Highlights
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Hypertrophic cardiomyopathy is frequently associated with mitral valve abnormalities.
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Standard surgical treatment of hypertrophic cardiomyopathy is septal myectomy, but cannot always address mitral valve abnormalities.
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Mitral valve repair with posterior leaflet shortening using neochords can address the mitral valve leaflet abnormalities and resolve left ventricular outflow tract obstruction.
Hypertrophic cardiomyopathy (HCM) is the most common heritable cardiomyopathy, and presents with left ventricular hypertrophy resulting in left ventricular outflow tract (LVOT) obstruction in 60% of patients. Standard surgical therapy for the relief of outflow tract obstruction is septal myectomy which can effectively reduce the outflow tract gradient to normal levels.
Several challenges exist when performing septal myectomy, especially in the cases of less basilar septal hypertrophy and elongated mitral leaflets. These include creation of a ventricular septal defect, injury to the conduction system requiring a permanent pacemaker, and failure to completely relieve the obstruction. In patients with elongated mitral leaflets, as is common in HCM, septal myectomy alone may be ineffective in completely relieving outflow tract obstruction. Mitral valve repair may be necessary to effectively eliminate any residual outflow tract gradient. Shortening the posterior leaflet with neochords is a repair technique that can move the mitral valve coaptation line posteriorly away from the septum and prevent anterior leaflet systolic motion into the outflow tract, thus relieving the outflow tract gradient. This can be achieved simply by placing neochords to the posterior leaflet through the aortic root and securing them to half the length of the existing cords. The posterior leaflet height is reduced, allowing the coaptation line to move away from the septum, and prevent systolic anterior motion of the anterior leaflet of the mitral valve. The obstruction is prevented, and normal mitral valve function is achieved. This repair technique is especially helpful when the basil ventricular septal thickness is less than 2 cm and the mitral valve leaflets are elongated.
Patients with hypertrophic cardiomyopathy can benefit from adjunctive posterior leaflet mitral valve repair using neochords to eliminate systolic anterior motion of the mitral valve.
Introduction
The standard treatment of HCM with asymmetric septal hypertrophy and left ventricular outflow tract obstruction is left ventricular septal myectomy. , The surgical procedure is highly technical, and requires considerable surgical experience to perform a very precise septal muscle excision to relieve the outflow obstruction and achieve an optimal outcome. The majority of these procedures are performed with very experienced surgical teams in high volume centers to achieve the best outcomes.
In addition to the ventricular hypertrophy, patients with HCM also frequently have abnormally elongated mitral valve leaflets. , Most experienced centers agree that a subset of patients undergoing ventricular septal myectomy would benefit from a concomitant mitral valve repair to obtain optimal relieve of outflow tract obstruction. The mitral repair allows the anterior leaflet to close properly in relation to the posterior mitral leaflet, reducing or eliminating any mitral regurgitation. It also prevents the anterior leaflet from moving into the left ventricular outflow tract and causing obstruction. Procedures on these elongated leaflets can include resection of abnormal muscular chords attached to the anterior leaflet or removing secondary chords to allow improved anterior leaflet motion towards the posterior leaflet. Also, the anterior leaflet can be folded either at its base, or along the leading edge, to achieve a shortened leaflet that will be less likely to obstruct the LVOT.
The procedure that we designed moves the coaptation line of the mitral valve posteriorly thus allowing the anterior mitral leaflet to close away and out of the left ventricular outflow tract. The mitral valve now has more normal leaflet motion, improves the coaptation position, reducing or eliminating any mitral regurgitation. It allows normal leaflet motion, eliminating systolic anterior motion of the anterior leaflet and reducing the left ventricular outflow tract gradient.
The procedure involves shortening the posterior mitral leaflet cords by replacing them with neochords that are half the length of the native chords. Generally, posterior chords are 14 mm in length, and the neochords are shortened to approximately 7 mm. These neochords are placed through the aortic valve in a manner similar to the performance of the myectomy. Minimally invasive shafted instruments are used to implant the neochords into the papillary muscles. Two neochords are placed in the lateral papillary muscles, and 2 are placed in the medial papillary muscles. The 2 neochords are placed in a looped fashion just lateral to the midportion of the posterior leaflet, and the neochords attached to the medial papillary muscles are placed just medial to the center of the posterior leaflet. The neochords are then placed 5 mm from the edge of the posterior leaflet in 2 passes to create a loop at the edge. This secures the leaflet while the neochords are tied in place to maintain the chosen length. This creates a symmetric reduction in height of the middle scallop of the posterior leaflet. The neochords can be shortened to any length, but our experience has found one half the length of the native chords allows for movement of the coaptation line towards the posterior mitral annulus and maintains a good coaptation length of the mitral valve.
This procedure, which can be performed as an adjunct to septal muscle resection, is especially helpful when the basilar septal thickness is less than 2 cm in the presence of elongated mitral valve leaflets. This scenario can be challenging to resect enough septal muscle to eliminate systolic anterior motion of the elongated anterior mitral leaflet and not create complications such as a ventricular septal defect or complete heart block. The mitral valve repair allows a less aggressive muscle resection that may help in reducing these complications.
The advantages of this mitral repair approach are in its simplicity and straightforward placement of new posterior neochords that are commonly used for surgeons involved in standard mitral valve repair surgery. In addition, the neochords can be removed and thus return the posterior leaflet back to its original position if the repair was not satisfactory. This adjunctive mitral repair in the setting of hypertrophic cardiomyopathy is not frequently necessary but can be very helpful in those patients with less basilar septal hypertrophy and elongated mitral valve leaflets. We have performed this technique in 10 patients with reduced basilar septal thickness and elongated leaflets with success in eliminating outflow tract obstruction and mitral insufficiency. None of these patients had the need for a permanent pacemaker and none have recurrent mitral insufficiency or elevated outflow gradients with up to 6 years of follow-up.
Operative Technique
The technique is detailed in the following images ( Figs. 1-7 , video):
