Cardiovascular unit 3 Flashcards
P wave
Atrial depolarization
PR interval
Time from depolarization of the SA node to the onset of ventricular depolarization (normal <0.2s). A prolonged PR interval indicates a slowing of conduction between the atria and ventricles, usually due to slow conduction through the AV node.
PR segment
Isoelectric time between atrial depolarization and ventricular depolarization. Includes the atrial contract and delay of signal conduction at AV node.
QRS complex
Ventricular depolarization, atrial repolarization hidden in this complex.
QT interval
Time from ventricular depolarization to ventricular repolarization. Prolongation of the QT interval can result from multiple medications, electrolyte abnormalities, and certain disease states.
ST segment
Isoelectric time between ventricular depolarization and repolarization.
T wave
Ventricular repolarization
This rhythm is the same as NSR however the QRS complexes are not evenly spaced due to the normal respiratory variation, becoming slower during exhalation and faster upon inhalation.
Sinus Arrhythmia
This rhythm is the same as NSR but rate is less than 60 BPM. This rhythm can be caused by vagal stimulation leading to nodal slowing or by medicines such as beta blockers. Commonly found in some well conditioned athletes.
Sinus Bradycardia
This rhythm is the same as NSR but rate is greater than 100 BPM
Sinus Tachycardia
A premature atrial contraction occurs when some other pacemaker cell in the atria fires at a rate faster than that of the SA node. The result is a complex that comes sooner than expected. The complexes are otherwise normal, though the P-wave of the premature beat may be obscured by the T-wave of the previous beat.
Premature Atrial Contraction (PAC)
A premature ventricular contraction is caused by the premature firing of a ventricular cell.
Premature Ventricular Contraction (PVC)
This rhythm is the chaotic firing of numerous intrinsic conduction cells in the atria in a totally haphazard fashion. The result is that there are no discernible P waves, and the QRS complexes are in an irregular pattern.
Atrial Fibrillation
this rhythm is caused by what is called a reentrant pattern in the atria. Reentry refers to a circuit in which previously excited tissue is re-excited, producing an extra beat or a sustained rhythm. The circuit causes the atria to beat at a rate of approximately 300 BPM. The rate at which the AV node conducts impulses from the atria can then be described as a ratio. In a normal heart, this ratio is 1:1. The most common atrial flutter is with a 2:1 block. This means for every 2 P waves, there is 1 QRS. Atrial flutter can also occur at a 3:1 block, 4:1 block, and so on. The electricity in the atria would look like it is conducting in a circular pattern.
Atrial Flutter
This rhythm occurs from a prolonged block in signal conduction to the AV node. The PR interval is constant and is greater than 0.2 seconds. The atrial impulse is still conducted through the normal pathway, there is just a delay at the AV node. This can occur because of medication, vagal stimulation, disease, an aging heart, or other.
First Degree AV block
This rhythm arises because the SA node is non-functional and cannot initiate normal pacemaking function. There is no p-wave. The heart rate then comes from the inherent firing rate of the AV node which stimulates both the atria and ventricles when it fires. Therefore, there will be no interval between the P wave and QRS. The rate is 40-60 BPM
Junctional Rhythm
This rhythm is a very fast ventricular rate that has a wide QRS complex (ventricular beat). This rhythm is similar to atrial flutter in that it is a reentrant rhythm. The difference is that the ventricles (rather than the atria) fire at a dangerously fast rate. The rate is 100-200 BPM. Each beat may or may not cause ejection of blood into the arteries. A few of these beats in a row are not that big of a problem, but if this pattern is sustained it requires medical treatment and may require the defibrillator (paddle). If a person gets this a lot, an internal defibrillator may be implanted.
Ventricular Tachycardia
: If you were going to draw a picture of cardiac chaos, this would be it. The ventricular pacers are all going haywire and firing at their own pace with no organized contraction possible. The result is a heart contraction that literally looks like shaking gelatin. This is a very bad rhythm and left untreated will result in death. This is a shockable rhythm!
Ventricular Fibrillation
