EKG - The Basics Flashcards
One small box = ___ seconds
0.04 sec (40 msec)
Five small boxes = 1 BIG box = ___ seconds
0.2 sec (200 msec)
Five BIX boxes = ___ seconds
1 seconds (5 x 0.2 sec)
How many limb leads are there?`
6 limb leads
What are the three standard limb leads?
Lead I, II, III
What are the three augmented limb leads?
aVL, aVR, aVF
What are the inferior leads?
II, III, aVF
What are the left lateral leads?
I, aVL, V5, V6 (they view the left lateral wall of heart)
What are the six precordial leads?
V1 - V6
What are the anterior leads?
V2, V3, V4
What are the R ventricular leads?
aVR, V1
Match each lead to its category: I II III aVL Anterior leads aVR Inferior leads aVF Left lateral leads V1 R ventricular leads V2 V3 V4 V5 V6
Inferior: II, III, aVF
Anterior: V2, V3, V4
Left lateral: I, aVL (L for lateral), V5, V6
R ventricular: aVR (R for right), V1
Atrial depolarization begins where?
Sinus node, high up in the top of the R atrium
Which atrium depolarizes first?
R atrium, then the L atrium
The height of one small square = __ mm and __ mV
One small square tall = 1 mm = 0.1 mV
What is the normal length of PR interval
0.12 - 0.2 seconds (max 1 big box / 5 small boxes)
What does a long PR interval ( > 1 big box 0.2 sec) ?
some degree of A-V blocks (1st; 2nd - type 1 Wenke or type 2 mobitz; 3rd-aka complete AV dissociation)
What is the difference between the types of AV blocks
1st degree: constant prolonged PR interval. Is > 0.2 sec but is fixed
2nd degree:
- — Type I aka Wenkebach: increasingly long PRi until non-conducted P wave occurs (QRS gets dropped )
- — Type II aka Mobitz: again fixed prolonged PRi, plus nonconducted P waves (QRS’s getting dropped)
3rd degree: complete A-V dissociation
What is the normal Q wave amplitude?
no greater than 0.1 mV ( 1 mm = 1 small box)
What is R wave progression?
increasing R wave amplitude from V1 to V5 (moving from right to left in the precordial leads) - note sometimes R wave in V6 is a little smaller than V5
What is a transition zone? Where is the normal transition zone?
Where the QRS goes from being predominantly negative to predominantly positive.
Normal transition zone = at leads V3 and V4
What is the amplitude of QRS so much greater than that of the P wave?
Because the ventricles have so much more muscle mass than do the atria, and can generate a much greater electrical potential.
What is a normal QRS interval duration?
0.06 to 0.1 seconds ( 1 - 2.5 small boxes, max half of a big box)
What does a mildly long QRS (0.1 - 0.12 s) indicate?
Incomplete RBBB or LBBB; nonspecific intraventricular conduction delay (IVCD), or L anterior or posterior fascicular block
What does a VERY long QRS ( > 0.12 sec) indicate?
Complete RBBB or LBBB; nonspecific IVCD; ectopic rhythms originating in the ventricles
QT interval (beginning of Q to end of T wave) normal duration =
< 0.44 sec (slightly more than 2 big boxes)
* note QT is heart rate dependent, so QTc is corrected for HR)
Causes of long QT (> 0.44 s) are…
Drugs (TCA, phenothiazines) Electrolytes (LOW K+, Mg+, Ca+) CNS dz (arachnoid hemorrhage, stroke, trauma Hereditary LQTS (Romano-Ward syndrome) Coronary dz (some post-MI pts)
What is the normal range of axis?
-30 to + 90 degrees)
On the circle, what degrees is aVL at? …aVF? …aVR?
aVL = -30 degrees aVF = + 90 degrees (straight down) aVR = - 150 degrees
P wave is usually (positive or negative) in the L lateral and inferior leads?
P wave is usually POSITIVE in the L lateral (I, aVL, V5, V6) and inferior (II, III, aVF) leads
P wave is often biphasic in which two leads?
P wave is usually biphasic in III and V1
P wave is usually most positive in ___ lead, and most negative in ___ lead.
Most positive in Lead II. Most negative in Lead aVR.
T waves are variable, but are usually positive in leads with tall ___ waves.
T waves are usually positive in leads with tall R waves.
