Kim M. Kerr, MD, is a board-certified pulmonologist. Her clinical and research interests are in chronic thromboembolic pulmonary hypertension (CTEPH) and critical care. She is involved in both inpatient and outpatient clinical trials studying pulmonary vascular disease and critical care medicine. Dr. Kerr is Clinical Professor of Medicine and the Medical Director of the Thornton Intensive Care Unit. Dr. Kerr discusses her work in the diagnosis and treatment of patients with CTEPH and the importance of the U.S. CTEPH Registry (www.usctephregistry.com).
My name is Kim Kerr, I'm a pulmonologist. I work at the University of California - San Diego.
I'm involved with the PTE Program there. CTEPH stands for chronic thromboembolic pulmonary hypertension. We've all probably heard about people who've had blood clots in their legs or people that had blood clots that have come to their lungs. There have been some famous people who've had what's called pulmonary emboli and it happens all the time in the United States. Estimates of up to a half a million people a year in the United States will have venous thromboembolism, pulmonary emboli.
The vast majority of those patients the clots will be dissolved and there's no ongoing significance for those patients. There's a small subset of those patients though whose clots don't go away and actually they develop pulmonary hypertension. These clots are no longer fresh clots, they're forming scars in the pulmonary artery. It puts a strain on the right heart and people get short of breath and they develop symptoms of right heart failure. We call them chronic blood clots but they're really scars. The way I explain it to patients is you have ... for instance, you break your leg, you put your leg in a cast and because you're not moving your leg you develop a clot in the vein in your leg.
Some of these patients or a lot of these patients, that clot in the vein breaks off and goes to the lung and lodges in the lung. Most of the time your body will break up most of that clot in your lung. There's something very unusual about a subset of patients. Probably, we don't know how many, estimates are one to maybe 8% of those patients something different happens. The clot doesn't break up, it really organizes into a scar. It doesn't go away. It pulls down on the pulmonary artery so it raises the pressures in the lung and you develop right heart failure.
What I explain to patients is that these aren't fresh clots anymore. They're very different. I say you cut your hand and you bleed. When the bleeding stops you have this jelly-like clot over the injury and then it forms a scab. When the scab falls off you have this white scar on your skin. That's what this looks like in the arteries now. Not like that jelly clot we all imagine is a clot but it's really more of a scar. That's why we can't dissolve it with clot busters. We can't suck them out. The only way to remove them is to have a surgeon go in and cut them out.
Recently, in the past 10 years or so, there's been a significant increase in interest in the diagnosis and treatment of patients with chronic thromboembolic pulmonary hypertension. People are just really excited about this disease. It's somewhat of a delayed but parallel course to the interest in pulmonary hypertension. You know, 25 years ago there were not many people interested in the disease, there was not much awareness of it and there weren't many treatments for it. I think as drugs became available for the treatment of pulmonary hypertension doctors were more interested in it. Hence, awareness increased and they began to look for the disease.
Perhaps that's part of the story with CTEPH as well. The treatment is, the recommended treatment for operable patients is for them to be treated with surgery. However, recently the first drug was FDA approved for the treatment of CTEPH when patients weren't operable or if they still had residual pulmonary hypertension after surgery. We've had a lot of efforts from industry as well as academia trying to raise awareness of this disease and the treatment of it.
The [U.S.] CTEPH Registry (www.usctephregistry.com) is really in its infancy at this point but we're very excited about it. This was born out of our concern that a lot of patients may have to travel a great distance to get their surgery. Then they go home and it's hard to get follow-up information on those people.
We also realize that there are patients that are never referred for surgery even though they have CTEPH and what happens to those people. We formed a steering committee consisting of a number of ... It's a multidisciplinary team. We have cardiologists, and pulmonologists, and surgeons, and an epidemiologist. We came up with a bunch of questions we wanted to answer about this disease. We began enrolling in April, 2015. All our sites are activated. We have 30 sites throughout the United States that are participating in this registry. We'd love to have more, we really would. There are a lot of great pulmonary hypertension centers out there but we are limited for financial reasons so we were trying to get good geographic representation throughout the United States.
We're just enrolling newly diagnosed patients with CTEPH at this point. People who have been diagnosed with CTEPH within the previous six months. We're gathering baseline information like their symptoms and what kind of doctors they saw. We also ask things like what other diagnoses were you given, essentially the wrong diagnosis, before someone made the right diagnosis and what kind of doctors were you seeing? We think that information will be helpful in targeting education in the future to medical providers.
We're capturing information about the therapies they're getting and their response to therapy. Something that's a little bit unique about this registry is we're looking at quality of life. Our subjects in the registry are filling out quality of life surveys for us every six months. We just don't want to know if, for instance, if you have surgery or you start on a medication is your six month walk distance better. We want to know is your life really better in response to these therapies. This will go on, we're going to enroll 750 subjects. The registry will end when subject 750 has been in the registry for one year. We anticipate that will take about five years to complete this project, we're excited about that.