And, first of all, I have to say that I was not part of the primary author group of this section of mapping of ventricular arrhythmia, so I just, on their behalf, hope I don't screw this up too bad. But on behalf of all the authors, I'd like to thank Fred, Frank, and Ed for leading the way and keeping us focused and making this manuscript as good as it is. And I think it's really worth reading it, so be invited to read not only the small book but the real large pager. So Section 8, Mapping and Imaging of Ventricular Arrhythmia, will be my topic, and this section was actually led by Katja Zeppenfeld, and there are many main authors. Some of them are here, and they have put together 35 pages of filled information, three figures and 12 recommendations, out of a total of 166 references. And I've just shown you here what the recommendations actually are. There are 7 class 1 recommendations, 4 class 2A recommendations, and 1 class 2B recommendations. There are also some aspects of mapping in individual substitute entities that are referring to a different section. And I will focus on this and try to be as short as possible. So as you know, mapping of ventricular arrhythmias is actually done to identify critical components of the ventricular arrhythmia mechanism to target these and then do the ablation. So it's a critical component of the VT ablation, but it's only a part of it. So we have put together a couple of sections on classical VT mapping, including activation mapping, entrainment mapping, pace mapping, and we have put up a huge amount of information in regard to substitute mapping, including some data on multi-electrode mapping. And then again, the last two paragraphs of this section are on intraprocedural imaging, electro-atomic mapping systems, and robotic navigation. Just to show you these two of the three figures, because I think they are so beautiful, activation entrainment mapping is used in tolerated VT to identify critical VT components and to perform a localized VT ablation. In this how to perform entrainment mapping, which I think is a very nice chapter of this section, you can see that we focus on the stimulation, entrainment stimulation, and the QRS complex during entrainment. We look at the post-pacing interval, and we look for the stimulus to QRS and compare that to the local electrogram to QRS complex. And by doing so, you can identify in what part of a reentrant mechanism you actually are. So there are some advantages of activation entrainment mapping over substitute-based ablation, and that is that you can reliably eliminate individual VTs with a few number of ablations. So that is the crucial point for doing activation and entrainment mapping, if the VT allows you to. On the other hand, we know that less than 10% of the patients that undergo VT ablation today have tolerated VT that may be eligible for all these classical EP maneuvers. Therefore, substitute-based ablation evolved, and these were initially done using classical definition of SCAR, using bipolar voltages. Just to keep you reminded, this was all done with single-tip catheters, which may have a high sampling error, and this was actually done all in ischemic VTs. So maybe not all of this, even though some of this may be true for the non-ischemic cardiomyopathy group, we just need to be aware that most of what we know about substitute mapping is actually on ischemic cardiomyopathy. And so this is what the recommendations that we came up with, and there may be some errors, and let me know if you detect them. I put them in deliberately, so just on purpose to make you. Because I typed them, and you can see that we came up with a Class 1 recommendation to use electro-atomic mapping if we do an ablation procedure in a structural heart case. And I think this is crucial, because most of what we do in structural heart disease is substitute-based, and only using electro-atomic mapping will help you to have a clear, three-dimensional view of what to target for. It is also helpful in ventricular arrhythmias that are idiopathic, even though the mechanism may be different, and in these cases, using an electro-atomic mapping system will at least allow you to reduce fluoroscopy, even though it may not increase the success of the procedure. There's also one recommendation, a 2A recommendation on magnetic catheter navigation, which can be useful to reduce fluoroscopy. Having said that, using single-tip catheters might create a bias in regard to your sampling. High-density mapping has been there for the last four to five years, using different vendors, using different systems, using different catheters, and you just have to be aware that independent to which of these you use, there may be different characteristics for your mapping, and you just have to be aware that this may not be transferable from one system to the other, or vice versa. But the most important thing on high-density mapping, I think, is not the substitute characterization, but the characterization and documenting of the electrical microsignals that you can see with this. And this is one case where you can see these nice late potentials, which turn into a diastolic pathway potential during VT, and you would have missed all of these potentials if you just mapped with a 3.5 millimeter ablation catheter, because they will not be there. So that has created, the knowledge of this has created some other recommendations. For example, the one that subset mapping is useful for prevention of arrhythmia recurrences in patients with scar-related VT, and high-density multi-electrode mapping is helpful to obtain a more comprehensive characterization of the arrhythmogenic tissue during catheter ablation of scar-related VT. And I think it is important to know that substitute mapping is just intended to overcome the limitations of conventional mapping, especially if you have a non-tolerated VT, and multi-electrode mapping catheters may save you time, create a higher mapping resolution, a higher electrical and substitute resolution, but on the other hand, it appears that in prospective studies there is no effect on outcome. All of these substitute mapping approaches are imperfect, and we know that, and ideally by doing substitute mapping, we would try to identify targets for ablation that are critical for the ventricular tachycardia of the patient. We know right now that only approximately 30% of the identified isthmi that we identify in substitute mapping actually are related to VTs, and I just brought you some histological specimen from a case where ablation was performed in the border zone of a myocardial scar, and you can see how diverse the substrate actually is. This is the ablation area, and you can see that there is viable myocardium surrounded by thick strands of fibrotic tissue, and you can just imagine how diverse the electrograms in this specific area will look like, and creating higher and higher density mapping approaches might be able to better characterize the underlying substrate. So coming to the last recommendations that are in this manuscript that are mostly on intraprocedural imaging, coronary angiography should be used to localize the coronary arteries if you're ablating close to them, so that is in aortic cusp during ablation in the coronary sinus or in the epicardium. And then there are three recommendations that do not come from Europe because they are all on ice, and in Europe we don't do ice because we're not getting reimbursed and we don't know how to. But ice is, I think in one scenario, really very helpful. That is papillary muscle ventricular arrhythmia. It gives you a real-time localization of the papillary muscle in correlation to your catheter, and I believe that it will create a higher success rate in these patients, even though there's no randomized study available. This was put in as a class one recommendation for doing ablations on the papillary muscle. I do agree that if you have ice in place, you will be very early in the detection of relevant complications like pericardial effusions, but on the other hand, probably if you have a problem with a patient in a clinical situation, transthoracic echocardiography will do so as well. So in conclusion, and I will keep it short, substrate-based approaches are recommended for structural VT but should implement classical EP maneuvers and require electro-atomic mapping. High-density mapping can be helpful to increase spatial and electrical resolution, leading to shorter procedures and ablation times. Electro-atomic mapping systems are recommended in structural heart disease and can be helpful in idiopathic ventricular arrhythmias, and intra-procedural imaging helps to reduce complications and allows for early detection of complications but may increase efficacy in a subset of patients. Thank you very much. Thank you.

mapping techniques

electro-anatomic mapping

high-density mapping

ventricular tachycardia targets

intra-procedural imaging techniques