Double speed 50 mm/sec

Double speed is a non-standard setting where the ECG waves will appear twice as wide as normal. This is because the ECG is recorded at twice the normal ‘paper speed’. At this setting, the calibration signal at the start of the trace will be 10 small squares wide instead of the usual 5 squares. It has been said that this setting can help to visualise difficult P waves, but all it really does is stretch out the same trace without adding any new information. Using this setting can also create confusion because none of the normal methods for calculating rate, segments or intervals will apply. A better solution to uncover difficult P waves might be to record a full 12 lead ECG (because P waves might be more clearly seen in other leads), or consider recording a Lewis Lead.

See also: Rate

Can you add to the information on this page?

This ECG Archive is an academic, non-commercial #FOAMed project aiming to crowdsource a free open access database of ECGs and signs. If you include your personal details such as your name you will be attributed for your contribution, unless you tell us that you don't want this to happen. Personal contact details such as email addresses will not be published but may be used to email you in reply. Full project details and participant information available here.

Featured Example

References

  • Hampton J, Hampton J. The ECG Made Easy. 9th edition. Elsevier

Topics

Before you can interpret an ECG you always need to check whether it was recorded at standard settings.

Standard settings include:

  • A 'paper speed' of 25 mm/sec
  • An amplitude of 10mm = 1mV

You can tell whether an ECG has been recorded at standard settings by checking for a calibration signal at the start of the trace.

Normal calibration

A normal calibration signal is 5 mm wide and 10 mm tall. This indicates that the ECG was recorded at standard settings of 25 mm/sec and 10 mm/mV.

Double speed

A double speed calibration signal is 10 mm wide and 10 mm tall. This means the paper speed was twice as fast (50 mm/sec) and the waves will all be twice as wide as normal.

Half height

A half height calibration signal is 5 mm tall. This means the waves will be half as high as normal, which might reduce the overlap between leads if the waves are very large.

Normal variant

Another type of normal calibration signal can be 10 mm tall (normal) but less than 5 mm wide. Some modern ECG machines do this with normal calibration settings. You will need to check the paper speed written elsewhere on the ECG to make sure it is set at a normal 25 mm/sec speed.

If you change the settings on an ECG machine, the ECG waves will look very different to normal and all the normal rules for calculating waves, segments, intervals and rate may not apply.

Most ECGs are printed onto two different size grids.

Understanding the basic ECG grids and standard settings allows us to be able to calculate the heart rate and important intervals later on.

ECGs are printed onto graph paper with two different size grids to make measurements easier. Even though many ECGs are now digital, we still use the same standard settings and grids so that we can interpret and compare ECGs easily.

Large grid

The large grid squares are 5 mm. One large square is 0.2 seconds long at standard settings (paper speed = 25 mm / second). This means that 5 large squares usually make up 1 second of an ECG recording.

Small grid

The small grid squares are 1 mm. One small square is 0.04 seconds (40 milliseconds) at standard settings.

ECG Library (6)

Sort by:
TitleDate
ASCDESC
Show:
Columns:
In the ECGquest archives, this ECG has been tagged with: - Chest pain Dyspnoea Double speed 50 mm/sec Normal Axis Normal rate Limb leads ECG of the Week CC-BY-NC-SA
ECG of the Week – 19th November 2018 – Interpretation

This ECG is from a man in his 30s who presented with dyspnoea and chest tightness.

This ECG shows a normal ECG recorded with a non-standard calibration of 50 mm/sec, making the trace look twice as slow as it really was.

In the ECGquest archives, this ECG has been tagged with: - Chest pain Double speed 50 mm/sec Hyperacute T waves Chest leads Dr Smith's ECG Blog CC BY-NC
Hyperacute T-waves and Concordant ST Elevation seen in PVCs only

This ECG is from a man in his 50s who had chest pain. His only risk factor for ischemia was hypertension.

This ECG shows bigeminy with PVCs showing concordant ST elevation in V2 and hyperacute T waves in V4-6.

In the ECGquest archives, this ECG has been tagged with: - Chest pain Double speed 50 mm/sec Hyperacute T waves ST elevation in a PVC Limb leads Dr Smith's ECG Blog CC BY-NC
Hyperacute T-waves and Concordant ST Elevation seen in PVCs only