Understanding Right Axis Deviation: When to Worry

An ECG (electrocardiogram) is a routine, non-invasive test that provides a snapshot of your heart’s electrical activity.² While most ECG reports show a perfectly normal rhythm, a report containing a finding like “Right Axis Deviation” (RAD) can be alarming. The term sounds like a significant problem, but the reality is more nuanced. Right Axis Deviation can be a completely benign, normal variant in a healthy person, or it can be a crucial red flag for a serious and potentially life-threatening condition.³ A doctor will never look at an ECG finding in isolation; they will always consider it in the context of a patient’s symptoms, medical history, and other diagnostic tests. This article will explain what right axis deviation is, detail its various causes, and provide a framework for understanding when it is a normal finding versus a critical warning sign.

To understand a right axis deviation, you first have to understand the heart’s electrical axis. Imagine the heart’s electrical signals as a flow of electricity. This flow has a main direction, or “axis.” For a normal, healthy heart, this axis points down and to the left, toward the heart’s most powerful chamber, the left ventricle. This is called a normal axis.

A Right Axis Deviation (RAD) is a shift of this electrical axis to the right.⁴ It is a mathematical calculation on an ECG printout, based on how the electrical signals appear in the different leads (viewpoints) that are placed on the body. ^[1] While a normal axis can range from roughly 0 to +90 degrees, an axis that falls between +90 and +180 degrees is considered a right axis deviation.⁶

The finding of RAD on an ECG is like a single clue in a detective story. It points to a number of possibilities, some of which are harmless and some of which are very serious.

In many cases, a right axis deviation is a perfectly normal finding that requires no further action.

• Normal in Infants and Young Children: At birth, the right ventricle of a baby’s heart is more muscular and dominant than the left. This means that a right axis deviation is the normal and expected finding on an infant’s ECG.⁷ As the child grows, the left ventricle becomes more dominant, and the axis shifts to a normal, leftward direction.
• Body Habitus (Physique): A person’s body shape can affect the physical position of their heart. In tall, thin individuals, the heart may be positioned more vertically in the chest, which can naturally result in a right axis deviation on the ECG.⁸ This is a normal, harmless finding.
• Normal Variant: In some healthy individuals, a right axis deviation is simply a normal variation of their heart’s electrical pattern. It is not associated with any underlying disease.

A right axis deviation becomes a red flag when it is caused by a condition that is putting strain on the right side of the heart.⁹ The axis shifts to the right because the right ventricle is either being overworked or has become thickened (hypertrophied).

• Right Ventricular Hypertrophy (RVH): This is a major cause of RAD.¹⁰ RVH is an enlargement and thickening of the right ventricle muscle.¹¹ When the right ventricle has to work harder, its electrical signal becomes stronger, pulling the axis to the right. RVH is almost always caused by a condition that increases pressure in the lungs.
  • Pulmonary Hypertension: High blood pressure in the arteries of the lungs forces the right ventricle to pump against higher resistance, leading to RVH.
  • COPD (Chronic Obstructive Pulmonary Disease): Long-term lung disease can lead to chronic hypoxemia and an increase in pressure in the pulmonary arteries, causing the right side of the heart to work harder.¹²
• Acute Pulmonary Embolism (PE): A PE is a life-threatening medical emergency. It occurs when a blood clot lodges in the pulmonary artery, creating a sudden, massive increase in pressure that the right ventricle must pump against.¹³ This acute overload on the right ventricle can cause a sudden and significant shift to RAD on the ECG. RAD, along with other ECG findings, is a crucial diagnostic clue for a PE. ^[4]
• Other Causes: Other, less common causes of RAD include congenital heart diseases (e.g., Tetralogy of Fallot) and conditions affecting the electrical conduction system of the heart.

A competent physician will never base a diagnosis on an ECG finding alone. A diagnosis of RAD is simply an electrical clue. The doctor will need to perform a full clinical evaluation to determine if the RAD is a normal variant or a sign of a serious underlying condition.

• Context is Key: The doctor will consider your medical history, including any history of lung disease, heart disease, or blood clots. They will also perform a physical exam and check for symptoms.
• Red Flag Symptoms: A doctor will be concerned if the RAD is accompanied by any of the following symptoms:
  • Shortness of breath: Especially if it is new or worsening.
  • Chest pain or pressure: A common symptom of a pulmonary embolism.¹⁴
  • Dizziness or fainting.
  • Swelling in the ankles or legs (edema): A sign of fluid buildup from a struggling right ventricle.
  • Fatigue or palpitations.
• Diagnostic Workup: If a pathological cause is suspected, the doctor will order further tests to confirm the diagnosis. The most important test is an echocardiogram (cardiac ultrasound), which can directly visualize the heart and confirm if there is any right ventricular enlargement or strain. Other tests may include a chest CT scan to rule out a pulmonary embolism, a lung function test (spirometry), or blood tests. ^[5]

The finding of Right Axis Deviation on an ECG can be a cause for concern, but it is not a reason to panic. For many people, it is a benign, incidental finding. For others, it is a critical early warning sign.

• Do not ignore it: Never dismiss a finding of RAD. Always follow up with your doctor.
• Ask Questions: Ask your doctor to explain the finding in the context of your specific health history.
• It’s a Clue, Not the Whole Story: Understand that an ECG is one piece of a larger diagnostic puzzle. The true picture of your heart’s health is only revealed when a doctor combines that clue with a thorough physical exam, a detailed patient history, and other diagnostic tests.