What does a jerky interventricular (IVS) septum mean?

Jerky Interventricular Septum: Clinical Significance and Diagnostic Approach

A jerky or abnormal interventricular septum (IVS) motion represents altered septal movement patterns that indicate underlying cardiac pathology, most commonly right ventricular pressure or volume overload, post-cardiac surgery changes, constrictive pericarditis, left bundle branch block, or ventricular pacing. 1, 2

Primary Causes and Mechanisms

Right Ventricular Pressure Overload

• The septum demonstrates abnormal flattening or leftward bowing throughout both systole and diastole when RV pressure is elevated 3
• Calculate the left ventricular eccentricity index (ratio of two perpendicular LV minor-axis diameters): values >1.1 in both systole and diastole indicate RV pressure overload 1, 3
• Measure tricuspid regurgitation velocity: >3.4 m/s strongly suggests pulmonary hypertension 2
• Assess RV/LV basal diameter ratio: >1.0 indicates RV enlargement 2
• Examine IVC diameter: >21 mm with <50% inspiratory collapse indicates elevated right atrial pressure 2

Right Ventricular Volume Overload

• The septum shows paradoxical motion primarily in diastole with preserved systolic geometry 3
• The eccentricity index is approximately 1.0 at end-systole but significantly increased at end-diastole (mean 1.26) 3
• This pattern is characteristic of atrial septal defects and significant tricuspid regurgitation without pulmonary hypertension 1, 3

Post-Cardiac Surgery

• Abnormal septal motion after cardiac surgery is directly related to events during cardiopulmonary bypass, not removal of pericardial restraint 4
• The mechanism involves cardiac translation with medial displacement of the entire heart rather than true regional wall motion abnormality 4
• Suboptimal right ventricular myocardial preservation impairs RV motion patterns, including abnormal tricuspid annular motion that translates to septal dysfunction 5
• This occurs in 76% of patients immediately after bypass and 86% after chest closure 5

Constrictive Pericarditis

• Document exaggerated respiratory variation in septal motion: marked changes with inspiration strongly suggest constriction 2
• Measure respiratory variation in Doppler flow velocities across AV valves: >25% variation is characteristic 1, 2
• Look for pericardial thickening, IVC enlargement, and mild atrial enlargement with normal-sized LV 2
• No single echocardiographic sign is diagnostic; the constellation of findings is required 2

Conduction Abnormalities

• Left bundle branch block and right ventricular pacing produce abnormal septal motion patterns due to altered activation sequence 1
• The septum demonstrates dyssynchronous contraction with delayed or paradoxical movement 1

Diagnostic Algorithm

Step 1: Characterize the Motion Pattern

• Determine timing: systolic only, diastolic only, or both phases 3, 6
• Assess respiratory variation: exaggerated changes suggest constrictive physiology 2
• Evaluate with floating reference system: if regional differences disappear, cardiac translation rather than true wall motion abnormality is present 4

Step 2: Comprehensive Echocardiographic Assessment

• Measure maximum diastolic wall thickness in all LV segments using 2D short-axis views to exclude hypertrophic cardiomyopathy 2
• Calculate eccentricity index at end-systole and end-diastole to differentiate RV pressure from volume overload 3
• Perform Doppler assessment of all four valves to identify regurgitant or stenotic lesions 2
• Evaluate RV size and function qualitatively given complex RV geometry 2
• Assess tricuspid annular plane systolic excursion (TAPSE) and systolic myocardial velocities for RV function 1

Step 3: Clinical Context Integration

• Obtain focused history: recent cardiac surgery, known lung disease, family history of cardiomyopathy, symptoms of heart failure 2
• Physical examination findings: elevated JVP, right ventricular heave, loud P2, peripheral edema, pericardial friction rub 2
• Review ECG: look for left bundle branch block, RV hypertrophy, or pacing patterns 1

Step 4: Advanced Imaging When Indicated

• Consider cardiac MRI for: poor echocardiographic windows, suspected apical hypertrophy, need for tissue characterization, or evaluation of RV in complex cases 2
• Consider right heart catheterization when: confirming pulmonary hypertension, differentiating pre-capillary from post-capillary PH, or assessing constrictive physiology 2

Critical Pitfalls to Avoid

• Do not assume all abnormal septal motion represents ischemia: regional wall motion abnormalities occur in myocarditis, sarcoidosis, and takotsubo cardiomyopathy without coronary disease 1
• Do not overlook post-surgical context: abnormal septal motion after cardiac surgery is expected and does not necessarily indicate myocardial dysfunction 4, 5
• Do not rely on visual assessment alone: quantitative measures like eccentricity index provide objective differentiation between pressure and volume overload 3
• Do not ignore diastolic dysfunction: often precedes systolic dysfunction and causes symptoms despite normal ejection fraction 2
• Do not use exercise Doppler for pulmonary hypertension screening: not recommended per guidelines 2

Prognostic Implications

• In RV pressure overload, the degree of septal flattening correlates with RV dysfunction severity and predicts adverse outcomes 1
• Post-surgical septal motion abnormalities typically persist but do not independently predict poor outcomes unless accompanied by RV dysfunction 5
• In constrictive pericarditis, failure to recognize the diagnosis leads to progressive symptoms requiring eventual pericardiectomy 2
• Monitor for progression with serial imaging and consider global longitudinal strain to detect early dysfunction before ejection fraction declines 2