The overall goal of the following experiment is to map the placental vasculature in monochorionic twin pregnancies with special attention to intertwine connections. This is achieved first by careful acquisition and preparation of the placenta after delivery to facilitate visualization of the vasculature. As a second step, catheters are inserted into the arterial and venous circulations of each twin, allowing for injection of dye into the vasculature.
Next, a different color dye is injected into the arteries and veins of each twin in order to demonstrate the number and type of intertwining connections. Finally, the morphology chief, the placental vasculature can be observed based on the vascular mapping demonstrated by the dye injection. My name is Eric Gellan and I'm a general surgery resident and fetal fellow in UCSF's fetal treatment center.
This method allows us to answer key questions about the fetal management of Monochorionic twins, such as which Monochorionic disease states benefit from fetal intervention. My name is Sam Schechter and I'm a general surgery resident and fetal fellow at the UCSF Fetal Treatment Center. The implications of this procedure extend towards the therapy and diagnosis of twin two, twin transfusion syndrome or TTTS.
It allows for the assessment of the efficacy of laser ablation for the inner twin connections. For TTTS Acquire the placenta as soon as possible after delivery to minimize clot formation, desiccation, and overall deterioration of the tissue. Place a large plastic or metal bowl that has precut holes that allow for drainage of placental fluids into a large stainless steel bowl.
Place the placenta into the inner of the two bowls, wash the placenta with warm saline, and then for better placental visualization, use Metzenbaum scissors to excise the inter intertwine amniotic membranes, being sure not to injure the placenta itself. Leave a one half centimeter cuff of intertwine membrane in place. Identify the cords of the respective twins confirming which cords supplied the presenting twin one at a time, keeping track of which cord is which transect each cord just below the clamps.
Then gently milk any clots out from the vessels. Identify the vein and arteries at the cut edge of the cord as seen in this representative image. There will be one vein as indicated by the arrow, and at least one usually two arteries indicated here by the arrowheads.
The most difficult part about performing this procedure is cannulating the umbilical artery. Some groups have found that not using a wire and just using umbilical artery catheter is actually quite successful and we've found this as well, but we find that using a guide wire facilitates a procedure and makes it much more efficient. Next, use a Kelly clamp to generate gentle counter tension on the nonvascular portion of the cut edge of the cord.
Then use a standard radial arterial line guide wire with a soft tip to gain access to an arterial orifice on the cut edge of twin a's quart. Turning the quart slightly to straighten the tortuous vessels may help advance the wire. Insert the guide, wire a minimum of three centimeters into the vessel using the cell dinger technique.
Thread a 20 centimeter long 0.6 to 1.19 millimeter inner diameter polyethylene catheter with a bluntly beveled distal end over the wire into the artery. Remove the wire after the catheter is seated at least three centimeters into the vessel. Ensure the proper placement of the catheter by injecting a small amount of saline into the vessel and observing the clearing of distal arteries.
Gentle finger sweeps on the vessels while injecting saline may help facilitate movement of any residual clots. Then using the same G wire procedure as for the artery and avoiding dislodging the arterial catheter. Place a catheter in the cord vein of twin a tie, a piece of umbilical tape, one centimeter distal to the cut edge around the cord in catheters.
After having successfully catheterized the cord of the non-res presenting twin. In the same way, ensure that the catheters in the umbilical artery and vein of each twin are secured with umbilical tape and that both circulations have been infused with saline as has been done for the placenta shown in this figure. Choose four contrasting colors with which to inject the arteries and veins of twins, A and B with the colors for the artery and vein for each twin being readily distinguishable.
Superficial anastomosis should be detectable by dye mixing and the formation of a different easily detectable blended color as evidenced in this figure by the presence of the green dye and as indicated by the arrow. Now, using a three milliliter syringe hand inject the artery of twin A with dye at low pressure, gently sweep one or two fingers along the vessels in the direction of the dye flow to ensure the filling of the entire vascular tree. If a superficial vascular anastomosis is identified, manual occlusion of the feeding vessel can be employed to allow the rest of the higher resistance vascular bed to fill.
Use a separate three milliliter syringe to hand inject the artery of twin B and then perform the venous injections in the same manner. Finally, use the high resolution digital camera to take an image after each injection. After all the injections are complete, remove the specimen from the bowls.
Place it against a color neutral background and re-image. Carefully document the number and type of connections seen between the twins circulations As seen in this figure, catheters have been placed in the umbilical vein and in one umbilical artery of each twin. The catheters have been secured and placed with umbilical tape ties around the entire cord.
The correct positioning of each catheter has been confirmed and intraluminal clots have been cleared by the injection of warmed normal saline. In this placenta, the arterial circulation of twin A has been injected with yellow dye as indicated by the arrow. The contrast clearly passes across the vascular equator into the arterial circulation of twin B.Here, the injection of the arterial circulation of twin B from the same placenta is in the previous figure, can be seen add mixing of the yellow dye from twin A and the blue dye from twin B resulted in green dye within the arterial arterial anastomosis or aa.
As demonstrated with the arrow. For this placenta, an AA had been prospectively identified in utero by doppler ultrasound. This finding was confirmed by the mixing of twin A arterial in yellow and twin B arterial in blue In a communicating arterial structure in green and further indicated by the arrow, the vein of twin A also has been injected with red dye, and the vein of twin B is orange and arterial venous anastomosis with flow directed from twin A toward twin B is delineated by the arrowhead.
Here an example of a monochorionic twin placenta that underwent laser therapy after postnatal injection is shown. The donor twins artery and vein are in yellow and green respectively. The recipient artery and vein are in blue and orange respectively.
No residual connections between the circulations were detected. The last figure shows another example of a monochorionic twin placenta after injection. The left-sided twins artery and vein are in yellow and red respectively.
The right-sided twins artery and vein are in blue and orange respectively. An AA is indicated by the arrowhead and Aveeno venous anastomosis as indicated by the arrow, are visible on the placental surface. Once mastered, this technique can be performed in 45 minutes.
If done correctly. After watching this video, you should have a good understanding of how to inject dye into the arterial and venous systems of monochorionic twin placentas to demonstrate vascular connections and anatomy.
