<div>Commentary: So Many Ways…</div><div>Enlargement of left ventricular outflow tract using an autologous
pericardial patch for the anterior mitral valve leaflet and septal
myectomy through trans-mitral approach for the treatment of hypertrophic
obstructive cardiomyopathy</div><div>Zhang et al (1) describe their experience in septal myectomy for
hypertrophic obstructive cardiomyopathy. Of 247 consecutive cases with
HOCM treated during 2016-2019 with a variety of techniques, this report
is on 16 patients who underwent trans-mitral septal myectomy and
enlargement of left ventricular outflow with an autologous pericardial
patch in transverse configuration. The technique reportedly decreased
the gradient from average 90+ to 10+ mm Hg and resolved systolic
anterior leaflet motion in all with only mild residual mitral
regurgitation. There were no deaths or any other major complications in
this group. It is a small group of patients with excellent result but no
definitive conclusion can be drawn regarding validity of the technique
from this study. The controversy remains regarding the approach,
trans-aortic vs. trans-mitral and whether leaflets should be left alone,
plicated or lengthened as well as whether mitral valve should be
repaired or replaced in addition to septal myectomy. One certainty
remains, extended myectomy done either way, is the foundation of the
surgical treatment of hypertrophic cardiomyopathy.</div><div>HCM is an autosomal dominant hereditary disease with variable
penetration affecting one in 500-1000 population. Obstructive type
comprises of 70% of disease spectrum (2). Mitral valve abnormalities
are frequent and in some, abnormal papillary muscles are present. In the
obstructive CM about 70% have abnormal mitral valve leaflets, usually
longer relative to the size of LV cavity. In nonobstructive subset, AML
is elongated as well, basically due to a phenotypic expression. An
average size of anterior mitral leaflet (AML) is 24 mm in normal
subjects, whereas patients with HOCM have average length of 34 mm. The
leaflet protrudes into LV 26 mm above the mitral annular plane vs.13 mm
in normal hearts. Often a residual AML extends past the coaptation
point. MV is only restricted by LV and these free-floating leaflets lead
to systolic anterior motion (SAM) of mitral valve (3).</div><div>Surgical septal reduction therapy in eligible patients refractory to
medical treatment is a Class I (LOE :C), Class IIa (LOE: B), eligibility
is defined as severe symptoms refractory to optimal medical treatment,
dynamic LVOT gradient &gt;50 mm Hg and targeted anterior
septal thickness sufficient to perform the procedure safely and
effectively, usually 18 mm or more (4). Trans-aortic approach to septal
reduction surgery is more widely practiced and with excellent results. A
vast majority of these cases did not require mitral valve intervention
despite having elongated AML (5). It was felt that an extended myectomy
beyond the point of septal contact adequately relieves LVOT obstruction,
SAM and its associated mitral regurgitation. The incidence of mitral
valve repair has been reported as low as 4.9% (5,8,10). In another
study of patients treated with surgical septal reduction, 62% had AML
plication (when elongated) in addition to extended septal myectomy and
were compared to those with just extended myectomy alone, no
statistically significant difference was found in reduction of gradient,
relief of SAM and survival. The procedures were performed transaortic
(6).</div><div>Trans-mitral approach whether through the left or right atrium has some
advantage in exposure especially if the aortic annulus is small or the
aorto-mitral angle is less than 120 degrees causing acute angulation
(7). The techniques to visualize the IV septum vary between cutting all
the AML attachments and then restoring these with artificial chords (9)
or detachment of AML from annulus and primary reattachment or patch
interposition as in the present study as well as others (1,13). The
modes of re-attachment were with or without autologous pericardial
patch. The results of have been generally very good but most of the
series have been small, consisting of less than 30 patients in most. The
approach may also be used primarily in patients with intrinsic MV
disease which is not repairable requiring mitral valve replacement (14).</div><div>When anterior leaflet extension is employed, the mechanism of reduction
