ECG Report Explainer
ECG printouts come with a machine-written summary full of phrases like 'nonspecific ST-T changes' or 'left axis deviation'. Paste it here and get each one in plain English, with a sense of what's usually fine and what isn't.
Browse every term (32)
Rhythm
Normal sinus rhythm
Usually fineEach heartbeat starts in the right place (the sinus node) and the rate is between 60 and 100 beats a minute. This is what you want to see.
Sinus bradycardia
Show your doctorA normal rhythm, but slower than 60 a minute. It's common in fit people, during rest, and in anyone on beta blockers. It matters more if there's dizziness, fainting or unusual tiredness.
Sinus tachycardia
Show your doctorA normal rhythm, but faster than 100 a minute. Usually it's the body reacting to something else, like fever, pain, anxiety, dehydration, anaemia or an overactive thyroid. The doctor will look for the reason.
Sinus arrhythmia
Usually fineThe rate speeds up a little when breathing in and slows when breathing out. It's normal, especially in younger people, despite the worrying name.
Atrial fibrillation (AF)
Show your doctorThe upper chambers quiver instead of beating in step, so the pulse is irregular. It's common in older adults and raises the risk of stroke, so a doctor needs to review it, often to discuss blood thinners. If it's new and comes with chest pain, breathlessness or fainting, get help the same day.
Atrial flutter
Show your doctorThe upper chambers beat very fast in a regular loop. It's a cousin of atrial fibrillation, carries a similar stroke risk, and needs a doctor's review.
Premature beats (ectopics)
Usually fineAn occasional extra beat that comes a little early, from the upper chambers (APC, PAC) or the lower ones (VPC, PVC). A few are very common and usually harmless. Mention them to the doctor if they're frequent, or if you feel palpitations.
Conduction
First-degree AV block
Usually fineThe signal takes slightly longer than usual (a PR interval over 200 ms) to pass from the upper to the lower chambers, but every beat still gets through. On its own it's usually harmless. Some heart and blood pressure medicines can cause it, so the doctor may check the list.
Second-degree AV block
Show your doctorSome beats from the upper chambers don't get through to the lower ones. The Wenckebach (Mobitz I) type is often mild. The Mobitz II type can progress, so show the report to a doctor soon.
Complete heart block
Needs urgent attentionNo signals get through from the upper to the lower chambers, so the heart runs on a slow backup rhythm. This needs urgent medical attention, usually at a hospital.
Right bundle branch block (RBBB)
Usually fineThe signal reaches the right side of the heart by a slower route. It's often found in healthy people. An 'incomplete' RBBB is even more common and is usually a normal variant. The doctor may compare it with an older ECG.
Left bundle branch block (LBBB)
Show your doctorThe signal reaches the left side of the heart by a slower route. Unlike RBBB, it more often points to an underlying heart condition, so the doctor will usually want an echo. If it's new and there's chest pain, treat it as an emergency.
Left anterior fascicular block
Usually fineA small branch of the left-side wiring conducts slowly, which shifts the axis to the left. On its own it's usually not a problem.
Numbers on the report
Heart rate / Vent rate
Usually fineBeats per minute. 60 to 100 is the usual resting range. Lower can be normal in fit people or on certain medicines; higher often reflects fever, pain or anxiety at the time.
PR interval
Usually fineHow long the signal takes to travel from the upper to the lower chambers. Normal is 120 to 200 ms. Longer than 200 ms is called first-degree AV block.
QRS duration
Usually fineHow long the lower chambers take to fire. Normal is under about 120 ms. A wide QRS (120 ms or more) usually means a bundle branch block.
QT / QTc
Show your doctorThe time the lower chambers take to recharge, corrected for heart rate (QTc). Roughly, up to 450 ms is normal for men and up to 460 ms for women. Above 500 ms is a concern, especially with medicines that lengthen it, such as some antibiotics, anti-nausea and psychiatric medicines. Show the doctor the full medicine list.
Axis (P-R-T axes)
Usually fineThe overall direction of the heart's electrical activity. Normal is between -30 and +90 degrees. Left axis deviation can come from a fascicular block or a thickened heart; right axis deviation is common in tall, young people and can also show up with lung disease. On its own it's rarely a diagnosis.
Shape of the tracing
Left ventricular hypertrophy (LVH)
Show your doctorTall waves that suggest the main pumping chamber has thickened, most often from years of high blood pressure. ECGs over-call this in slim and young people, so an echo is the way to confirm it.
ST elevation
Needs urgent attentionPart of the tracing sits higher than it should. With chest pain, sweating or breathlessness, this can mean a heart attack is happening: call 108 or go to a hospital now. Without symptoms it is sometimes a harmless pattern called early repolarisation, but only a doctor can say which.
ST depression
Show your doctorPart of the tracing sits lower than it should. It can mean the heart muscle isn't getting enough blood, or it can come from a thickened heart, some medicines like digoxin, or nothing specific. Show it to a doctor, and sooner if there's chest discomfort.
T wave inversion
Show your doctorA wave that normally points up is pointing down. In some leads (aVR, V1, sometimes III) that's normal. Elsewhere it can reflect strain, reduced blood supply or an old change, so it's worth comparing with any earlier ECG.
Nonspecific ST-T changes
Usually fineSmall changes that don't point to any one cause. This is one of the most common phrases on machine reports and is often nothing. The doctor reads it alongside symptoms and older ECGs.
Q waves / old infarct
Show your doctorA pattern that can be left behind by an earlier heart attack, sometimes one nobody noticed. Machines flag it quite often when it isn't really there, so the doctor may compare with older ECGs or ask for an echo.
Poor R wave progression
Usually fineThe waves across the chest leads don't grow as expected. Most of the time it's down to electrode placement or body shape. Occasionally it reflects an old heart attack at the front of the heart.
Low voltage
Show your doctorThe waves are smaller than usual. Body size, lung disease such as COPD, or fluid around the heart can all cause it. The doctor decides if it needs looking into.
Early repolarisation
Usually fineA slight lift in part of the tracing that's a normal variant, common in young and athletic people.
Report wording
Borderline ECG
Usually fineSomething measured just outside the textbook range. Very often it means nothing, but the doctor should glance at it.
Abnormal ECG
Show your doctorThe machine found at least one thing outside normal limits. Many of these turn out to be minor, so read the specific findings above it rather than the word 'abnormal'.
Unconfirmed / computer interpretation
Usually fineThe summary was written by the machine, not yet checked by a doctor. Machines tend to over-call, so a doctor's reading is the one that counts.
Artifact / baseline wander
Usually fineInterference from movement, shivering, talking or a loose sticker. It can mimic real problems, so the ECG may need repeating with the patient lying still and warm.
Lead reversal
Usually fineTwo electrodes were probably swapped. It makes the tracing look odd but says nothing about the heart. The test should be repeated.
How it's calculated
We match the words in your report against more than thirty common ECG findings, from rhythm and conduction to the numbers printed at the top (rate, PR, QRS, QT/QTc and axis). Each one gets a short explanation written for families, not cardiologists.
How to read your result
Read the specific findings rather than the headline. 'Abnormal ECG' at the bottom of a machine report often sits on top of something minor, while one line in the middle can matter. Labels here are a rough guide only. A doctor who can see the full tracing, the symptoms and any older ECGs makes the call.
Common questions
That each heartbeat starts in the heart's natural pacemaker and the rate is between 60 and 100 a minute. It's the normal rhythm.
Method: Standard adult 12-lead ECG reference ranges and terminology.