Heart valve and coronary artery treatment procedures are very complicated. Open heart surgery and percutaneous transcatheter procedures are sometimes combined. The correct method of treatment has to be chosen and adjusted for each patient with heart disease. What diagnostic imaging studies are used to plan heart valve treatments today?
So, first of all, diagnostic imaging is being as important in the evolution of new heart disease treatments as the development of new technologies, new devices. So there has been a parallel pathway [in diagnostic imaging and treatment innovation]. On one side, we have been innovating in implantable devices. On the other side, we have been innovating and seeing, and using innovation in diagnostic imaging. So diagnostic imaging is fundamental not only for the planning of heart disease treatment but also for the conduction of treatment procedures. Endovascular structural intervention [heart valve and heart failure treatment] is guided by diagnostic imaging. Now, as far as planning, we have learned that in the structural interventions today, we have massive use of preprocedural diagnostic imaging. Specifically, I would say today. We use a lot of CT scans. Heart CT is becoming standard practice. In my practice, cardiac CT is standard not only for cardiac endovascular procedures but also for open cardiac surgical procedures.
In every patient I treat, I like to have a CT scan of the heart for many reasons. First of all, it is a one-stop shop for all the information about coronary artery access, coronary artery anatomy, coronary calcifications, and everything. Second, cardiac CT scan shows in a significant number of patients with some unexpected findings. Unfortunately, sometimes we find some tumors or other problems that need to have medical attention. So, in general, a cardiac CT scan is becoming a necessary step for each patient who indicates a structural heart disease intervention. But obviously, the mainstay of our decision-making is Doppler echocardiography. This diagnostic test remains today. Echocardiography is the first step for diagnosis of heart disease, for screening. Echocardiography is very simple to be performed. It is widely available, echocardiography is available at the bedside. It is becoming every year more and more sophisticated. There are 3D technologies, all kinds of predictive algorithms, etc.
Cardiac MRI is also emerging as an interesting diagnostic test. It's a functional diagnostic test. It also can be used for identifying the right timing of treatment and indications for treatment. So in general, we see the transition away from the classical heart disease diagnostic pathway where it was mainly driven by echocardiography and angiography. We move towards a more integrated multimodality diagnostic imaging approach. We have patients undergoing two or three different diagnostic imaging modalities to set up the indication for treatment. We develop the strategy to select the correct medical device in case of cardiac endovascular procedures. Even in the case of open-heart surgery we use multimodality diagnostic imaging to plan the procedure and prepare for the procedure.
In some cases, we even have simulators of the planned intervention. We are simulating the effect of an implant on the heart. We have simulators where sometimes you can even train yourself in the simulator before the intervention for complex cardiac procedures, and so on.
So you see that cardiac diagnostic imaging is an incredible field. It is becoming as important as the heart operation itself. Because through diagnostic imaging today, we can really predict what is going to happen with these heart treatment procedures. And the next step is going to be the application of finite element models and other technologies to predict the effect of an implant [on cardiac physiology and structure]. Imagine today you can predict the effect of a coronary artery angioplasty on the flow dynamics of the coronary arteries. Or you can predict what happens with a coronary artery bypass grafting in one lesion. You can predict how the calcium will distribute after you implant a TAVI. You can predict if there will be some atrioventricular block or if there will be some perivalvular leak. This can be all simulated with current diagnostic imaging technologies. They are becoming more and more available. And this means that our profession is becoming less and less about improvisation and more and more about planning, standardization, and, in the end, selecting the ideal treatment solution for the individual patient. This is individualized medicine, truly personalized medicine for all these structural cardiac treatment interventions.
Well, that's very important! And obviously, the CT scan of the heart also follows echocardiography, transthoracic versus transesophageal echocardiography. It helps to plan the heart treatment procedure. Are there any particular differences in diagnostic tests for people undergoing a mitral valve or aortic valve intervention versus patients undergoing perhaps heart failure surgery or other procedures? Is there a particular procedure-planning path that you use for different groups of patients?
Every pathology has a different multimodality diagnostic imaging package. It depends on the questions you need to answer. Let's make an example of a patient undergoing mitral valve or tricuspid valve surgery. These valves look very similar. They are both atrioventricular heart valves. But imagine, first of all, the CT scan for a mitral valve is done by a different protocol than the CT scan for tricuspid valve. The timing of the image acquisition is different because obviously, you need to catch the dye [in the right heart chamber]. In the right side of the heart, if you want to do a CT scan for the tricuspid valve, we really need to measure the right heart function with the right heart catheterization. Right heart categorization is very rarely performed for mitral valve interventions. For instance, intraprocedural guidance is done by transesophageal echocardiography. It is perfect for my job. It doesn't work so well for the tricuspid valve assessment. We still use it, but we are looking for alternatives.
We are looking for an intracardiac echocardiography, for instance, because of the quality of the image that you get from a transesophageal echocardiography in this particular application. And it also depends very much on the heart treatment procedure we plan to do. There are some procedures that are totally based on the echocardiography data. For some other heart disease treatment procedures, we rely more on fluoroscopy. And in some occasions, we even use fusion imaging. For the diagnostic phase, so this is a phase before the cardiac interventions. It very much depends on the questions we are asking.
Let's say you have a patient with aortic stenosis who will undergo an aortic valve replacement or TAVI. This patient's situation usually has two main questions. The number one question is this. Is the aortic stenosis severe? Yes or no? And the second question, what should I do? Should I do surgery or a TAVI? These are two questions that can be answered by echocardiography and by a heart CT scan. With quick answers to these two big questions, you answer 99% of the problems that are needed to make the decision [how to treat a patient with aortic valve stenosis]. Then you can check the coronary arteries, usually by a CT scan and many other tests. But you know, at the end of the day, you don't need so many diagnostic imaging steps. The situation is very different if you talk about heart failure patients that require structural surgical intervention.
So these are patients with tricuspid regurgitation, mitral regurgitation, low flow or low gradient across the aortic valve. In these cases, the diagnostic pathway is a bit more sophisticated. You need more diagnostic examinations, more functional data. In this field, cardiac MRI is not yet well established, but it's growing in importance. I think we start learning what to do with cardiac MRI. Cardiac MRI is also today focusing on intracardiac fluid flow, fluid dynamics, which is an emerging field. We see this information but we don't know what to do with that data. So we see the flow, how the blood moves in the chamber, how pathology is affecting these flow dynamics, but we don't know yet how to use them. I'm pretty sure that this is going to be one of the fundamental pieces of information that we want to achieve to plan cardiac treatment procedures.