Systolic anterior motion of mitral valve after valve repair

Systolic anterior motion of mitral valve after valve repair

Systolic anterior motion (SAM) of anterior mitral leaflet (AML) is a classical finding in hypertrophic obstructive cardiomyopathy and it is a factor causing the obstruction as well as associated mitral regurgitation. But systolic anterior motion of the anterior mitral leaflet can also occur without hypertrophic cardiomyopathy, after repair of mitral valve. If the leaflet is very redundant and myxomatous, there can be SAM when the left ventricular size decreases after valve repair and if the ventricle is hyperdynamic. This is more likely when the distance between the valve coaptation point and the interventricular septum is short. Undersized annuloplasty ring also contributes to the development of post mitral valve repair SAM. A non dilated, hyperdynamic left ventricle is another contributory factor [1].

A thick basal interventricular septum of more than 15 mm, short distance between the leaflet coaptation point and interventricular septum of less than 25 mm, a narrow aorto-mitral angle of less than 120 degrees, an anterior displacement of the papillary muscles, presence of excessive leaflet tissue,  and a ratio between the heights of the anterior and posterior leaflets less than or equal to 1.3 have been cited as the predictors of SAM after mitral valve repair [2].

Methods to prevent SAM and left ventricular outflow tract obstruction (LVOTO) after mitral valve repair have been described [1]. Triangular or quadrangular resection of the mid portion of the posterior leaflet and posterior band annuloplasty were performed. Posteriorly directed mid posterior leaflet secondary chordae which would otherwise have been resected, were transferred to the underside of the middle of the mid anterior leaflet with a small piece of associated valve as anchoring pledget. This was to prevent SAM and LVOTO. The redundant anterior leaflet edge was thus kept away from the left ventricular outflow tract. No post operative SAM or LVOTO were observed in these cases after mitral valve repair. Authors suggest the use of extra chordae tendinea whenever available, to tether the redundant anterior leaflet from flipping to the left ventricular outflow tract.

A study from Mayo Clinic identified 174 cases of SAM after mitral valve repair by intraoperative echocardiography. This was among 2076 patients operated from1993 to 2002. Initial management was with a combination of beta blockers along with vasoconstriction with phenylephrine and intravascular volume expansion if needed. Four patients had revision of repair for persistent SAM. None of the remaining 167 patients needed late reoperation for SAM or LVOTO over a median follow up period of 5.4 years. Follow up echocardiogram was available in 93 patients. Of these 13 had SAM and 4 had SAM with LVOTO [3].

Another study reported SAM in 52 of 785 mitral valve repairs between 2002 and 2012. 41 of these were identified in the operating room while 11 were found in the predischarge echocardiogram. 35 of the intraoperatively detected SAM resolved by medical management, while 6 required surgical repair while in the operating room. None of them required mitral valve replacement for SAM. 7 of the cases which had resolution in the operating room had recurrence on predischarge echocardiogram. 17 of the 18 predischarge SAM had resolution at follow up, while one had mild SAM. Mean echocardiographic follow up was 1.3 years [4].

References

1. Leonid Sternik, Kenton J Zehr. Systolic Anterior Motion of the Mitral Valve After Mitral Valve Repair: A Method of Prevention. Tex Heart Inst J. 2005;32(1):47-9.
2. Alfieri O, Lapenna E. Systolic anterior motion after mitral valve repair: where do we stand in 2015? Eur J Cardiothorac Surg. 2015 Sep;48(3):344-6. doi: 10.1093/ejcts/ezv230. Epub 2015 Jul 4. PMID: 26142473.
3. Brown ML, Abel MD, Click RL, Morford RG, Dearani JA, Sundt TM, Orszulak TA, Schaff HV. Systolic anterior motion after mitral valve repair: is surgical intervention necessary? J Thorac Cardiovasc Surg. 2007 Jan;133(1):136-43. doi: 10.1016/j.jtcvs.2006.09.024. Epub 2006 Dec 4. PMID: 17198799.
4. Varghese R, Anyanwu AC, Itagaki S, Milla F, Castillo J, Adams DH. Management of systolic anterior motion after mitral valve repair: an algorithm. J Thorac Cardiovasc Surg. 2012 Apr;143(4 Suppl):S2-7. doi: 10.1016/j.jtcvs.2012.01.063. PMID: 22423603.