The R wave is the first upward deflection after the P wave and part of the QRS complex. The R wave morphology itself is not of great clinical importance but can vary at times. Throughout the precordial leads (V1-V6), the R wave becomes larger — to the point that the R wave is larger than the S wave in lead V4.
The P wave represents the depolarization of the left and right atrium and also corresponds to atrial contraction. Strictly speaking, the atria contract a split second after the P wave begins. Because it is so small, atrial repolarization is usually not visible on ECG.
Atrial and ventricular depolarization and repolarization are represented on the ECG as a series of waves: the P wave followed by the QRS complex and the T wave. Typically this complex has a series of 3 deflections that reflect the current associated with right and left ventricular depolarization.
P-waves travel 60% faster than S-waves on average because the interior of the Earth does not react the same way to both of them. P-waves are compression waves that apply a force in the direction of propagation. The energy is thus less easily transmitted through the medium, and S-waves are slower.
Usually people can only feel the bump and rattle of these waves. P waves are also known as compressional waves, because of the pushing and pulling they do.
The DIRECTION of the
P Wave in lead II is positive (upright). The DURATION is 0.10 seconds or less. The SHAPE is normally smooth and rounded.
The Normal ECG Tracing.
| P wave | 3 small blocks tall |
|---|
| up to 5 small blocks high in remaining leeds. |
| PR interval | up to 5 small blocks in length (0.20 second) |
Atrial tachycardia - a series of 3 or more consecutive atrial premature beats occurring at a frequency >100/min; usually due to abnormal focus within the atria and paroxysmal in nature, therefore appearance of P wave is altered in different ECG leads. This type of rhythm includes paroxysmal atrial tachycardia (PAT).
A normal T-wave usually has amplitude of less than 5mm in the precordial leads and less than 10mm in the limb leads [1]. The normal shape of a T-wave is asymmetric, with a slow upstroke and a rapid down stroke.
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 first measurement is known as the "P-R interval" and is measured from the beginning of the upslope of the P wave to the beginning of the QRS wave. This measurement should be 0.12-0.20 seconds, or 3-5 small squares in duration.
A short QRS complex is desirable as it proves that the ventricles are depolarized rapidly, which in turn implies that the conduction system functions properly. Wide (also referred to as broad) QRS complexes indicate that ventricular depolarization is slow, which may be due to dysfunction in the conduction system.
The P wave will be the first wiggle that is bigger than the rest of the little ones (the microseisms). Because P waves are the fastest seismic waves, they will usually be the first ones that your seismograph records. The next set of seismic waves on your seismogram will be the S waves.
If the p-wave is enlarged, the atria are enlarged. If the P wave is inverted, it is most likely an ectopic atrial rhythm not originating from the sinus node. Altered P wave morphology is seen in left or right atrial enlargement. The PTa segment can be used to diagnose pericarditis or atrial infarction.
For seismic waves through the bulk material the longitudinal or compressional waves are called P waves (for "primary" waves) whereas the transverse waves are callled S waves ("secondary" waves). Since any material, solid or liquid (fluid) is subject to compression, the P waves can travel through any kind of material.
Junctional escape beats originate in the AV junction and are late in timing. They often occur during sinus arrest or after premature atrial complexes. The QRS complex will be measured at 0.10 sec or less. Rhythm will be regular with a rate of 40-60 bpm.
When an atrial impulse is completely blocked there will be a P wave without a QRS complex. This pattern is often referred to as a “dropped beat.” Mobitz type I occurs because each depolarization results in the prolongation of the refractory period of the atrioventricular (AV) node.
…the pacemaker cells of the sinoatrial node. Under pathological conditions, and with some pharmacological interventions, other pacemakers elsewhere in the heart may become dominant. The rate at which the sinoatrial node produces electrical impulses is determined by the autonomic nervous system.
The sinus node creates an electrical pulse that travels through your heart muscle, causing it to contract, or beat. You can think of the sinus node as a natural pacemaker. While similar, sinus rhythm is different from heart rate. Your heart rate refers to the number of times your heart beats in a minute.
Normal range up to 120 ms (3 small squares on ECG paper). QT interval (measured from first deflection of QRS complex to end of T wave at isoelectric line). Normal range up to 440 ms (though varies with heart rate and may be slightly longer in females)
First-degree heart block is a condition in which the wiring of the heart is slow to send electrical signals but all of the signals are able to pass successfully. There is no electrical block but rather a slowing or delay of the signal. It usually does not cause problems.
A junctional rhythm is characterized by QRS complexes of morphology identical to that of sinus rhythm without preceding P waves. This rhythm is slower than the expected sinus rate.
A “wide QRS complex” refers to a QRS complex duration ≥120 ms. Widening of the QRS complex is related to slower spread of ventricular depolarization, either due to disease of the His-Purkinje network and/or reliance on slower, muscle-to-muscle spread of depolarization.
