Understanding Your ECG Test: What the Results Mean
By Dr. Subhkam Arya in Cardiology Interventional Cardiology
Jul 29, 2025
An Electrocardiogram (ECG or EKG) is a fast, painless, and non-invasive test that records the heart’s electrical activity to help detect various cardiac conditions. By placing small electrode patches on your chest, arms, and legs, the ECG captures and displays the rhythm and electrical activity of the heart in real time. Widely used in both emergency and routine health checkups, this simple test plays a crucial role in identifying irregular heart rhythms, signs of heart attack, and other cardiac abnormalities. Despite its simplicity, an ECG provides critical insights into the heart’s overall health and functioning, making it a fundamental tool in modern cardiology.
But once you’ve undergone an ECG test, how do you make sense of the results? Let’s explore what an ECG shows, why it’s important, and what different patterns might indicate.
What Is an ECG?
Every heartbeat is triggered by an electrical signal that originates in a part of the heart called the sinoatrial (SA) node. This electrical activity can be measured on the skin’s surface using electrodes. During an ECG test, small electrode patches are attached to the chest, arms, and legs, and these record the heart’s electrical impulses as waveforms on a screen or paper.
An ECG typically records for 10 seconds and produces a graph that shows the P wave, QRS complex, and T wave — which correspond to different phases of the heartbeat.
Why Is an ECG Done?
Doctors recommend an ECG for several reasons:
- To investigate symptoms like chest pain, dizziness, palpitations, or shortness of breath
- To detect abnormal heart rhythms (arrhythmias)
- To assess damage from a previous heart attack
- To monitor the effects of heart medications
- To check the function of a pacemaker
- As part of a routine heart checkup in people with risk factors like diabetes, hypertension, or a family history of heart disease
How to Read an ECG – The Basics
Understanding your ECG printout involves interpreting several key elements:
1. Heart Rate
A normal heart rate ranges between 60 to 100 beats per minute (bpm).
- Bradycardia: A slower-than-normal heart rate (under 60 bpm)
- Tachycardia: A faster-than-normal heart rate (over 100 bpm)
2. Rhythm
A normal heart rhythm, known as sinus rhythm, occurs when electrical impulses originate from the sinoatrial (SA) node in a consistent pattern. Any irregularity in this rhythm may suggest conditions like atrial fibrillation, ventricular arrhythmias, or various types of heart blocks.
3. P Wave
This indicates the duration it takes for the electrical impulse to travel from the atria to the ventricles. An extended PR interval may be a sign of a heart block.
4. PR Interval
This interval represents the duration it takes for the electrical signal to move from the atria to the ventricles. If the PR interval is longer than normal, it may indicate a delay or blockage in the heart’s conduction system, known as a heart block.
5. QRS Complex
This represents ventricular contraction. A widened QRS may indicate bundle branch block, ventricular hypertrophy, or premature ventricular contractions.
6. ST Segment and T Wave
These parts of the ECG are crucial for diagnosing ischemia or heart attacks.
- ST elevation on an ECG may point to an ongoing heart attack (myocardial infarction), indicating that a portion of the heart muscle is not receiving enough blood and may be sustaining damage.
- ST depression or an inverted T wave can signal reduced blood flow or past heart damage
What Abnormal Results Could Mean
Let’s decode some common ECG abnormalities:
1. Myocardial Infarction (Heart Attack)
An acute heart attack often shows as ST elevation in certain leads. Old heart attacks may leave Q waves behind on the ECG.
2. Atrial Fibrillation
This rhythm disorder causes the atria to quiver instead of beat regularly. On ECG, it shows no clear P waves and an irregularly irregular rhythm.
3. Heart Block
There are three degrees of heart block:
- First-degree: Slow conduction; seen as prolonged PR interval
- Second-degree: Some impulses don’t reach the ventricles
- Third-degree (complete): No impulses pass; atria & ventricles beat independently
4. Bundle Branch Block
This occurs when there is a delay or blockage in the pathways that send electrical impulses to the ventricles. It shows as a wide QRS complex.
5. Ventricular Hypertrophy
In conditions like hypertension or valve disease, the heart muscle thickens. The ECG reveals tall QRS complexes, particularly noticeable in the chest (precordial) leads.
Can ECG Be Normal Even If You Have a Heart Problem?
Yes. An ECG provides a snapshot of the heart at one point in time. Some heart conditions, especially those that occur intermittently (like paroxysmal arrhythmias or minor ischemia), might not appear on a routine ECG.
In such cases, doctors may recommend:
- Holter monitoring (24- to 48-hour ECG)
- Stress ECG (ECG during treadmill exercise)
- Echocardiogram (ultrasound of the heart)
- Cardiac MRI or CT
How to Prepare for an ECG
An ECG doesn’t require any special preparation. However:
- Avoid applying creams or oils on the chest before the test
- Inform your doctor about any medications you’re taking
- Stay relaxed — anxiety can increase your heart rate
Final Thoughts: Don’t Panic Over ECG Terminology
Reading your own ECG report can feel overwhelming, especially when medical terms like “sinus tachycardia” or “ST depression” appear. But these don’t always mean something serious. Many ECG changes are benign or temporary.
Always discuss your ECG results with a qualified doctor, preferably a cardiologist, who can interpret them in the context of your symptoms, medical history, and other test results.
Conclusion
An ECG is a powerful diagnostic tool that helps in early detection of heart issues. While the lines and spikes on the report might look confusing, each wave tells a story about your heart’s health. The key is to not jump to conclusions but to consult your healthcare provider for a comprehensive understanding of what your ECG results really mean.
