What Does Borderline ECG Mean? A Quick Clinical Guide

If you’re a healthcare assistant, nurse, or newly qualified clinician, you may encounter a confusing term called ‘Borderline ECG’ in patient reports. According to a 2022 study published in the European Heart Journal – Digital Health, automated ECGs show findings that are marked as “borderline” appear in over 20% of routine ECG screenings, especially among patients without clear cardiac symptoms.

These findings lead to considerable uncertainty and confusion among junior healthcare professionals. In this guide, we will explain the borderline ECG definition, its causes, how to interpret the findings, and the appropriate response if you encounter it in reports.

What Is an ECG and Why It’s Done

According to the NHS, an electrocardiogram (ECG) is a quick test used to assess a patient’s heart condition. Small patches, called electrodes, are attached to the person’s chest, arms, and legs.

After ECG lead placement, these electrodes are connected to an ECG machine, which measures, interprets, and prints out the electrical activity of the heart. Sometimes, a Lead II rhythm strip is used to monitor irregularities in the heart rhythm closely.

ECGs are done for the following reasons:

• To identify irregular heartbeat rhythms, also known as arrhythmias.
• To detect any signs of chest pain or a potential heart attack.
• To assess overall heart health before undergoing surgery.
• To determine heart-related conditions such as fatigue, shortness of breath, dizziness, or fainting.

What Does Borderline ECG Mean?

A borderline ECG means that a patient’s ECG reports are not clearly normal or abnormal. It is a grey zone situation that occurs when certain parts of the ECG fall within the normal range, while others show slight deviations.

Since doctors cannot interpret a borderline ECG test, they are labelled as inconclusive. Further tests are conducted to get a clear picture of the patient’s heart condition.

What Causes Borderline ECG?

Borderline ECG occurs due to several factors:

• Stress, caffeine, or a lack of sleep can cause fluctuations in heart rhythms, leading to minor variations.
• Imbalances in electrolytes, such as potassium level, calcium, and magnesium, can cause ECG changes, as seen in hypokalemia ECG. Severe electrolyte disturbances may result in an ECG sine wave pattern that requires urgent care.
• Certain medications can alter the heart’s normal rhythm.
• Physiological differences resulting from body position during the ECG can lead to borderline results.
• Hidden heart conditions that are still undetectable also cause abnormal heart rhythms, leading to borderline ECGs. People with conditions such as hypertension, diabetes, or a family history of heart disease need to be closely monitored.

It is essential to note that sometimes borderline ECG findings can occur due to technical factors rather than the patient’s underlying heart health. Technical errors include:

• Incorrect ECG lead placement on the patient’s body.
• Poor skin-to-electrode contact.
• Too much patient movement.
• Electrical interference from external devices.

This is why it’s essential to ensure that the ECG machine calibration and electrode positioning are accurate. Also, limit patient movements while recording to reduce false ECG borderline readings.

How to Recognise Common Borderline ECG Findings?

As a healthcare assistant or care worker, it’s important to recognise common findings that indicate borderline ECG results. They are as follows:

Mild ST changes

The ST segment of the ECG waveform will deviate from its normal position. Although borderline ECGs don’t show a clear ST elevation, it is a concern that should not be treated lightly.

Slight tachycardia or bradycardia

There will be indications of tachycardia (a faster heart rate) or bradycardia (a slower heart rate) that suggest a slight deviation from the normal heart rhythm.

Minor conduction delays

A slowing down of the electrical signals as they travel through the heart, leading to slight conduction delays, is often reflected in a widened or altered QRS complexes.

Non-specific T wave changes

Any changes in the shape or direction of the T Wave are also an important indicator of borderline ECG.

Slight PR interval changes

Look for slight changes in the PR interval. This can also indicate a minor delay in the heart’s conduction system.

How Should You Respond to a Borderline ECG Result?

As a healthcare professional, here are the steps to take when you encounter a patient’s ECG results that are borderline:

1. Acknowledge the ECG results, and do not ignore them. Although the results are inconclusive, there may be underlying health issues that have yet to be revealed.
2. Run further diagnostic tests on the patients to achieve clear results. Some of these tests might include a stress test, an echocardiogram, or Ambulatory ECG monitoring (Holter monitor).
3. Review the patient’s past medical history, including any cardiac events, family history, and current medications. Check for symptoms such as chest pain, shortness of breath, or palpitations in the heart.
4. Gather information about their lifestyle, specifically regarding their diet, exercise habits, smoking status, and alcohol consumption.
5. Inform the patients about the borderline ECG results, their meaning, and the importance of scheduling follow-up appointments.
6. If the results are complex or confusing, recommend that they visit a cardiologist. If you want to be an expert in understanding the equipment and ECG reading, consider our ECG training electrocardiogram course. It is a CPD-accredited, practical, hands-on training course in both London and Birmingham, led by expert tutors, that teaches you how to set up an ECG machine, perform accurate 12-lead ECG recordings, interpret and recognise basic ECG waves, intervals, and segments.
7. Document all the findings, investigations, and plans in the patient’s medical record.
8. If the results are borderline ECG but the patient experiences severe chest pain or shortness of breath, consider it an emergency and consult with other healthcare assistants.

FAQ

Here are some frequently asked questions regarding borderline ECGs:

1. What does borderline mean on an ECG?

Borderline ECG results indicate that the results fall neither within the normal range nor the abnormal range. It falls under the grey area where further tests are required to determine heart health.

2. Can anxiety cause a borderline ECG?

Yes, sometimes anxiety or stress can cause minor variations in the heart rhythm, leading to borderline ECG results.

3. What is a normal ECG report?

A normal adult heart rate ranges from 60 to 100 beats per minute (bpm), with a normal rhythm. A normal ECG report maintains a sinus rhythm.

4. Is a borderline ECG serious?

While the results do not clearly indicate any problem, it should not be ignored. There may be early signs of potential heart problems; therefore, clinical follow-ups are highly recommended.

5. What are the 12 leads of an ECG?

In a standard 12 lead ECG, ten electrodes are placed on the limbs and chest to measure the heart’s electrical potential from twelve different angles, recording data over a period of ten seconds.

6. How to calculate heart rate from ECG?​

For regular rhythms, count the number of large squares between two consecutive R waves and divide 300 by that number. For irregular rhythms, count the number of QRS complexes within a 6-second interval (usually marked on the ECG paper) and multiply by 10.

Conclusion

Borderline ECG results can be confusing to interpret and analyse as they show that certain parts of the ECG fall within the normal range, while others show slight deviations.

They can be caused by a number of factors, including stress, electrolyte imbalances, certain medications, physiological differences, or underlying heart issues.

As a healthcare assistant, you should know how to respond immediately. Follow the steps mentioned in this blog.

The good news is that due to the recent advancements in AI and automation, there are fewer cases of borderline ECG reports. These newer AI-assisted ECG machines provide results that are more accurate and better than those of previous ECG machines.

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