You are in: eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiothoracic Surgery Patent Ductus Arteriosus: Surgical PerspectiveArticle Last Updated: Nov 8, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Mary C Mancini, MD, PhD, Director of Cardiothoracic Transplantation, Professor, Department of Surgery, Louisiana State University Health Sciences Center Mary C Mancini is a member of the following medical societies: American Heart Association, American Medical Association, American Thoracic Society, Association for Academic Surgery, Association for Surgical Education, International College of Surgeons, International Society for Heart and Lung Transplantation, New York Academy of Sciences, Phi Beta Kappa, and Southern Thoracic Surgical Association Editors: Jonah Odim, MD, PhD, MBA, Senior Medical Officer, Transplantation Immunology Branch, Division of Allergy, Immunology, and Transplantation, National Institute of Allergy and Infectious Diseases, National Institutes of Health; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; John Myers, MD, Director, Pediatric and Congenital Cardiovascular Surgery, Departments of Surgery and Pediatrics, Professor, Penn State Children's Hospital, Milton S Hershey Medical Center; Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine; Stuart Berger, MD, Professor of Pediatrics, Division of Cardiology, Medical College of Wisconsin; Chief of Pediatric Cardiology, Medical Director of Pediatric Heart Transplant Program, Medical Director of The Heart Center, Children's Hospital of Wisconsin Author and Editor Disclosure Synonyms and related keywords: patent ductus arteriosus, PDA, persistent ductus arteriosus, aortopulmonary connection, heart defect, cardiac defect, pediatric cardiac surgery, catheter-based closure of PDA, thoracotomy, PDA closure, right aortic arch, pulmonary vascular resistance, rubella infection, pulmonary engorgement, heart murmur, congestive heart failure INTRODUCTIONSection 2 of 12
  The ductus arteriosus connects the main pulmonary trunk to the descending aorta distal to the origin of the left subclavian artery. In most individuals, the ductus arteriosus is located on the left side; however, if a right aortic arch is present, the ductus arteriosus may be located on the right or left side. The ductus arteriosus is very rarely bilateral. The structure varies in length and diameter. Histologically, the media of the ductus is composed of smooth muscle, and the intima is much thicker than the aorta. Contraction of this muscular media after birth causes shortening of the ductus and its functional closure. Folding of the endothelium and proliferation of the subintimal layers cause permanent closure, which usually occurs during the first 2-3 weeks of life. Persistence of a patent ductus occurs in several conditions. History of the ProcedureMunro initially described surgical ligation of the patent ductus arteriosus in 1907. Gross performed the first successful operation in 1939.1 Catheter-based closure of the structure was first performed in 1971. ProblemIn normal fetal circulation, the unexpanded lungs receive only 5-8% of the blood entering the pulmonary artery. The ductus arteriosus serves as the predominant route of circulation passing through the right ventricle and pulmonary artery. Approximately 55-60% of the systemic circulation passes from right to left through the ductus. In the fetus, the oxygen tension is relatively low because the pulmonary system is nonfunctional. This, coupled with high levels of circulating prostaglandins, acts to keep the ductus open. The high levels of prostaglandins result from the little amount of pulmonary circulation and the high levels of production in the placenta. At birth, the placenta is removed, eliminating a major source of prostaglandin production, and the lungs expand, activating the organ in which most prostaglandins are metabolized. In addition, with the onset of normal respiration, oxygen tension in the blood markedly increases. Pulmonary vascular resistance decreases with this activity. These events result in contraction of the smooth muscle within the wall of the ductus, which results in its closure. A preferential shift of blood flow occurs; the blood moves away from the ductus and directly from the right ventricle into the lungs. Until functional closure is complete and pulmonary vascular resistance is lower than systemic vascular resistance, some residual left-to-right flow occurs from the aorta through the ductus and into the pulmonary arteries. Alterations in any one of the aforementioned steps results in persistent ductal patency, left-to-right flow through the structure, and increased pulmonary blood flow. FrequencyA persistent ductus arteriosus has been estimated to occur in 