Can IVL help cardiologists treat mitral valve disease?
With the success of intravascular lithotripsy (IVL) being used to break up calcium in arteries during revascularization, many researchers have wondered if IVL could also be used to break up severe stenosis in heart valves. A couple centers have experimented with this idea, using multiple Shockwave Medical balloons together in a valve annulus.
Jaffar Khan, MD, director of interventional electrosurgery and cardiac innovation at St. Francis Hospital and Heart Center in Roslyn, New York, said this concept seemed like it would not work from a physics standpoint. His research team undertook a cadaver study to find out, learning that the technique does work, but not very well. He said a dedicated technology needs to be developed to enhance the effectiveness.
Khan presented his team's research at the ACC.25 in Chicago. The group used Shockwave Medical IVL balloons in a cadaver heart with severe mitral annular calcification (MAC) to show proof of concept and to determine what design elements are needed to upsize the technology to treat much thicker calcium in valves. Khan said arterial calcium is usually about the thickness of an eggshell and is easy to break up using IVL, but annular calcium can be centimeters thick, creating challenges.
MAC remains a challenging problem in structural heart interventions. Traditional balloon valvuloplasty with high pressure balloons can cause damage to the valve and is not always effective at breaking heavy annular calcifications.
"I think MAC and calcified mitral valve disease are real problems, and we don't have many therapeutic options," Khan explained. "You can't repair these patients with clips because they get severe stenosis and you will have to replace their valves in the majority of cases. You can't just do a standard balloon valvuloplasty because the leaflets rip and you get severe mitral regurgitation. And TMVR is really limited in this population because of all the screen failures from LVOT obstruction and problems with paravalvular leak."
IVL, already used in coronary and peripheral vessels, is highly effective in thin arterial calcium, but the much thicker valvular calcium is another story. The IVL balloons designed for much smaller vessels are less effective. The largest available peripheral IVL balloon, Shockwave’s L6 catheter, measures 7 mm in diameter, far smaller than the typical 30–35 mm mitral orifice, Khan added.
Khan’s team performed a bench study using a cadaver heart with severe MAC. They imaged the calcification with a photon-counting CT scanner, positioned multiple L6 IVL balloons against the annulus, and delivered 600 pulses at low inflation pressure (4 atmospheres) to avoid mechanical damage. Post-treatment imaging, including micro-CT, revealed scattered linear fracture lines characteristic of shockwave calcium disruption.
"I think the exciting thing is, for the first time, we've shown that the Shockwave balloons can cause some fractures onto this really thick valvular calcium. I think we've also demonstrated that it's probably not enough to cause a clinical impact. So the next steps would be a device that has perfusion, but also much more energy to try and impact and modify the calcium on this valve," Khan concluded.
He believes advancing the technique will require new device designs with larger balloons that can maintain stable contact with the annulus and deliver much higher energy. The device also requires perfusion through the center of the balloon to allow longer treatment times without obstructing blood flow,
"You need a lot more energy, especially if you are paving the way for transcatheter mitral valve replacement (TMVR). But TMVR comes with a lot of other issues, not just paravalvular leak. But if you are going to pave the way for transcatheter edge-to-edge repair (TEER) to make the leaflets pliable enough so you can repair them, you need to do a lot more," Khan explained.
While clinical application is still distant, Khan sees this proof-of-concept as an important first step toward a potential new tool for treating one of the most stubborn problems in structural heart disease.
Dave Fornell has covered healthcare for more than 17 years, with a focus in cardiology and radiology. Fornell is a 5-time winner of a Jesse H. Neal Award, the most prestigious editorial honors in the field of specialized journalism. The wins included best technical content, best use of social media and best COVID-19 coverage. Fornell was also a three-time Neal finalist for best range of work by a single author. He produces more than 100 editorial videos each year, most of them interviews with key opinion leaders in medicine. He also writes technical articles, covers key trends, conducts video hospital site visits, and is very involved with social media. E-mail: [email protected]