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Borderline ECG Meaning: Unraveling the Causes Behind Ambiguous Heart Tracings

Editorial Team
Updated Jun 04, 2024
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What Does Borderline ECG Mean?

Navigating the complexities of heart health, a borderline electrocardiogram (ECG) can be a source of concern. According to the American Heart Association, an ECG is a fundamental tool that records the heart's electrical activity and helps detect various cardiac conditions. A borderline ECG means the test has detected irregularities that may or may not signify an underlying issue. While a borderline ECG result can be unsettling, it's crucial to understand that such findings are not uncommon and may stem from benign causes. Patients are encouraged to consult with their healthcare provider for a comprehensive assessment to elucidate the borderline ECG meaning in their specific context.


In a borderline ECG, some of the readings do not look quite right, but they are not pushed into the margin where they are an immediate cause for concern. Sometimes, this occurs simply because a patient was stressed out or worried. Many patients are nervous before an ECG, and this can cause small variations in their heart rates that may appear on the test. The doctor might discard the results if the patient appeared especially worried, and request a new test to see if more accurate values can be obtained.

Another reason for a borderline ECG is improper procedure during the test. Sometimes the electrodes are not placed correctly or there is something wrong with the machine and the reading is off. Patients with large breasts or significant deposits of fat in their chests are more likely to have a borderline ECG because it is harder to place the electrodes. The technician may spot the problem if she has access to a real-time readout, and may halt the test to reposition and get a better reading.

A borderline ECG can also occur when a patient does have a genuine anomaly, but it is minor. The test will show small variations in the heart rhythm and function, but they are not significant enough to be a cause for concern. If a patient has a borderline ECG, the doctor might recommend testing again in the future to monitor the issue. Otherwise, the doctor may simply note the finding in the patient's chart so it will be available for future reference.

Patients should be aware that ECG equipment often marks up the printout with notations like “borderline” on the basis of stored algorithms. The equipment is sometimes wrong, because it does not account for patient history and other factors. A doctor can review the test result and determine whether it is significant. If it is, he will recommend some additional testing to learn more about the patient's situation. When it is not, the doctor will assure the patient that it is not anything he needs to worry about.

What Are ECGs Used For?

The procedure known as an ECG measures electrical activity in the heart. ECGs are different from another heart test called an echocardiogram, which uses ultrasound to monitor heart activity. Doctors use ECGs as diagnostic tools in multiple situations. This procedure offers a way to get a clearer idea of the pattern of heart beats. This test is also known as an EKG.

Checking for Potential Illness

Doctors use ECGs to look for signs of potential heart disease. Irregularities in the rhythm or pattern of heart beats could signal problems. By catching any irregularities early, doctors hope to be able to treat heart disease effectively. ECGs may also help doctors understand why a patient is having chest pains.

Doctors may order ECGs if a patient has sudden or unusual symptoms, including:

  • Fatigue, weakness, or inability to exercise or function physically
  • Shortness of breath
  • Confusion or dizziness
  • Faintness or nausea
  • Fast pulse
  • Palpitations of the heart
  • Pains in the chest or arms

Additional Purposes

Doctors also use ECGs to monitor the effect of specific medications on a patient's heart. This procedure also can help doctors determine the thickness of heart chamber walls. Additionally, doctors use ECGs to keep an eye on how well implanted pacemakers are working. ECGs can also indicate whether a patient has had a previous heart attack.

What Does Borderline ECG Mean?

Doctors read ECG results through a series of spikes and drops traced onto paper. These tracings are recordings of heartbeat activity. They are a real-time visual of how a patient's heart is functioning. Any results that do not fit into a safe, expected range are considered either abnormal or borderline.

Abnormal vs. Normal

Science places a normal human heartbeat rhythm in the range between 60 and 100 beats per minute. If a patient displays bradycardia (slow beat activity) of less than 60 or tachycardia (fast beat activity) of greater than 100, the ECG is generally considered abnormal, unless a doctor has specific reasons for thinking the results may be flawed or invalid, such as a patient who is visibly upset or frightened.


If an ECG result has an element of abnormality, it might be considered as a borderline ECG. This could mean there is something about the results that make the doctor unsure about the conclusion to draw. An ECG may be considered as borderline if a doctor is not able to conclusively determine whether or not the findings have clinical significance.

