Does a sigmoid septum warrant a referral to cardiology?

Sigmoid Septum and Cardiology Referral

A sigmoid septum is a benign cardiac anatomical variant that does not routinely warrant referral to cardiology unless the patient develops exertional symptoms (dyspnea, chest pain, syncope) suggestive of left ventricular outflow tract obstruction. 1

Understanding Sigmoid Septum

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. 1 This condition is typically seen in elderly hypertensive patients and is associated with increased angulation between the interventricular septum and ascending aorta. 2, 1

The key clinical point is that this is generally a benign finding with limited data suggesting individuals are less likely to have familial disease or sarcomeric protein gene mutations compared to true hypertrophic cardiomyopathy (HCM). 2, 1

Critical Distinguishing Features from HCM

Before considering referral, it's essential to differentiate sigmoid septum from true HCM, as management differs substantially:

ECG Findings

• Sigmoid septum: Normal ECG or isolated voltage increases without marked repolarization abnormalities 2, 1
• HCM: Significant repolarization changes, conduction disease, or Q-waves 2

Imaging Characteristics

• Sigmoid septum: Absence of right ventricular hypertrophy; different late gadolinium enhancement patterns on cardiac MRI (when present, differs from the RV insertion point pattern typical of HCM) 2, 1
• HCM: Late gadolinium enhancement at RV insertion points or localized to segments of maximum LV thickening 2

Functional Severity

• Sigmoid septum: Less severe diastolic dysfunction 2, 1
• HCM: Severe diastolic dysfunction 2

Clinical Context

• Sigmoid septum: Older patients (typically >70 years), history of hypertension, regression of LVH with tight blood pressure control 2, 1
• HCM: Family history of HCM, younger age, no regression with blood pressure control 2

When Cardiology Referral IS Appropriate

Refer to cardiology (not neurology or other specialties) specifically when patients develop: 1

1. Exertional dyspnea that cannot be explained by other causes 1, 3
2. Chest pain or angina with exertion 1, 4
3. Syncope or presyncope 1, 4

These symptoms suggest provocable left ventricular outflow tract (LVOT) obstruction, which can occur in sigmoid septum despite its generally benign nature. 2, 5, 3

Important Caveat About Resting Echocardiography

Resting echocardiography may appear completely normal in symptomatic patients with sigmoid septum. 3 The LVOT pressure gradient may be low at rest with no systolic anterior motion (SAM) of the mitral valve, but during Valsalva maneuver or dobutamine stress, the gradient can increase significantly with appearance of SAM. 3, 4 This is why provocative testing is essential in symptomatic patients. 2, 1

Management Pathway for Symptomatic Patients

When cardiology referral is made for symptomatic sigmoid septum:

1. Stress echocardiography with physiological provocation should be performed to assess for latent LVOT obstruction, using the same evaluation approach as for HCM. 2, 1

2. First-line medical therapy includes beta-blockers or calcium channel blockers (verapamil) for symptomatic obstruction. 1

3. Interventional options for refractory cases include percutaneous transluminal septal myocardial ablation (PTSMA) or endocardial radiofrequency ablation, which have shown success in reducing LVOT gradients and improving symptoms. 3, 4

Family Screening Considerations

Family screening is generally NOT necessary for sigmoid septum, unlike true HCM. 2, 1 However, advice should be guided by the presence of suspicious symptoms in relatives and implications for family members if there is any diagnostic uncertainty. 2, 1

Common Pitfalls to Avoid

Misdiagnosis as HCM

The most critical error is misdiagnosing sigmoid septum as HCM. 2, 1 Sigmoid septum patients are typically older, hypertensive, with normal or minimally abnormal ECGs. 1 Regression of septal thickness with blood pressure control strongly suggests hypertension rather than HCM. 2, 1

Overlooking Symptomatic LVOT Obstruction

Always perform provocative testing (Valsalva maneuver or dobutamine stress echo) in symptomatic patients, as resting echocardiography may appear normal. 2, 1, 3 This is a common cause of cryptogenic exertional dyspnea that can be missed without appropriate provocation. 3

Inappropriate Workup

This is a cardiac finding that does not warrant neurological or neurosurgical evaluation. 1 Referral should be to cardiology if indicated, not other specialties.

Suboptimal Blood Pressure Management

Optimize blood pressure control in all patients with sigmoid septum, as hypertension management may reduce septal thickness over time. 1 This is both diagnostic (regression suggests hypertensive etiology) and therapeutic.

Asymptomatic Patients: No Referral Needed

For asymptomatic patients with incidentally discovered sigmoid septum on imaging, no cardiology referral is necessary. 2, 1 Management should focus on:

• Optimizing blood pressure control 1
• Routine cardiovascular risk factor management 2
• Patient education about symptoms that would warrant re-evaluation 1

The definitive Framingham Heart Study of 3,562 subjects demonstrated that upper septal hypertrophy (sigmoid septum) correlated with age and blood pressure, but after adjusting for risk factors, it was unrelated to cardiovascular disease or mortality at 15 years. 2 This provides strong reassurance about the benign natural history of asymptomatic sigmoid septum.