What's new
Every change to ECG Sweep, newest first.
October 2026
- Improved
CardioLab is now ECG Sweep
Before
The site was called CardioLab, at cardiolab.io. GE sells a cardiac recording system with the same name, so it was time for one of our own.
After
It's ECG Sweep, at ecgsweep.com, named for the trace that sweeps across the paper. Nothing else has changed, and every old cardiolab.io link, embed and shared card still works: it takes you to the same page here.
- Fixed
The 12-lead's Normal is always a normal ECG
On hyperkalaemia's sine wave and VF, the grey Normal drew a ventricular rhythm, and then the same fibrillation, instead of a normal ECG; on the torsades form it drew the torsades too. Normal is now always a normal sinus ECG: the trace's own beats with the condition taken out where the rhythm is still sinus, and a normal rhythm at 75 bpm beside the sine wave and VF. Inspecting a lead compares it with a normal beat.
- Improved
A redesign, built for phones first
Before
Pages looked different from one another, and on a phone the 12-lead was a long column of leads, a turned flashcard could slip off the screen and the homepage ran to eleven sections.
After
One look across the site. On a phone the 12-lead is the standard 6 × 2 with squares large enough to read, and a tapped lead opens its wave and measurements in one sheet. Flashcards mark your answer before they turn. Articles open with one sentence and let you read each strip before showing the answer. The homepage is shorter, with every tool on it.
September 2026
- New
Hyperkalaemia and hypokalaemia on the 12-lead
Both potassium disorders as progressions you can step through. Hyperkalaemia from peaked T waves at K⁺ 6, through a long PR and a wide QRS, to the sine wave and ventricular fibrillation. Hypokalaemia from a flatter T and a small U at K⁺ 3.0, through ST depression and a U taller than the T, to torsades de pointes. Each form has its own short article, and tapping a lead shows its measurements beside the normal range.
- New
ECG flashcards
A deck of ECG flashcards: a strip and a question, four answers to choose from, then the card turns over to the findings, the look-alikes and a link to the live 12-lead. The first card is up; more are added every week.
- Removed
The MI and hyperkalaemia 12-lead pages are paused while they are rebuilt
Anterior MI, MI evolution and hyperkalaemia were drawn by an older model of the 12-lead. They are being rebuilt on the same model of the heart as the conduction blocks, and each will come back at its own address; until then those links open the 12-lead page.
- New
Left anterior and left posterior fascicular block on the 12-lead
Both fascicular blocks, drawn from the part of the left ventricle each one reaches late, each with an article and a With RBBB variant for bifascicular block. Each links to the axis page at its own angle.
- Improved
The axis page opens at any angle from a link
Before
The axis page always opened at the normal axis, so a page about a cause of axis deviation could only send readers to it and ask them to find the angle.
After
A link can open it at an angle, such as −54° for left anterior fascicular block, and the address follows the dial as you turn it, so any setting can be shared.
- New
Incomplete right and left bundle branch block
Both bundle branch blocks now have an incomplete variant, chosen beside the title: the same pattern with a QRS of 110 to 119 ms, drawn from the same late activation, shorter. Each article explains how to tell it from the complete block.
- New
A Normal switch draws the normal ECG behind the whole 12-lead
Under the tracing, a Normal switch draws the same ECG without the condition in grey behind every lead. The grey hides under the trace wherever nothing changed, so in right bundle branch block it shows only the late QRS and the turned-over T waves. N turns it on and off, and the page remembers your choice.
- Improved
The 12-lead inspect box compares a lead with normal, and colours the QRS by the part of the heart that drew it
Before
Tapping a lead showed its wave and its measurements, but not what the condition had changed, or which part of the heart each wave of the QRS came from.
After
A Normal button draws the same lead without the condition in grey behind it and lists what changed, such as rS becoming rSR′ in V1. The QRS view colours the septum, the left ventricle and, in right bundle branch block, the late right ventricle, and says which wave each one draws in that lead.
- Improved
The 12-lead is laid out like a printed sheet, and the inspect panel fits the window
Before
The paper's scale followed the window's width, so on a laptop the rows were squeezed, tall R waves were cut off at the row above, a band of empty paper sat at the bottom, and the inspect panel ran off the bottom of the screen.
After
The sheet keeps printed proportions, with 40 mm rows, the rhythm strip included, a calibration pulse at the start of each row and marks where the leads change. On a wide screen the inspect panel sits beside the paper without covering any lead, and arrow keys move it from lead to lead; on smaller screens it stays inside the window.
