An Intrapericardial Technique for PDA Ligation: Surgical Description and Clinical Outcome in 35 Dogs
A number of surgical techniques have been reported for dissection and ligation of patent ductus arteriosi (PDAs) in dogs. The objectives of this study were to provide a detailed description of an intrapericardial technique for PDA dissection and ligation and to report the clinical outcome of that technique in dogs. Medical records of 35 dogs were retrospectively reviewed for signalment, clinical signs, echocardiographic findings, surgical time, intra- and postoperative complications, and completeness of ductal closure. Median surgery time was 60 min (range, 35–125 min). Neither intraoperative nor postoperative complications occurred. Within 48 hr of surgery, the continuous left basilar heart murmur was absent in all dogs, and complete echocardiographic closure was confirmed in 29 of 32 dogs. Residual flow was identified echocardiographically in three dogs within 48 hr of surgery. Residual flow was decreased in one dog at 1 mo, which resolved within 33 mo. One dog had mild residual flow postoperatively but did not return for follow-up. The intrapericardial technique was successful for PDA dissection and ligation and had a lower rate (6%) of echocardiographic residual flow compared with previously reported techniques.
Introduction
Patent ductus arteriosus (PDA) is the most common congenital cardiac defect in dogs.1 If left untreated, PDAs can lead to left ventricular overload, which results in severe dilation of the left ventricle, mitral regurgitation, and congestive heart failure. PDAs are commonly treated by surgical ligation, accomplished via a left-sided, fourth intercostal thoracotomy.2–6 Although surgical ligation is a highly successful treatment option, transcatheter PDA occlusion has gained popularity and, when available, provides a minimally invasive treatment option with devices such as vascular embolization coils, vascular occlusion plugsa, and canine duct occludersb.7–9 Surgical ligation can also be performed in a minimally invasive manner using titanium ligating clips placed by either video-enhanced minithoracotomy or thoracoscopy.10 Surgical ligation is preferred for PDA morphologies not amenable to catheter-based closure and in small dogs weighing < 2.5 kg.11,12
A variety of extrapericardial and intrapericardial dissection techniques have been reported for PDA dissection and ligation.2–6 With the extrapericardial techniques, the PDA is exposed and isolated without opening the pericardium, followed by passage of nonabsorbable suture circumferentially around the PDA for ligation.4–6 With the Jackson-Henderson modification of the extrapericardial technique, extrapericardial dissection around the dorsal aorta is performed to facilitate passage of suture from dorsal to the aorta to cranial to the ductus then passage of the suture from dorsal to the aorta to caudal to the ductus, allowing the suture to encircle the ductus. Although the Jackson-Henderson technique was developed to decrease the risk of intraoperative PDA rupture, more periductal tissue is included in the ligature, which may either increase the risk of residual flow or recanalization of the ductus.13 The intrapericardial technique involves making an incision through the pericardium and mediastinal pleura perpendicular to the ductus at the level where the ductus enters the pulmonary artery. Although a brief discussion of the intrapericardial technique has been provided in several textbooks of veterinary surgery, to the authors’ knowledge, a detailed description of the intrapericardial dissection technique with clinical follow-up has yet to be reported.3,14,15 The purposes of this study were to provide a detailed description of the intrapericardial surgical technique for PDA ligation and to report surgical time, intra- and postoperative complication rates, echocardiographic findings, completeness of ductal closure, and clinical outcome in dogs.
