The Electrocardiogram Flashcards
There are 3 bipolar leads which are derived from two electrodes. What are they?
Leads I-III
The unipolar leads are derived from an electrode and Wilson’s Central Terminal. What are they?
V1-V6, aVL, aVR, and aVF
In an EKG, each small box is
0.040 seconds
In an EKG, every 5 boxes equals
0.2 second
Beginning of atrial to beginning of ventricular activation
PR interval
The normal duration of the PR interval is
0.12-0.2 seconds
The normal duration of QRS is
Less than 0.12 seconds
Normal conduction down His-Purkinje tissue and through ventricles
Normal WRS
What is a normal QT interval?
Less than 440ms for men and 460ms for women
How do we calculate corrected QT?
QTc = QT / square root of RR interval
Quick estimate of rate in an EKG is
300/n where n = number of big boxes
Functions as a natural pacemaker and initiates each atrial contraction
SA node
Strictly speaking, ‘sinus rhythm” refers only to what is happening in the
Atrium
Implies that the atrial rhythm originates in the sinus node and there is 1:1 conduction to the ventricle and the rate is 60-100 BPM
Normal Sinus Rhythm
A normal P and QRS axis for an EKG is
-30 to 90 degrees
What is the quick way to determine normal axis?
Lead I positive and lead II positive
What is the quick way to see left axis deviation?
Lead I positive, lead II negative
Right axis deviation is characterized as
Lead I negative and AVF positive
EXTREME right axis deviation is characterized by
Lead I negative and AVF negative
MI, left anterior fascicular block, and LVH can cause
LAD
Widened QRS, RSR’ in V1 (rabbit ears), and prominent S in V6 is characteristic of
RBBB
Widened QRS, broad notches R in V6, and absent R and prominent S in V1 is characteristic of
LBBB
Initial depolarization is normal, septal q-waves are intact, and late forces are upwards and leftwards
Left Anterior Fascicular Block
Overall QRS is less than 120 ms, RS in II, III, and aVF, and frontal axis is less than 45 degrees
Left anterior Fascicular Block
Initial depolarization is normal, and late forces are DOWNWARDS and rightwards
Left Posterior Fascicular Block
In a left posterior Fascicular Block, the precordial axis is
Rightwards (90-180 degrees)
Right atrial enlargement can be see with
- ) V1 positive deflection of P wave (greater than 1.5 mm)
2. ) Lead II P wave amplitude is greater than 3 mm (boxes)
Characterized by a P wave that is broad (greater than 0.04 secs) in V1 and a P wave in II greater than 0.12
Left Atrial Enlargement
RAD w/ prominent R wave in V1 (greater than 7 mm)
RVH
Sum of amplitudes of S wave in V1 + R wave in V5 or V6 is greater than 35 mm
LVH
Has an aVL R wave greater than 11 mm
LVH
Trans mural ischemia shows on an EKG as
ST elevation and Q-waves
Non-transmural ischemia is seen on an EKG as
ST depression
-Not associated w/ Q waves
Has more positive resting potential and shorter AP duration
Ischemic tissue
When we see the appearance of new Q waves, we have an
Infarction
Shows up anterior, apical, and lateral
Left Anterior Descending artery ischemia
Show up on posterior and lateral heart and inferior wall
Circumflex Artery Ischemia
Shows in right ventricle and posterior and inferior 80%) heart
Right coronary artery ischemia