- New
Right and left bundle branch block on the 12-lead
12-lead tracings of complete right and left bundle branch block, each drawn from the heart's own late activation, with an article on reading it. Right: the rSR′ in V1 and the broad S in I and V6. Left: the QS in V1, the broad notched R in I and V6, the discordant ST and T, and why the usual signs of infarction cannot be read.
- Improved
The axis page turns only the QRS, and shows the leads as an ECG prints them
Before
The whole beat turned with the axis, so the P and T moved with the QRS, and the six leads were laid out only in Cabrera order.
After
Only the QRS turns; the P and T stay where a normal heart puts them. The leads default to the standard printed layout with Cabrera as an option, each axis deviation lists its causes, and the quadrant method opens first, as most courses teach it.
- Improved
The 12-lead's numbers now come from the tracing you see
Before
The PR, QRS and QT beside the normal tracing came from the older model's settings rather than the beat on screen, so the PR read 26 ms short and the QRS 14 ms long, and the ST segment was dead flat.
After
The numbers are measured off the drawn beat, QTc uses Fridericia's formula and is labelled QTcF, and V2 and V3 show the small upsloping ST that most normal ECGs have.
- Improved
Tap a lead on the 12-lead to see its own measurements
Before
Tapping a lead zoomed into its wave with one number per wave, the same all-leads figure under every lead, and nothing to show where it came from.
After
The view shows the lead's own measurements: QRS shape, R and S heights, the ST at the J point with that lead's STEMI threshold, and its T and P, with calipers on the wave marking where each number comes from.
- New
Articles for the five sinus rhythms
Normal sinus rhythm, sinus bradycardia, sinus tachycardia, sinus arrhythmia and sinus arrest each have an article: how to recognise it, why it happens and what it can be mistaken for.
- New
Every rhythm article has a strip to read yourself, and the same strip annotated
Each article now carries a 30 second strip drawn by the simulator to work through first, then the same strip marked up with every interval measured.
- Improved
A new home page with a live simulator
Before
The home page showed a static screenshot and described some features that no longer existed.
After
It opens on a working lead II trace you can switch between rhythms, and shows what is new.
- Improved
The AV block family rewritten
Before
The AV block pages had short notes, and the simulator did not always draw the block its page described.
After
First degree, Mobitz I, Mobitz II, 2:1, 3:1 and complete heart block each have a full article, and the simulator draws each the way its article describes.
- Fixed
AFib and flutter baselines now match what their articles describe
The fibrillatory and flutter waves were redrawn so what you see on the trace is what the article tells you to look for.
- New
The PAC family: PACs, blocked PACs and aberrant PACs
Three articles on premature atrial contractions, with bigeminy and trigeminy, and two simulation faults they exposed fixed along the way.
- New
A cardiac axis page with three ways to read the axis
Drag the axis around the dial and watch the six limb leads follow, then work it out by the quadrant, isoelectric or three-lead method.
- Improved
The ventricular rhythms brought into line with their articles
Before
PVCs, idioventricular rhythms and VT on the simulator did not match the widths, shapes and rates their articles described.
After
They draw what their articles describe.
- Improved
Mobitz II and 2:1 block in the sidebar, with clearer page addresses
Before
Mobitz II and 2:1 block had no sidebar entries of their own, and AV block pages had addresses such as av-block-2-i.
After
Both have their own sidebar entries, and every AV block page has an address you can read, such as second-degree-av-block-mobitz-1.
- New
Articles for 17 rhythms
Each rhythm's page now explains how to recognise it, why it happens and what it can be mistaken for, beside the live trace.
- Fixed
Polymorphic VT and idioventricular rhythm drawn more faithfully
Polymorphic VT's beats now vary the way they should, and the idioventricular complex has a truer shape.
- New
Wolff-Parkinson-White pattern
A short PR and a delta wave slurring the start of a wide QRS, the triad that defines the pattern.
- New
The SVT family: AVNRT, AVRT and focal atrial tachycardia
Three narrow-complex tachycardias, each drawn with the features that tell them apart.
- New
Comment on a rhythm, or request one
Every rhythm has a way to send a comment, and a request page takes suggestions for rhythms to add.
- Improved
PACs reset the sinus node and pause the way real ones do
Before
A premature atrial beat left the sinus timing untouched, so the pause after it was the wrong length.
After
It resets the sinus node, so the pause after it is the length a real one would be.