EKG Axis and Blocks Flashcards
Axis range for Left Axis Deviation (LAD)
-90 to -30
Axis range for Right Axis Deviation (RAD)
+90 to +180
Axis range for normal axis
-30 to +90
Axis range for extreme axis
+180 to -90
Qualitative approach to finding axis deviation
Look at leads I and aVF. I is + and aVF is -, look at lead II. + in lead II is normal and - is LAD.
Equiphasic approach to finding axis deviation
- Equiphasic
- Lead 90 degrees to that
- lead, QRS is that angle
- lead, QRS is 180 degrees of that angle
What does is mean when all leads are equiphasic?
COPD
What are the EKG signs of right atrial enlargement?
Lead II P wave is >2.5mm Lead V1 (biphasic) P wave is bigger + (>1 small box)
What are the EKG signs of left atrial enlargement?
Lead II P wave has two humps and >120ms Lead V1 (biphasic) P wave is bigger - (>1 small box)
What are the EKG signs of right ventricular hypertrophy?
QRS axis shifted to the right >+90
Tall R +/- secondary repolarization abnormalities (Downsloping T wave and T wave inversion) in V1 and V2
RAE
RBBB
What are the EKG signs of left ventricular hypertrophy?
QRS axis shifted to the left
LAE
Increased R wave in left leads
Increased S wave in right leads (There are criteria to quantitatively calculate QRS voltage).
RBBB Criteria
QRS >120ms
M shaped QRS in V1
Prominent s wave in I and aVL
Secondary abnormalities in V1 and V2
LBBB Criteria
QRS >120ms Broad R wave in I, aVL, V6 Lack of septal q waves in I and v6 Secondary abnormalities in I, aVL, V6 V1 negative QRS Lead I and V6 positive New LBBB with an acute MI increases mortality and morbidity.
What is normal septal depolarization direction?
q wave which is left to right.
Morphology of an incomplete BBB
Same morphology, QRS < 120ms
An important etiology of LBBB
acute anterior MI
1st degree AV Block
PR interval > 200ms. Can get even if healthy. If QRS is wide, there is a block distal to sinus node (BBB?).
2nd degree AV Block Type I
PR interval progressively lengthens until QRS complex is blocked. PP intervals are regular. Usually due to functional suppression of the AV conduction system. Results in “grouped” beating, detectable on exam as a regular irr rhythm.
2nd degree AV Block Type II
PR interval is constant, random QRS complex dropped, often at unpredictable times. His-Purkinje system block due to structural damage. If QRS is wide, block is distal to the Bundle of His. Narrow QRS is intranodal (AV).
3rd degree AV Block
No atrial conduction to the ventricles. Complete AV Dissociation. P waves are constant. Wide QRS is ventricular escape rhythm. Narrow QRS is AV or His escape rhythm.
Left Anterior Fascicular Block (LAFB)
Initial vector is downward and rightward. Then upward and leftward. LAD small q: I and aVL small r and big S: II, III, aVF Intrinsicoid deflection >45ms Increased limb lead QRS voltage
Left Posterior Fascicular Block (LPFB)
Initial vector is upward and to the left, then the electrical activity spreads freely down the ventricle. RAD small q and tall R: II, III, aVF small r and deep S wave: I, aVL Intrinsicoid deflection >45ms No additional evidence of RVH
How would you quantitatively calculate LVH criteria (specific one)?
Sokolov-Lyon criteria: S wave in V1 and tallest R wave in V5 or V6 > 35mm
What should you remember when diagnosing LVH?
Use both voltage and non-voltage criteria.
What is the voltage criteria for LVH in the limb leads?
R wave in lead I + S wave in lead III > 25mm
R wave in aVL > 11mm
R wave in aVF > 20mm
S wave in aVR > 14mm
What is the voltage criteria for LVH in the precordial leads?
R wave in V4, V5, or V6 > 26mm
Sokolov-Lyon Criteria (S V1 + R V5 or V6 > 35mm)
Largest R wave + largest S wave >45mm
What is the NON-voltage criteria for LVH?
Increased R wave peak time aka intrinsicoid deflection (>50ms)
ST depression and T wave inversion in left-sided leads “Strain pattern”. ST elevation in V1-V3 (discordant to ST depression in left-side)
