Imagine that you are chronically fatigued and short of breath even when lying down. Your legs and ankles are swollen, and you have an increased heart rate.

Almost 6 million Americans contend with these symptoms because they have heart failure — the inability of the heart to pump enough blood throughout the body to keep organs and tissues healthy.

If you have this condition, it can cause the heart muscle to weaken and stretch out like an overblown balloon. That pulls apart the mitral valve, which is a kind of door between the heart's upper left-hand chamber (the atrium) and the lower left-hand chamber (the ventricle).

When that happens, the flow of oxygen-rich blood out of your heart to the rest of your body backs up, and you develop what's called mitral regurgitation. Your symptoms worsen and your risk of death from heart failure increases.

Until now, heart failure with mitral valve regurgitation often made mitral valve repair or replacement necessary, complete with cracking open your ribcage and stopping your heart so that surgeons can go deep inside it.

But what if doctors developed a stealthy treatment that allowed them to sneak inside your heart without the trauma and risk of open heart surgery?

In a stunning example of medical innovation, doctors, engineers, and entrepreneurs worked for two decades to develop the MitraClip, which is attached to a sagging mitral valve and allows the valve to once again open and then close completely in synchronization with a beating heart.

The mitral valve works like a zipper, and when it fails in this way, all surgeons need to do is place one stitch to restart the closing process. Once stitched, the faulty valve naturally snaps shut again on its own.

There had been some resistance to the device because large clinical trials hadn't yet demonstrated success. Well, that's old news now.

In a recent study in the New England Journal of Medicine, lead author Greg Stone and dozens of collaborators published evidence of the MitraClip's effectiveness. Their study followed 614 patients (303 received the device; the rest received standard treatments) for more than two years. Those receiving the clip saw their risk of getting admitted to the hospital cut in half.

Even more importantly, over five years of follow-up, the device reduced risk of death in those who received it by an astounding 38 percent.