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The QRS complex (ventricular complex): normal and abnormal configurations and intervals. A complete QRS complex consists of a Q-, R- and S-wave. However, all three waves may not be visible and there is always variation between the leads. Some leads may display all waves, whereas others might only display one of the waves.
- P-Wave, PR Interval, PR Segment
The P-wave is virtually always positive in leads aVL, aVF,...
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Basic anatomy & physiology; Introduction to ECG...
- P-Wave, PR Interval, PR Segment
Apr 24, 2022 · This makes the action potentials discrete events and means the impulse can only travel in one direction. This is essential for the successful and efficient transmission of nerve impulses along neurones. The five stages of an action potential: stimulus, depolarisation, repolarisation, hyperpolarisation and return to resting state.
S Wave. The S wave is the first downward deflection of the QRS complex that occurs after the R wave. However, a S wave may not be present in all ECG leads in a given patient. In the normal ECG ...
You will also have seen a small negative wave following the large R wave. This is known as an S wave and represents depolarisation in the Purkinje fibres. The S wave travels in the opposite direction to the large R wave because, as can be seen on the earlier picture, the Purkinje fibres spread throughout the ventricles from top to bottom and then back up through the walls of the ventricles.
- What Is An ECG?
- Parts of The ECG Explained
- How to Read ECG Paper
- How The 12-Lead ECG Works
- The Shape of The ECG Waveform
- Localising Pathology on The ECG
- Cardiac Axis
- Want to Learn More About Ecgs?
ECG is the abbreviated term for an electrocardiogram. It is used to record the electrical activity of the heart from different angles to both identify and locate pathology. Electrodes are placed on different parts of a patient’slimbs and chestto record the electrical activity.
P waves
P waves represent atrial depolarisation. In healthy individuals, there should be aP wave preceding each QRScomplex.
PR interval
The PR interval begins at thestart of the P wave and ends at the beginning of the Q wave. It represents the time for electrical activity to movebetween the atria and the ventricles.
QRS complex
The QRS complex represents the depolarisation of the ventricles. It appears as three closely related waves on the ECG (the Q, R and S wave).
The paper used to record ECGs is standardisedacross most hospitals and has the following characteristics: 1. Each small square represents 0.04 seconds 2. Each large square represents 0.2 seconds 3. 5 large squares = 1 second 4. 300 large squares =1 minute
Understanding the difference between an ECG electrode and an ECG leadis important: 1. An ECG electrode is a conductive pad attached to the skin to record electrical activity. 2. An ECG lead is a graphical representation of the heart’s electrical activity which is calculated by analysing data from several ECG electrodes. A 12-lead ECG records 12 lea...
Each lead’s ECG recording is slightly different in shape. This is because each lead is recording the heart’s electrical activity from a different direction (a.k.a viewpoint). When the electrical activity within the heart travels towards a lead, you get a positive deflection. When the electrical activity within the heart travels away from a lead, yo...
It’s important to understand which leads represent which anatomical territory of the heart, as this allows you to localise pathology to a particular heart region. For example, if there is ST elevation in leads V3 and V4, it suggests an anterior myocardial infarction (MI). You can then combine this with some anatomical knowledge of the heart’s blood...
In healthy individuals, the electrical activity of the heart begins at the sinoatrialnode then spreads to the atrioventricular (AV)node. It then spreads down the bundle of His and Purkinje fibres to cause ventricular contraction. Whenever the direction of electrical activity moves towards a lead, a positive deflection is produced. Whenever the dire...
We have several other articles relevant to ECGs: 1. How to read an ECG: a step by step guide to reading ECGs 2. Cardiac axis explained: a simple guide to the cardiac axis 3. How to record a 12-lead ECG: an OSCE guide to recording a 12-lead ECG 4. How to document an ECG: a guide to documenting your ECG interpretation in the notes 5. Bundle branch bl...
- Dr Lewis Potter
High voltage exists if the amplitudes are too high, i.e. if the following condition is satisfied: S-wave V1 or V2 + R-wave V5 >35 mm. Look for pathological Q-waves. Pathological Q-waves are ≥0,03 s and/or amplitude ≥25% of R-wave amplitude in the same lead, in at least 2 anatomically contiguous leads.
People also ask
What is the difference between R wave and S wave?
What is the difference between A S wave and a QS wave?
What is a S wave in a normal ECG?
What is the difference between Q wave and R wave?
Why does A S wave travel in the opposite direction?
What does a small negative wave mean?
May 19, 2024 · R' and S' waves: when more than a R or S wave are present, they are referred to as R’ wave and S’ wave. Remember: if in the QRS complex there’s a minimal initial positive wave, no matter how small it might be, this is an R wave. The following negative wave should be an S wave, not a Q wave. Confusing the two is a common mistake.
