Exam 2 Flashcards
What is the function of the AV node?
Pace setter. Relays and intensifies impulse generated by SA node. It can fire an impulse if the SA node fails.
What is the function of the SA node?
Pacemaker.
What is the normal rate of the SA node?
50-100 per min
What is the normal rate of the AV node?
40-60 per min
How many second’s is each small box on an EKG strip? How about the big box?
- 04 sec per small box
0. 2 per large box
What is the amplitude of each small box on a EKG?
And a big box?
1 mm or 0.1 mV
5 mm or 0.5 mV
What is the P wave? and what is it’s normal duration?
Atrial depolarization (SA node firing.) Does not exceed 3mm in amplitude.
What does a change in the P wave mean?
The cardiac impulse originated from somewhere other than the SA node.
What is the PR interval measure?
Time it takes for impulse to depolarize the atria, travel to AV node and dwell there before entering the bundle of His.
How long is a normal PR interval? What does it mean is it is too fast/too slow?
A. 0.12-0.20 seconds. (3-5 small boxes wide)
B. Conduction is either delayed in the AV node, or abnormally fast.
What is QRS complex?
Ventricular depolarization.
How do you determine a a pathological Q wave? and what does it mean?
Has a width of 0.04 seconds and depth greater than one fourth of R wave amplitude.
Indicates myocardial infarctions.
What is the T wave?
What is it’s shape?
What is it’s normal height?
A. Ventricular repolarization
B. Asymmetrical (bigger than P wave)
C. No higher than 5mm or 5 small boxes
At what time do you measure ST segment changes? And what do you uses as a reference point?
0.04 secs after J point.
The isoelectric PR segment.
What does a wider QRS complex signify?
Greater than 0.10 seconds means delayed conduction.
Caused by either MI, atherosclerosis, or cardiomyopathy.
What does a change in direction or amplitude in T wave mean?
Electrical disturbances from electrolyte imbalances, myocardial ischemia, or injury.
Example: hyperkalemia- tall peaked T waves. And ischemia causes inverted T wave.
What does a large U wave mean?
Hypokalemia, cardiomyopathy, and digoxin toxicity.
What does QT interval measure?
The total time for ventricular depolarization and repolarization.
What causes depolarization? (4)
- SA node creates electrical current.
- This current changes the cell permeability.
- K- rushes out of the cell and Na+ rushes in causing a contraction
- Ca slowly diffuses into the cell to maintain a longer contraction
What is the U wave?
What is its height?
Repolarization of small segments of the ventricles.
Less than 2mm in height.
What does a large U wave mean?
Hypokalemia, cardiomyopathy, and digoxin toxicity.
How do you determine heart rate using the small box method?
Count the number of small boxes between QRS wave forms and divide that number into 1500.
When can’t you use the large and small box method?
When the rate is irregular.
How do you determine heart rate using the six-second method?
Count the number of QRS wave forms and multiply by 10 to get bpm.
How do you determine heart rate using the large box method?
Count the number of large boxes between QRS wave forms and divide that number into 300.
What is a first degree heart block?
Delayed AV node conduction represented by a prolonged PR interval (greater than 5 boxes or 0.20 secs)
What causes a third degree hear block?
A blockage from the atria to the ventricles occurring in either the AV node, bundle of His, or bundle branches.
What is the rate and rhythm of a third degree blockage?
20-40 bpm.
Atrial rate is greater than ventricular.
P-P and R-R are at regular intervals but have no association,
What are the causes and main treatment for a third degree block?
Causes: A. Ischemic heart disease B. Acute MI C. Conduction system disease Treatment: PPM
How does breathing effect sinus arrhythmias?
Inspire = increase rate Expire = decrease rate
How to identify atrial fibrillation on a rhythm strip? (4)
- No P wave
- Atrial rate 350-700 bpm
- QRS less than 0.12 secs.
- Irregular rhythm
What causes A-fib? (3)
Ischemic heart disease, lung disease, and valvular disease.
How to identify atrial flutter on a rhythm strip?
- No P wave
- Narrow QRS (less than 0.12)
- Regular HR
- Regularity sawtooth shaped flutters
What are the conduction rates of the AV node and the SA node?
SA: 60-100 bpm
AV: 40-60 bpm
How do you identify 3rd degree heart block on EKG?
- P waves have no association to QRS complex.
- Wide QRS interval
- Ventricular rate 20-40 bpm / Atrial rate 60-100
