EP Doctor Maps Out the Future with GE

Interviewed by Jodie Miller
Interviewed by Jodie Miller
I was very happy to meet with Dr. Sra at this year s NASPE meeting in Washington, DC. Dr. Sra s background in electrophysiology is very extensive. He was the first American Clinical Investigator to implant an atrial defibrillator, he helped implant the first multi-programmable defibrillator for ventricular arrhythmia at one of India s most prestigious medical centers, as well as helping to establish the first Indian catheter ablation program. Currently his focus is on research, specifically in studying the mechanisms of atrial fibrillation. In addition, Dr. Sra is cworking to develop an optimal pacing lead delivery system for implantation into heart failure patients. In this interview, he describes his current research and projects. Surprisingly, I had no idea what electrophysiology was until I came to Milwaukee. I did my residency in Rochester, New York, and before that in England and India, then came to do a cardiology fellowship in Milwaukee. This hospital was one of the first centers in the country to start an electrophysiology program. Our first lab was started by Dr. Akhtar in 1977. So doing my fellowship here was very intellectually stimulating. In 1990 I finished my fellowship in electrophysiology, and since that time I ve stayed with the electrophysiology program in Milwaukee. We are with the University of Wisconsin and are part of the clinical faculty of the Milwaukee Clinical Campus. The reason I got interested in this part of electrophysiology is because of my interest in atrial fibrillation. We implanted the first atrial defibrillator in the U.S. in 1996 at St. Luke s Hospital. The company that manufactured the device was InControl, Inc. and the device was a stand-along defibrillator. There was a lot of work being done in atrial fibrillation at the time. If you look at the timeline of the development of treatment for atrial fibrillation in electrophysiology, physicians realized that atrial fibrillation was a rhythm that started from the left upper chamber, or the left atrium of the heart. Most of the triggers or PACs initiating atrial fibrillation originate from the pulmonary veins. The left atrium, along with the pulmonary veins, has a very complex three-dimensional geometry so the conventional catheter techniques for isolating these trigger sites and other strategic areas were not adequate. We had a meeting about two years ago with GE staff, at which it was decided to set up a program to deal with this problem in a systematic fashion. The first step was to create a three-dimensional image of the left atrium. The best way to do that was with a scan, such as a CT scan. We worked with GE Medical Systems to go through the process of imaging the heart and segmenting out the left atrium so that we could see the left atrium and the pulmonary veins the way they truly were, not the way we see them in the laboratory using other mapping technologies. This was possible because CT imaging created a three-dimensional structure of the left atrium and the pulmonary veins. Once we had that, we asked ourselves if we could look inside the left atrium as well. Showing not only the three-dimensional views, but also looking at the chamber from the inside, helped us to see how the veins really looked. This gave us a roadmap for ablation and helped us document the presence of one of the many complications of atrial fibrillation, pulmonary vein stenosis. The second step was that we needed to transfer the 3D images to our laboratories so we could view them in real time. We did this with a process called registration that we developed at the time. In this process, we took the three-dimensional images created by the CT and transferred them mathematically to our workstation in the EP lab. We were then able to see the images in real time. The third step was to be able to see the electrical impulses and ablation catheter on these images. For example, when we put the catheter into an image, we knew exactly where that catheter was in relationship to the complex geometry of the atrium and we were able to move the catheter around more precisely. We have not yet gotten to the last stage, that of using these techniques to do an ablation, but that is coming. We should be able to isolate these areas very easily using virtual reality imaging and registration of the catheters on these images in real time, similar to the way a surgeon would do in the operating room. We will now be able to see exactly where the pulmonary veins are and isolate them. I think the idea is that we should be able to see what we are doing, be able to move a catheter right into those areas, maneuver around them and isolate them very, very quickly. The whole idea is to make this process more efficient. Of course, there will never be a zero percent risk, but the process will be much less risky and easier to perform. Rather than merely 5% of EP physicians attempting ablation of atrial fibrillation because of its complexity, it will probably become the therapy of choice and most electrophysiologists will be able to perform the procedure. Although many catheters are already approved for ablation, I think the next stage is to get the right type of catheter which can be used to very quickly isolate the pulmonary veins. With the right type of catheter, instead of going from point to point, we can move very quickly around