Transaortic Chordal Cutting: Mitral Valve Repair for Hypertrophic Cardiomyopathy
What are the clinical and hemodynamic results of a shallow myectomy combined with cutting thickened secondary mitral valve chordae in patients with symptomatic obstructive hypertrophic cardiomyopathy (HCM)?
Between January 2011 and December 2013, 39 HCM patients with septal thickness ≤19 mm and left ventricular outflow tract gradient ≥50 mm at rest or with provocation underwent shallow septal myectomy combined with chordal cutting. All patients were severely symptomatic. Echocardiographic parameters included determination of septal thickness, outflow tract gradients, as well as multiple descriptors of mitral valve anatomy including mitral valve tenting area, severity of mitral regurgitation, and interior mitral leaflet annulus ratio. These 39 patients were compared to 25 consecutive patients operated in a previous time frame with similar clinical profiles and septal thickness who underwent isolated myectomy.
In patients undergoing concurrent chordal cutting, New York Heart Association (NYHA) class prior to surgery was class II in 7, and class III, IV in 32 patients. At the time of most recent evaluation, 34 patients were in NYHA class I and 5 in class II, and none in class III, IV. Resting outflow tract gradient decreased from 82 ± 43 mm Hg to 9 ± 5 mm Hg and basal septal thickness from 17 ± 1 mm to 14 ± 2 mm (both p < 0.001). Preoperatively, 17 patients had grade 1 mitral regurgitation, 13 grade 2, 7 grade 3, and 2 grade 4. At the time of follow-up, 3 had grade 1, 5 grade 2, and 1 grade 3. When compared to patients with chordal cutting, patients without chordal cutting were slightly more likely to have residual NYHA class III, IV symptoms and a residual outflow tract gradient ≥30 mm Hg. For patients undergoing chordal cutting, mitral valve tenting area decreased from 2.14 ± 0.62 cm2 to 1.51 ± 0.54 cm2 (p < 0.001). For those without chordal cutting, mitral valve tenting area remained relatively stable at 1.78 ± 0.48 cm2 preoperatively and 1.70 ± 0.4 cm2 postoperatively.
Transaortic chordal cutting combined with a shallow myectomy abolishes left ventricular outflow tract gradient, avoids the need for mitral valve replacement, and results in significant symptomatic benefit.
This study nicely defines an additional surgical technique for patients with hypertrophic cardiomyopathy. It dealt with a subset of patients with relatively mild ventricular hypertrophy, defined as ≤19 mm, where a deep extensive myectomy may not be feasible. Shallow myectomy, combined with chordal cutting to reduce the magnitude of mitral valve tenting and the dynamic nature of outflow tract obstruction related to mitral valve systolic interior motion, resulted in a significant decrease in left ventricular outflow tract gradient, reduction in severity of mitral regurgitation, and symptomatic improvement. This was a single-center study and all procedures were performed by a single cardiac surgeon with extensive experience with hypertrophic cardiomyopathy. This was not a randomized controlled study, which introduces some limitations; however, the procedure was accomplished with no excess morbidity or mortality and appeared to provide a benefit compared to isolated myectomy alone in a reference population. The clinical and research findings are nicely supported by objective echocardiographic data demonstrating alteration in mitral valve geometry following this procedure.
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