Materials and Methods
Data Collection
Medical records were reviewed for dogs that had an intrapericardial PDA ligation for treatment of a PDA (left-to-right shunting) between 2005 and 2010. Use of the intrapericardial technique was based on surgeon preference. Information obtained from the medical records included signalment; body weight; clinical signs at the time of presentation; and the results of preoperative physical examination, blood work, thoracic radiographs, and echocardiography. Perioperative complications were also recorded, and total surgical time was calculated as the time from skin incision to completion of skin closure (based on the information in the surgical report). The primary surgeon was recorded, and a note was made regarding whether they were a faculty surgeon or a resident. If the surgeon was a resident, their year of training and if either a board-certified or faculty surgeon supervised the surgery was recorded. Postoperative auscultation and echocardiography results (performed both postoperatively and again between 1 mo and 56 mo postoperatively) for assessment of residual ductal flow were recorded. If present, the severity of residual ductal flow was reported as previously described.9
Anesthetic Protocol
Each dog was premedicated with hydromorphonec (0.1 mg/kg subcutaneously) and glycopyrrolated (0.01 mg/kg subcutaneously). General anesthesia was induced with diazepame (0.2 mg/kg IV) followed by etomidatef (1–3 mg/kg IV to effect). A surgical plane of anesthesia was maintained with sevofluraneg in oxygen and intermittent positive pressure ventilation was applied. Intraoperative monitoring included arterial blood pressure (invasive and noninvasive), electrocardiography, pulse oximetry, capnography, and either rectal or esophageal temperature monitoring. Lactated Ringer’s solutionh was administered IV. An intercostal block was performed, infiltrating the intercostal nerves caudal to the third, fourth, fifth, and sixth ribs using bupivacainei (1.5 mg/kg). The intercostal block was performed either preoperatively or intraoperatively, depending on the clinician’s preference. Blood gas analysis and additional analgesia with a constant rate IV infusion of fentanylj (0.8 μg/kg/min) and midazolamk (8 μg/kg/min) were administered at the discretion of the attending anesthesiologist.
Surgical Technique
A standard, left-sided, fourth intercostal thoracotomy was performed in all cases.16 A Finochietto retractor was placed, and the left cranial lung lobe was retracted caudally with a moistened gauze sponge, allowing visualization of the left heart base and associated structures (Figure 1). The vagus and phrenic nerves were identified. A combined mediastinal, pleural, and pericardial incision were made ventral and parallel to the vagus nerve using either the coagulate or a blend of the cut and coagulate settings at 15–20 watts on a electrosurgical generatorl. A fold of pericardium and pleura was elevated with DeBakey forceps. An assistant, standing on the opposite side of the table, gently grasped the fold of pericardium and pleura ventral to the vagus nerve while the surgeon gently grasped the pleura and pericardium dorsal to the phrenic nerve, creating tension between the tissue grasped between the paired Debakey forceps. A small incision was made using a burst of energy from the electrosurgical unit while maintaining tension on the fold of pericardial and pleural tissue (Figure 2A). The electrosurgical pencil tip was then used (unenergized) to push the cauterized edges of the incision gently apart. Pericardial fluid was gently suctioned using a Cooley suction tip. The combined mediastinal pleural and pericardial incision allowed direct visualization of the ventral aorta, main pulmonary artery, and both the cranial and caudal margins of the ductus arteriosus (Figure 2B). This incision was located opposite to the transverse pericardial sinus and could be used in the event of sudden significant hemorrhage to place a long vascular clamp through the transverse pericardial sinus across both the pulmonary trunk and ascending aorta proximal to the ductus.17,18 Occlusion of the distal aorta, brachiocephalic trunk, and left subclavian artery could also be performed to prevent backflow from vessels cranial to the ductus.17,18
Citation: Journal of the American Animal Hospital Association 49, 1; 10.5326/JAAHA-MS-5838
Citation: Journal of the American Animal Hospital Association 49, 1; 10.5326/JAAHA-MS-5838
Two dissection planes were subsequently created adjacent to the PDA (one cranial and one caudal to the ductus) to create an avenue for passage of right-angle forceps and suture. For creation of the cranial dissection plane, a fold of mediastinal pleura and periductal tissue cranial to the PDA and caudal and ventral to the aorta was identified and grasped with DeBakey forceps. Care was again taken to avoid grasping the vagus and recurrent laryngeal nerves. An assistant, standing on the opposite side of the table, gently grasped the caudal tissue while the surgeon gently grasped the cranial tissue, creating tension between the tissues. A small pulse of energy (as described above) was then used to desiccate the tissue between the forceps, opening the tissue plane cranial to the PDA (Figure 3A). To create the caudal dissection plane, care was taken to identify the main pulmonary artery and bifurcation of the pulmonary artery. The caudal plane was then made immediately caudal to the PDA. Periductal tissue caudal to the PDA was grasped with DeBakey forceps, and periductal tissue proximal to the bifurcation of the pulmonary artery was grasped with DeBakey forceps. Tension was created in the tissues, and a small pulse of energy was then used to desiccate the tissue between the forceps, opening the caudal dissection plane (Figure 3B). Once the dissection planes were created, the surgeon gently placed the distal 4–5mm of the tips of the DeBakey forceps into the dissection planes with the tips of the forceps in a closed position. The surgeon then gently allowed the DeBakey forceps to slowly open (tips opening in the transverse plane relative to the thorax) in a controlled manner to enlarge each dissection plane (Figure 4). Although simultaneous enlargement of dissection planes is illustrated in Figure 4, enlargement of the cranial and caudal dissection planes was typically performed by alternating between cranial and caudal dissection planes.
