Abstract 18951: Is Sigmoid Septum an Age Related Phenomenon or a Variant of Hypertrophic Cardiomyopathy?
Background: It is uncertain if sigmoid septum (SS) is a variant of hypertrophic cardiomyopathy (HCM) particularly in the setting of SS with left ventricular outflow tract obstruction (LVOTO) when it is often categorized as sigmoid hypertrophic cardiomyopathy (sHCM). We sought to assess the prevalence of SS and to compare echocardiographic characteristics in patients with and without obstruction.
Methods: Echocardiograms performed on 4104 consecutive patients during 6 months at a secondary hospital and a community cardiology practice (without specialized HCM services) was retrospectively reviewed. SS was identified if patients had isolated hypertrophy (>15 mm) of the basal left ventricular septum (LVS) without hypertrophy elsewhere. Clinical and echocardiographic characteristics were compared between patients with and without LVOTO.
Results:: 240 (5.84%;) patients had a SS on echocardiography. Frequency of SS increased with age (median age 78.1y, IQR 70.3–83.4y, see Figure 1) with 51.7%; male. In those with SS, mean SS thickness was 17.8 ± 0.24mm with a SS/Posterior wall ratio of 1.76 ± 0.31. Resting or provoked LVOT gradient (>20 mmHg) was present in 11/132 (4.58%;) of patients. Patients with LVOTO were younger (median 72.0 v 76.3y, p = 0.025) with hypercontractile LV function (fractional shortening 51.5%; vs 41.0%;, p = 0.009) but had similar SS thickness (17.5mm vs 17.8mm, p=0.54). Greater displacement of the mitral valve co-aptation point apically (p < 0.001) and towards the septum (p < 0.001) was present in those with SS and obstruction with no difference in the LV-aortic root angle (p = 0.580).
Conclusion: Prevalence of SS in our study markedly exceeds the expected 1/500 genetic frequency of HCM. sHCM differ from SS only in the MV characteristics and LV hypercontractility that allow LVOTO to develop rather than any difference in myocardial hypertrophy.
- © 2010 by American Heart Association, Inc.