1 in 2500-5000 live births. As an isolated lesion, it represents 9-12% of all congenital heart lesions. The female-to-male ratio is 2:1. EtiologyThe factors responsible for continued patency of the ductus arteriosus are unknown, and even the conditions that have an effect on patency are not well understood. Prematurity or immaturity of the infant at the time of delivery contributes to the patency of the ductus. Several factors are involved, including immaturity of the smooth muscle within the structure or the inability of the immature lungs to clear the circulating prostaglandins that remain from gestation. These mechanisms are not fully understood. Conditions that contribute to low oxygen tension in the blood, such as immature lungs, coexisting congenital heart defects, and high altitude, are associated with persistent patency of the ductus. The incidence of rubella infection in the first trimester of pregnancy, particularly through 4 weeks' gestation, associated with patent ductus arteriosus is very high (£85%). Incidence of patent ductus arteriosus is as much as 2-4% in siblings of patients with the condition. A socioeconomic association without a racial factor has also been observed with patency; an increased incidence of patients with patent ductus arteriosus appears to arise from lower socioeconomic origins. PathophysiologyWith patency of the ductus and a decrease in pulmonary vascular resistance to below the level of systemic vascular resistance, blood flows from the aorta into the pulmonary artery through the ductus, resulting in a left-to-right shunt. The flow occurs through systole and diastole. This combination of blood passes through the lungs, into the left atrium, into the left ventricle, and back into the aorta. The result is an increased volume load on the left atrium and left ventricle. The increase in left ventricular stroke volume is proportional to the size of the ductus. The increased left ventricular stroke volume and the central runoff from the aorta into the pulmonary artery results in a widened pulse pressure. An absolute increase occurs in the total circulating volume of the patient, which is proportional to the amount through the left-to-right shunt. Pulmonary engorgement results with decreased pulmonary compliance. The reaction of the pulmonary vasculature to the increased blood flow is unpredictable. The amount of blood that flows through the ductus is related to the size and shape of the structure and to the differences between the systemic and pulmonary resistances. The wider and shorter the ductus, the greater the blood flow through it. Higher systemic pressures provide a higher driving force behind the blood flowing through the structure. The lower the pulmonary resistance, the less the impediment affects ductal flow. Conversely, higher pulmonary vascular resistance can sometimes reverse the flow through the patent ductus arteriosus. ClinicalNo typical clinical history is observed in patients with patent ductus arteriosus. Most patients are asymptomatic and are found to have a heart murmur on physical examination. At times, the patient may report decreased exercise tolerance or pulmonary congestion in conjunction with a murmur. Patients can present at any age. However, 3- to 6-week-old infants can present with tachypnea, diaphoresis, inability or difficulty with feeding, and weight loss or no weight gain. Patients usually appear well and have normal respirations and heart rates. A widened pulse pressure may be noted when the blood pressure is obtained. Suprasternal or carotid pulsations may be prominent. A continuous machinery murmur is the hallmark physical finding of patent ductus arteriosus. The murmur begins shortly after the first heart sound, peaks at approximately the second heart sound, and diminishes through diastole. The murmur may be local or widely radiate, and it may vary in intensity from very soft to grade 6. A thrill may be palpated. Often, a left ventricular heave or lift may be felt on palpation of the chest. The second heart sound is increased in intensity and widely split because of the increased pulmonary blood flow. In patients with a larger ductus, a diastolic rumble may be heard. The peripheral pulses are prominent and bounding in small patients with a large ductus. INDICATIONSSection 3 of 12
Congestive heart failure is an indication for ductal closure in infancy. If medical therapy is ineffective, urgent intervention to close the structure should be undertaken. All patent ductus arteriosus should be closed because of the risk of bacterial endocarditis associated with the open structure. Over time, the increased pulmonary blood flow precipitates pulmonary vascular obstructive disease, which is ultimately fatal. RELEVANT ANATOMYSection 4 of 12
