Key result
Bidirectional bulging of the basal septum, driven by a deep wedged aorta, defines the morphology of the sigmoid septum and is significantly associated with left ventricular outflow tract narrowing.
Why the study?
The sigmoid septum has generally been evaluated subjectively and qualitatively, without detailed examination of its diversity, anatomical background, and impact on LVOT morphology.
Cross-Sectional (n=100)
No
Effect estimate: β = 0.5382
p-value: p=<0.0001
The sigmoid septum exhibits bidirectional bulging that deforms and narrows the LVOT, primarily driven by deep aortic wedging rather than the aortic-to-left ventricular angle.
May refine echocardiographic assessment of sigmoid septum; leaves open its clinical and prognostic relevance.
BACKGROUND: The sigmoid septum has been generally evaluated subjectively and qualitatively, without detailed examination of its diversity, impact on the morphology of the left ventricular outflow tract (LVOT), and anatomical background. METHODS: We enrolled 100 patients without any background cardiac diseases (67.5 ± 12.8 years old; 43% women) who underwent cardiac computed tomography. Basal septal morphology was evaluated using antero-superior and medial bulging angles (bidirectional angulation of the basal septum relative to the LVOT). The eccentricity index of the LVOT, area narrowing ratio (LVOT/virtual basal ring area), aortic-to-left ventricular axial angle (angulation of the aortic root relative to the left ventricle), and wedged height (non-coronary aortic sinus to inferior epicardium distance) were also quantified. RESULTS: The antero-superior bulging, medial bulging, aortic-to-left ventricular axial angles, LVOT eccentricity index, area narrowing ratio, and wedged height were 76° ± 17°, 166° ± 27°, 127° ± 9°, 1.8 ± 0.5, 1.0 ± 0.2, and 41.2 ± 9.1 mm, respectively. Both bulging angles were correlated with each other and contributed to the narrowing and deformation of the LVOT. Angulated aortic root was not correlated with either bidirectional septal bulge or LVOT narrowing. Clockwise rotation of the aortic root rotation was an independent predictor of prominent antero-superior septal bulge. Deeper aortic wedging was a common independent predictor of bidirectional septal bulge. CONCLUSIONS: The extent of septal bulge varies in normal hearts. Along with deep aortic wedging, the bidirectional bulge of the basal septum deforms and narrows the LVOT without affecting the virtual basal ring morphology.
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Tsuda et al. (2022) conducted a cross-sectional in Sigmoid septum (n=100). Morphological features of the aortic root and sigmoid septum (evaluated via cardiac CT) was evaluated on Correlation between Antero-Superior Bulging Angle and Medial Bulging Angle (β = 0.5382, p=<0.0001). Bidirectional bulging of the basal septum, driven by a deep wedged aorta, defines the morphology of the sigmoid septum and is significantly associated with left ventricular outflow tract narrowing.
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