Indian Pacing Electrophysiol. J.
Indian Pacing Electrophysiol. J. 2010;
10(7):310-312Point of View
Mitral Annuloplasty Using a Cardiac Resynchronization Device
Download PDF 201 KBAndrabi Syed Manzoor Ali, Khurshid Iqbal, Nisar Ahmed Trambu
Department of Cardiology, SKIMS, Soura, Srinagar 190010, India.
Address for correspondence: Andrabi Syed Manzoor Ali, Department of Cardiology, SKIMS, Soura, Srinagar 190010, India. E-mail: syedmanzoorali/at/rediffmail.com
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.Key words: Mitral annuloplasty, Cardiac Resynchronization Device
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.
Figure 1: Proposed left ventricular lead bifurcating distally at 'd' into outer jacket for annuloplasty and core lead for CRT both having separate stylets 'a' and 'b' for manipulation.'C' and 'e' show the cross sections of lead at proximal and distal ends after bifurcation.
Figure 2: After withdrawing the stylet 'a' out of the annuloplasty lead, its distal end 'e' takes predefined hemispherical shape which will help in scaffolding of mitral annulus improving mitral leaflet coaptation while 'c' the CRT lead is positioned in one of the lateral cardiac veins.
Figure 3: After reaching the desired lateral cardiac vein 'e' in the coronary sinus 'd' the CRT lead 'h' is directed across its ostium to the tip while the annuloplasty jacket lead is pushed distally as far as possible in the coronary sinus surrounding mitral valve annulus 'b'. 'c' coronary sinus ostium.'f' left ventricular lead.
Figure 4: Final position of the bifurcated lead with annuloplasty part 'g' in the coronary sinus surrounding major part of mitral valve 'a' annulus 'b' and the CRT lead 'h' in the desired lateral cardiac vein 'e'.The distal annuloplasty segment can be made of material that utilizes a slow conformational change because of delayed breakdown of biodegradeable polymer over 3 to 6 weeks resulting in further narrowing of mitral annulus.