From the Guidelines
Left axis deviation is a significant electrocardiographic finding that may be associated with left ventricular hypertrophy (LVH), and its presence should prompt further evaluation to determine the underlying cause, as stated in the 2009 American Heart Association recommendations 1. When evaluating left axis deviation, it is essential to consider the potential causes, including LVH, left anterior fascicular block, and other factors that may contribute to a more leftward axis with increasing age.
- The electrocardiogram changes associated with cardiac chamber hypertrophy, as discussed in the 2009 study 1, highlight the importance of interpreting left axis deviation in the context of other ECG findings and clinical factors.
- The study notes that left axis deviation may be used to support a diagnosis of LVH, rather than making the diagnosis alone 1.
- Management of left axis deviation should focus on addressing the underlying cause, such as controlling blood pressure with medications like ACE inhibitors or beta-blockers if the cause is hypertension-related LVH.
- Regular cardiac monitoring may be necessary if the left axis deviation is due to a conduction disorder like left anterior fascicular block.
- The clinical significance of left axis deviation depends on its cause and associated findings, and new-onset left axis deviation warrants further cardiac evaluation to determine its etiology and clinical relevance.
From the Research
Definition and Causes of Left Axis Deviation
- 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.
- Many of the causes of left axis deviation are apparent from the clinical findings, with left anterior fascicular block being one of the commonest causes and having specific ECG criteria for its diagnosis 2.
- The normal QRS axis is age-dependent, and left axis deviation must be considered accordingly, with a gradual leftward drift of the QRS governed principally by left anterior fascicular conduction 3.
Diagnostic Approach
- In children with left axis deviation but without previously known heart disease, an echocardiogram may be warranted, especially if there are ECG cardiac chamber enlargement or hypertrophy, a QRS axis ≤-42°, and/or abnormal cardiac physical examination findings 4.
- Stress testing and post-exercise systolic time intervals can also contribute to the diagnostic approach, with prolongation of left ventricular ejection time corrected for heart rate (LVETc) of 8 msecs or more from rest to post-exercise considered an abnormal STI response 5.
Association with Heart Disease
- Left axis deviation can be associated with heart disease, including left ventricular diastolic dysfunction, and the presence of coronary artery disease can impact the accuracy of echocardiographic diagnosis 6.
- The addition of echocardiographic isovolumetric relaxation time (IVRT) may improve early left ventricular diastolic dysfunction diagnostics, especially when the presence of coronary artery disease is unknown 6.