A specific example of a borderline ECG could be a result showing a heart activity rhythm just below or above the cutoff range. Such a close result may indicate a problem with that patient's heart, or it might not.

Beyond a Borderline ECG Result

An ECG procedure measures a number of delicate heart activities. They include:

  • Heart rhythm, regulated by the heart's electrical system
  • Heart rate, in case a patient's pulse is unusual or difficult to count
  • Abnormalities of the heart structure
  • Insufficient oxygen and blood supplies to the heart

These fragile measurements could be slightly off for a number of reasons, including heart problems. However, patients whose ECG results are returned as borderline need not panic. Instead, they can be proactive.

Ask for a Review of the Results

Sometimes ECG results are returned by a machine set to specific parameters. Any results that fall outside these calibrations, whether or not they indicate health problems, are termed as borderline or abnormal by the machine. The machine does not know a patient's specific medical background, and it cannot talk to a patient. Therefore, patients with doubts or questions about their test should talk to their doctor and ask for a review of their ECG results.

Consider Individual Differences

One patient's abnormal results could be another patient's normal heart functioning. Although medical science has set parameters to help doctors measure so-called normal heart functioning, not every individual falls into those neat categories, even though their hearts are functioning perfectly normally for them. Patients should discuss their cases with their doctors.

Explain Current Health and Medications Fully

Before having an ECG, patients should fully explain their current health to their doctors. They should disclose all medicines they are taking, including over-the-counter painkillers as well as herbal supplements. Some medications not related to the heart can affect blood pressure or rate. Life situations can also potentially affect ECG readings, including high stress levels from events such as losing a job, being hired in a new position, or relocating, and large emotional upheavals such as recently losing a loved one through death or divorce.

The Health Board is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Editorial Team
By Editorial Team
Our Editorial Team, made up of seasoned professionals, prioritizes accuracy and quality in every piece of content. With years of experience in journalism and publishing, we work diligently to deliver reliable and well-researched content to our readers.
Discussion Comments
By anon989951 — On Mar 29, 2015

My test ECG indicated borderline, as well and more scary, possible septal infarct. My doctor said nothing, but after I looked it up, I am alarmed.

By ysmina — On Nov 08, 2011

@feruze-- Do you have any uncommon symptoms like pain in the chest area, arms or difficulty breathing?

I think if your doctor wants more tests done, you should definitely get it checked out. I think doctors also look for symptoms of coronary heart disease when there is a borderline ECG test to continue looking into it. Even if you don't have symptoms, I think it's worth having it done. I don't mean to worry you but I've heard of people who have had a stroke or heart attack without any symptoms whatsoever.

You should probably get a second interpretation with your ECG results from another doctor or have the test repeated if you don't trust your current doctor about this.

By bear78 — On Nov 07, 2011

@alisha-- I just had an ECG and it came out borderline as well but my doctor is sending me to a specialist to get more tests done.

Do you think this is unnecessary then? Or maybe he saw something else that he didn't tell me about?

Maybe I should get another ECG interpretation from another doctor. I don't really want to go to a specialist for more tests if this is unnecessary as I'm going to have to pay quite a lot for it.

By discographer — On Nov 07, 2011

I have had several ECGs taken until now, and I've noticed that doctors don't generally mention a borderline ECG when they don't suspect that anything is wrong. I can't blame them because I think patients (including myself sometimes) tend to get hyped up about test results because we take them too seriously and assume that they always work perfectly.

A friend of mine had the same experience where she had an ECG taken with borderline results that the doctor didn't even mention. She saw the results later and was really upset that the doctor hadn't discussed this with her. Apparently he said that all is well and that she doesn't have a cause for worry.

I tried to assure her that this is normal and happens a lot. After all, doctors have a lot of experience with ECG machines and they know when something is really off versus the machine not working right or the patient being especially stressed that day. I'd prefer my doctor to not tell me about that rather than have me worry for no reason because I don't know what's going on.

Editorial Team
Editorial Team
Our Editorial Team, made up of seasoned professionals, prioritizes accuracy and quality in every piece of content. With years of experience in journalism and publishing, we work diligently to deliver reliable and well-researched content to our readers.
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