoscopic ligation of the PDA has emerged as a less invasive but equally effective treatment modality with the potential to mitigate the long-term complications of an open thoracotomy in a neonate.
The ability to divert most of the fetal ventricular outflow away from the underdeveloped pulmonary system makes the ductus arteriosus (DA) essential to the well being of a developing fetus in-utero. Connecting the pulmonary artery to the aorta, it allows 60% of fetal blood flow to bypass the immature lungs and eventually enter the umbilical arteries to again be re-oxygenated(1). In this regard it functions as a normal right-left shunt helping to maintain systemic blood flow while also giving the fetal lungs time needed to mature.
Normally the DA is held patent through prostaglandin production and low oxygen tension. During the initial postnatal period, the newborn takes it first breath resulting in a decreased resistance in the pulmonary vessels,increased pressures in the left atrium, and subsequent closure of the DA. While the mechanism has yet to be fully elucidated, smooth muscle cells in the ductus arteriosus constrict after sensing increased oxygen partial pressure and decreasing prostaglandin production, namely PGI2 and PGE2(2). It is thought that the closing of this lumen occurs in two phases(1). The absence of the placenta, which has been shown to produce large amounts of prostaglandins, causes an inherent loss of muscle relaxation in the DA. Following this, an increase in DA oxygen tension is believed to be the additional impetus for vasoconstriction. Within weeks the DA is fibrosed closed, forming the ligamentum arteriosum. Blood now flows through the pulmonary system to become oxygenated before returning to the left heart to be ejected to the rest of the body.
Research has shown that premature infants are less sensitive to oxygen as it relates to the constriction of the DA(2) and have lower intrinsic tone of the DA. The postnatal PDA causes a left-right shunt secondary to the increased pressures found in the aorta in comparison to the pulmonary artery. This can lead to congestive heart failure (CHF) in the newborn and is associated with comorbidities such as chronic lung disease, intraventricular hemorrhage (IVH), neurologic complications, renal failure, necrotizing enterocolitis and death. Surviving newborns may go onto develop pulmonary hypertension, right-sided heart failure and/or bacterial endocarditis.
Clinical Presentation and Evaluation
Depending upon the severity of the disease, newborns with a PDA may be asymptomatic or may present with clinical manifestations, including CHF with dyspnea, respiratory distress, cyanosis, etc. In addition, tachycardia and strong bounding pulses can be present. Helpful in the diagnosis is the classic machine gun like heart murmur heard on auscultation, though it’s absence does not rule out the abnormality. Furthermore, on chest x-ray, one may see an enlarged cardiac silhouette or widened ascending aorta(1). Ultimately, the diagnostic gold standard is an echocardiogram. This assessment will likely show an increased left atrium to left aortic root diameter, left atrial enlargement and holodiastolyc flow reversal in the descending aorta2 along with any other intracardiac lesions. Moreover, it can be used postoperatively to evaluate the impact of the operation.
Typically, a COX inhibitor to prevent prostaglandin formation, such as Ibuprofen or Indomethacin, is the first approach in the medical management of a PDA. This pharmacologic approach has a 70-80% success rate(3). If the neonate fails to close the ductus with the first course of medical management, they are given a second course before surgical management is considered(4). Surgical intervention is also indicated in symptomatic patients, significant left to right shunt causing severe left heart enlargement4 and those with a contradiction to pharmacologic therapy, such as azotemia, thrombocytopenia, IVH, gut ischemia1.
The traditional approach to surgical ligation is through a left posterolateral thoracotomy. In recent years the thoracoscopic approach to PDA ligation has gained favor due its decreased pain and average hospital stay, improved shoulder strength, and early pulmonary improvement. Additionally, it’s decreased incidence of late thoracotomy complications such as scoliosis, winged scapula, chest deformity and rib fusion causing respiratory compromise(5) also make a sound argument towards more widespread use of the thoracoscopic approach. Likewise, outside of severe pulmonary arterial hypertension, there are relatively few contraindications to surgery(6).
