Preview of the ACC: Percutaneous Mitral Valve Repair

"[The procedure is] very new and involves repairing my leaky valve using a clip device, without open heart surgery, so that my heart will function better"

-Elizabeth Taylor, via Twitter 6 Oct 2009

Percutaneous mitral valve repair will be the talk of the ACC Scientific Sessions for interventional cardiology this year, especially since coronary artery stent procedures are so, well, yesterday.

One valve repair technology popularized by Ms. Taylor's tweet that corrects a leaky mitral valve will be presented Sunday morning at the ACC meeting in Atlanta when the EVEREST II trial results are released (Larry Husten over at Cardiobrief.org has a nice outline of the late-breaking clinical trial schedule).

The EVEREST II trial is a phase 3 trial that compares the percutaneous mitral valve repair head-to-head with more conventional open mitral-valve surgery. The trial is sponsored by E-valve, Inc. (bought a year ago by Abbott). Since our center has participated in the trial (note to SEC: I have no clue about the results), it might be interesting to review the background and provide a few pictures on the technology. (By the way, this was NOT Elizabeth Taylor's procedure!)

(Important disclaimer: This device is NOT YET APPROVED for use in the US. Further, I have no financial interest in the manufacturer(s) and was not an investigator for the EVEREST I or EVEREST II trials, but I do work at one of the trial centers).

Background

In 1998, a report of correcting mitral valve insifficiency (leakage) was reported by Ottavio Alfieri and colleagues in the European Journal of Cardiovascular Surgery describing a technique to plicate (suture together) the mid-portion of the mitral valve, effectively creating a "bowtie" orifice to correct the leakage:

The experimental technique reported in this study could permit minimally invasive correction of the mitral insufficiency. These patients are often not referred for surgical repair, because they are believed “too sick” for conventional surgery. The experimental technology described in this report would avoid cardiopulmonary bypass and its consequences, and thus represents a more palatable alternative for these patients.

The long-term results of this technique were favorable and lead to the development of a minimally-invasive (yet transthoracic) approach for this same repair and later, thanks to the wonders of clever engineers, a completely percutaneous approach using a clip instead of sutures.

Equipment

(Note: Thanks to Dr. Ted Feldman for use of these great pictures) and the clinical trial nurses who make this all possible.

While minimally invasive, this procedure takes a village, so to speak, to perform: the interventional cardiologists, an echocardiographer and a well-hidden anesthesiologist (can you say "Where's Waldo?") barely seen behind the plastic drapes above the patient's head (yes, the patient gets to sleep for the procedure):

The personnel and equipment required to perform percutaneous repair of the mitral valve as viewed from the patient's feet. Note the Frankenstein-like steering-and-release contraption with all the IV tubing coming from it in front of the doctors used to place the mitral clip.
(Click image to enlarge)

A view from behind the implanting physicians. Note that all eyes are on the echocardiographic images to the right as the clip is positioned, rather than the fluroscopic images immedicately in front of the operators.
(Click image to enlarge)

The back end of the catheter delivery system looks just a bit complicated, since it steers the clip, grasps each leaflet of the mitral valve, and releases the clip when seated properly:

Click image to enlarge

The business end of the device is a small mechanical clip that grasps the center of the posterior and anterior leaflets of the mitral valve in an attempt to replicate the "bowtie" surgical repair originally described:

A cartoon rendition (top) and a photo of the clip (bottom) used to clip together the leaflets of the mitral valve

While the fluoro images of the procedure are interesting to view as the device is deployed:

An RAO fluoroscopic view of the mitral valve clip passed to the left atrium above the mitral valve.

The mitral valve clip is advanced below the mitral valve into the left ventricle in preparation of grasping the mitral valve.

The valve leaflets are grasped and the side "wings" of the clip closed.

The clip is deployed and fixes permanently to the mitral valve leaflets.

Although these fluoroscopic images are amazing, this procedure would not be possible without the ability to see the valve leaflets in realtime using transesophageal echocardiography:

Transesophageal echocardiographic images of the clip (outlined in orange) being placed below the mitral valve leaflets.

The clip is withdrawn until the leaflets of the mitral valve are engaged in the clip. (Note the "wings" of the clip are still open)

The wings of the clip are closed tightly to grasp the valve leaflets.

Will the Device Work?

Although preliminary results of the EVEREST I trial were promising, the EVEREST II trial will be the pivotal comparative effectiveness study comparing this approach to open mitral valve repair.

One thing's for sure after seeing all this: innovation in cardiology is alive and well!

See you Sunday!

-Wes

The Malignancy of Heart Failure

With the release of the results of the EVEREST trial at the American College of Cardiology Meeting in New Orleans and simultaneous publication in the Journal of the American Medical Association, a surprising revelation occurred to cardiologists who treat heart failure: fluid loss means little to overall survival.

For those unfamiliar with the EVEREST trial, it tested the effectiveness of a vasopressin inhibitor, tolvaptan, at reducing fluid retention in heart failure as a means to improve cardiovascular mortality. Vasopressin’s (also called “anti-diuretic hormone”) action in the kidney is to retain free water in the distal collecting tubules of the nephron in the kidney. It is alcohol’s inhibition of vasopressin that causes a brisk diuresis that contributes to the post-drinking hang-over and dehydration. Ah, enough about my college days…

Anyway, the drug tolvaptan also inhibits vasopressin, and permits excretion of increased free water (as evidenced by the sustained volume loss and elevation of serum salt (sodium) levels in this study). Unfortunately, these beneficial effects had no effect on all-cause or cardiovascular mortality after two years of follow-up in the trial.

What struck me was the high incidence of cardiovascular mortality in this heart failure patient population (NYHA Class III and IV): an incidence of about 20% - even in spite of aggressive therapy with beta blockers (70.2% of patients), angiotensin receptor blockers (ARBs) or angiotensin converting enzyme (ACE) inhibitors (84.2%), and diuretics (96.8%).

It seems we have a long way to go to improve mortality in this population.

Which then begs the question: in light of the improvements in mortality in severe heart failure documented in the MIRACLE, COMPANION, CARE-HF and SCD-HeFT trials, why is there no mention of device-based heart failure therapies in this trial? Were these devices implanted in these patients? If so, in whom?

Perhaps if these device therapies were deployed earlier in the course of treatment in this severe heart failure population, we could better impact this abysmal mortality rate.

-Wes