What is right axis deviation on an electrocardiogram (ECG)?

Right Axis Deviation on ECG

Right axis deviation (RAD) on an electrocardiogram is defined as a mean frontal plane QRS axis of +91° to +180°, characterized by a negative QRS complex in lead I and a positive QRS complex in lead aVF. 1

Definition and Identification

Right axis deviation can be determined using the following method:

• Examine the QRS complexes in leads I and aVF:
  • If lead I is negative and lead aVF is positive, this indicates right axis deviation (+91° to +180°) 1

The American College of Cardiology provides a systematic approach to axis determination using the following table:

Lead I	Lead aVF	Axis Interpretation
Positive	Positive	Normal axis (0° to +90°)
Positive	Negative	Left axis deviation (-1° to -90°)
Negative	Positive	Right axis deviation (+91° to +180°)
Negative	Negative	Extreme right axis deviation (+181° to -91°)

Age-Specific Considerations

It's important to note that normal axis ranges vary by age:

• Adults: +30° to +90° (normal)
• Children 8-16 years: up to +120° may be normal
• Children 5-8 years: up to +140° may be normal
• Children 1-5 years: +10° to +110° is normal
• Neonates: +30° to +190° is normal 1

This means that what would be considered RAD in adults may be normal in children and infants.

Clinical Significance and Associated Conditions

Right axis deviation can be associated with various clinical conditions:

1. Pulmonary Conditions:

   • Pulmonary embolism - may present with RAD along with other ECG findings such as S1Q3T3 pattern 2
   • Pulmonary hypertension - although ECG has limited sensitivity (73%) for detecting this condition 1

2. Cardiac Conditions:

   • Right ventricular hypertrophy
   • Lateral wall myocardial infarction
   • Right bundle branch block - complete RBBB is detected in approximately 1% of the general population and 0.5% to 2.5% of young adult athletes 3
   • Congenital heart disease

3. Other Causes:

   • Normal variant (especially in children and young adults)
   • Hereditary patterns - some families may have hereditary RAD without structural cardiac abnormalities 4
   • Body position changes - turning to one side can cause axis shifts 5

Clinical Implications

RAD can have significant prognostic implications in certain clinical scenarios:

• In acute myocardial infarction, new-onset extreme RAD and RBBB may indicate severe disease and poor prognosis 6
• In heart failure patients requiring cardiac resynchronization therapy, the presence of RAD may require special consideration for pacing timing 7

Evaluation Approach

When RAD is identified on ECG:

1. Confirm true RAD by examining leads I and aVF

2. Look for associated ECG findings such as:

   • RBBB pattern
   • RV hypertrophy voltage criteria
   • S1Q3T3 pattern (suggestive of pulmonary embolism)
   • ST-T wave abnormalities

3. Consider further evaluation based on clinical context:

   • Echocardiography is essential for evaluating ventricular size and function, presence of congenital heart defects, and evidence of pulmonary hypertension 1
   • In athletes with isolated axis deviation without other abnormal findings, further assessment may not be warranted 3
   • In children without known heart disease, isolated RAD may not require further investigation if there are no symptoms or abnormal exam findings 1

Pitfalls and Caveats

• RAD alone is not diagnostic of any specific condition and must be interpreted in clinical context
• Body position can affect the ECG axis, so consider repeating the ECG in a supine position if the finding is new 5
• Complete RBBB in athletes may represent physiological cardiac remodeling rather than pathology 3
• ECG has limited sensitivity for detecting pulmonary hypertension, so a normal ECG does not rule out significant disease 1

Remember that RAD is an ECG finding that requires clinical correlation and may warrant further cardiac evaluation depending on the patient's age, symptoms, and other clinical factors.