From the Guidelines
Axis deviation on an ECG is primarily caused by cardiac conditions such as left ventricular hypertrophy, left anterior fascicular block, and right ventricular hypertrophy, as well as non-cardiac conditions like incorrect electrode placement and electrolyte disturbances. The causes of axis deviation can be broadly categorized into cardiac and non-cardiac conditions. Cardiac conditions that can lead to axis deviation include:
- Left ventricular hypertrophy (LVH), which can cause left axis deviation (LAD) 1
- Left anterior fascicular block, which can also cause LAD
- Right ventricular hypertrophy, which can cause right axis deviation (RAD)
- Inferior myocardial infarction, which can cause LAD
- Congenital heart defects like ostium primum atrial septal defect, which can cause LAD
- Right bundle branch block, which can cause RAD
- Lateral wall myocardial infarction, which can cause RAD
- Left posterior fascicular block, which can cause RAD
- Pulmonary embolism, which can cause RAD
- Chronic lung diseases like COPD, which can cause RAD
Non-cardiac causes of axis deviation include:
- Incorrect electrode placement during ECG recording
- Dextrocardia (heart positioned on the right side)
- Pregnancy (due to diaphragm elevation)
- Significant obesity
- Electrolyte disturbances, particularly hyperkalemia, which can affect cardiac conduction and lead to axis changes. Understanding these causes is important for proper ECG interpretation, as axis deviation often serves as an early indicator of underlying cardiac pathology that may require further investigation or treatment.
From the Research
Causes of Axis Deviation on ECG
- Electrolyte imbalances, such as hyperkalemia and hypokalemia, can cause axis deviation on an ECG 2, 3, 4, 5, 6
- Hyperkalemia can cause widening of the QRS complex, increased atrial and ventricular pacing thresholds, and increased latency 2
- Hypokalemia can cause prolonged ventricular repolarization, slowed conduction, and abnormal pacemaker activity, leading to arrhythmias 3, 4, 5, 6
- Hypokalemia can also cause Ca2+ overload, Ca2+/Calmodulin-dependent kinase II (CaMKII) activation, and development of afterdepolarizations, leading to arrhythmias 5
- Distinct mechanisms underlie hypokalemia-induced arrhythmia in the ventricle and atrium, and also vary between atrial myocytes depending on subcellular structure and electrophysiology 6
Electrolyte Imbalances and Axis Deviation
- Hyperkalemia can cause axis deviation by affecting the conduction velocity and pacing thresholds of the heart 2
- Hypokalemia can cause axis deviation by affecting the repolarization and conduction of the heart, leading to arrhythmias 3, 4, 5, 6
Clinical Implications
- Electrolyte imbalances, such as hyperkalemia and hypokalemia, can have significant clinical implications, including increased risk of arrhythmias and sudden cardiac death 2, 3, 4, 5, 6
- Understanding the mechanisms of electrolyte imbalances and axis deviation can help guide treatment strategies and improve patient outcomes 5, 6