Recognizing Cardiac Arrhythmias Flashcards
What is the ability to transmit the impulse to the next cell?
Conductivity
What is the ability to spontaneously initiate an electrical impulse?
Automaticity
What is the ability to shorten the fibers in the heart when receiving the impulse?
Contractility
What is the ability to respond to an electrical stimulus?
Excitability
What is the sequence of a normal electrical impulse in the heart?
SA node Atria AV node Bundle of His Bundle of Branches Purkinje Fibers
What is the natural pacemaker of the heart?
SA node
Where is the SA node found?
Endocardial surface of right atrium near superior vena cava
Normally, what is the rate of impulse for SA node?
60 to 100 times a minute
What is the function of the AV node?
The AV node slows the impulse conduction between atria and ventricles; allows time for contracting atria to fill ventricles before ventricles contract
Where is the AV node located?
Low in the septal wall of the right atrium
What are modified muscle fibers in the heart called?
Bundle of His
What are the distal bundle branches called and where are they found?
Purkinje fibers are found across the surface of the ventricles from the endocardium to the myocardium
What do the Purkinje fibers do?
The Purkinje fibers that receive an impulse signals the blood filled ventricles to contract
What are the two safety measures of the heart if the SA node fails to fire?
AV node will generate an impulse 40-60 times a minute
The ventricles will fire an impulse at 20-40 times a minute if both SA and AV nodes fail to generate an impulse
What causes a disturbance in impulse?
Automaticity or conductivity
What causes tachycardia?
An increase in automaticity
What causes bradycardia?
A decrease in automaticity
If there is an increase in conductivity what kind of arrhythmia occurs?
Wolff-Parkinson-White syndrome
What kind of arrhythmia occurs of conductivity is too slow?
An AV block
What is an example of a combined automaticity and conductivity disturbance?
Atrial Tachycardia with a 4:1 block
What is commonly used to monitor the precise sequence of electrical events in cardiac cycle?
ECG
What are two types of ECG recordings?
12 lead and single lead(rhythm strip)
What are the wave forms in one cardiac cycle?
P, Q, R, S, T
What does the P wave represent?
Atrial depolarization
What does the PR interval represent?
The time it takes for an impulse to travel from atria through atrioventricular nodes and Bundle of His; PR interval measures from the beginning of P wave to the beginning of QRS complex
What does the QRS complex represent?
Ventricular depolarization(the Rome it takes for an impulse to travel through the Bundle of His to the Purkinje fibers)
What does the ST segment represent?
Part of ventricular repolarization
What does the T wave represent?
Ventricular repolarization
What does the U wave represent?
U wave signifies a problem and is not seen in most patients
What does the QT interval represent?
Ventricular depolarization and repolarization
Using a 5 lead wire system, what is the placement of electrodes?
RA-right arm/white (2nd superior R rib) LA-left arm/black (2nd superior L rib) RL-right leg/green (under last R rib) LL-left leg/red (under last L rib) C-chest/brown (midway sternum R side)
What are the 8 steps for interpreting a rhythm strip?
Determine Rhythm Determine Rate Duration of PR interval Duration of QRS complex Evaluate T wave Duration of QT interval Evaluate other components
What are two ways of measuring rhythm?
Paper and pencil
Calipers method
Using the paper and pencil method, what do you measure?
R to R distance between QRS complexes. If equidistant, patient has a regular ventricular rhythm
Using paper and pencil method, measuring what indicates regular atrial rhythm if equidistant ?
P to P waves
What are three methods of determining heart rate?
X 10 method
1,500 method
Sequence method
What is the simplest, most common technique for calculating heart rate?
X 10 method
Best of heart rate is irregular
Count P waves to determine atrial rate and R waves to determine ventricular rate over a 6 second time period and multiply by 10
Which method of determining heart rate is best used if heart rate is regular?
1,500 method
Locate to P waves, identify identical points in each wave and count the number of small boxes between the two points, then divide 1,500 by the number of small boxes (1,500 small boxes=1 minute) to determine atrial rate. To determine ventricular rate, use same method using two consecutive R waves.
Which method is best used to get an estimated heart rate only?
Sequence method
Find a P wave that peaks on heavy black line. Assign the numbers 300, 150, 100, 75, 60, and 50 to next 6 heavy black lines. Find P next wave peak and estimate atrial rate based in the number assigned to nearest heavy black line. Estimate ventricular rate using same procedure using R wave.
