Adult: Hypertrophic Cardiomyopathy
Is anterior mitral valve leaflet length important in outcome of septal myectomy for obstructive hypertrophic cardiomyopathy?

Accepted for the 100th Annual Meeting of The American Association for Thoracic Surgery.
https://doi.org/10.1016/j.jtcvs.2020.12.143Get rights and content

Abstract

Objectives

Elongation of mitral valve leaflets is a phenotypic feature of hypertrophic cardiomyopathy, and some surgeons advocate plication of the anterior leaflet at the time of septal myectomy. The present study investigates mitral valve leaflet length and outcomes of patients undergoing septal myectomy for obstructive hypertrophic cardiomyopathy.

Methods

We reviewed the records and echocardiograms of 564 patients who underwent transaortic septal myectomy for obstructive hypertrophic cardiomyopathy between February 2015 and April 2018. Extended septal myectomy without plication of the anterior leaflet was the standard procedure. From intraoperative prebypass transesophageal echocardiograms, we measured anterior and posterior mitral valve leaflets and their coaptation length. For comparison, we performed these mitral valve leaflet measurements in 90 patients who underwent isolated coronary artery bypass grafting and 92 patients undergoing aortic valve replacement in the same period. Among patients with hypertrophic cardiomyopathy undergoing septal myectomy, we assessed left ventricular outflow tract gradient relief and 1-year survival in relation to leaflet length.

Results

Median patient age (interquartile range) was 60.3 (50.2-67.7) years, and 54.1% were male. Concomitant mitral valve repair was performed in 36 patients (6.4%), and mitral valve replacement was performed in 8 patients (1.4%), primarily for intrinsic mitral valve disease. Patients in the hypertrophic cardiomyopathy cohort had significantly longer mitral valve leaflet measurements compared with patients undergoing coronary artery bypass grafting or aortic valve replacement (P < .001 for all 3 measurements). Preoperative resting left ventricular outflow tract gradients were not related to leaflet length (<30 mm, median 49 [21, 81.5] mm Hg vs ≥30 mm, 50.5 [21, 77] mm Hg; P = .76). Further, gradient reduction after myectomy was not related to leaflet length; patients with less than 30 mm anterior leaflet length had a median gradient reduction of 33 (69, 6) mm Hg compared with 36.5 (62, 6) mm Hg for patients with leaflet length 30 mm or more (P = .36). Anterior mitral valve leaflet length was not associated with increased 1-year mortality (P = .758).

Conclusions

Our study confirms previous findings that patients with hypertrophic cardiomyopathy have slight (5 mm) elongation of mitral valve leaflets. In contrast to other reports, increased anterior mitral valve leaflet length was not associated with higher left ventricular outflow tract gradients. Importantly, we found no significant relationship between anterior mitral valve leaflet length and postoperative left ventricular outflow tract resting gradients or gradient relief. Thus, in the absence of intrinsic mitral valve disease, transaortic septal myectomy with focus on extending the excision beyond the point of septal contact is sufficient for almost all patients.

Section snippets

Study Patients

Following approval by our Institutional Review Board, we examined the records of 564 consecutive patients with HCM undergoing septal myectomy for LVOT obstruction between February 2015 and April 2018. We gathered data from our surgical database, operative notes, and reports of preoperative and postoperative transthoracic echocardiograms (TTEs). For anatomic comparison, we accessed our cardiac surgery database for all isolated coronary artery bypass grafting (CABG) operations and aortic valve

Study Population

Baseline characteristics of HCM patients undergoing septal myectomy are shown in Table 1 along with data of patients undergoing AVR and CABG who served as controls for assessment of MV leaflet length. Median age at the time of septal myectomy was 60.3 (50.2-67.7) years, significantly younger than 66.4 (59.4-73.2) years and 71 (64.3, 76) years in the isolated CABG and isolated AVR cohorts, respectively (P < .001). The proportion of female patients was higher in the myectomy and isolated AVR

Discussion

The present study extends the understanding of MV pathology in patients with obstructive HCM, especially with regard to extended septal myectomy for relief of LVOT obstruction. Our findings support previous pathologic, echocardiographic, and cardiovascular magnetic resonance imaging studies that document increased leaflet length in patients with HCM compared with controls.2,10, 11, 12, 13, 14, 15 Increased leaflet length, however, did not impact surgical outcome as measured by LVOT gradient

Conclusions

MV leaflet elongation is a feature of obstructive HCM, but the median extent of elongation is small. We have found no clinically important association between the length of MV leaflets and the severity of LVOT obstruction or postoperative outcomes in patients undergoing surgical treatment. In our experience, in the absence of intrinsic MV disease, adjunctive leaflet procedures are rarely necessary and properly performed transaortic extended septal myectomy reliably relieves dynamic LVOT

References (35)

Cited by (11)

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    Citation Excerpt :

    It should be noted that 46 of the 49 patients in this study had LVOT obstruction, and obstructive physiology is present in a minority of the general population of patients with HCM.17 Also, the risk of chordal rupture may be influenced by morphologic abnormalities of the mitral valve that have been described in HCM.18,19 In this study, the median interval between diagnosis of HCM and identification of ruptured chordae was 7 years, and myxomatous degeneration was identified on pathologic examination in two-thirds of the patients with excised valve tissue.

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This work was supported by the Paul and Ruby Tsai Family.

Institutional Review Board 19-003279 (approved April 11, 2019).

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