What is a sigmoid septum and is referral to a neurologist (neurology specialist) or neurosurgeon (brain and nervous system surgeon) necessary?

What is a Sigmoid Septum and Is Referral Necessary?

A sigmoid septum is a benign cardiac anatomical variant characterized by focal basal septal hypertrophy with increased angulation between the interventricular septum and ascending aorta, typically seen in elderly hypertensive patients, and does not routinely require referral to a neurologist or neurosurgeon unless symptomatic left ventricular outflow tract obstruction develops—in which case cardiology referral is appropriate. 1

Definition and Clinical Significance

A sigmoid septum represents isolated basal interventricular septal hypertrophy (≥13mm in men, ≥12mm in women) that exceeds 50% of the median septal thickness, creating an S-shaped or "bulging" appearance of the basal septum. 2 This condition is:

• Most commonly found in elderly individuals with a history of hypertension, often associated with mitral annular calcification 1
• Distinct from hypertrophic cardiomyopathy (HCM), though differentiation can be challenging 1, 2
• Generally benign with limited data suggesting individuals are less likely to have familial disease or sarcomeric protein gene mutations 1

The prevalence is approximately 3.3% in echocardiographic studies, with Type 1 (≤14mm) occurring in 1.5% and Type 2 (≥15mm) in 1.9% of patients. 2

Key Distinguishing Features from HCM

Sigmoid septum differs from true HCM in several critical ways:

• Age and comorbidities: Patients are typically older (mean age 73 years) with established hypertension (84.8% prevalence) 2
• ECG findings: Normal or isolated voltage increases without marked repolarization abnormalities, unlike HCM which shows significant repolarization changes, conduction disease, or Q-waves 1
• Cardiac imaging: Absence of right ventricular hypertrophy and different late gadolinium enhancement patterns on cardiac MRI (when present, enhancement in sigmoid septum differs from the RV insertion point pattern typical of HCM) 1
• Severity of dysfunction: Less severe diastolic dysfunction compared to HCM 1

When Symptoms Develop: Latent LVOT Obstruction

The critical clinical concern is latent left ventricular outflow tract (LVOT) obstruction, which occurs when:

• No resting pressure gradient exists, but provocative maneuvers (Valsalva, dobutamine stress, exercise) induce gradients ≥30 mmHg 3, 4
• Systolic anterior motion (SAM) of the mitral valve appears during provocation 4, 5
• Symptoms include: exertional dyspnea, angina, syncope, or presyncope 3, 4, 5

This latent obstruction can be unmasked by conditions causing increased cardiac contractility or decreased preload/afterload (dehydration, anemia, certain medications). 3 In rare cases, conventional cardiopulmonary resuscitation can paradoxically worsen obstruction due to catecholamine-induced hypercontractility. 3

Appropriate Referral Pathway

Referral to a neurologist or neurosurgeon is NOT indicated for sigmoid septum, as this is a cardiac structural variant without neurological implications. The provided guidelines on neurosurgical referral address entirely different conditions (pediatric neurosurgical problems, trauma, epilepsy). 1

Instead, the appropriate management pathway is:

For Asymptomatic Patients:

• No specialist referral required if incidentally discovered on imaging 1
• Reassurance that this represents a benign age-related cardiac remodeling pattern 1
• Blood pressure optimization if hypertensive 1

For Symptomatic Patients:

• Cardiology referral (not neurology) for patients with exertional symptoms (dyspnea, chest pain, syncope) 4, 5
• Stress echocardiography with physiological provocation to assess for latent LVOT obstruction, performed similarly to HCM evaluation 1, 4
• Medical management with beta-blockers (carvedilol) and calcium channel blockers (verapamil) as first-line therapy for symptomatic obstruction 3
• Advanced interventions (percutaneous transluminal septal myocardial ablation or radiofrequency ablation) reserved for drug-refractory cases with documented significant LVOT gradients 4, 5

Family Screening Considerations

Family screening is generally not necessary for sigmoid septum, unlike true HCM. 1 However, advice should be guided by:

• Presence of suspicious symptoms in relatives 1
• Implications for family members if there is any diagnostic uncertainty 1

Common Pitfalls to Avoid

• Misdiagnosing as HCM: Sigmoid septum patients are older, hypertensive, with normal ECGs—regression with blood pressure control suggests hypertension rather than HCM 1
• Overlooking symptomatic LVOT obstruction: Always perform provocative testing in symptomatic patients, as resting echocardiography may appear normal 4, 5
• Inappropriate neurological workup: This cardiac finding does not warrant neurological or neurosurgical evaluation 1
• Failing to optimize blood pressure: Hypertension management may reduce septal thickness over time 1