those veins since we will have the imaging now to virtually see the catheters. I think that the atrial defibrillator did not pan out as the treatment of choice because patients with the defibrillator did feel discomfort during the shock. When they were going in and out of atrial fibrillation they got multiple shocks and did not like that experience. However, atrial defibrillation has become an important component in the defibrillators implanted in patients with ventricular tachycardia who also suffer from atrial fibrillation. Thus, although atrial defibrillation was found useful in a limited group of patients, our work along these lines gave me great insight into what an immense problem atrial fibrillation really is and provided a roadmap to solve the problem. The InControl, Inc. company is no longer in existence, so we were unable to continue to offer patients this alternative, but some of our defibrillator patients have since undergone ablation of their atrial fibrillation. Thus, we do not have active patients with the InControl devices anymore. I think these devices were a stepping-stone in learning about atrial fibrillation. However, I think the work we are doing today is really the future of atrial fibrillation treatment. We have to cure AF, and the only way to cure it is when you are able to really see what you are doing while ablating. The only way to see what you are doing during these EP procedures is to have a true three-dimensional image. Currently, the two most important ailments which electrophysiology treats (in terms of sheer volume) are atrial fibrillation, which affects more than 2 million people, and congestive heart failure, which affects more than 5 million people. In a subgroup of patients, one of the treatments for congestive heart failure is biventricular pacing. In patients with heart failure and left bundle branch block, instead of simultaneous activation of both ventricles, the right ventricle is activated much earlier than the left ventricle, leading to a sequential activation pattern. The biventricular pacing principle is that you put a lead into a branch of the coronary sinus or from outside (epicardially). Then you can pace both the right ventricle and the left ventricle simultaneously, a process called resynchronization. The FDA has approved these biventricular devices. There is clear evidence that the devices improve quality of life, decrease hospitalization, and even decrease patient mortality. Unfortunately, it can take a long time to locate the coronary sinus and its branches. In about 10 to 15 percent of patients, we can t even find the coronary sinus because it is occluded or distorted. So we started looking more at left ventricle imaging and coronary sinus imaging; eventually the idea is that we should have a roadmap of the left ventricle and coronary sinus. We will be able to know beforehand whether we should even attempt to put a lead into the coronary sinus or whether we should go straight for the epicardial approach. In understanding anatomy and knowing where those blood vessels are, we will be able to figure out what segment we should really put the lead in. This will optimize the therapy and make it much quicker. I think this is going to be the next big thing in imaging and pacing in terms of heart failure. Yes, in India we performed the first multi-programmable defibrillator implantation. I have a teaching program in which we train people from India and other countries, in fact, many of the EP physicians in India have gone through our lab. Putting in the first programmable defibrillator in India was one of the most amazing experiences for me, because this patient was extremely poor. She was only 30 years of age, was post partum and had been in cardiac arrest. She lived 300 miles away from Delhi where we implanted the ICD. She did not even have the money to come to Delhi. The local staff was able to collect the money and send the patient to Delhi and Medtronic provided the device for free. The money was provided for her to go home and return back every six months to have the device checked. We put the defibrillator in her and her heart recovered completely after two years; she used the ICD three times. I think the whole future of electrophysiology is going to change. I just had a meeting with some people who wanted to know how the electrophysiology program will be 5 years from now, not next month or six months from now. My advice to all of the doctors that come out of our EP program is that they retain their perspective, that whatever we have now will change completely in the next five years. The rapidly evolving technology will make all the difference. Another piece of advice I have is that you must have the right personnel to start a program. If you don t have the right staff it becomes extremely difficult to have a good program. Also, you need the right type of equipment, which should include a mapping device. Then you should have a plan based upon what we have talked about. If you work in a hospital or lab that does not have access to imaging technology such as CT or MRI, you will fall behind. The technological advancements led by GE Medical Systems will be available soon, and patients will demand that type of care. I think that we have to be careful when designing EP labs today, they have to have some sort of infrastructure so that an intra-hospital or inter-hospital data transfer of 3D images will be possible.