Systematic cutting of selected secondary mitral valve chordae, in association with a shallow myectomy, in obstructive hypertrophic cardiomyopathy:impact on mitral valve function and patient management
Authors: Margonato D , Abete R , Zyrianov A , Sorropago A , Chioffi M , Vaccari G , Poggio D , Mortara A , Boni L , Spirito P , Ferrazzi P 
Published: November 2020

Abstract

Introduction
Few centers worldwide have large experience with performing an extended septal myectomy in patients with obstructive hypertrophic cardiomyopathy (HCM). Therefore, many HCM patients eligible for surgical relief of left ventricular (LV) outflow gradient do not have access to treatment. In a previous study, cutting fibrotic anterior mitral leaflet secondary chordae, in association with only a shallow myectomy, proved highly effective in moving the mitral valve (MV) apparatus away from the LV outflow tract and relieving the outflow gradient in our HCM patients with mild hypertrophy (&lt;19 mm), a surgical approach that simplifies the operation.

Purpose
To assess whether chordal cutting is equally effective in improving MV geometry and relieving LV outflow gradient and heart failure symptoms in HCM patients with more marked hypertrophy.

Methods
Surgical outcome and MV geometry and function were assessed in 226 consecutive HCM patients who underwent systematic cutting of fibrotic anterior mitral leaflet secondary chordae, in association with a shallow myectomy and independently of magnitude of septal thickness, at our center from January 2015 to December 2018.

Results
Of 226 study patients, 1 (0.4%) died perioperatively. None had iatrogenic septal defect. Postoperatively, LV outflow gradient at rest decreased from 70±36 to 10±2 mmHg (P&lt;0.001). In the 77 patients in whom data on the outflow gradient provoked with physiologic maneuvers after surgery were available, the provocable gradient was 16±10 mmHg. NYHA functional class improved significantly (P&lt;0.001), with the number of patients in class III-IV decreasing from 178 (79%) to 2 (0.9%). No patient had residual severe MV regurgitation and only 4 (1.7%) had moderate-to-severe regurgitation. Quality of the echocardiogram allowed assessment of MV geometry in 212 (94%) patients. In the 62 patients with mild hypertrophy, anterior leaflet-annulus ratio increased 27% postoperatively, from 0.43+0.06 to 0.55+0.06 and MV tenting area decreased 34% from 2.9+0.6 to 1.9+0.4 cm2 (P&lt;0.001), indicating repositioning of MV coaptation away from the outflow tract (with increased outflow tract dimension). Similarly, in 150 patients with marked hypertrophy, anterior leaflet-annulus ratio increased 27% from 0.43+0.05 to 0.55+0.06 and tenting area decreased 28% from 2.9+0.6 to 2.1+0.4 cm2 (P&lt;0.001).

Conclusions
Our results show that cutting fibrotic anterior mitral leaflet secondary chordae, by moving the MV apparatus away from the LV outflow tract and independently of the magnitude of septal hypertrophy, contributes to improve the results of septal myectomy and reduces the need for a deep septal excision (and associated risk of iatrogenic septal defect) in patients with obstructive HCM. Therefore, chordal cutting could make the myectomy operation more accessible to surgeons, increasing the availability of surgical treatment for HCM patients eligible for invasive abolition of LV outflow obstruction.

Funding Acknowledgement
Type of funding source: None