What is the initial workup for left axis deviation?

Initial Workup for Left Axis Deviation

The initial workup for left axis deviation should include an echocardiogram to exclude underlying structural heart disease, particularly when accompanied by ECG evidence of chamber enlargement/hypertrophy, a QRS axis ≤-42°, or abnormal cardiac physical examination findings. 1

Definition and Significance

• Left axis deviation (LAD) is defined as a mean frontal plane QRS axis between -30° and -90° in adults 2
• Moderate LAD ranges from -30° to -45°, while marked LAD ranges from -45° to -90° 2
• LAD is one of the most commonly encountered ECG abnormalities and should alert clinicians to the possibility of underlying structural heart disease 3

Causes of Left Axis Deviation

Left axis deviation may be associated with:

• Left anterior fascicular block (most common cause) 2, 3
• Cardiomyopathies (hypertrophic, dilated, arrhythmogenic) 2
• Congenital heart defects (especially those with underdevelopment of the right ventricle, such as tricuspid atresia) 2
• Complete atrioventricular septal defect 2
• Left ventricular hypertrophy with non-voltage criteria 2
• Left bundle branch block with myocardial disease 4
• Coronary artery disease 5

Initial Workup Algorithm

Step 1: Detailed ECG Analysis

• Determine the exact QRS axis (more negative values, especially ≤-42°, warrant more concern) 1
• Look for additional ECG abnormalities that may suggest specific pathology:
  • Non-voltage criteria for LVH (left atrial enlargement, delayed intrinsicoid deflection, ST-segment and T-wave abnormalities, pathological Q-waves) 2
  • Conduction abnormalities (bundle branch blocks, fascicular blocks) 2
  • Chamber enlargement patterns 1
  • Repolarization abnormalities 2

Step 2: Clinical Assessment

• Evaluate for symptoms (syncope, chest pain, dyspnea, palpitations) 2, 1
• Perform thorough cardiac physical examination (murmurs, abnormal heart sounds, signs of heart failure) 1
• Assess for family history of cardiac disease or sudden cardiac death 2

Step 3: Imaging Studies

• Echocardiography is the primary imaging modality and should be performed in patients with:
  • ECG evidence of cardiac chamber enlargement or hypertrophy 1
  • QRS axis ≤-42° 1
  • Abnormal cardiac physical examination findings 1
  • Symptoms suggestive of cardiovascular disease 2
  • Family history of cardiomyopathy or sudden cardiac death 2

Step 4: Additional Testing (Based on Initial Findings)

• Exercise testing may be useful to evaluate exercise capacity and detect ischemia 2
• Cardiac MRI if echocardiography is inconclusive or to better characterize myocardial tissue (particularly to assess for scar burden) 4
• Cardiac catheterization in older patients to rule out coronary artery disease 2
• Electrophysiologic studies in selected cases with conduction abnormalities 5

Special Considerations

Pediatric Patients

• Normal QRS axis varies by age in children:
  • Neonates: 60° to 190° 2
  • Ages 1-5 years: 10° to 110° 2
  • Ages 5-8 years: 10° to 140° 2
  • Ages 8-16 years: 10° to 120° 2
• Isolated LAD in asymptomatic pediatric patients without other ECG abnormalities may not necessitate further cardiovascular investigation 1

Athletes

• LAD in athletes may indicate pathological LV hypertrophy rather than physiological adaptation 2
• In athletes with LAD and non-voltage criteria for LVH, echocardiographic evaluation is recommended to exclude underlying structural heart disease 2

Patients with Left Bundle Branch Block

• LAD in patients with LBBB is associated with:
  • More advanced myocardial disease 5
  • Greater incidence of myocardial dysfunction 5
  • More advanced conduction disease 5
  • Higher cardiovascular mortality 5
  • Poorer response to cardiac resynchronization therapy 4
  • Higher myocardial scar burden 4

Pitfalls to Avoid

• Do not dismiss LAD as a benign finding without appropriate evaluation, especially when accompanied by other ECG abnormalities 2, 1
• Recognize that LAD may be the only early sign of underlying cardiomyopathy before structural changes become evident 2
• Avoid overinvestigation of isolated LAD in asymptomatic patients with no other concerning findings 1
• Remember that the significance of LAD varies by age, especially in pediatric populations 2, 1