Receiving an electrocardiogram (EKG) result that mentions “borderline right axis deviation” can be concerning. While “borderline” suggests the abnormality is not severe, “deviation” implies the heart is not functioning as expected. This finding is a specific measurement of the heart’s electrical activity, often incidental and carrying little risk. However, because it can sometimes be the first subtle sign of an underlying health issue, understanding this reading is important. This article explains the finding, its measurement, and the necessary next steps for interpretation.
Understanding the Heart’s Electrical Axis
The heart’s electrical axis represents the average direction of the electrical current as it spreads through the ventricles during a heartbeat. An EKG measures this activity by focusing on the QRS complex, the spike reflecting the electrical depolarization that triggers the main pumping chambers. Since the left ventricle is the largest and most muscular chamber, the electrical signal normally points downward and slightly to the left, reflecting the heart’s natural orientation.
Clinicians use a coordinate system, measured in degrees, to define this electrical direction. The normal range for the QRS axis in adults typically falls between -30 and +90 degrees. If the electrical signal deviates outside of this standard range, it is categorized as an axis deviation. A shift toward the right, known as Right Axis Deviation (RAD), indicates the net electrical force is pulling toward the right side of the body.
Defining the Borderline Measurement
The term “borderline right axis deviation” refers to an axis measurement just outside the upper limit of the normal range. While full Right Axis Deviation (RAD) is generally defined as an axis greater than +90 degrees, a borderline reading commonly falls between +90 and +110 degrees. This exact angular measurement is frequently determined by the EKG machine’s internal computer algorithm.
This slight shift is often non-specific, meaning it may not point to any single cause and can be common in the general population. The small numerical difference between a normal axis of +89 degrees and a borderline axis of +91 degrees may not be clinically significant alone. Therefore, a borderline reading must always be evaluated in the context of a person’s overall health and any symptoms they may be experiencing.
Potential Underlying Conditions
A borderline right axis deviation can be caused by benign factors or more significant underlying medical conditions. In many healthy individuals, the finding is simply due to a vertical heart position, often seen in tall, slender body types. This anatomical variation repositions the heart in the chest, causing a natural, harmless shift in the electrical axis.
However, the deviation can also indicate conditions that increase pressure on the right side of the heart. Chronic lung diseases, such as Chronic Obstructive Pulmonary Disease (COPD) or emphysema, can raise blood pressure in the lung arteries, leading to right ventricular strain. Right ventricular hypertrophy, where the muscle wall thickens in response to this increased workload, is a common cause of axis shift. Other potential causes include congenital heart defects or conduction disturbances like a left posterior fascicular block.
Interpreting Risk and Next Steps
Borderline right axis deviation is rarely dangerous in isolation and should not cause immediate alarm. The risk associated with this EKG finding depends entirely on the underlying cause, if one exists. For an otherwise healthy, asymptomatic person, a borderline reading may be considered a normal variant requiring no further action. However, if the finding is new or if the person has symptoms such as shortness of breath, fatigue, or a history of lung disease, it warrants further investigation.
The next step involves a consultation with a cardiologist or primary care physician to interpret the result within the full clinical picture. This may lead to additional tests to rule out serious conditions. An echocardiogram, which uses ultrasound to visualize the heart’s structure and function, specifically checks for right ventricular enlargement or pulmonary hypertension. Other tests may include chest X-rays or pulmonary function tests to evaluate lung health, ensuring this electrical finding is not overlooked as a possible early sign of a treatable condition.