KU Medical Center physicians testing new procedure for patients at high risk for severe heart failure
March 22, 2019
By Kristi Birch
A team of physician-researchers at the University of Kansas Medical Center is testing a new procedure that replaces a leaky heart valve for patients who are at high risk for heart failure but are too frail or ill for open heart surgery. The procedure is part of the APOLLO clinical trial, which is designed to test a novel replacement mitral valve placed in a minimally invasive surgery.
The mitral valve helps keep blood flowing the correct direction to deliver oxygen and other nutrients throughout the body. Mitral regurgitation (MR), a condition in which the mitral valve is faulty and allows the blood to flow backward into the heart's upper left chamber, affects 4 million Americans. The new procedure, known as transcatheter mitral valve replacement (TMVR), provides an alternative to open-heart surgery, a more invasive operation with a more difficult recovery.
So far, the KU team has performed the TMVR procedure successfully on three study participants. Of the heart's four valves, the mitral valve is the one most commonly in need of repair or replacement, yet it often goes untreated because those suffering from it are not able to withstand open-heart surgery.
"There's a huge unmet need for something like this. I believe it is really going to change our approach to heart valve replacement," said Mark Wiley, M.D., chair of the Department of Cardiovascular Medicine at the University of Kansas School of Medicine and a co-principal investigator on the study. "Only 20 to 30 percent of mitral disease that should be treated, is treated."
The KU Medical Center was one of the first of 43 institutions invited by valve-maker Medtronic to participate in the APOLLO trial, and one of the first to perform TVMR. Wiley believes this is a testament to the reputation of the structural heart program at the KU Medical Center and the University of Kansas Health System, one in which the cardiovascular medicine and cardiothoracic surgery departments collaborate.
Emmanuel Daon, M.D., FACS, program director of the Cardiothoracic Surgery Residency Program at the KU School of Medicine and a co-principal investigator on the study, agrees: "Usually it's more in silos, but Dr. Wiley and I work together on a lot of cases. That's unusual for our specialties."
How it works
The mitral valve is one of the four valves located at the exits of the heart's four chambers. The valves open and close with each heartbeat and make sure the blood flows through the chambers in only one direction. The mitral valve functions as a one-way gate that controls the blood flow from the heart's upper left chamber into the lower left chamber. When the mitral valve becomes misshapen-because of birth abnormalities, wear and tear from age, or damage caused by infections or a heart attack-it doesn't shut tight when it closes, allowing blood to back up into the upper left chamber. That's MR.
Open heart surgery successfully repairs the leaky valve, but only in otherwise healthy patients. "The problem is, it's a huge operation," said Daon. "For someone healthy, the risk of complications is very low, but if it's someone who is elderly or who has additional medical problems, the risk of this operation goes up quite a bit. And the recovery time could take six months or even a year."
These patients typically can only take diuretics and other drugs to alleviate their symptoms, which include fatigue and shortness of breath. MR causes the heart to work extra hard to compensate for the disrupted blood flow. In severe cases, blood and fluid can also back up into the lungs. Patients might become easily winded walking across a room, or even while lying down. They also can experience dizziness, heart palpitations and swelling in their legs and feet. Left untreated, these patients can go into advanced heart failure.
Some patients can be treated by repairing the valve with the MitraClip, a device approved by the FDA in 2013. The MitraClip is like a tiny clothespin inserted via a blood vessel in the thigh up into the heart to hold together the two flaps of the mitral valve. "The clip is a quick and easy procedure, but it's not the whole answer," said Wiley. "Sometimes the valve is too friable [brittle] or too thickened for a clip. There are limitations to what we can fix with a MitraClip that may be addressed by this new technology."
The APOLLO study participants are high-risk patients. Unlike the conventional open-heart surgery, TMVR does not require putting them on bypass or making a long incision down the chest. Instead, the team makes an incision three inches long between the ribs and, using imaging technology known as echo-guidance, inserts a delivery tube (catheter) the width of a Sharpie into the heart. That tube contains a compressed replacement valve. The physicians then expand the new valve within the malfunctioning mitral valve.
The procedure takes about two hours, compared to up to six hours for open heart surgery, and recovery is just two to three weeks.
A team of three to performs the TMVR: Daon, the surgeon; Wiley, the interventional cardiologist; and Jon Freeman, M.D., the imaging cardiologist and clinical assistant professor of medicine at the KU School of Medicine. These procedures are performed in a hybrid operating room at the University of Kanas Health System. This enables the physicians to change from a minimally invasive approach to open-heart surgery if necessary. So far, that step has not been necessary in this trial.
Eventually, the team plans to begin inserting the valve through a vein in the leg, rather than through an incision made between the ribs. This is how a similar procedure used to replace aortic heart valves-transcatheter aortic valve replacement (TAVR)-is done. TAVR was developed in the 2000s, and the University of Kansas Health System has performed more than a thousand of them since the procedure was approved. "The new delivery system for the mitral valve should happen about halfway through the APOLLO study," said Wiley. "There will be no chest incision at all."
If the APOLLO trial is successful, the next step is FDA approval, and the procedure will move from an experimental clinical trial to a standard treatment. Since TMVR is a new procedure, Daon notes that more studies will be needed to evaluate the procedure long-term, to evaluate, for example, how the valve will perform 20 years hence. But both he and Wiley are optimistic.
"This is an important trial for us to be part of," said Daon. "It's giving us a tool for people who have no other options."