From the Guidelines
Left axis deviation on an electrocardiogram is a significant finding that requires clinical correlation and may indicate underlying cardiac pathology, and management should focus on identifying and addressing the underlying cause rather than treating the axis deviation itself. Left axis deviation (LAD) is defined as a QRS axis between -30° and -90° and can be caused by several conditions including left ventricular hypertrophy, left anterior fascicular block, inferior myocardial infarction, or congenital heart defects. According to the American Heart Association electrocardiography and arrhythmias committee 1, left axis deviation may be associated with left ventricular hypertrophy (LVH), but it is not known whether left axis deviation results from hypertrophy itself, a degree of left anterior fascicular block, or other factors.
When LAD is identified, a thorough clinical evaluation should be performed, including a detailed history, physical examination, and possibly additional cardiac testing such as echocardiography to determine the cause. The 2010 ACCF/AHA guideline for assessment of cardiovascular risk in asymptomatic adults 1 highlights the importance of considering ECG findings, including left axis deviation, in the context of overall cardiovascular risk assessment. In asymptomatic patients with isolated LAD and no other concerning findings, close monitoring may be sufficient. However, if LAD is associated with symptoms like chest pain, shortness of breath, or syncope, or if it appears with other concerning ECG abnormalities, prompt cardiology referral is warranted.
Key considerations in the management of LAD include:
- Clinical correlation to identify underlying cardiac pathology
- Thorough clinical evaluation, including history, physical examination, and additional cardiac testing as needed
- Management focused on addressing the underlying cause rather than treating the axis deviation itself
- Consideration of overall cardiovascular risk assessment in asymptomatic patients
- Prompt cardiology referral for symptomatic patients or those with concerning ECG abnormalities.
From the Research
Significance of Left Axis Deviation on EKG
- Left axis deviation is one of the most commonly encountered ECG abnormalities, and its presence should alert medical directors and underwriters to the possibility of underlying structural heart disease 2.
- The causes of left axis deviation can be apparent from clinical findings, with left anterior fascicular block being one of the commonest causes, having specific ECG criteria for its diagnosis 2.
- In patients with chronic left bundle branch block, left axis deviation is associated with a greater incidence of myocardial dysfunction, more advanced conduction disease, and greater cardiovascular mortality compared to those with a normal axis 3.
Management of Left Axis Deviation
- The optimal diagnostic approach in a seemingly healthy child with left axis deviation is unclear, but an echocardiogram may be warranted in patients with left axis deviation and ECG cardiac chamber enlargement or hypertrophy, a QRS axis ≤-42°, and/or the presence of abnormal cardiac physical examination findings 4.
- In patients with left axis deviation on ECG, the sensitivity, specificity, and positive and negative predictive values of physical examination by a pediatric cardiologist are excellent at identifying congenital heart disease, making an echocardiogram cost-effective only in the presence of an abnormal physical examination 5.
- Left axis deviation can also occur in patients with acute pulmonary embolism, although it is less common than other electrocardiographic abnormalities such as nonspecific T wave changes and nonspecific abnormalities of the RST segment 6.
Clinical Implications
- Left axis deviation discovered in isolation in the asymptomatic pediatric patient may not necessitate further cardiovascular investigation 4.
- However, in patients with left axis deviation and underlying structural heart disease, further evaluation and management may be necessary to prevent complications and improve outcomes 2, 3.
- The cost of performing an echocardiogram in patients with left axis deviation on ECG can be significant, and a decision tree model can help analyze the cost-effectiveness of this diagnostic test 5.