From the Guidelines
Left axis deviation of the heart is not normal in adults and typically indicates an underlying cardiac condition. According to the American Heart Association electrocardiography and arrhythmias committee, council on clinical cardiology, the normal QRS axis in adults is considered to be within 30° and 90°, and left-axis deviation is defined as an axis of -30° and beyond 1. This condition can be associated with various cardiac abnormalities, such as left ventricular hypertrophy, left anterior fascicular block, and certain congenital heart defects.
Key Points to Consider
- The mean frontal plane electrical axis depends on age and body habitus, and it shifts to the left with increasing age 1.
- In children, the QRS axis normally shifts from a rightward direction at birth to a more leftward direction throughout childhood, but in adults, a leftward shift beyond -30° is considered abnormal 1.
- The presence of left axis deviation warrants further cardiac evaluation to identify the underlying cause, and additional tests such as an echocardiogram, stress test, or cardiac MRI may be recommended depending on symptoms and risk factors.
Clinical Implications
- The significance of left axis deviation varies based on age, other medical conditions, and accompanying ECG abnormalities 1.
- In some cases, left axis deviation may be a normal variant in very tall, thin individuals or in those with certain chest configurations, but this should be determined by a healthcare provider rather than assumed.
- It is essential to consult a cardiologist to determine the underlying cause of left axis deviation and to develop an appropriate treatment plan.
From the Research
Left Axis Deviation of the Heart
- 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 are often apparent from clinical findings, with left anterior fascicular block being one of the most common causes 2.
Relationship to Heart Failure
- Left axis deviation in patients with left bundle branch block is a marker of myocardial disease associated with poor response to cardiac resynchronization therapy 3.
- Patients with left axis deviation and left bundle branch block tend to have more scar tissue, severe left ventricular hypertrophy, and less activation delay compared to those with a normal axis 3.
Electrophysiological Abnormalities
- Left axis deviation in patients with nonischemic heart failure and left bundle branch block appears to be due to electrophysiological abnormalities rather than structural factors or cardiac anatomic axis 4.
- The total activation times are longer in patients with left axis deviation, and the left ventricular activation pattern is from apex to base, in contrast to a circumferential pattern in patients with a normal axis 4.
Treatment and Management
- Beta-blockers and ACE-inhibitors are cornerstones in the treatment of systolic heart failure, with beta-blockers such as bisoprolol, metoprolol, and carvedilol reducing all-cause death by 34-5% 5.
- The choice of beta-blocker is important, as the benefit is not a class-effect, and some beta-blockers with intrinsic sympathomimetic activity may diminish efficacy 5.