Asian Cardiovasc Thorac Ann 2008;16:288-291
© 2008 Asia Publishing EXchange Ltd
Esophageal Stethoscope in Thoracoscopic Interruption of Patent Ductus Arteriosus
Mahdi Kahrom, MD,
Hadi Kahrom, MD1
Department of Cardiothoracic Surgery
1 Department of Anesthesiology, Qaem Hospital, Mashhad University of Medical Sciences, Mashhad, Iran
For reprint information contact: Mahdi Kahrom, MD, Tel: 98 915 501 7276, Fax: 98 511 867 4939, Email: Kahrom{at}Irimc.org, Department of Cardiothoracic Surgery, Qaem Hospital, Mashhad University of Medical Sciences, Mashhad, 9195977178 Iran.
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ABSTRACT
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There is a significant rate of residual or recurrent ductal patency after video-assisted thoracoscopic closure of patent ductus arteriosus. Between February 2000 and October 2004, this procedure was carried out on 145 consecutive patients in whom heart sounds were monitored intraoperatively with an esophageal stethoscope. Changes in continuous cardiac murmurs were recorded after placing the 1st and 2nd vascular clips. There was no ductal flow after clipping twice in 138 (95%) patients; in the other 7, residual flow was abolished at the 3rd attempt. All patients left the operating room with no residual ductal patency on echocardiography. After 6 months, there was no incidence of residual patency. Intraoperative esophageal stethoscopy provides remarkably loud and clear heart sounds for direct monitoring and reliable evaluation of the entire course of thoracoscopic patent ductus arteriosus closure, without interrupting the surgical procedure, thus avoiding re-intervention and complications associated with residual ductal flow.
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INTRODUCTION
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Patent ductus arteriosus (PDA) was first successfully ligated in 1938.1 The management of PDA has evolved considerably since this surgical milestone. Before 1991, the standard operative approach to PDA was through a posterolateral thoracotomy. Recently, video-assisted thoracoscopic surgery (VATS) has assumed a prime role in the management of cardiothoracic diseases, including PDA interruption. Although VATS has been shown to have several advantages over an open thoracotomy, and become the preferred approach for PDA interruption, it is associated with a significant rate of residual ductal patency.2,3 We hypothesized that an intraoperative esophageal stethoscope could detect residual ductal flow and thus reduce the incidence of postoperative ductal patency. The purpose of this study was to determine the efficacy of esophageal stethoscopic monitoring as a simple method to improve the surgical result and eliminate re-interventions and complications associated with residual ductal flow after PDA clipping by VATS.
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PATIENTS AND METHODS
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We retrospectively reviewed our experience of 145 consecutive patients with PDA who underwent VATS clipping in our institution from February 2000 to October 2004. The protocols were approved by our committee on clinical investigation, and informed consent was obtained from the patients or their parents. The indication for PDA closure in infants was the presence of a clinically or instrumentally significant shunt. In older children, the indication was persistent patency. Excluded from this series were patients with associated cardiac lesions that required additional intracardiac surgery. Ductus diameter > 9 mm, previous thoracotomy, and the presence of calcification, active infection, or aneurysm were considered contraindications to VATS. The mean age at surgery was 4.2 years (range, 7 days–23 years), and the mean weight was 14.6 kg (range, 1.3–55 kg). All patients underwent preoperative echocardiography to confirm the diagnosis of PDA. Ductal size ranged from 3.2 to 7.9 mm (mean, 5.8 mm).