What is the normal rate?
60-100 beats per minute
In a normal cardiac rhythm, are the P wave and R wave intervals the same?
Yes
When evaluating the P wave, what should you consider?
Are P waves present?
Do they have the same shape?
Is the shape normal?
Do all P waves point in the same direction?
Do P waves have a 1:1 ratio with QRS complexes?
Is the distance between each P wave and its QRS complex the same?
What is the normal duration of the PR interval?
0.12-0.20 seconds
What is the normal duration of the QRS complex?
0.06-0.10 seconds
When evaluating the T wave, what should you analyze?
Are T waves present?
Do all T waves have the same size and shape?
Could a P wave be hidden in a T wave?
Do the T waves point in the same direction of QRS complexes?
What is the usual duration of a QT interval?
0.36-0.44 seconds (9-11 squares)
In NSR, what is seen in a rhythm strip?
- Atrial and ventricular rhythms are regular
- Atrial and ventricular rates are 60-100 beats/ minute
- P wave is present for each QRS complex and upright and rounded in shape
- PR interval is 0.12-0.20 seconds
- QRS complex is 0.06-0.10 seconds
- T wave is normally shapes and upright
- QT interval is 0.36-0.44 seconds
What two things occur during narrow complex tachycardias?
Accelerated heart rate and a narrow QRS complex
What are some examples of narrow complex tachycardias?
Sinus tachycardia Atrial fibrillation Atrial flutter Atrial tachycardia Multi focal atrial tachycardia (MAT) Wolff-Parkinson's-White syndrome (WPW) Junctional tachycardia
In sinus tachycardia, what is the range of heart rates?
100-150 beats/minute
Persistent sinus tachycardia may lead to what two problems, especially if associated with acute myocardial infarction?
Ischemia and myocardial damage die to raising O2 requirements
In sinus tachycardia, is NSR present?
Yes
In sinus tachycardia, is the P wave present and is there a 1:1 ratio of P waves to QRS complex?
Yes
In sinus tachycardia, how do the PR interval, QRS complex, and T wave appear?
Within normal limits and constant
What interval is often shortened but within normal limits?
QT interval
What are some common causes for sinus tachycardia?
Caffeine Smoking Alcohol Exercise Fever Stress Pain Increase in sympathetic tone/decrease in vagal tone
What are common symptoms of sinus tachycardia?
Rapid, regular heart rate of 100-150 beats/ minute
Palpitations or angina
If patient is symptomatic for sinus tachycardia, what medication is usually given?
A beta-blocker such as metoprolol (Lopressor)
What is atrial fibrillation?
Chaotic, asynchronous, electrical activity in atrial tissue
What Is an ectopic beat?
A contraction that occurs as an impulse generated from a site other than the SA node
An ectopic impulse causes the atria to quiver instead of contract at how many beats per minute?
400-600 times/minute
Are P waves discernible on an ECG?
No. P waves are represented by f waves or fibrillatory waves
Is A-fib constant?
No. A-funny occur paroxysmal or sustained
Can A-fib occur after a PAC?
Yes. PAC (premature atrial contraction)
On an ECG, is the rhythm regular during A-fib?
No. Grossly irregular.
Is the atrial rate discernible in A-fib?
Atrial rate is between 400-600 beats/ minute.
Ventricular rate varies from 40-250 beats/minute
Is a P wave present in A-fib?
No. f waves represent atrial tetanization from rapid atrial depolarizations
Is the PR interval discernible in A-fib?
No
Is the QRS complex abnormal in A-fib?
QRS complex is normal on duration and configuration
Is the QT interval measurable in A-fib?
No
What are some common causes of A-fib?
Rheumatic heart disease Hypertension Valvular disorders MÍ CAD Cardiomyopathy COPD Increased sympathetic activity during exercise
What are common symptoms to look for in A-fib?
Irregular pulse rhythm with a normal or rapid rate
Signs or symptoms of decrease cardiac output
How would you treat A-fib?
If hemodynamically unstable, use synchronized cardioversion at 120-200 joules
Use a beta-andrenergic blocker such as esmolol I.V., calcium channel blocker such as diltiazem (Cardizem)
If A-fib< 48 hrs, administer amiodarone (Cordarone), or digoxin
Consider anticoagulants if A-fib> 49 hours