What does an abnormality in the anterior 2/3rds of the interventricular septum on an echocardiogram (echo) indicate?

Anterior 2/3rds of Interventricular Septum on Echocardiography

The anterior 2/3rds of the interventricular septum visualized in the parasternal long-axis view represents the territory supplied by the left anterior descending artery (LAD) and its septal perforators, making abnormalities in this region highly specific for anteroseptal myocardial infarction or LAD disease. 1

Anatomical and Clinical Significance

Blood Supply Territory

• The anterior interventricular septum (visualized in parasternal long-axis view) corresponds to LAD territory, while the posterior septum (seen in apical four-chamber view) reflects the posterior descending artery distribution 1
• Complete asynergy of the interventricular septum in the parasternal long-axis view indicates anteroseptal myocardial infarction with proximal LAD stenosis in 80% of cases 1
• Distal septal abnormalities in this view occur with stenosis distal to the first septal perforator 1

Pathological Patterns

Myocardial Infarction:

• Interventricular septal asynergy in the parasternal long-axis view is present in 96% of patients with transmural anteroseptal infarction 1
• The anterior 2/3rds demonstrates wall motion abnormalities specifically associated with anteroseptal infarction, not inferior infarction 1

Volume and Pressure Overload:

• Rapid anterior motion of the interventricular septum at the onset of systole (during isovolumic contraction) represents a qualitative sign of right ventricular volume overload due to severe tricuspid regurgitation 2
• Paradoxical septal motion (posterior in early systole followed by anterior movement) indicates more severe cardiac dysfunction, with lower ejection fractions (52% vs 62.9%) and higher pulmonary artery pressures (43.3 mmHg vs 28.7 mmHg) compared to normal septal motion 3

Post-Surgical Considerations

• Abnormal septal motion after cardiac surgery results from cardiac translation related to cardiopulmonary bypass events, not from removal of pericardial restraint 4
• This translational movement increases more than fourfold after bypass, continuing in a medial direction even after chest closure 4

Diagnostic Approach

When evaluating anterior septal abnormalities:

• Use parasternal long-axis view to assess the anterior 2/3rds specifically for LAD territory disease 1
• Distinguish between true wall motion abnormalities and apparent septal dropout, which may mimic pathology 5
• Assess the extent of asynergy: complete involvement suggests proximal LAD disease, while distal involvement alone suggests more distal stenosis 1
• Evaluate for right ventricular volume or pressure overload if paradoxical motion is present 2, 3

Common Pitfalls

• The interventricular septum attempts to maintain its characteristic concave shape during systole regardless of diastolic configuration, except in right ventricular pressure overload 6
• Apparent medial hypokinesis may represent cardiac translation rather than true regional dysfunction, particularly in post-surgical patients 4
• Different echocardiographic views visualize different portions of the septum: parasternal long-axis shows anterior septum, while apical four-chamber shows posterior septum 1