In the normal heart with a left aortic arch, the patent ductus arteriosus forms a connection between the pulmonary artery and the aorta, just distal to the origin of the left subclavian artery. It passes from the anterior aspect of the pulmonary artery to the posterior aspect of the aorta. Typically, the ductus has a conical shape with a large aortic end tapering into the small pulmonary connection. The ductus may take many shapes and forms, from short and tubular to long and tortuous. An anatomic marker of the ductus is the recurrent laryngeal nerve, which encircles the left subclavian artery and can be found adjacent to the ductus. CONTRAINDICATIONSSection 5 of 12
Relatively few contraindications to closure of the ductus arteriosus are recognized. Clearly, attention must be paid to the existence of other congenital heart lesions that impair pulmonary blood flow. In these patients, all attempts should be made to preserve ductal flow until a more permanent palliative shunt can be constructed or definitive repair can be undertaken. Contraindications to catheter-based closure currently involve the size of the patient. Very small premature infants still require surgical closure. Contraindications to surgical closure include concurrent uncontrolled sepsis and an inability of the patient to tolerate general anesthesia. WORKUPSection 6 of 12
Lab Studies
Imaging Studies
Other Tests
Diagnostic Procedures
Histologic FindingsThe walls of the ductus contain intima, media, and adventitia. The medial layer of the structure is composed of longitudinal smooth muscle in the inner layer and circumferentially arranged smooth muscle in the outer layers. This is in contrast to true arterial structures, which contain a medium primarily composed of circumferential elastic fibers. These layers of smooth muscle contain concentric loose lamina of elastic tissue and a network of tiny thin-walled vessels. The intimal layer is irregularly thickened and contains a considerable amount of mucoid material. TREATMENTSection 7 of 12
Medical therapyBecause patients presenting with a patent ductus arteriosus are usually asymptomatic, no acute management is needed. However, until the patency of the ductus is corrected, administer antibiotics in patients during instances of high exposure to bacteremia (eg, instrumentation, dental procedures), as recommended by the American Heart Association for the prevention of bacterial endocarditis. For more information, see Antibiotic Prophylactic Regimens for Endocarditis. In infants who present with congestive heart failure, the standard treatment of digoxin and diuretic therapy usually palliates the condition. These children can be treated until they are several years old and are good candidates for ductal closure. When medical treatment of congestive heart failure fails in infants, the patients are referred early for surgical closure of the structure. Closure of the patent ductus arteriosus is stimulated by administration of prostaglandin synthesis inhibitors, such as indomethacin or aspirin, which is effective in premature infants. Indomethacin (0.1 mg/kg body weight) is administered orally at 8-hour intervals. This treatment is particularly valuable in premature infants presenting with respiratory distress syndrome complicated by left-to-right shunting through the ductus. Surgical therapyTwo forms of surgical therapy are performed in patients with patent ductus arteriosus, namely, the traditional surgical approach, which entails a thoracotomy, and catheter closure. The advent of the catheter-closure technique has changed the policies for ductal management in most institutions. Currently, catheter closure is the accepted treatment for closure of a patent ductus arteriosus in most countries in which pediatric cardiac catheterization can be performed. Preoperative detailsWhichever mode of surgical therapy is used, the appropriate preoperative diagnostic testing is obtained to define other coexisting congenital heart lesions. If the catheter-based method is contemplated, the child is hydrated before the procedure to minimize the potential for dye-induced renal insufficiency. If the traditional surgical approach is used, appropriate preoperative laboratory studies are obtained to assess bleeding tendencies, concurrent infections, or pneumonia in the child. Intraoperative detailsCatheter-based closure For catheter closure of the ductus, the patient is prepared and taken to the cardiac catheterization laboratory. The occlusion device is delivered to the ductus through a special 8-French delivery catheter via the arterial or venous route. The device is positioned in the ductus, and the closure mechanism delivered. Traditional surgical closure (thoracotomy) When the traditional