A Tale of Two Valves: Why Is Surgery Still the Preferred Treatment for Mitral Valve Disease?

Transcatheter aortic valve replacement (TAVR) has become a mainstream treatment for aortic valve stenosis, a disease that affects the heart’s aortic valve.

As the technique has grown in popularity, many patients are wondering whether similar minimally invasive approaches can be used to treat disease in other heart valves. However, each of the heart’s valves has its own unique anatomy and presents its own unique challenges.

TAVR Takes Over

TAVR was initially approved for patients at high risk of experiencing complications from surgical valve replacement. By 2015, a third of patients being treated for aortic valve stenosis underwent TAVR. And in late 2016, the Food and Drug Administration (FDA) approved TAVR for treating patients at moderate surgical risk after clinical trials showed it was safe and effective for them.

Experts predict the number of patients undergoing TAVR will grow significantly in the next five years, overtaking surgical valve replacement as the most common treatment for aortic valve stenosis.

How We Treat Mitral Valve Disease Today

Now patients and healthcare professionals are wondering: Could the same concept be used to repair other heart valves?

There’s great interest in doing so, especially for treating mitral valve disease – a condition that affects far more patients than aortic valve disease. In fact, experts estimate that several billion dollars have already been spent on research and development of transcatheter therapies for mitral valve disease.

Despite all that activity, though, the only device approved for mitral valve disease so far is the MitraClip. This device has been shown to be somewhat effective in treating mitral regurgitation (backward fow of blood into the heart) in patients with severe disease, who aren’t good surgical candidates.

MitraClip has so far been approved only for treatment of degenerative mitral valve disease, a condition that is the result of pathology of mitral valve itself. Only a mi purity of patients with mitral valve disease have degenarative disease. However, the results of Coapt trial recently presented showed that this device could be as effective in functioitral regurgitation a condition that caused malfunctioning of the mitral valve as a result of dilitation of left ventricule.By far the majority of patients with severe mitral regurgitation have functional disease.

The Mitral Valve’s Tricky Anatomy

While Mitraclip has certainly shown promise in treatment of mitral regurgitation, transcatheter mitral therapies are yet to show similar effectiveness in treatment of mitral valve disease as surgery in all comers. Why is it, then, that transcatheter techniques have been so effective for aortic valves but not for mitral valves? The answer lies in the anatomy and location of these two valves:

  • Shape: The aortic valve is a circular apparatus sitting at the end of a tube. The mitral valve, on the other hand, is noncircular saddle shape and sits in the middle of the heart. As a result, it’s influenced by the many different forces that act on the heart.
  • Location: In addition, the mitral valve is located close to the left ventricle outflow tract, an area in which blood flows out of the heart and into the major arteries. Those factors make mitral valve replacement much more challenging.

Unanswered Questions

While there continues to be a lot of enthusiasm for transcatheter mitral valve therapies, we have a long road ahead before these techniques become mainstream. There are many repair or replacement devices that are being studied. We also don’t know yet whether minimally invasive techniques might be more effective for repairing or for replacing the mitral valve. So far, it seems that mitral valve repair techniques are safer but less effective than mitral valve replacements using these catheter-based approaches.

It took a while before TAVR reached prime time – and it only got there after years of development and proof that the technique was as good or better than surgery. New mitral valve therapies must also pass that test before they become established as an alternative to surgery in patients healthy enough for operations.