in SAM and MR could possibly be stiffening of the AML counteracting the
flow drag thus preventing inward displacement of papillary muscles and
buckling of central portion of MV apparatus (12). This effect may not be
solely due to leaflet extension with a patch.</div><div>The recognition of MV abnormalities have led to a variety of approaches
to the mitral valve with septal reduction. Perhaps tailoring the
procedure to the morphology such as in patient with less hypertrophy
(septal thickness &lt; 18 mm) and more dynamic obstruction with
SAM, additional mitral valve procedures such as horizontal plication of
AML or transverse patch approximation of detached AML would be
beneficial. Mitral valve replacement for those where valves are not
repairable due to rheumatic disease (14). A trans-aortic or trans-mitral
approach to correction of hypertrophic obstructive cardiomyopathy hinges
on the dominant anatomical feature of the disease (15). Full sternotomy,
partial sternotomy, right anterior mini-thoracotomy, lateral approach or
robotic assisted, are all dealers’ choices.</div><div>References:</div><div>Zhang H, Zhu K, Yang Z, Yang S, Wang C</div><div>Enlargement of left ventricular outflow tract using an autologous
pericardial patch for the anterior mitral valve leaflet and septal
myectomy through trans-mitral approach for the treatment of hypertrophic
obstructive cardiomyopathy</div><div>JOCS-2021-OA-723</div><div>Prinz C, Farr M, Hering D, et al</div><div>The Diagnosis and Treatment of Hypertrophic Cardiomyopathy</div><div>Dtsch.Arztebl.Int. 2011 April;108(13):209-215</div><div>Sherrid M, Balaram S, Kim B, Axel L, Swistel D</div><div>The Mitral Valve in Hypertrophic Cardiomyopathy: A Test in Context</div><div>J Am Coll Cardiol. 2016 April; 67(15): 1846-1858</div><div>Gersh B, Maron B, Bonow R, Deerani j, etal</div><div>2011 ACCF/AHA Guidelines for the Diagnosis and Treatment of Hypertrophic</div><div>Cardiomyopathy; A Report of the American College of Cardiology
Foundation/American</div><div>Heart Association Task Force on Practice Guidelines, Circulation 2011;
124 (24) : e783-831</div><div>Lentz Carvalho J, Schaff HV, Nishimura RA et al</div><div>Is anterior mitral valve leaflet length important in outcomes of septal
myectomy for obstructive hypertrophic cardiomyopathy? J Thorac
Cardiovasc Surg 2021 January;1-9</div><div>Balaram S, Ross R, Sherrid M, et al</div><div>Role of mitral valve plication in the surgical management of
hypertrophic cardiomyopathy.</div><div>Ann. Thorac. Surg. 2012 Dec;94(6):1990-1997</div><div>Mihaileanu S, Marino JP, Chavaud S, Perier P, et al</div><div>Left ventricular outflow obstruction after mitral valve repair
(Carpentier’s technique).</div><div>Proposed mechanism of disease</div><div>Circul. 1988 Sep; 78(3 Pt 2):178-84</div><div>Verghese R, , Itagaki S, Anyanwu AC, et al</div><div>Predicting systolic anterior motion after mitral valve reconstruction:
using intraoperative transoesophageal echocardiography to identify those
at greatest risk.</div><div>Eur J Cardiothorac Surg. 2014 Jan;45(1):132-7</div><div>Schaff HV, Said SM,</div><div>Transaortic Extended Septal Myectomy for Hypertrophic Cardiomyopathy</div><div>Oper. Tech. Thorac. Cardiovascu. Surg. 2012; 17:238-50</div><div>Hong JH, Nguyen A, Schaff HV</div><div>Management of the mitral valve in patients with obstructive
cardiomyopathy</div><div>Indian J Thorac. Cardiovasc. Surg. January 2020;36 (Suppl 1):534-543</div><div>Meier S, Noack T, Mohr FW, et al</div><div>Transmitral myectomy and how to deal with systolic anterior motion (SAM)
in hypertrophic cardiomyopathy</div><div>Ann Cardiothorac Surg. 2017;6(4):416-8</div><div>van der Lee, Kofflard MJ, van Hewerden L</div><div>Sustained improvement after combined anterior mitral leaflet extension
and myomectomy in obstructive cardiomyopathy Circul. 108(2003) pp
2088-2092</div><div>Wehman B, Ghoreishi M, Foster N, Wang L, et al</div><div>Trans mitral Septal Myectomy for hypertrophic Obstructive Cardiomyopathy</div><div>Ann Thorac Surg 2018;105(4):1102-1108</div><div>Deerani JA, Ommen SR, Gersh BA, et al</div><div>Surgery insight: septal myectomy for obstructive cardiomyopathy-Mayo
Clinic experience.</div><div>Nat Clin Pract Cardiovasc Med. 2007; 4:503-512</div><div>Varma PK, Krishna N, Jose, Gopal K, Ahamed H</div><div>“Do alternative approaches work in surgical septal myectomy?”</div><div>Asian Cardiovasc Thorac Annals. 2021; 0(0)</div>