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Percutaneous Transvenous Mitral Annuloplasty for mitral regurgitation is in early stages of development and involves a complex intervention which can not be done in patients with left ventricular leads. Since functional mitral regurgitation is common in low ejection fraction states, we propose a device which can serve for annuloplasty in addition to cardiac resynchronization therapy and simplifying the intervention.
Treatment of dilated cardiomyopathy has evolved considerably over years leading to marked improvement in quality of life and survival. This has been possible by intervening at the various biochemical, hemodynamic and electrical abnormalities by drugs and use of various devices. The role of cardiac resynchronization therapy (CRT) is an established one resulting in improvement in quality of life and survival and lately studies have shown its benefit even in patients with moderate fall in ejection fraction.
One important accompaniment of dilated heart is functional mitral regurgitation secondary to mitral annular dilatation, apical displacement of papillary muscles and reduced transmitral closure force secondary to LV systolic dysfunction.
Cardiac resynchronization therapy helps by synchronizing the contractions of the postero-lateral wall and the interventricular septum and thereby improving the ejection fraction and by decreasing the functional mitral regurgitation by its presumed effect of synchronizing the motion of two papillary muscles and increasing transmitral closure force.
Percutaneous transvenous mitral annuloplasty (PTMA) for ischemic or functional mitral regurgitation is in its evolution. The procedure involves cannulation of coronary sinus via subclavian or internal jugular vein and delivering a hemispherical structure from coronary sinus ostium posteriorly to the anerior interventricular branch of the great cardiac vein anteriorly. As the coronary sinus forms the lateral half of the mitral annulus, the device alters the geometry of the mitral annulus thereby causing better apposition of two valve cusps and decreasing mitral regurgitation. Three such devices under investigation include Viacor PTMA device, CARILLON contour system and MONARC (previously VIKING) PTMA system all utilizing the various modifications of the same principle. These PTMA devices cannot be placed in patients who have coronary sinus leads of CRT devices. Since low ejection fraction states are usually associated with functional mitral regurgitation hence to produce a device which can address both issues seems compelling.
Although the left ventricular leads of CRT devices are soft and may not significantly bring about conformational changes in the mitral annulus, part of reduction of mitral regurgitation can be expected by left ventricular lead especially once the lead is distally nicely fixed and under some tension. However left ventricular lead is placed in the lateral most vein which may include only one fourth of the mitral annulus. If left ventricular lead is modified in such a way that it is rendered stiff in its distal part and part of the stiff end projects anteriorly upto anterior interventricular groove it can serve as well for annuloplasty in addition to CRT. Otherwise a stiff annuloplasty hemisphere can be delivered over the left ventricular lead hence simplifying the procedure and simultaneously addressing both issues.