Impact of secondary mitral valve chordal cutting on valve geometry in obstructive hypertrophic cardiomyopathy with marked septal hypertrophy

Abstract

Aims In patients with obstructive hypertrophic cardiomyopathy (HCM) and mild septal thickness undergoing myectomy, resecting fibrotic anterior mitral leaflet (AML) secondary chordae moves the mitral valve (MV) away from the outflow tract and ejection flow, reducing the need for a deep septal excision. Aim of the present study was to assess whether chordal resection has similarly favourable effects in patients with important hypertrophy, who represent the majority of patients with obstructive HCM. Methods and results The MV position in the ventricular cavity, assessed from echocardiography as AML-annulus ratio, was compared before and after chordal resection in 150 consecutive HCM patients with important (≥20 mm) and 62 with mild (≤19 mm) septal thickness undergoing myectomy. Preoperatively, MV position was displaced towards the septum to a similar extent in both groups. Postoperatively, AML-annulus ratio increased of an equal degree in both groups, from 0.43 ± 0.05 to 0.55 ± 0.06 (P < 0.001) a 28% increase, and from 0.43 ± 0.06 to 0.55 ± 0.06 (P < 0.001) a 26% increase, respectively, indicating a similar MV shift away from the outflow tract. When AML-annulus ratio was compared in the study cohort and 124 normal subjects, MV position was within normal range in <4% of patients preoperatively and normalized in >50% postoperatively. Conclusions In obstructive HCM, displacement of the MV apparatus into the outflow tract interferes with the ejection flow. Resection of fibrotic secondary chordae moves the MV apparatus away from the outflow tract and enlarges the outflow area independently of septal thickness, facilitating septal myectomy by reducing the need for a deep muscular excision.

The mitral valve in hypertrophic cardiomyopathy

“…Thickened and fibrosed secondary chordae (Fig. 3) pull the mitral valve anteriorly into the LVOT independently of septal thickness [20].…”

“…The presence of less severe septal hypertrophy (defined by echocardiography and CMR) in patients referred for myectomy is not uncommon, occurring between 7 and 29% of patients referred for surgical myectomy [20,24,44,45]. This is a challenging patient population: often only a limited septal myectomy is possible to avoid a postoperative ventricular septal defect (VSD).…”

“…Transaortic secondary chordal resection and papillary muscle release, combined with shallow septal surgical myectomy is an effective strategy for LVOTO reduction and improvement of NYHA class [47] in both severe and more mild hypertrophy. Resection of the secondary mitral valve chords results in the displacement of the mitral valve apparatus away from the LVOT, defined by increased anterior mitral leaflet to annulus coaptation ratio at the onset of systole, independent of septal thickness [20].…”