A simple device for vascular occlusion of acardiac twins

Abstract

The case recently reported by Quintero et al.1 highlights the complexity of some of the currently available options for the treatment of acardiac twins. These authors used remote broadband telemedicine to guide a fetoscopic umbilical cord laser occlusion of an acardiac twin, which took almost 2 h to complete. It is obvious that simpler, cheaper and more widely available techniques to occlude the circulation of acardiac twins are urgently needed. This issue is even more relevant in centers in developing countries, which frequently do not have the proper equipment nor the appropriately trained personnel to perform these complex interventions, unlike tertiary referral centers across Europe and America. We report the use of a simple device to ablate the vascular supply to acardiac twins using monopolar diathermy (Figure 1). It consists of a 1-mm insulated, semi-rigid, solid wire obtained from a six-wire phone cable, which can be housed in an 18-gauge disposable Echotip® needle (Cook Medical Products, Spencer, IN, USA). A piece of the insulated wire measuring at least 60 cm was prepared, bared at both ends by 5 mm and autoclaved. Once in the operating room, a diathermy pad was applied to the maternal thigh and the abdomen cleaned and draped. Color Doppler ultrasound was used to select the best access to target the main intra-abdominal vessel of the acardiac twin2. Under sterile conditions, local anesthesia and continuous ultrasound control, the needle was advanced until its echogenic tip was placed close to the targeted vessel (Figure 2a). The stylet was removed and the insulated wire introduced through the lumen of the needle until its tip passed the tip of the needle for at least 10 mm. This was critical to ensure that the bare tip of the wire was not in contact with the non-insulated needle and therefore preventing the risk of thermal injury along the track of the needle. The distal end of the wire was handed to an assistant, who completed the diathermy circuit by connecting the distal end of the wire to the knife diathermy lead in a non-sterile fashion. The power was set at 30–40 W and several pulses were delivered until a hyperechogenic area surrounding the tip of the wire was evident (Figure 2b). If blood flow was still present, the wire was carefully pulled out, the tip was cut and bared again and the procedure then repeated until blood flow stopped. Alternatively, a new wire can be used at further attempts. (a) The 1-mm insulated wire with bare tips at both ends in a 18-gauge needle. (b) After the needle is directed percutaneously into the main intra-abdominal vessel of the acardiac twin, the wire is introduced through its lumen until the bare tip is no longer in contact with the needle (step 1). The diathermy circuit is then completed by connecting the distal end of the wire to the knife diathermy lead (step 2). (a) Color Doppler ultrasound shows the targeted intra-abdominal vessel of the acardiac twin and both the needle and wire in position for monopolar diathermy. (b) Color Doppler ultrasound after firing diathermy energy shows a hyperechogenic area surrounding the tip of the wire with occlusion of the fetal vessel. We used this technique to occlude the vascular supply to two acardiac twins, one from a monochorionic–diamniotic twin pregnancy at 29 weeks and the other from a monochorionic–diamniotic triplet pregnancy at 16 weeks in which the acardiac twin was in its own amniotic sac. In both cases the size of the acardiac twin exceeded 70% the size of the normal twin(s). The first case was also complicated by polyhydramnios and premature contractions and amniodrainage of 2 L had been performed 5 days before. The procedure was carried out in two public hospitals in Chile, following local ethics committee regulations, and full informed consent was obtained from the parents. Both procedures were uncomplicated, achieving complete ablation at the third and second attempt, respectively, and intervention lasted for less than 20 min. Antibiotic prophylaxis and intravenous tocolysis were used and the women were discharged on the third postoperative day in good condition after ultrasound documentation of well-being in the surviving fetuses and absent blood flow signals in the acardiac twin. Unfortunately, the surviving monoamniotic twins from the second case died of cord entanglement. The other pregnancy presented with rupture of membranes and early labor at 31 weeks and a Cesarean section was performed. The pump twin weighed 1504 g and the macerated acardiac fetus 503 g. The normal twin had mild complications and was discharged in good condition on day 47. Postmortem examination of the acardiac twins confirmed complete occlusion of the main intra-abdominal vessel (Figure 3). Photograph of the corresponding pathological specimen shows the ablated area (arrows). Most of the available techniques for the treatment of acardiac twins require complex and expensive equipment3. Fetoscopic-guided ligation and laser coagulation of the acardiac twin's umbilical cord is only available in a few centers around the world, having the inherent risks associated with prolonged operative time, the need for general anesthesia and the use of relatively large-diameter operative instruments3-6. These limitations are also applicable to the recently developed techniques of bipolar cord coagulation7, 8 and radiofrequency9, which use ports of 3–5 mm thus increasing the risk of rupture of the membranes. The use of an ablative material such as alcohol, although having the advantage of being administered through an amniocentesis needle10, has the theoretical risk of crossing to the normal twin. Recently, the use of monopolar thermocoagulation using an 18-gauge needle was reported11, a technique which is simple however the insulated wire is purpose-made and at present not commercially available. Another simple technique is ultrasound-guided interstitial laser, but it requires expensive Nd : YAG laser equipment and fibers which are not universally available12, 13. Our technique, a modification of the one originally described by Rodeck et al.11, is minimally invasive, requires minimum material and uses needles and diathermy machines already available in any hospital, therefore removing the need for expensive and more cumbersome techniques. In addition, the insulated wire described here can be easily obtained from the local electrical warehouse and it only requires sterilization to be ready for use. This technique may provide the simplest invasive technique for the treatment of acardiac twins in clinical settings where interstitial laser is not available. Because the needle is the same as that used for chorionic villus sampling in the first trimester, it may also be useful for the elective ablation of acardiac twins in the early second trimester of pregnancy. However, although this technique looks promising, the safety and impact on perinatal outcome of the normal twin remain to be fully evaluated in a larger series of patients. We are grateful to Prof. C. H. Rodeck and Mr D. Talbert for their expert advice and to Dr R. Wimalasundera for his useful comments.