surgical approach is used, the patient is prepared for surgery. General anesthesia is used. Because the ductus is usually located on the left, the patient is positioned for a left thoracotomy (for a ductus on the right, a right thoracotomy is used). The chest is opened. The left superior intercostal vein is identified and ligated. The aorta and main pulmonary artery and the vagus and recurrent laryngeal nerves are identified. Care must also be taken to preserve the thoracic duct. The pericardium is opened, and the ductus is identified. Closure can be accomplished by division and oversewing of both sides of the structure, simple ligation with a heavy suture, or clipping with a large hemoclip. The method of closure used depends on the size of the ductus arteriosus and the experience of the surgeon. Cardiopulmonary bypass is usually not needed for the procedure but is used in rare instances when the ductus is calcified and closure can be accomplished only via patch closure from the inside the aorta. In these patients, cardiopulmonary bypass is instituted through the femoral approach. The left chest is opened. The aorta is clamped above and below the ductus. The aorta is opened, and a synthetic patch is sewn over the orifice of the ductus. The aorta is closed, and the patient is weaned from cardiopulmonary bypass in the standard fashion. At the termination of the procedure, chest tubes remain in the thoracic cavity to evacuate air and drain any residual fluid. Postoperative detailsCatheter-based closure: Patients undergoing transcatheter closure of the ductus arteriosus spend the night following the catheterization in the hospital for observation of the puncture site. They are discharged the following day to full normal activity. Traditional surgical closure: Surgical repair of the ductus is associated with low, but not absent, morbidity and mortality rates. After the thoracotomy, the patient usually requires a chest tube for 24 hours and a hospital convalescence of 3-5 days. Once discharged, patients usually require an additional 6-8 weeks of convalescence before returning to unrestricted activity. Follow-upRegardless of the method of closure used, patients return for a follow-up echocardiography 2-3 weeks after the procedure to assess the closure of the structure. If the traditional surgical approach is used, the patient is also checked for the presence of pulmonary complications (eg, atelectasis, pleural effusion) and for the healing status of the wound. COMPLICATIONSSection 8 of 12
Catheter-based closure: Complications from transcatheter closure of the ductus arteriosus include bleeding at the catheterization site, rupture of blood vessels, tachyarrhythmias, bradyarrhythmias, vascular occlusion, inappropriate deployment of the device, migration of the device, and incomplete closure of the ductus. To date, no deaths have been reported. Traditional surgical closure: Complications of the surgical approach include bleeding, injury to the recurrent laryngeal nerve, disruption of the thoracic duct with resultant chylothorax, and injury to the vagus nerve. The more serious complications of surgical closure include ligation of the left pulmonary artery, ligation of the descending aorta, or ligation of other arterial structures within the chest; the results of such mishaps are catastrophic. OUTCOME AND PROGNOSISSection 9 of 12
Excellent results from surgical and catheter closure of a patent ductus arteriosus have been reported. The mortality risk from surgical closure is less than 0.5%. If additional cardiac anomalies are present, the risk increases. A high risk is reported in the presence of associated lesions, increased pulmonary vascular resistance, or when the ductus is calcified or aneurysmal. The surgical mortality rate in premature infants ranges from 20-41%. No deaths have been reported from catheter closure; however, patients undergoing this procedure are part of a select group and have a generally good prognosis otherwise. FUTURE AND CONTROVERSIESSection 10 of 12
The future of the technique lies in further development of more sophisticated catheter methodologies to facilitate closure. As catheters shrink, the procedure may become appropriate in infants, and the traditional surgical approach may be used in premature patients and those in whom catheter approach is not possible. The future of pharmacologic therapy in the closure of a patent ductus arteriosus remains undetermined. The medical approach depends on a better understanding of the factors that precipitate closure of the ductus and of ductal histology. MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
Patent Ductus Arteriosus: Surgical Perspective excerpt Article Last Updated: Nov 8, 2007 | |||||||||||||||||||||||||||||||||