Citation: Journal of the American Animal Hospital Association 49, 1; 10.5326/JAAHA-MS-5838
Citation: Journal of the American Animal Hospital Association 49, 1; 10.5326/JAAHA-MS-5838
Once the cranial and caudal tissue dissection was completed, closed right-angle forceps were passed into the caudal dissection plane with the tips directed dorsally. The instrument tips were then rotated and advanced laterally and cranially until visible in the previously created dissection plane cranial to the PDA. Opening and closing of the right-angle forceps was not necessary when the forceps tips were not visible (medial to the ductus), thereby eliminating the need for blind, blunt dissection. At this point in the procedure, a thin layer of translucent areolar tissue was often present over the instrument tips. Either a sterile cotton tip applicators or DeBakey forceps were used to probe over the tips of the instrument until the tips penetrated this tissue layer and could then be passed laterally, out the cranial dissection plane (Figure 5). A premoistened, doubled strand of 2-0, 0, or 1 silk suture was then grasped by the right-angle forceps and passed from cranial to caudal by retracting the right-angle forceps through the previously created dissection planes. The ductus was ligated with two encircling ligatures. The combined mediastinal and pericardial incision was not closed.
Citation: Journal of the American Animal Hospital Association 49, 1; 10.5326/JAAHA-MS-5838
Prior to closure of the chest wall, either a 14-gauge, 3.25-inch angiocatheterm or 18-gauge IV catheter was introduced through a more caudal intercostal space into the left side of the thoracic cavity to facilitate evacuation of air using a three-way stopcock system. A routine thoracotomy closure was performed. Once the thoracotomy was closed, air and fluid were aspirated through the chest and the thoracic catheter was removed.
Postoperative Care
For the first 12–24 hr postoperatively, dogs were administered either a continuous rate IV infusion of fentanyl (3–4 μg/kg/hr) either with or without lidocainen (25 μg/kg/min) or IV boluses of hydromorphone (0.05–0.2 mg/kg q 4–6 hr). Five dogs received IV meloxicamo postoperatively (0.1–0.2 mg/kg). Between 12 hr and 24 hr postsurgically, dogs were transitioned to either IV buprenorphinep (0.01–0.02 mg/kg q 6–8 hr) or oral tramadolq (3–5 mg/kg q 6–8 hr).
Preoperative, Postoperative, and Follow-up Echocardiography
Echocardiographyr was performed by board-certified cardiologists and cardiology residents. The right, parasternal, short-axis, basilar and left, cranial, short-axis views were used to assess the PDA and residual flow postligation, depending on which view provided the clearest image in each individual dog.
Statistical Analysis
The age and weight of the dogs at the time of surgery, total surgical time, and the timing of follow-up echocardiography were described by median and range. Descriptive statistics were calculated using a standard software programs.
