Sigmoid septum: A variant of the ventricular hypertrophy or of the hypertrophic cardiomyopathy?

Abstract

Sigmoid septum and hypertrophic cardiomyopathy presenting with left ventricular hypertrophy and, although they appear to be different entities, often involve problems in the differential diagnosis. This study was carried out to assess the prevalence and characteristics of the echocardiographic sigmoid septum and its differential findings regarding hypertrophic cardiomyopathy. Descriptive, observational and prospective study. A total of 1,770 patients were studied by echocardiography. Sigmoid septum (focal and isolated hypertrophy of the basal interventricular septum≥13mm in men and ≥12mm in women, exceeding ≥50% of the median septum thickness) was classified as «Type 1» (≤14mm) and «Type 2» (≥15mm). There were 59 cases of sigmoid septum (prevalence of 3.3%): 26 (1.5%) patients with type 1 (50% male) and 33 (1.9%) patients with type 2 (72.7% male); there were 25 (1.4%) cases of hypertrophic cardiomyopathy (76% male). The group with type 2 sigmoid septum differed from hypertrophic cardiomyopathy in: was older (73±10.5years; P<.0001), with more hypertension (84.8%; P<.0001), lower glomerular filtering (73.3±21.4ml/min; P=.007), lower repolarization abnormalities (18.2%; P=.004) and Cornell index (in men, 22.2±11mm; P=.041), more diastolic dysfunction (75%; P=.0089) and in ventricular morphology and fibrosis location in magnetic resonance. Regarding the hypertrophic cardiomyopathy, patients with type 2 sigmoid septum are older and generally hypertensive; otherwise, often they have no clear differences in their clinical, electrocardiographic or echocardiographic characteristics. Therefore, cardiac resonance is helpful in the differential diagnosis.