Test 2 Flashcards
What is the normal time range for a PR interval?
120 - 200 ms
What is the normal time range for a QRS complex?
80 - 120 ms
What is the normal time range for an ST segment?
<120 ms
What is the normal time range for QT interval?
330 - 350 ms
What is the normal time range for QTc?
QT/√RR = ~440 ms
How long (time) is one big box on an ECG rhythm strip?
1 big box = 0.2 seconds = 200 ms
How long (time) is one small box on an ECG rhythm strip?
1 small box = 0.04 seconds = 40 ms
What are the 3 requirements for normal sinus rhythm?
1) HR is between 60 - 100 bpm
2) P wave is positive in lead II and negative in aVR
3) 1:1 P to QRS
What is the big box and divide rule for determining regular rhythm on an ECG?
300 / #big boxes
What is the 2nd big box rule for determining regular rhythm on an ECG?
For normal rhythms:
1 big box = 300 bpm 2 big box = 150 bpm 3 big box = 100 bpm 4 big box = 75 bpm 5 big box = 60 bpm 6 big box = 50 bpm
What is small box and divide rule for determining regular rhythm on an ECG?
1500 / #small boxes
What is the method for analyzing an ECG?
1) rate
2) rhythm
3) axis
Do it the same way EVERY time!!!
What are the bipolar leads?
I, II, III
What re the unipolar leads?
aVF, aVR, aVL
What are the precordial leads?
V1 - V6
What plane do the bipolar and unipolar leads record?
Voltage from a frontal plane
What plane do the precordial leads record?
Voltage from a horizontal plane
How does an ectopic pacemaker change the direction of the P wave in lead II and aVR?
downward in lead II
upward in aVR
explanation:
ectopic pacemaker: atrial depolarization must spread up the atria in a retrograde direction, which is just the opposite of what happens with normal sinus rhythm. Therefore, an arrow representing the spread of atrial depolarization with AV junctional rhythm points upward and to the right , just the reverse of what happens with normal sinus rhythm.
Define inotropy
contractility
what is an inotrope?
a substance that increases contractility
What is contractility? What is contractility dependent upon?
the property of myocardial cells to develop a force at a given muscle cell length.
1) the size of the inward calcium current at the L-type channels
2) the amount of calcium stored in the sarcoplasmic reticulum