Maternal and fetal cardiometabolic recovery following ultrasound-guided high-intensity focused ultrasound placental vascular occlusion

Abstract

High-intensity focused ultrasound (HIFU) is a non-invasive method of selective placental vascular occlusion, providing a potential therapy for conditions such as twin–twin transfusion syndrome. In order to translate this technique into human studies, evidence of prolonged fetal recovery and maintenance of a healthy fetal physiology following exposure to HIFU is essential. At 116 ± 2 days gestation, 12 pregnant ewes were assigned to control ( n = 6) or HIFU vascular occlusion ( n = 6) groups and anaesthetized. Placental blood vessels were identified using colour Doppler ultrasound; HIFU-mediated vascular occlusion was performed through intact maternal skin (1.66 MHz, 5 s duration, in situ I SPTA 1.8–3.9 kW cm −2 ). Unidentifiable colour Doppler signals in targeted vessels following HIFU exposure denoted successful occlusion. Ewes and fetuses were then surgically instrumented with vascular catheters and transonic flow probes and recovered from anaesthesia. A custom-made wireless data acquisition system, which records continuous maternal and fetal cardiovascular data, and daily blood sampling were used to assess wellbeing for 20 days, followed by post-mortem examination. Based on a comparison of pre- and post-treatment colour Doppler imaging, 100% (36/36) of placental vessels were occluded following HIFU, and occlusion persisted for 20 days. All fetuses survived. No differences in maternal or fetal blood pressure, heart rate, heart rate variability, metabolic status or oxygenation were observed between treatment groups. There was evidence of normal fetal maturation and no evidence of chronic fetal stress. There were no maternal injuries and no placental vascular haemorrhage. There was both a uterine and fetal burn, which did not result in any obstetric or fetal complications. This study demonstrates normal long-term recovery of fetal sheep from exposure to HIFU-mediated placental vascular occlusion and underlines the potential of HIFU as a potential non-invasive therapy in human pregnancy.

Early‐onset twin–twin transfusion syndrome: Case series and systematic review

“…[40][41][42][43] In this proposed human treatment, thermal energy generated by externally placed, ultrasound guided, HIFU transducers will be used to selectively occlude placental anastomoses along the vascular equator of the monochorionic placenta, without the requirement to enter the intrauterine space. [40][41][42][43] In this proposed human treatment, thermal energy generated by externally placed, ultrasound guided, HIFU transducers will be used to selectively occlude placental anastomoses along the vascular equator of the monochorionic placenta, without the requirement to enter the intrauterine space.…”

“…Non-invasive treatments for TTTS are particularly suitable at earlier gestations prior to membrane fusion; our group has reported early stage proof of principle studies of high-intensity focused ultrasound (HIFU) selective occlusion of placental vessels in sheep, which appears to be both effective and safe, and first in human studies are planned. [40][41][42][43] In this proposed human treatment, thermal energy generated by externally placed, ultrasound guided, HIFU transducers will be used to selectively occlude placental anastomoses along the vascular equator of the monochorionic placenta, without the requirement to enter the intrauterine space. If non-invasive occlusion of placental anastomoses were possible, with an associated reduction in procedure-related risks, this would represent a paradigm shift in the gestations and severity at which TTTS could be treated.…”

Twin Reversed Arterial Perfusion Sequence: Prenatal Diagnosis and Treatment

“…Therefore, a noninvasive approach using high-intensity focused ultrasound to the intrafetal umbilical vessels has also been tried. 28,29 BCC Since its introduction by Deprest et al 30 in 2000 in treating complicated MC twin pregnancies, BCC has been used to occlude the umbilical cord.…”

“…An anteriorly located placenta may limit access, and sometimes, the target twin is below the placenta or the pump twin, making the procedure more challenging. Therefore, a noninvasive approach using high-intensity focused ultrasound to the intrafetal umbilical vessels has also been tried 28,29 …”

Complex multiple pregnancies: what's new?

“…Ultimately, however, we need an even deeper understanding of the pathophysiology of TTTS and sIUGR and factors triggering these conditions to better predict or even prevent their occurrence. If that is not possible, we should aim for less invasive treatments such as high‐intensity focused ultrasound 26 or medical treatments. The Prenatal Diagnosis editors certainly look forward to receiving further submissions in this field and hope you will enjoy reading this special issue!…”