Results
Between 2005 and 2010, 35 dogs underwent intrapericardial PDA ligation. Median age was 4 mo (range, 2–84 mo). Median body weight was 2.6 kg (range, 0.7–8.6 kg). In total, 29 dogs were female, five were male, and one dog was a castrated male. Chihuahuas were the most commonly represented breed (n = 5), followed by mixed-breed dogs (n = 4), bichon frises (n = 3), Yorkshire terriers (n = 3), Maltese (n = 3), miniature poodles (n = 3), and dachshunds (n = 2). Twelve different pure breeds were represented by one dog each (border collie, cockapoo, Coton de Tulear, German shepherd dog, Alaskan Klee Kai, Havanese, Japanese spaniel, Polish Lowland sheepdog, Pomeranian, miniature schnauzer, Scottish terrier, and Shetland sheepdog).
Twenty-two dogs showed no clinical signs referable to either heart disease or heart failure at the time of presentation. Coughing was present in 5 of 35 dogs, tachypnea in 2 of 35 dogs, lethargy in 2 of 35 dogs, exercise intolerance in 2 of 35 dogs, and lethargy and dyspnea in 1 of 35 dogs. Continuous, left, basilar murmurs were auscultated in all dogs.
A complete blood cell count was performed on 13 dogs and a serum biochemical panel was performed on 27 dogs. Biochemical abnormalities were detected in one dog, which included hypocholesterolemia (92 mg/dL; range, 120–247 mg/dL), hypoalbuminemia (1.8 g/dL; range, 2.4–3.6 g/dL), and hyperammonemia (481 μg/dL; range, 0–50 μg/dL). A single, extrahepatic portosystemic shunt was confirmed on abdominal ultrasound in that dog. The portosystemic shunt was managed medically after the dog recovered from the PDA surgery, and an ameroid constrictor was surgically placed 1 mo after PDA ligation. No significant abnormalities were identified on blood work from any other dogs.
Thoracic radiographs showed evidence of generalized cardiac enlargement and pulmonary over circulation in all 35 dogs. In one dog, an alveolar pattern in the right cranial lung lobe was reported and bronchopneumonia was suspected; however, the dog was asymptomatic. Oral amoxicillin trihydrate/clavulanate potassiumt was prescribed, and the PDA ligation was performed the following day without complication.
A PDA (left-to-right shunting) was confirmed via echocardiography in all 35 dogs. Additional congenital cardiac defects were present in three dogs, including valvular aortic stenosis (n = 1), pulmonic stenosis (n = 1), and possible interatrial (left-to-right shunting) consistent with either a patent foramen ovale or atrial septal defect (n = 1).
Median surgery time was 60 min (range, 35–125 min). Surgery residents performed 26 surgeries, 24 of which were supervised by a faculty member. Two surgeries were performed unsupervised by third year residents. The residents performing the surgeries were in their first year in 9 cases, second year in 5 cases, and third year in 12 cases. Faculty surgeons performed the remaining nine cases. There were no intraoperative complications in any case. A 60 mo old dog developed sinus bradycardia (35–60 beats/min) in the postoperative period following PDA ligation, consistent with Branham’s sign.19 The bradycardia resolved spontaneously 2 hr after surgery.
Within 48 hr of surgical ligation, no continuous murmur was auscultated in any dog. Echocardiography was performed within 48 hr of surgery in 32 of 35 dogs, and complete closure of the PDA was documented in 29 of 32 of those dogs (91%). Residual ductal flow was documented in 3 of 32 dogs (9%). Residual flow was documented to be trivial (n = 1), mild (n = 1), and moderate (n = 1).
