The heart’s electrical system coordinates contraction, generating a wave of current called depolarization. The overall average direction of this current is the electrical axis. In a healthy heart, the massive left ventricle dominates the signal, directing the current downward and toward the left side. This electrical axis is measured in degrees and indicates the heart’s health and physical orientation.
Defining Right Axis Deviation
Right Axis Deviation (RAD) is a finding, not a disease, describing a shift in the heart’s electrical axis beyond its normal range. The normal electrical axis in adults falls between approximately -30 degrees and +90 degrees. RAD occurs when the average electrical current swings further to the right, registering a measurement greater than +90 degrees, sometimes extending to +180 degrees.
This observation is typically made using an electrocardiogram (EKG), which records the heart’s electrical activity. The deviation signifies that the right side of the heart’s electrical influence has become disproportionately large compared to the left. This shift suggests a physical change in structure, a delay in the electrical conduction system, or an alteration in the heart’s position.
Underlying Conditions That Cause RAD
RAD is almost always caused by a condition that increases the right ventricle’s electrical influence, either by enlarging muscle mass or delaying the electrical signal to the left side. The most frequent cause is right ventricular hypertrophy (RVH), an enlargement of the right ventricle’s muscle. This hypertrophy develops when the right ventricle must work against high resistance or pressure in the pulmonary circulation.
Conditions leading to this increased resistance include severe lung diseases like Chronic Obstructive Pulmonary Disease (COPD) and pulmonary hypertension. In COPD, chronic lack of oxygen causes blood vessels in the lungs to constrict, forcing the right ventricle to pump harder. An acute event, such as a large pulmonary embolism, can also cause acute right heart strain and rapid RAD development.
Congenital heart defects are another common cause, particularly those resulting in shunting or obstruction to the right side. Defects like a large atrial septal defect (ASD) or ventricular septal defect (VSD) increase blood flow, leading to volume overload and subsequent RVH. Conditions such as Tetralogy of Fallot or severe pulmonary valve stenosis cause pressure overload and right-sided muscle growth.
In some cases, the deviation is purely electrical and not due to muscle enlargement. A left posterior fascicular block (LPFB) is a conduction abnormality where the electrical signal to a portion of the left ventricle is delayed. This delay allows the right ventricle’s depolarization to dominate the overall electrical vector, resulting in a marked right axis shift.
Treating the Root Cause
Since RAD is a symptom, “curing” the deviation requires treating the source pathology that caused the electrical shift. Successfully managing the primary condition may reduce strain on the right ventricle, potentially allowing the electrical axis to return to the normal range. However, the deviation can sometimes be permanent even if the underlying disease is controlled.
If RAD is linked to pulmonary hypertension, treatment focuses on lowering pressure within the pulmonary arteries. This involves specific medications like pulmonary vasodilators, such as sildenafil or endothelin receptor antagonists, which help relax and open the blood vessels. Diuretics may also be used to manage fluid retention accompanying right heart strain.
When the cause is chronic lung disease, like COPD, management is directed at improving lung function and oxygenation. This includes optimizing bronchodilators and providing supplemental oxygen therapy to reduce the hypoxemia that drives pulmonary artery constriction. Pulmonary rehabilitation programs are also a valuable part of comprehensive care.
Congenital heart defects typically require a structural intervention to resolve abnormal blood flow or pressure. For defects such as an atrial or ventricular septal defect, surgical or catheter-based repair is necessary to close the hole, eliminating the overload on the right ventricle. Corrective surgery for defects like Tetralogy of Fallot aims to relieve the obstruction to blood flow, reversing the pressure-induced hypertrophy.
If the deviation is caused by an acute event, such as a pulmonary embolism, immediate treatment aims at dissolving the clot through anticoagulation or thrombolytic therapy.
When RAD Requires No Treatment
Right Axis Deviation does not always signal serious heart or lung disease and is often considered a benign variant requiring no intervention. One such scenario relates to the physical orientation of the heart within the chest cavity, common in individuals who are very tall and thin.
A vertical heart position naturally shifts the electrical current downward and to the right, making the axis measurement appear outside the standard adult range. This finding is purely anatomical and does not reflect any underlying pathology or functional impairment. Technical factors during an EKG recording, such as incorrect placement of limb leads, can also artificially create the appearance of RAD.
RAD is also a normal physiological finding in infants and young children. The right ventricle is dominant at birth due to the circulatory system’s structure, meaning the electrical axis is naturally directed rightward. The normal range for the axis in a newborn can be as high as +160 degrees and gradually shifts leftward as the child grows.