Patients are placed under general anesthesia, ideally with selective right lung intubation, and placed in the right lateral decubitus position. A left upper extremity pulse oximeter or arterial line can be used to monitor for unintentional left subclavian artery occlusion. Four 3-5 mm thoracostomy ports are placed, including a camera port just below the scapula in the forth intercostal space, a lung retractor port between the mid and posterior axillary line, a working port behind the scapular edge and halfway between the midline of the back, and a grasper port which can be placed over the third rib in the mid-axillary line. If the left lung remains inflated, a small amount of CO2 insufflation may be used to compress the lung and improve visualization of the aorta and ductus. The pleural reflection is grasped and cauterized longitudinally over the aorta creating a flap paralleling the aorta. With anteromedial traction placed on this flap, the DA, vagus nerve, and recurrent laryngeal nerve can be exposed. Using careful blunt dissection, a plane can be created above and below the DA. A test occlusion may be performed to ensure perfusion to the left upper extremity is not compromised. An appropriate size clip should be placed across the ductus, taking special care not to clip the recurrent laryngeal nerve. Before closing, inspect the pleural flap for bleeding or lymphatic leak and position a small, anterolateral chest tube under thoracoscopic guidance through one of the port sites. All four ports sites should be injected generously with a local anesthetic, closed with absorbable sutures and dressed.
Postoperative Care and Complications
Conversion to an open thoracotomy may be necessary due to anatomic variances8, bleeding concerns or insufficient exposure of the surgical field7. The percentage of converted cases has been reported to range anywhere from 1% -7%9,10 in the hands of experienced surgeons. Postoperatively infants are given scheduled analgesics and monitored for any complications. Potential complications include pneumothorax, chylothorax, vocal cord paralysis, atelectasis and pleural effusions(7). The incidence of long-term morbidities associated with the operation is exceedingly low, but can include bronchopulmonary dysplasia and neurodevelopmental abnormalities(11). Residual patency of the PDA has also been described. In its earlier years, thoracoscopic ligation of a PDA was reported as having incidences of residual patency as high as 12%(13). Recently though, reported incidence of this negative outcome has been as low as 0.7%14 which would speak to the increased experience and skill set progression displayed by the surgeons carrying out the procedure.
Mortality rates directly linked to the PDA ligation very low, with mortality from a thoracoscopic procedure estimated as even lower, often reported as non-existent(12).
Due to its high rate of occurrence in newborns a PDA is an issue that will likely be encountered by every healthcare practitioner working in the area of neonatal care. In the event though that medical therapy has failed to close a PDA or is contraindicated, surgery is the standard of care for closure of the patent vessel. In comparison to open thoracotomy, thoracoscopic PDA ligation offers a less morbid avenue by which post-operational length of hospital stay is decreased. With its’ relatively few complications, high success rate, and low mortality rate, thoracoscopic PDA ligation is increasingly the procedure of choice for surgical therapy.
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2. Shannon E.G. Hamrick and Georg Hansmann Patent Ductus Arteriosus of the Preterm Infant Pediatrics 2010; 125:5 1020-1030; published ahead of print April 26, 2010, doi:10.1542/peds.2009-3506
3. Corff KE, Sekar KC. J Clinical considerations for the pharmacologic management of patent ductus arteriosus with cyclooxygenase inhibitors in premature infants.
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Is There an Optimal Timing for Surgical Ligation of Patent Ductus Arteriosus in Preterm Infants? Ann Thorac Surg 2009 87: 1509-1516
5. Hines, Michael H., Bensky, Andrew S., Hammon, John W., Jr, Pennington, D. Glenn
Video-assisted thoracoscopic ligation of patent ductus arteriosus: safe and outpatient Ann Thorac Surg 1998 66: 853-859
6. Michele D’Alto and Vaikom S. Mahadevan Pulmonary arterial hypertension associated with congenital heart disease Eur Respir Rev December 1, 2012 vol. 21 no. 126:328-337
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10. Villa E, Vanden Eynden F, Le Bret E, Folliguet T, Laborde F
Pediatric video-assisted thoracoscopic clipping of patent ductus arteriosus: experience in more than 700 cases Eur J Cardiothorac Surg. 2004 Mar;25(3):387-93.
11. Ronald I. Clyman Surgical Ligation of the Patent Ductus Arteriosus: Treatment or Morbidity? Journal of Pediatrics, The, 2012-10-01, Volume 161, Issue 4, Pages 583-584
12. Laborde, Francois, Folliguet, Thierry, Batisse, Alain, Dibie, Alain, Da-Cruz, Edouardo, Carbognani, Daniel, Cunningham, Sponsored by Joseph N. VIDEO-ASSISTED THORACOSCOPIC SURGICAL INTERRUPTION: THE TECHNIQUE OF CHOICE FOR PATENT DUCTUS ARTERIOSUSRoutine experience in 230 pediatric cases J Thorac Cardiovasc Surg 1995 110: 1681-1685