Follow-up echocardiographic studies were performed on 20 dogs at a median time of 3.5 mo (range, 1–56 mo) following ductal ligation. Complete ductal closure was confirmed in 19 of 20 of those dogs (95%). Of the three dogs with postoperative residual flow, two had follow-up echocardiograms, but the one dog with mild flow detected on postoperative echocardiogram did not return for follow-up echocardiogram. One of the two dogs with follow-up echocardiograms had moderate residual flow postoperatively, which decreased to trivial residual flow by 1 mo postoperatively. The other dog had follow-up echocardiograms at 3 mo and 33 mo postoperatively, and the residual flow was documented to be trivial at 3 mo. At 33 mo postoperatively, no residual flow was found, indicating complete ductal closure. At the early follow-up examinations in both of those dogs, the size of the left atrium and ventricle was smaller compared with the initial postoperative echocardiograms. No further treatment was recommended at the early follow-up examinations because the flow was determined to be clinically insignificant. Recanalization of the ductus was not documented in any dog that had a follow-up echocardiogram performed. Overall, complete closure of the ductus was confirmed echocardiographically at either the initial postoperative or follow-up time in 32 of 34 dogs (94%). Persistent, but trivial, residual flow was present in 2 of 34 dogs (6.0%). One dog did not have either postoperative or a follow-up echocardiogram but did not have a continuous murmur auscultated following surgery.
Discussion
PDA ligation was performed successfully in 35 dogs in this study using the intrapericardial technique without intraoperative complications. This technique was performed in dogs of various ages, breeds, and by surgeons with different experience levels, ranging from first year residents with faculty supervision to board-certified surgeons.
The majority of dogs in this study were either young, small breed dogs or dogs with large PDAs, both of which precluded the use of transcatheter arterial ductal occlusion techniques used at the authors’ institution. The ductal morphology of each dog’s PDA was not reported in this study because this information was not reported in the original echocardiographic reports. Thus, no conclusions about the applicability of this technique for different PDA morphologies can be made.
An understanding of the anatomy of the heart base is necessary for successfully employing this approach. The fibrous pericardium is a thin sac that covers most of the heart. At the heart base, the fibrous pericardium blends directly with both the adventitia of the aorta at the level of the brachiocephalic trunk and the adventitia of the main pulmonary artery proximal to the bifurcation. The ductus arteriosus originates proximal to the bifurcation of the pulmonary trunk and extends to the aorta. The fibrous pericardium inserts at the level of the ductus arteriosus.20 The combined mediastinal pleural and pericardial incision is performed in the pericardial sac immediately ventral to this insertion. Dissection at the cranial and caudal aspects of the PDA involves a small amount of dissection through the pericardial reflection. It is important when developing the caudal dissection plane to carefully identify the main pulmonary artery and the bifurcation of the pulmonary trunk to properly determine the location of the caudal plane of dissection proximal to the bifurcation of the pulmonary trunk immediately caudal to the PDA. Lack of anatomic knowledge of this area could lead to either accidental ligation of the main pulmonary artery or inclusion of the right pulmonary artery within the ligature. Neither of those problems was encountered in the cases included in this study.
The combined mediastinal and pericardial incision performed with the intrapericardial technique subjectively leads to excellent exposure and access to the cranial and caudal aspects of the PDA for development of the dissection planes. This exposure is also useful in the event of severe hemorrhage following rupture of the ductus arteriosus because the position of the opening of the pericardium lies opposite to the transverse pericardial sinus. Intrapericardial exposure allows placement of a long vascular clamp across the pulmonary trunk and ascending aorta to assist with control of hemorrhage.17,18
Blind dissection around the medial aspect of the PDA was not required in any of the included cases. The intrapericardial approach facilitated the creation of two dissection planes, initiated from within the pericardium, but located cranial and caudal to the ductus arteriosus (Figure 4). Those dissection planes were created with a focused burst from the electrosurgical unit applied to a tensioned fold of pericardium and mediastinal pleura that was gently lifted away from the ductus. In the authors’ opinion, creation of those two dissection planes from within the pericardium reduces the amount of tissue that must be negotiated and dissected during passage of right-angle forceps medial to the ductus arteriosus. Right-angle forceps can be passed in a caudal to cranial direction, around the medial aspect of the ductus arteriosus, without either blind or blunt dissection medial to the ductus arteriosus. A thin layer of translucent areolar connective tissue is often present overlying the tips of the right-angle forceps. That tissue is readily separated using either cotton tip applicators or DeBakey forceps. The exposure and lack of blind dissection medial to the ductus arteriosus are potential advantages of this technique. The above-described advantages may explain the absence of hemorrhage in dogs included in this study and may have reduced the risk of rupture of the ductus arteriosus in the hands of multiple surgeons with different experience levels. The rate of intraoperative ductal hemorrhage was very low, falling within the range of previously reported rates of hemorrhage (0–15%).13,21–25
The surgery time required for intrapericardial PDA ligation was a median of 60 min when the surgery was performed by different surgeons with varying amounts of experience. This is within the range of operative times reported for extrapericardial techniques, including the Jackson-Henderson modification (range, 20–88.4 min).2,21,26,27
In the postoperative period, one dog had Branham’s sign, which is a physiologic response associated with closure of the ductus arteriosus, resulting in bradycardia.15 Branham’s sign can occur following PDA occlusion due to the sudden cessation of arteriovenous shunting.19 Branham’s sign has been reported with a number of PDA surgery techniques but, to the authors’ knowledge, the normal duration of the sign and prevalence has not been reported.21,28 The affected dog’s bradycardia resolved within 2 hr of surgery without treatment.
