An electrocardiogram (EKG) is a quick, non-invasive test assessing the heart’s electrical activity. It records the heart’s electrical impulses via electrodes placed on the body, translating them into a wave pattern that maps its rhythm and function. EKGs provide information on heart rate, rhythm, and the timing of electrical signals. Changes in the EKG pattern can indicate various heart-related conditions. One such finding is “axis deviation,” an abnormal direction of the heart’s electrical activity.
Understanding Left Axis Deviation
The heart’s electrical axis shows the general direction of electrical current through the ventricles. Normally, this electrical activity flows downwards and slightly to the left, reflecting the larger muscle mass of the left ventricle. The normal cardiac axis typically falls within a range of -30 to +90 degrees.
Left Axis Deviation (LAD) occurs when this electrical axis shifts left, falling between -30 and -90 degrees. This shift indicates that the electrical forces of the heart are predominantly moving in an upward and leftward direction. LAD is identified by examining leads I and aVF on the EKG. A positive QRS complex in lead I and a negative complex in lead aVF, especially if also negative in lead II, suggests LAD.
Common Causes of Left Axis Deviation
LAD can stem from various factors, including physiological variations and underlying medical conditions. Physiological causes often involve normal variations or changes in body structure that shift the heart’s position. For instance, a high diaphragm, which can occur with obesity or pregnancy, may push the heart upward and to the left, leading to LAD.
As people age, the heart’s electrical axis can naturally shift slightly to the left, making LAD a common finding in older individuals without significant heart disease. Certain body types can also influence the heart’s position and its electrical axis. These benign causes typically do not require specific intervention for the LAD itself.
Pathological causes relate to conditions affecting the heart’s structure or electrical conduction. Left ventricular hypertrophy (thickening of the left heart chamber) can cause LAD due to increased muscle mass generating stronger electrical signals. Heart muscle damage, such as an inferior myocardial infarction (heart attack affecting the lower part of the heart), can also disrupt the normal electrical pathway.
Conduction system abnormalities, such as left anterior fascicular block (a delay or interruption in electrical signals to part of the left ventricle), are frequent causes of LAD. Certain lung conditions like emphysema can also lead to LAD due to changes in chest cavity pressure and heart position. Other less common causes include congenital heart defects or certain electrolyte imbalances.
Interpreting Seriousness: What LAD Indicates
The seriousness of LAD depends on its underlying cause. LAD is an EKG observation, not a disease, and its significance is determined by what it reveals about heart health. Often, LAD is a benign finding, especially when minor or present in older adults or those with certain body types without other heart disease symptoms.
As an isolated finding in a healthy individual, LAD may be a normal variant, particularly when the axis is just beyond the normal range (e.g., -30 to -45 degrees) with no other cardiac issues. Such cases typically do not require further medical intervention.
However, LAD can signal a serious underlying heart condition. When pronounced or accompanied by other EKG abnormalities or clinical symptoms, it often indicates structural heart disease or an electrical system problem. For example, LAD associated with left ventricular hypertrophy suggests the heart is working harder than it should, possibly due to high blood pressure or valve problems.
LAD can also mark past heart damage, such as an old inferior myocardial infarction, even if asymptomatic. Its presence might also point to issues like left bundle branch block, which affects the heart’s ability to conduct electrical impulses efficiently. Therefore, LAD’s detection warrants investigation to determine if it is a benign variation or indicates a more significant cardiac issue.
Next Steps After Diagnosis
If an EKG reveals LAD, further evaluation is necessary to determine its cause and significance. A healthcare provider will take a detailed medical history, including symptoms and family history, and conduct a physical examination for heart or lung problems.
Additional diagnostic tests are often ordered. An echocardiogram, using sound waves to image the heart, is often performed to assess heart structure and function. Other imaging tests, like cardiac MRI, may also be recommended. Blood tests may also be part of the evaluation. These steps aim to differentiate between benign LAD and one caused by a treatable condition.
Consult a doctor for proper interpretation and to discuss the management plan. If an underlying condition is identified, treatment focuses on addressing that specific cause. Managing the root cause, such as high blood pressure, can improve heart health and potentially normalize the electrical axis.