Esophageal Doppler Monitor: A New Tool in Monitoring Video Assisted Thoracoscopic Surgery for Ligation of Patent Ductus Arteriosus

Abstract

To the Editor: Video assisted thoracoscopic surgery (VATS) has become the standard approach for patent ductus arteriosus PDA closure in many centers. Although this technique has many advantages, it carries a risk of residual ductal shunting.1 Because incomplete PDA ligation may necessitate reoperation or a need for lifelong infection prophylaxis, it is important to identify patients with residual ductal flow. Several authors have reported the usefulness of transesophageal echocardiography (TEE) to evaluate residual ductal patency.2,3 However, TEE examinations in children requires an echocardiographic specialist and may not be available in some centers. Instead of TEE we used esophageal Doppler monitor (EDM) to examine the ductal flow pattern. Eight pediatric patients were scheduled to undergo PDA closure using VATS. All patients were monitored with five-lead ECG, noninvasive arterial blood pressure, pulse oximeter, capnography, and body temperature. The device used is a Doppler monitor EDM (CardioQ, Deltex Medical, Chichester, UK) with a transesophageal Doppler probe. At the tip of the probe the Doppler transducer emits a 4-MHz continuous wave signal at an angle of 45 degrees to the long axis of the probe. Emitting the Doppler signal at 45 degrees facilitates the interrogation by the Doppler beam of the PDA opening in the descending aorta (Fig. 1).Figure 1.: Anatomical orientation of esophageal Doppler image: this figure demonstrates the relationship between the esophagus, Doppler probe, and PDA in the upper esophagus.After obtaining the best arterial waveform, the probe was withdrawn gradually and rotated anteriorly (so that esophagus is now posterior to aorta) until flow reversal in upper part of descending aorta appears. Then, the probe was further withdrawn until the characteristic high velocity flow pattern of PDA was obtained (Fig. 2).Figure 2.: High-velocity continuous flow is seen through systole and diastole. It can be seen that the direction of flow is predominantly above the baseline, consistent with flow from the ductus.Surgery was performed with the patient in the right lateral decubitus position. Successful PDA ligation was confirmed in the eight patients by the disappearance of the high velocity pattern (Fig. 3) and the absence of diastolic flow reversal in the descending aorta.Figure 3.: No residual ductal flow after application of vascular clip.The higher sensitivity of TEE for detection of residual shunt may be related to color flow mapping guidance.4 Although EDM uses only spectral Doppler analysis, none of our patients had a residual ductal flow during postoperative TTE examination. Our report represents a new application of esophageal Doppler monitor during VATS PDA closure. Because of small number of the patients in this report, we cannot judge with confidence whether EDM can replace TEE as a monitor of VATS PDA ligation. Ahmed M. Mukhtar, MD Gihan Obayah, MD Department of Anesthesia and Intensive Care Faculty of Medicine, Cairo University Cairo, Egypt [email protected]