The rate of residual ductal flow reported for the extrapericardial dissection and ligation techniques ranges from 21% to 53%.13,25,28 There are two studies that reported substantially lower residual flow rates. One study reported 5% persistent residual flow with extrapericardial dissection and hemoclips and the second reported 2.2% hemodynamically significant residual flow with an unspecified surgical PDA ligation technique.26,29 All of the dogs in the current study were screened carefully for continuous murmurs following PDA ligation. Although auscultation alone may be helpful in predicting successful PDA ligation, Doppler echocardiography is more sensitive than auscultation at detecting residual ductal flow.13 In the present report, none of the dogs had a continuous murmur postsurgically, but residual ductal flow was detected echocardiographically in 3 of 32 dogs that had postoperative echocardiography within 48 hr of surgery. At the time of the last echocardiogram, residual flow was present in 2 of those 3 dogs, but this flow (considered trivial in one dog and mild in the other dog) was determined to be clinically insignificant, and no further treatment was recommended. The residual flow rate of 6% in the current study, determined by postoperative echocardiography, compares favorably with previously reported residual flow rates. To the authors’ knowledge, the residual ductal flow rate has not been reported in dogs treated with intrapericardial PDA dissection and ligation. Based on the authors’ experience with this technique, intrapericardial dissection may reduce the quantity of periductal tissue included within the encircling ligatures and allow improved tightening of the ligatures compared with extrapericardial techniques, including the Jackson-Henderson modification. The intrapericardial technique could potentially result in lower residual flow and recanalization rates, although a randomized and controlled prospective study would be necessary to test this hypothesis.
Recanalization is suspected clinically if a continuous left basilar murmur characteristic of a PDA occurs postoperatively. Recanalization has been reported at a rate of 1–3% for extrapericardial PDA ligations, developing from 6 wk to longer than 37 mo following surgery.22,30 Recanalization may occur due to inadequate dissection around the PDA and incorporation of surrounding tissues into the ligature.31 In the current study, absence of recanalization was confirmed echocardiographically in 20 of 34 dogs between 1 mo and 56 mo after PDA ligation. This low recanalization rate may indicate a potential advantage of the intrapericardial technique due to the incorporation of minimal amounts of periductal tissue within the ligatures; however, the ability to detect recanalization may have been impaired in this study by low case numbers and the fact that a number of dogs in this study (15 of 35 dogs) did not have echocardiography performed subsequent to 48 hr postoperatively due to client’s inability to return to the hospital. The authors of this report acknowledge that more cases and long-term follow-up could increase the recanalization rate.
Several study limitations should be considered when interpreting these results. The most important include bias of the patient population presented for surgical ligation at the authors’ institution, the lack of a treatment group utilizing an extrapericardial technique, and the retrospective study design.
