Septum

The cardiac septum should be assessed for thickness, motion, integrity, and abnormal shunting. Septal findings may provide important clues to ventricular loading conditions, conduction abnormalities, constrictive physiology, and congenital heart disease.

Interventricular Septal Thickness¶

Measure septal thickness at end diastole from the parasternal long-axis view, perpendicular to the LV long axis and below the mitral leaflet tips.

Sex	Normal	Mildly increased	Moderately increased	Severely increased
Men	0.6–1.0 cm	1.1–1.3 cm	1.4–1.6 cm	>1.6 cm
Women	0.6–0.9 cm	1.0–1.2 cm	1.3–1.5 cm	>1.5 cm

Avoid including RV trabeculations, moderator-band insertion, or nonseptal structures in the measurement.

See Left Ventricle for LV mass and geometric classification.

Abnormal Septal Motion¶

RV pressure overload¶

Septal flattening during systole and diastole
Produces a D-shaped LV in the parasternal short-axis view
Seen with pulmonary hypertension, pulmonic stenosis, or RV outflow obstruction
May progress to leftward septal displacement with severe RV pressure loading

RV volume overload¶

Septal flattening predominantly during diastole
Seen with significant tricuspid or pulmonic regurgitation
Also occurs with ASD or partial anomalous pulmonary venous return

Conduction and pacing¶

Abnormal electrical activation can produce paradoxical septal motion:

Left bundle-branch block
Right ventricular pacing
Ventricular pre-excitation
Postoperative conduction disturbance

The motion abnormality should not automatically be interpreted as ischemia.

Postoperative septal motion¶

Paradoxical septal motion is common after cardiac surgery and may persist despite preserved septal thickening and normal global LV systolic function.

Constrictive physiology¶

A septal bounce or respirophasic septal shift may occur with constrictive pericarditis because of exaggerated ventricular interdependence.

The finding should be integrated with:

Respiratory variation in mitral and tricuspid inflow
Hepatic vein expiratory diastolic flow reversal
Preserved or increased medial mitral annular e′
Pericardial findings

Interatrial Septum¶

Assess the interatrial septum from multiple views:

Subcostal four-chamber
Apical four-chamber
Parasternal short-axis at the aortic-valve level

The subcostal view usually provides the most perpendicular insonation and is preferred for color Doppler assessment.

Evaluate for:

Atrial septal defect
Patent foramen ovale
Atrial septal aneurysm
Lipomatous hypertrophy
Septal patch or closure device
Residual shunting

A dropout seen only in the apical four-chamber view may represent artifact because the ultrasound beam is parallel to the septum.

See Intracardiac Shunts for color Doppler, spectral Doppler, and agitated-saline assessment.

Reporting¶

The interatrial and interventricular septa are structurally and
functionally normal.

There is systolic and diastolic interventricular septal flattening,
consistent with RV pressure overload.

There is predominantly diastolic septal flattening, consistent
with RV volume overload.

Paradoxical septal motion is present, likely related to
[conduction abnormality/RV pacing/prior cardiac surgery].

There is respirophasic septal shift, which may support
constrictive physiology in the appropriate clinical context.

Pitfalls¶

Measuring RV trabeculation as part of the interventricular septum
Diagnosing ischemia from paradoxical septal motion alone
Reversing the pressure- and volume-overload patterns
Mistaking apical interatrial septal dropout for an ASD
Diagnosing constriction from septal bounce alone
Failing to assess the septum in multiple views
Ignoring pacing, bundle-branch block, or prior cardiac surgery

Key Points¶

Measure septal thickness at end diastole.
Systolic and diastolic flattening → RV pressure overload.
Predominantly diastolic flattening → RV volume overload.
Septal bounce plus respiratory ventricular interaction suggests constriction.
The subcostal view is preferred for assessing interatrial septal integrity.
Abnormal septal motion is not synonymous with ischemia.