Under general anesthesia with single-lumen endotracheal intubation, the patient was placed in the right lateral decubitus position. All patients were monitored by 5-lead electrocardiogram, noninvasive blood pressure measurements, pulse oximetry, capnography, and temperature probe. In addition, patients presenting with signs or symptoms of congestive heart failure were monitored by intraarterial catheter. A 6F–24F (6–24-mm circumference) esophageal stethoscope probe (depending on patient size and anesthesiologist preference) was introduced shortly after induction of anesthesia, and gradually moved to the depth that yielded the maximal amplitude of continuous PDA murmur. Baseline evaluation was performed while the patient was being prepared and draped. All examinations were performed by the same anesthesiologist. Four small 3–5-mm thoracostomy incisions were made in the posterolateral chest wall to admit grasping forceps, cotton swabs for lung retraction, a 2.7-mm endoscope, and an L-shaped cautery device. No chest wall muscles were cut, and the ribs were not retracted. Exposure was achieved by retracting the inflated left upper lobe inferomedially. The parietal pleura overlying the duct was opened. The upper and lower angles of the PDA were dissected free, taking care to protect the vagus and recurrent laryngeal nerves, which were easily visualized. Two 10-mm titanium endoscopic clips were placed to interrupt the PDA. During the procedure, heart sounds were monitored by the anesthesiologist through the esophageal stethoscope. Changes in continuous cardiac murmurs were recorded after the 1st and 2nd clipping to check whether they had disappeared completely. Rapid conversion to thoracotomy was possible to control bleeding, although this was never necessary. A thoracostomy tube was placed through one of the ports while the others were closed. The lung was re-expanded, and the thoracostomy tube was removed in the operating room. All patients were extubated immediately after the procedure. Color-flow Doppler echocardiography was carried out in the operating room immediately after surgery to confirm the absence of residual ductal flow. Postoperatively, patients recovered in the post-anesthetic care unit. The referring pediatric cardiologists followed up each patient by echocardiography on the 7th postoperative day and after 6 months.
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RESULTS
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There was no operative (30-day) mortality. Mean operative time was 23 min (from incision to placement of surgical dressing) and median postoperative stay was 20 hours. The lowest intraoperative core temperature ranged from 34.8°C to 36.6°C. Associated mild cardiac anomalies were present in 5 patients, but none required treatment by sternotomy or open thoracotomy. All morbid events were recorded with particular attention to: residual ductal patency, VATS redo clipping, thoracotomy, transfusion for bleeding, clinically detected transient laryngeal nerve dysfunction (hoarseness, stridor, voice changes), persistent laryngeal nerve dysfunction, phrenic nerve injury, pneumothorax (requiring placement of a new drain), chylothorax, wound infection, aneurysm formation, pulmonary artery stenosis, inadvertent clipping of another vessel, endarteritis, endocarditis, or hemolysis. A complicated course was defined if any of these events happened at any time after the operation; such morbidity occurred in 5.5% of patients (Table 1
). There was no residual flow detected intraoperatively in 133 patients (91.7%) after placing a single clip and in 138 patients (95.2%) after the 2nd clipping. Seven patients (4.8%) had residual ductal flow immediately after placement of the 2nd vascular clip. It was detected by esophageal stethoscopy and promptly abolished by placing a 3rd clip. The immediate detection of residual flow in these patients did not prolong the surgical time significantly and avoided the need for another intervention. Transthoracic echocardiography (TTE) confirmed the elimination of ductal flow in all patients upon leaving the operating room. They were discharged home on the 1st postoperative day and underwent follow-up echocardiography 6 months later. A cardiologist blinded to the surgical details reviewed the echocardiography to confirm the appropriateness of the views taken and the absence of residual shunt. Neither residual nor recurrent ductal patency was revealed by color Doppler echocardiography in any case during outpatient follow-up.
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DISCUSSION
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Patent ductus arteriosus is reported to be the 3rd most common congenital cardiac lesion. Closure of an isolated PDA diagnosed in infancy removes the hemodynamic burden of the shunt, which may be responsible at times for severe congestive heart failure. In older children or adults, suppression of the shunt is advised to prevent infective endarteritis, pulmonary hypertension, heart failure, aneurysm formation, pulmonary or systemic thromboembolism, and to avoid the associated shortened life expectancy.4
Although PDA ligation via thoracotomy is a highly successful procedure, the advantages of VATS ligation include better preservation of pulmonary mechanics, shorter hospital stay, decreased postoperative pain, and prevention of post-thoracotomy syndrome which is characterized by spinal column and chest wall deformities that may proceed to decrease pulmonary function.5 Video-assisted thoracoscopic surgery offers other advantages to pediatric patients, including decreased incidence of scoliosis after thoracotomy, reported to be 22% to 33%. Other late complications include impaired shoulder strength, winged scapulas, breast disfigurement, and rib fusion with respiratory compromise in patients who have undergone a thoracotomy. Thoracoscopic interruption is thus becoming an attractive alternative to thoracotomy; however, assessing the efficacy of surgical closure by palpating the duct is impossible through diminutive thoracoscopic windows, and thus concerns have been raised over the adequacy of PDA ligation using thoracoscopy.
