What are different types of aortic valves that are used in transcatheter aortic valve replacement? Dr. Anton Titov, MD. It is called TAVR. Or transcatheter aortic valve implantation, TAVI, as it is known in Europe. Dr. Jeffrey Popma, MD. We as interventional cardiologists didn't really know all that much about surgical aortic valves. We certainly knew that mechanical valves were preferred in younger patients. Because although patients were required to take warfarin, the valve durability was excellent. Patients would go for 20-30 years with the mechanical valve. Dr. Anton Titov, MD. They will not have any degeneration occur. But when we get into patients who are a little bit elderly. We take the choice of either a porcine or bovine bioprosthesis aortic valve surgically. There are both stented and stentless aortic valve systems. Dr. Jeffrey Popma, MD. On the transcatheter side with a number of devices with either bovine pericardial shape valves or porcine pericardial shape valves. We realized that there is a few design differences between TAVR and surgical aortic valves. They will lead to differences in outcomes. The question right now is all about hemodynamic performance. Dr. Jeffrey Popma, MD. For a typical patient with severe aortic stenosis this is true. A mean gradient would be 40 millimeters of mercury. Sometimes we are going to call it severe. It is an index for how severely narrow the aortic valve is. We do a surgical aortic valve replacement. We can reduce aortic valve gradient down to 12 millimeters of mercury. Dr. Anton Titov, MD. It sounds great, right? You have gone from 40 to 12 and patient will be very functional. But some of our newer transcatheter aortic valves perform very well. Because TAVI aortic valves have a lower profile in some valves. Dr. Jeffrey Popma, MD. Because of the fact that the aortic valve apparatus is above the valve in others. Then we can now get in some patients gradients of 6 - 8 - 10 millimeters of mercury. This is compared to the 12 or so on our surgical aortic valves. In fact, now we look at the three-year outcomes for high-risk patients. Dr. Jeffrey Popma, MD. We look at two-year outcomes in the intermediate risk patients. The echocardiographic indices of valve performance are better with the transcatheter aortic valves than they are with surgically replaced aortic valves. Dr. Jeffrey Popma, MD. We don't know whether or not that translates into a long-term benefit for the patients. Sometimes whatever starting platform you have is going to affect long-term outcome. We are still sorting it out in long-term studies of transcatheter aortic valve replacement. But certainly we have learned that we can get very low residual gradients with our transcatheter aortic valves. Gradients are better than what we will find thus far with surgical aortic valves. Dr. Jeffrey Popma, MD. Although I suspect that the surgeons are now coming up with other ways to get very low aortic valve gradients as well. Dr. Anton Titov, MD. The hemodynamic performance is still one of those unmet needs. It differentiates the surgical and the different transcatheter aortic valves.