This week, snare transaction speed during EMR on the ASGE SuTab tip of the week. So the concept is that if we increase the transaction speed, we cut through the tissue faster, that in and of itself will limit the thermal injury. And we can do that by squeezing the snare more tightly before we hit the electrocautery. So the opposite of that is we close on the lesion to the point where the snare is just touching it, and then initiate electrocautery, the burn is going to be slower. That slower burn will tend to be associated with more submucosal thermal injury. On the other hand, if we squeeze the snare very tightly to the point where we really feel some mechanical resistance to further snare closure before we apply the cautery, then when we initiate the cautery, the current density in this smaller snare will be very high, will tend to transect very rapidly, and that by itself helps to limit thermal injury to the submucosa. So I want to try to demonstrate that this method of squeezing the snare really tightly before applying the electrocautery reduces the differences that we see between coagulation current and cutting current delivered by a microprocessor-controlled unit pretty substantially. So we're going to resect the left-hand side of this lesion using coagulation current and the right-hand side using cutting current. Just to make clear, what we're going to try to demonstrate here, I've got a picture of this EMR about halfway through, and I've got these two big arrows on here, one blue and one white. And what we're going to demonstrate is the impact of going down the longitudinal axis of the lesion on the left-hand side with coagulation current, the blue petal, and on the right-hand side, endocut, the yellow petal. And what we're going to look at is transection speed, which is going to be a little bit faster with endocut, but not a lot faster. And also the thermal effects or our estimate of the thermal effects on the submucosa. So first we'll demonstrate transection speed on the right side using the cutting current, the endocut current. So we're getting a grip on the tissue. We have it nice and tight. You can see my hand tap, and it comes through. You saw the snare close there in about a second, I think a count of about one. We'll demonstrate that again. Grab a tissue, maybe a centimeter and a half of tissue, and now you'll see my hand in just a second. Watch the hand snap when the foot touches. There's the foot touch, and we're through that quickly. So almost instantaneous transection of pieces about a centimeter and a half to two centimeters in size using endocut. Let's look at speed of transection on the left-hand side, the side where we're using coagulation current. Looking at the defect where we've removed the polyps so far, actually there's less evidence of thermal injury on the left-hand side than the right-hand side. The right-hand side is where we're using endocut. Now maybe there's just more fibrosis over there, but certainly there's not evidence of charring on the left-hand side where we're using coagulation current. So we're grabbing now a pretty good sized piece of tissue. Obviously if you grab a really small piece of tissue and squeeze it very tightly, you can mechanically transect it. That's not going to happen with a larger piece of tissue. And once we've grabbed it, I'm going to take the snare from the technician, and I've got a really tight grip, really can't squeeze it any tighter. And then we're going to tap the blue pedal, and we'll look at when the foot goes down and then estimate the transection speed. And I would say it's between one and two seconds, a little bit longer than with endocut, but still very rapid transection and no significant evidence of thermal charring on the left-hand side with coag current. Let's look at the next piece of tissue resected with coagulation current. Please forgive me for not having the lighting better here, but I hope you can get the sense that the speed of transection is quick even with coag current. So we're squeezing the tissue, the technician is handing me the snare, and when the foot goes down, you can see that the transection speed is quite quick even with the coag current. The final defect after resection before application of STSC to the margin, looking at the submucosa for evidence of thermal injury for charring, the two sides look very similar. Certainly no obvious difference between the left side removed with coag current, the right side removed with endocut, but both of them with a focus on rapid speed of transection. So going back to the randomized trial that we discussed last week, the first randomized trial to compare currents in EMR or polypectomy, the study by Heiko Pohl and colleagues published in Gastroenterology, this multi-center group of EMR investigators comparing forced coagulation current to endocut Q on the 2-1-4 setting, looking at the all-important endpoint of delayed hemorrhage and showing no difference between the two current types, but the risk of immediate hemorrhage higher with endocut. And I mentioned my own suspicion that actually the risk of muscle injury is maybe greater with endocut Q compared to forced coagulation current. So the evidence now actually supports that we use forced coag current to perform EMR. In my own case, I've sort of gone back in time because early in my training, I used forced coagulation current, and then I went through a long phase of using only endocut, believing that that was the way to minimize thermal injury to the submucosa. And now forced coagulation current again, but with a couple of important differences, no longer the fixed output generator, but rather a microprocessor controlled generator and using tight closure of the snare before applying electrocautery to get rapid speed of transsection and also contributing to limiting thermal injury by that mechanism. Thanks and see you next week on the ASGE SuTab tip of the week.

transaction speed

EMR

endoscopic mucosal resection

thermal injury

snare closure