A Surgical Experience of Symptomatic Sigmoid Septum: Drastic Exacerbation of Mitral Regurgitation after Sufficient Ventricular Septal Myectomy

Abstract

A 74-year-old woman presented with progressive dyspnea on exertion. Transthoracic echocardiography (TTE) demonstrated significant left ventricular outflow tract (LVOT) obstruction with a pressure gradient of 100 mmHg caused by a sigmoid septum (SS). Mitral regurgitation (MR) of a mild to moderate degree occurred due to systolic anterior motion (SAM) of the anterior mitral leaflet (AML), with no intrinsic mitral valve (MV) abnormality. Myectomy of the hypertrophied septal bulge ameliorated the pressure gradient to 8 mmHg with similar MR. However, just before the sternal closure, hemodynamic status deteriorated drastically to ventricular fibrillation. MR exacerbated to a severe degree with an uncertain etiology; thus, a mechanical prosthetic valve was implanted. The postoperative course was complicated by prolonged mechanical ventilation due to massive pulmonary edema and complete atrioventricular block (CAVB) requiring permanent pacemaker implantation. One year postoperatively, the patient is asymptomatic and TTE revealed no residual pressure gradient with an iatrogenic ventricular septal defect (VSD). This case, the first published surgical experience of SS, may indicate that secondary MR, which is usually relieved by sufficient myectomy in hypertrophic cardiomyopathy (HCM), can exacerbate markedly, and that myectomy might not be advisable in SS. The therapeutic strategy must be considered carefully before embarking on surgical intervention.

Total Clinical Course and Autopsy Findings of Left Ventricular Outflow Tract Obstruction Due to Sigmoid Septum: Histologically Proven Isolated Basal Septal Hypertrophy

“…Belenkie et al ( 6 ) reported that an autopsy performed in one patient with localized septal hypertrophy and without SAM showed no fiber disarray. In addition, according to Fujita et al ( 7 ), a specimen of the resected septum in sigmoid septum with LVOTO showed only slight myocardial disarray, which was not compatible with HCM. In the present case, HCM was completely ruled out as a cause of basal septal bulge based on the autopsy findings.…”

The evolution of basal septal hypertrophy: From benign and age‐related normal variant to potentially obstructive and symptomatic cardiomyopathy

“…Accumulating evidence suggests that mitral valve abnormalities can be critically involved in LVOTO in HCM. [29][30][31][32][33][34][35][36] Alhaj et al 35 thickness measurement method such that "the actual tissue-blood interface, rather than the distance between the leading edge echoes," be utilized.…”

“…Accumulating evidence suggests that mitral valve abnormalities can be critically involved in LVOTO in HCM . Alhaj et al .…”

Surgery for Left Ventricular Outflow Tract Obstruction with a Relatively Thin Interventricular Septum

“…Although the mechanisms of SAM and LVOTO are partly the same as that of HOCM and isolated muscle resection could be sufficient, deterioration of MR after myectomy has been reported. 7 Fujita et al reported a patient with SAM and LVOTO due to sigmoid septum and normal mitral valve pathology who presented with severe MR just after myectomy. 7 The mitral valve had to be finally replaced in this case.…”

“…6 There exists a report about a failure, that is, exacerbation of mitral regurgitation (MR) after isolated myectomy for SAM and left ventricular outflow tract obstruction (LVOTO) in sigmoid septum with relatively thin interventricular septum. 7 The authors speculated that abnormal papillary muscle attachment might have caused the failure. We believe that the effect of isolated myectomy is limited when the interventricular septum is relatively thin (<20 mm), we employed mitral valve repair concomitant with myectomy for HOCM cases with SAM and LVOTO when MR is more than mild.…”