Clinical consequences of residual patency include hemodynamically significant left-to-right shunting that may result in congestive heart failure and pulmonary edema, the continued need for antibiotic prophylaxis against bacterial endocarditis, and perhaps even re-intervention. Furthermore, high flow velocity, as seen with residual patency, is associated with an increased risk of endocarditis. Several studies have documented residual and recurrent flow after VATS clipping, ranging from 1.4% to 10% during follow-up, while residual flow after open PDA interruption has been seen in 0% to 23% of patients.5–9 Closure in the catheterization laboratory is performed increasingly, but some restrictions on body weight and ductus morphology limit this possibility. Furthermore, interventional techniques have shown a variable rate of residual patency. Although a complete occlusion rate of 99.5% in midterm follow-up has been reported after transcatheter coil occlusion, an intermediate (1 year) residual shunt was present in 5% of patients enrolled in the European Registry.10,11 However, immediate residual patency was 41%, and it is unknown how often complete occlusion occurs. Persistent residual shunt seems to occur more often in larger PDAs.12,13
Concerns about ductal patency have led us and others to pursue intraoperative diagnostic tools during VATS to ascertain complete ductal interruption in the operating room and minimize the incidence of residual patency. The sensitivity and specificity of TTE in diagnosing PDA are well established. However, the use of TTE intraoperatively has several disadvantages. The probe is cumbersome and may become a hindrance during the procedure as 4 thoracostomies are used to manipulate and dissect the anatomical structures. In a small child, these thoracostomies along with the inserted instruments do not leave sufficient room for the TTE probe. The probe may also compromise the sterility of the surgical field. Furthermore, the chest cavity is filled with air, as the ipsilateral lung is retracted, and this medium has little echogenicity. Thus intraoperative TTE may be of poorer quality than the preoperative evaluation. With good technique, intraoperative transesophageal echocardiography can be useful to detect residual patency during VATS, providing high resolution for direct evaluation of the entire course of PDA ligation.12,14,15 However, it is not without complications and limitations. Laryngeal and esophageal damage has been known to occur on placement of the transesophageal probe in adults.16 In children, arrhythmias have been reported as well as isolated cases of bronchial and vascular obstruction.17–19 These complications occur infrequently and usually disappear with reduced anteflexion of the probe or by its removal. In some conditions, intraoperative transesophageal echocardiography is impossible or inapplicable due to patient size, especially in smaller children and premature infants.20
The esophageal stethoscope has been used for continuous auscultation during anesthesia for more than 50 years, but its efficacy and accuracy for monitoring the course of PDA ligation by VATS has never been investigated.
Although its use has recently declined, continuous auscultation during anesthesia is advocated in numerous anesthesiology text books because of its efficacy in monitoring apnea, myocardial depression, arrhythmias, endobronchial intubation, airway secretions, wheezing, and air embolus; it is also easy to use and incurs negligible expense. Our study suggests that an intraoperative esophageal stethoscope is a safe and effective alternative for monitoring VATS for PDA interruption. We demonstrated that esophageal stethoscopy detected residual flow in all cases precisely, as documented by immediately postoperative and scheduled follow-up echocardiography, and without any related complication. In situations where transesophageal Doppler monitoring is not available, it can be used for direct monitoring and reliable evaluation of the entire course of PDA ligation by VATS, without interrupting the surgical procedure. The availability of small-sized probes allows this technique to be applied to small children and premature infants.
Presented at the 16th World Congress of the World Society of Cardio-Thoracic Surgeons, Ottawa, Canada, August 17–20, 2006.
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REFERENCES
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ABSTRACT
INTRODUCTION
