Right Axis Deviation on EKG: Clinical Significance and Interpretation
Right axis deviation (RAD) on an electrocardiogram indicates a rightward shift of the QRS electrical vector, which may signify right ventricular hypertrophy, pulmonary hypertension, congenital heart disease, or other cardiac abnormalities requiring further evaluation.
Definition and Determination
Right axis deviation is defined as a QRS axis between +91° and +180° in adults 1. The axis can be systematically determined by examining leads I and aVF:
| 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 Normal Ranges
It's important to note that normal QRS axis varies by age 1:
- Neonates: +30° to +190° (rightward axis is normal)
- Children 1-5 years: +10° to +110°
- Children 5-8 years: up to +140°
- Children 8-16 years: up to +120°
- Adults: +30° to +90°
Clinical Significance
1. Right Ventricular Hypertrophy (RVH)
Right axis deviation is a key component in diagnosing RVH, though the sensitivity of ECG criteria for RVH is generally low 2. RVH should be suspected when:
- RAD is present with tall R waves in right precordial leads
- Secondary ST-T abnormalities appear in right precordial leads
- The R-wave peak time in V1 is prolonged
2. Congenital Heart Disease
RAD has the greatest diagnostic accuracy in congenital heart disease 2. It commonly appears in:
- Atrial septal defects
- Tetralogy of Fallot
- Pulmonary stenosis
- Other conditions with right ventricular pressure or volume overload
3. Pulmonary Disease
In chronic obstructive pulmonary disease, RAD often appears with:
- Low voltage in limb leads
- Rightward P-wave axis (>60°)
- Persistent S waves in all precordial leads
- Low R-wave amplitude in V6 2
4. Conduction Abnormalities
RAD may be associated with:
- Left posterior fascicular block (LPFB), characterized by:
- Axis between 90° and 180° in adults
- rS pattern in leads I and aVL
- qR pattern in leads III and aVF
- QRS duration <120 ms 2
- Incomplete right bundle branch block
5. Acute Conditions
RAD can develop transiently during:
- Acute myocardial infarction, particularly anterior wall MI 3, 4
- Pulmonary embolism (acute cor pulmonale)
Diagnostic Approach
When RAD is identified:
Evaluate for RVH:
- Apply criteria from Table 2 in the AHA/ACC guidelines 2
- Consider the clinical context (congenital heart disease, valvular disease, pulmonary disease)
Rule out conduction disorders:
- Assess for LPFB criteria 2
- Look for RBBB patterns
Consider echocardiography to evaluate:
- Right ventricular size and function
- Presence of congenital heart defects
- Evidence of pulmonary hypertension 1
Clinical Pitfalls and Caveats
- Normal variant: RAD can be a normal variant, especially in children and young adults 5
- False positives: Various conditions other than RVH can cause RAD 2
- Changing axis: Rarely, patients may show intermittent RAD, which can have specific clinical implications 6
- Extreme RAD: An axis between +181° and -91° (negative in both leads I and aVF) may indicate severe pathology and poor prognosis in acute settings 3
Management Implications
The finding of RAD should prompt:
- Evaluation for underlying cardiac or pulmonary pathology
- Echocardiography to assess ventricular size and function
- Regular clinical assessment to monitor for progression of disease
- Appropriate management of underlying conditions (pulmonary hypertension, congenital heart disease, etc.)
For RAD associated with structural heart disease, treatment should focus on managing the underlying condition, with regular clinical assessment and serial echocardiography to monitor progression 1.