To the authors’ knowledge, there are no clear guidelines to aid surgeons in selecting dissection technique. In one surgery textbook, it was suggested that extrapericardial dissection can be used in most young dogs but in dogs with a short ductus or in older dogs, an intrapericardial dissection may be required because the periductal tissue is more fibrous and dissection could be more difficult.3 In the dogs included in the current study, the intrapericardial technique was easily performed on all dogs regardless of age.
Conclusion
This manuscript provided a detailed description of the intrapericardial technique for PDA isolation and ligation. This technique was successfully used in 35 dogs with low complication rates that compared favorably to other reported techniques. The intrapericardial technique should be considered as an alternate technique for PDA dissection and ligation for surgeons of different levels of experience.
Photograph showing the intraoperative appearance of the left heart base following a left, fourth intercostal thoracotomy. The aorta is denoted by an asterisk (*), the left pulmonary artery is denoted by an arrowhead, and the vagus and phrenic nerves are denoted by the upper and lower arrows, respectively.
Photographs showing the intraoperative appearance of the left heart base. A: Initiation of the combined mediastinal pleural and pericardial incision between the vagus nerve (short arrow) and phrenic nerve (long arrow). In this location, the pleura and pericardium can be elevated with DeBakey forceps. A monopolar electrosurgical handpiece is then used at a low setting (15–20 watts) to incise the tissue, resulting in the creation of a small window in the pericardium (arrowhead). The aorta is denoted by an asterisk (*). B: Completion of the incision allows visualization of the main pulmonary artery (arrowhead), left pulmonary artery (LPA), and left auricle (solid arrow). The aorta is denoted by the asterisk (*), and the patent ductus arteriosus (PDA) is denoted by the dashed arrow. In this photograph, the pericardial reflection immediately caudal to the PDA can be visualized. This is where the caudal dissection plane is created. LPA, left pulmonary artery.
Photograph of the intraoperative appearance of the left heart base. A: Following incision of the pericardial reflection over cranial aspect of the PDA (arrow), a cranial dissection plane is created (arrowhead). The aorta is denoted by the asterisk (*). To create the cranial dissection plane, a fold of mediastinal pleura and periductal tissue immediately cranial to the PDA and ventral to the aorta is identified and grasped with DeBakey forceps. A small pulse of energy is then used to desiccate the tissue between the forceps, opening the tissue plane cranial to the PDA. B: To create the caudal dissection plane (arrowhead), care is taken to identify the main pulmonary artery (MPA) and the bifurcation of the pulmonary artery. The caudal plane is then developed proximal to the bifurcation of the pulmonary artery immediately caudal to the PDA. The periductal tissue caudal to the PDA and craniodorsal to the main MPA is grasped with DeBakey forceps. A small pulse of energy is then used to desiccate the tissue between the forceps, opening the tissue plane caudal to the PDA. The aorta is denoted by the asterisk (*), and the left pulmonary artery is denoted by LPA. MPA, main pulmonary artery.
Photograph of the left heart base. The tips of the DeBakey forceps are positioned within the cranial and caudal dissection planes and allowed to gently open in the transverse plane, resulting in subsequent enlargement of both dissection planes. Although simultaneous enlargement of the dissection planes is illustrated, enlargement of the cranial and caudal dissection planes is typically performed by alternating between the two planes. The aorta is denoted by the asterisk (*), and the PDA is denoted by the arrow.
Photograph of the intraoperative appearance of the isolated PDA. Right-angle forceps are passed from caudal to cranial around the ductus arteriosus, using the previously created dissection planes. The tissue medial to the ductus arteriosus has been displaced into the cranial window, and a thin layer of translucent areolar tissue over the instrument tips is present. Sterile cotton tip applicators or DeBakey forceps are used to probe over the tips of the instrument until the tips penetrate this tissue layer and pass laterally out of the cranial dissection plane. The right-angle forceps are then opened to receive the double loop of suture that is subsequently pulled caudally into the caudal window. The aorta is denoted by the asterisk (*), and the PDA is denoted by the arrow.
Contributor Notes
L. Selmic’s updated credentials since article acceptance are BVetMed, DACVS.
