Case report
A nine-month-old boy was diagnosed with ventricular septal defect (VSD) and patent ductus arterious (PDA) during birth. This patient was admitted to the hospital for surgical VSD repair and PDA ligation.
After anesthesia and intubation were administered, intra-operative transesophageal echocardiography (TEE) was performed. A complete TEE examination was conducted before cardiopulmonary bypass (CPB) using a Phillips IE33 ultrasound system equipped with 2D pulsed, continuous, and color Doppler capabilities and Oldelft minimulti TEE probe S7-3t (10.7 mm to 8.0 mm diameter tip with a 7.4 mm diameter shaft for patients>3.5 kg).
TEE in the mid-esophageal two-chamber view showed the following: left atrial and ventricular enlargement (LA= 26 mm, LV= 35 mm, EDD= 36 mm); moderate to severe eccentric mitral regurgitation with normal mitral valve anatomy; mild tricuspid regurgitation with normal valve anatomy; and normal-sized right heart. The mid-esophageal aortic valve LAX view and the mid-esophageal four-chamber view revealed VSD (3 mm). The mid-esophageal right ventricular inflow-outflow view showed a dilated main pulmonary artery without pulmonary valve regurgitation. A PDA that measured 6 mm long and 4 mm wide with a left-to-right shunt was detected in the modified upper esophageal aortic arch short axis view (Fig. 1). Continuous wave Doppler showed a continuous spectrum. The peak velocities of the systolic shunt flow and the diastolic flow were 3.4 m/s and 1.3 m/s, respectively, yielding a peak gradient of 46 mmHg between the descending aortic artery and the pulmonary artery. The diastolic velocity of 1.3 m/s yielded the lowest gradient of 7 mmHg.
After CPB was initiated, PDA was ligated under TEE monitoring before the aorta was clamped, showing that the normal-colored Doppler blood flow signal in the descending aorta disappeared. Instead, two blood flow signals from the intercostal artery crossed the descending aorta, which we could visualize in the mid-esophageal descending aortic short axis and long axis views (Fig. 2A). Blood flow in the left renal artery could not be detected by TEE (Fig. 2C).
After we excluded the possibility of an error made by the surgeons who might have ligated the descending aorta instead of the PDA, co-arctation of aorta (CoA) was immediately suspected. The surgeons released the ligation at the PDA immediately, and the aortic arch and the descending aorta were surgically investigated. A co-arctation of the descending aorta was found close to the PDA. After PDA was completely ligated, the narrowed segment of the aorta with extended end-to-end anastomosis was excised under deep hypothermic circulatory arrest. Fig.3 shows the excised segment of the CoA.
Post-operative TEE showed normal blood flow in the descending aorta supplying the intercostal arteries (Fig. 2B). The left renal artery had normal blood flow (Fig. 2D). No residual left-to-right shunt was detected. The patient had an uneventful post-operative recovery.
Discussion
CoA is the fifth most common congenital heart defect accounting for 6% to 8% of live births with congenital heart disease. CoA is usually manifested as a discrete constriction of the aortic isthmus [
1]. The diagnosis of CoA depends on typical clinical symptoms such as hypertension, a pressure gradient between arms and legs, absent or diminished femoral pulses, differential cyanosis, and imaging findings (transthoracic echocardiography (TTE), angiography, MRI) [
2]. Co-arctation has three types: ductal, preductal, and postductal co-arctation. The narrow part of ductal co-arctation is found at the insertion of the ductus arteriosus. Ductal co-arctation usually appears when the ductus arteriosus closes. In this case, a patient’s ductal co-arctation is difficult to diagnose by clinical presentation and is more difficult to find by TTE and TEE compared with preductal and postductal co-arctation.
However, ductal and preductal CoA are common in infants and sometimes associated with various defects such as PDA, bicuspid aortic valve, VSD, and mitral regurgitation [
3]. These conditions result in a more complex pathophysiology and the diagnosis becomes more difficult. The narrowing of preductal co-arctation is proximal to the insertion of the ductus arteriosus, and this finding is common in infants. Postductal co-arctation is more common in adults.
PDA is an important factor in the progression of the disease. Closure of PDA, which possibly constricts at 3βd to 5 d of age or by elective surgery, is often the precipitating factor for cardiopulmonary decompensation in this age group [
4].
To minimize the symptoms of CoA, PDA involves different mechanisms. For patients with a left-to-right shunt, PDA possibly functions as a conduit bypassing the site for CoA [
4]. For patients with right-to-left shunt in PDA, blood flow from pulmonary artery supplies the descending aorta (Fig. 4).
Preoperative TTE and TEE of this patient both showed a left-to-right shunt by PDA, and cyanosis was not noted in the baby before surgery. We concluded that PDA functions as a conduit for bypass (Fig. 3A). After surgeons clipped the PDA, the blood flow in the descending aorta suddenly dropped. Fortunately, the entire surgical procedure of PDA closure was monitored by TEE, which helped the anesthesiologist find the lesion immediately.
TEE monitoring has been a routine technique for PDA ligation in our hospital. TEE has been proven as an effective monitoring technique to evaluate residual patency and detect some undiagnosed cardiac lesions [
5]. However, the use of TEE to detect some rare complications of PDA ligation has not been reported yet. Our article is the first to monitor the descending artery blood flow during the entire PDA ligation procedure by performing TEE. To monitor the blood flow in the descending aorta, we initially inserted a probe on the mid-esophageal plane, moved the probe counterclockwise to find and visualize the aorta in the middle of the image, and advanced the probe across a 5 cm range. We found the short axis and long axis views of the descending aorta by rotating the omniplane angle from 0° to 100°, where we can monitor the blood flow from the ascending aorta to the descending aorta (distal aortic arch to descending aorta). We further moved the TEE probe in the fundus of the stomach and turned it posteriorly to find the abdominal aorta. We subsequently turned the probe counterclockwise to find the left renal artery originating from the abdominal aorta.
In the presence of a large PDA, CoA cannot be clinically diagnosed because PDA masks the clinical features. This condition impedes the identification of CoA by TTE [
2]. For anesthesiologists, this condition should be considered when the ductus is surgically interrupted in neonates and infants. During surgery, anesthesiologists should pay attention to the lower aortic segment. A few traditional methods can be used to monitor lower aortic blood supply. These methods include pulse oximetry of the lower limb and non-invasive or invasive lower limb blood pressure, which are easy to practice. For patients undergoing PDA ligation but have not been previously diagnosed with CoA, upper and lower limb blood pressures as well as pulse oximetry are not routine methods. By contrast, TEE has been a routine method for every patient undergoing cardiac surgery. TEE can monitor PDA ligation and detect abnormal descending aorta directly and promptly.
Compliance with ethics guidelines
Fei Liu, Ming-chon Hsiung, Haibo Song , Ke Dian, Hong Tang, and Jin Liu declare that they have no conflict of interest.
All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000 (5). Informed consent was obtained from all patients for being included in the study.
Higher Education Press and Springer-Verlag Berlin Heidelberg
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