From the Guidelines
Right axis deviation (RAD) is primarily caused by right ventricular hypertrophy, often due to pulmonary hypertension or congenital heart disease, as well as other conditions such as right bundle branch block, posterior wall myocardial infarction, left posterior fascicular block, and pulmonary embolism.
Causes of Right Axis Deviation
The causes of RAD can be categorized into several groups, including:
- Right ventricular hypertrophy (RVH) due to pulmonary hypertension or congenital heart disease
- Right bundle branch block
- Posterior wall myocardial infarction
- Left posterior fascicular block
- Pulmonary embolism
- Normal variant in children and thin adults
Diagnosis and Management
Diagnosis of RAD requires ECG interpretation, specifically examining leads I and aVF, where RAD is present when lead I shows a negative QRS deflection and aVF shows a positive deflection 1. Management focuses on treating the underlying cause rather than the axis deviation itself. For example, if pulmonary hypertension is causing RAD, medications like sildenafil or bosentan might be prescribed, as suggested by guidelines for the diagnosis and treatment of pulmonary hypertension 1. RAD itself doesn't require specific treatment but serves as an important diagnostic clue to underlying cardiac or pulmonary conditions that may need attention.
Clinical Considerations
It's essential to consider the clinical context when interpreting ECG findings, including RAD. The ECG may provide suggestive or supportive evidence of pulmonary hypertension by demonstrating RV hypertrophy and strain, and right atrial dilatation 1. However, the absence of these findings does not exclude the presence of pulmonary hypertension nor does it exclude severe hemodynamic abnormalities. The ECG has insufficient sensitivity and specificity to be a screening tool for detecting significant pulmonary hypertension 1.
Guideline Recommendations
Guidelines for the management of adults with congenital heart disease recommend using the ECG to assess for right-axis deviation and RV hypertrophy, particularly in patients with prior atrial baffle procedures 1. The ECG is usually normal when the RV systolic pressure is less than 60 mm Hg, but more severe obstruction leads to right atrial enlargement, right-axis deviation, and RV hypertrophy 1.
From the Research
Causes of Right Axis Deviation (RAD)
- Right axis deviation can occur due to various factors, including myocardial infarction (MI) 2
- Extensive myocardial ischemia and/or necrosis may cause an "electrical escaping" with an extreme dislocation of the QRS axis, leading to right axis deviation 2
- Other potential causes of RAD may include cardiac arrhythmias, hemodynamic complications, and cardiovascular disease 2, 3
Electrocardiographic Findings
- A right axis deviation of +95 degrees or greater on an electrocardiogram may be an indicator of underlying cardiac defects 3
- However, the use of echocardiography to screen for disqualifying cardiac defects based on a finding of right axis deviation on electrocardiogram may not be cost-effective 3