Why does the QRS complex have greater amplitude than P wave?
The QRS complex indicates ventricular depolarization. Depolarization triggers contraction of the ventricles. Because of the larger tissue mass, the QRS complex is larger than the P wave.
Why does the QRS complex have the largest amplitude in lead II compared to other leads?
The amplitude of this wave is relatively small, because the atrial muscle mass is limited. The QRS complex corresponds to the largest wave, since it represents the depolarization of the right and left ventricles, being the heart chambers with substantial mass.
What creates the large QRS peak on an ECG?
It is usually the central and most visually obvious part of the tracing; in other words, it’s the main spike seen on an ECG line. It corresponds to the depolarization of the right and left ventricles of the human heart and contraction of the large ventricular muscles.
Does the amplitude of the QRS complex change with the pulse amplitudes Why or why not?
The amplitude of the Q-R-S complex does change as the pulse amplitude changes. The Q-R-S complex is caused by depolarization of the ventricles. The Q-R-S complex and pulse both measure when the heart is in systole, therefore when the pulse amplitude changes, so does the amplitude of the Q-R-S complex. 5.
What does the QRS complex indicate?
The QRS complex represents ventricular depolarization. Ventricular rate can be calculated by determining the time interval between QRS complexes.
How do you find the amplitude of a QRS complex?
Here are some simple steps on how to measure the QRS complex:
- Find the QRS on the EKG strip.
- Determine where the QRS complex is, and to do this you start measuring the END of the PR interval to the END of S- wave.
- Count the SMALL boxes between there measurements.
- Remember each box represents 0.04 seconds.
Why is the S wave negative?
You will also have seen a small negative wave following the large R wave. 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 do the P QRS and T waves represent?
The P wave in an ECG complex indicates atrial depolarization. The QRS is responsible for ventricular depolarization and the T wave is ventricular repolarization. If a P wave is absent there is a lack of atrial depolarization.
What is the normal duration of the QRS complex?
The QRS duration represents the time for ventricular depolarization. The duration is normally 0.06 to 0.10 seconds.
What is considered an abnormal characteristic of the QRS complex?
Duration of an abnormal QRS complex is greater than 0.12 seconds. Shape of an abnormal QRS complex varies from almost normal to wide and bizarre and/or slurred and notched. Tall QRS complexes are usually caused by hypertrophy of one or both ventricles, or by an abnormal pacemaker or aberrantly conducted beat.
How do you treat a wide QRS complex?
If QRS width greater than or equal to 0.12 seconds, assess if the rhythm is regular (and obtain expert consultation). For regular WCTs, if VT or uncertain rhythm, amiodarone; prepare for elective synchronized cardioversion. If SVT with aberrancy, treat with IV adenosine (vagal maneuvers).
What does a negative QRS complex mean?
When the QRS complex is clearly positive, it means that the electric impulse flows towards the lead; if the QRS complex is negative, the impulse flows away from the lead; if the QRS complex is biphasic it means the direction of the impulse is perpendicular to the lead.
Which factors can influence the amplitude of the ECG signal?
The amplitude and direction of the R wave depends on the “electrical picture” the recording electrodes “see” as current spreads through the ventricular conduction system. The closer the mean QRS axis is to the electrical axis of Lead II, the larger the amplitude of the R wave.
What is the amplitude of ECG signal?
The amplitude, or voltage, of the recorded electrical signal is expressed on an ECG in the vertical dimension and is measured in millivolts (mV). On standard ECG paper 1mV is represented by a deflection of 10 mm.
What factors affect the amplitude of the R wave recorded on the different leads?
Factors affecting amplitude of the R wave are physical mass of the heart, the path the electrical signals that spread from AV node to the conduction system of the ventricles, the positions of the recording, the electrodes in contact with the skin, and the way the heart is positioned with the nodes.