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Terms in this set (52)
P wave represents what?
atrial depolarization (contraction)
the QRS complex represents what?
ventricular depolarization (contraction)
The T wave represents what?
ventricular repolarization (relaxation)
What does the R wave represent?
How many seconds is the P wave?
The period of time from the onset of the P wave to the beginning of the QRS complex is termed the P-R interval
-The time lag of the P-R interval allows atrial systole to occur and represents the time between the onset of atrial depolarization and the onset of ventricular depolarization
How many seconds is the PR interval normally?
If the PR interval is longer than 0.20 seconds, then what?
there is an AV conduction block or 1st degree heart block
How many seconds should the QRS complex be normally?
What happens when the QRS is greater than 0.12 seconds/abnormal?
a premature ventricular contraction (PVC)
What does the ST segment represent?
the interval between the ventricular depolarization and repolarization
Which one Non-STEMI vs STEMI have elevated ST segment?
how many seconds is a 12-lead ECG strip?
How do you calculate bpm with boxes?
1500/(# of boxes/beat)= #bpm
normal resting HR for adults?
resting HR >100 bpm
resting HR < 60 bpm
the heartbeat is irregular; to fast or too slow
What are the different types of arrhythmias?
· Atrial arrhythmia
· Ventricular arrhythmia
· Heart blocks
Atrial Arrhythmia-Sinus Bradycardia
-the SA node is depressed resulting in a slowing of the cardiac rate to any rate below 60 beats per minute
-normal sinus rhythm just a greater period of time between QRS complexes
-The only abnormality is rate
What are some possible causes of sinus bradycardia?
parasympathetic stimulation, myocardial infarction, drug intoxication, especially digitalis or beta receptor blocking agents.
T/F: it is normal in athletes to have sinus bradycardia?
T; People who regularly practice sports may have sinus bradycardia because their trained hearts can pump enough blood in each contraction to allow a low resting heart rate
Atrial Arrhythmia-Atrial Tachycardia
-problem in which the heart's electrical impulse comes from an ectopic pacemaker in the atria rather than from the SA node
-normal sinus rhythm just increased rate
What can cause atrial tachycardia?
drug toxicities, such as digoxin toxicity
What are people at risk for with atrial tachycardia?
Atrial tachycardia- atrial flutter
-atria of the heart rapidly beats due to an anomaly in the atria electrical system
-often degenerated to atrial fibrillation
-"F" wave for flutter
Atrial tachycardia- atrial fibrillation
-The "f" waves also differ from the "F" waves in that the "f" waves occur at a rate of 350 or more beats per minute
-QRS is normal
-R waves are not regular, or paced at a specific rate
-This is due to the "hit and miss" manner in which the action potential from the atria "escapes" into the AV node
What are patients at risk for developing in atrial fibrillation?
thrombus in the left atrial appendage
Ventricular Arrhythmia- PVC
-A (PVC) is a relatively common event where the heartbeat is initiated by Purkinje fibers in the ventricles rather than by the AV node
-perceived as a "skipped beat"
-single PVC's do not pose danger
Common causes for PVC's
· Cardiomyopathy, hypertrophic or dilated.
· Hypokalemia (low blood levels of potassium) and Hypomagnesemia (low blood levels of magnesium) that usually occur in patients taking diuretics.
· Medications such as digoxin, aminophylline, tricyclic antidepressants, and ephedrine.
· Stimulants including caffeine, cocaine, and amphetamines.
American Heart Association has established the following criteria for cautionary PVCs that are associated with increased cardiovascular risk and increased mortality
·5 or more PVCs/minute
· PVCs that are close coupled (bigeminy and trigeminy)
· PVCs that occur in pairs or in runs.
· PVCs that are multi-formed.
Close Coupled PVC's are dangerous why?
-it can cause an action potential (QRS complex of PVC) to occur during ventricular repolarization
-This may cause a disorganized response which can set in motion a life-threatening dysrhythmia, such as ventricular fibrillation
PVC couplet vs PVC triplet or run
-two PVC's in a row
-two or more PVC's in a row
What does multiformed or multifocal mean?
-means the ectopic beats have more than one shape form, indicating that there are multiple ectopic foci
-PVCs that originate from one ectopic foci are shaped alike and are unifocal (or uniform).
Any ectopy occurring every other beat is identified as a bigeminal rhythm or as bigeminy
Ectopy occurring every third beat is trigeminal or trigeminy
-a type of tachycardia that arises from improper electrical activity in the ventricles (i.e., not SA node controlled)
-can lead to ventricular fibrillation
Causes of ventricular tachycardia
occurs due to either coronary heart disease, cardiomyopathy, electrolyte imbalances, or a heart attack
Diagnosis is shown by an ECG of how many bpm?
Types of ventricular tachycardia
-Monomorphic Ventricular tachycardia.
-Polymorphic ventricular tachycardia (torsades de pointes);
Monomorphic Ventricular Tachycardia
-the appearance of all beats matches each other in each ECG lead
-usually scar tissue-related from a previous heart attack
Polymorphic ventricular tachycardia (Torsades de Pointes)
-outline looks like a party streamer
-Polymorphic ventricular tachycardia has beat-to-beat variations
-Ventricular fibrillation is when the heart quivers (like a bowl of worms) instead of pumping due to disorganized electrical activity in the ventricles
-results in cardiac arrest w/ LOC and no pulse
AV nodal heart blocks, and types?
Sometimes the signal from the heart's upper to lower chambers is impaired or doesn't transmit. This is an AV nodal heart block
· First-degree heart block;
· Second-degree heart block;
· Third-degree heart block.
First Degree Heart Block
-prolonged PR interval, but consistent in length
-the impulse conducting from the atria to ventricles through the AV node is delayed and travels slower than normal
-0.12-0.20 is normal, but in 1st degree it is >0.20s
Most common cause of 1st degree heart block
AV nodal disease, enhanced vagal tone, electrolyte disturbances and medication.
2nd degree heart block, two types?
-when one or more (but not all) of the atrial impulses fail to conduct to the ventricles due to impaired conduction
-Type 1 (Mobitz I/Wenckebach)
-Type 2 (Mobitz II)
In both types of 2nd degree heart block what happens to the P wave?
blocked from initiating a QRS complex
Type 1 (Mobitz I/Wenckebach) 2nd degree heart block
-PR interval gets increasing longer, then you have a dropped QRS
Type 2 (Mobitz II) 2nd degree heart block
-fixed PR interval, and all sudden you have a dropped QRS
-can be described as 2:1 ratio (for every 2 P waves you have 1 QRS)
-can progress to cardiac arrest or complete heart block
3rd degree (complete) AV block
-atria and ventricle are disjointed. P-P has its own rhythm, and R-R has another rhythm
-Because the SA impulse is blocked, an accessory pacemaker in the lower chambers will typically activate the ventricles. This is known as escape rhythm.
-two independent rhythms on the ECG
An ECG with pacemaker spike
-The impulse occurring when a pacemaker fires is a vertical deflection known as a spike, which is usually short and very fast.
-The spike is usually followed by a QRS complex
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